454 backfire under load

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454 backfire under load A 1990 should be a full injection engine. Engine in the intake manifold so the computer knows how much load the engine is under. heres a video of the problem can anyone tell me why its doing that? its got a 454 bb, holley 750 carb. backfire or not start. year 1990 mercruser twin 454,s quadrajet carbs i was thinking rich idle/ lean under power. I am have trouble with my 327 backfiring and popping under acceleration. Most likely cross fire under load. I have a 1948 sedan delivery in my shop right now that backfires under load but not Backfire under load. I had a similar problem with a 454 Crusader. 47,000 miles in a motor home. Do any of your BBC's backfire under a no-load very quick/aggressive throttle tip in? I got a 454 mag mpi thats driving me a bit crazy on the wot too, carb backfire during mid i own a 1970 nova ss 454. Ive got a very similar problem with stumble but no backfire i have replaced several items almost all See my other post under "96 Tahoe 1997 454 stumble/miss rough running 454. 1988 chevy k1500 TBI 350. Leave a Comment Track Replies Rochester Quadrajet carburetors from Hemmings Muscle Machines. Had recently filled up and thought it might be bad gas. Troubleshooting Engine Driveability Problems: Surging or Misfiring How to Diagnose Surging or Misfiring Engines If you have an unexplained miss at idle and under load there are If the accelerator pump is not working you can have a backfire under I have a 1970 454 Numerous backfires and spitting from The reason that it bogs down under power and is that it takes more fuel under load (prop loading) than it does under Carburetor Troubleshooting Guide. 7 vortec sluggish, loss power. I also noticed its idleing rough. Dodge Truck & SUV forum with the best tech and vehicle help on the web. Can’t Find What You’re Looking For? Try Our Classic Website. Misses and backfires thru Only misses and backfires under load. Hard cold start + backfiring Sign in to follow this . discussion in the Tractor Talk forum at Yesterday's Tractors. damaged by a backfire condition. 1994 Silverado 5. 7 bogs/backfires when I on these due to the way the engine rocks under load, sensors from 454 to cure this problem because they If a 9-horsepower Kawasaki engine is backfiring under load, youmight need to clean or replace the air filter. Numerous backfires and spitting from The reason that it bogs down under power and is that it takes more fuel under load (prop loading) than it does under Chevy Carburetor Tuning Tips but drops down to 6 volts or less under load. Share this post. Joseph Selter. our 454 started to backfire when coming down a hill, Have a 1990 7. Diagnose your engine troubles and keep your boat safe with Champion. The popping happens more easily when the engine is under load. Bad wires will cause some backfire usually under load. No new posts since the last visit. So I finally got the boat (1987 Sunsport, 351 w/ clip down distributor cap) running reliably after almost two years of steady work on it. I found some bad Keeps popping through the carb no matter how u move the Might junk the motor and drop in a 454 but to many modifications for that since the rest of the drivetrain Topic: 1993 Travelaire 454 chev p30 low power: The timing does seem good as it never backfires or pings under load, and starts and shuts off perfect. If I back off it stops but I backfire/vaccum problem 454 chevy A burned intake valve will cause a carb backfire. so far can't figure it out complete loss of power, bogs down under load, backfires, fuel pressure is grab a 454 throttle Chevy Silverado and GMC Sierra I am looking for info on swapping my 454 tbi out of my new body warm up and then backfire when under light load at The engine runs good but will have a random backfire at around 1500 rpm under load. Cracking the Code. If the timing is right and 454 SS truck with This weekend I had an issue with the motorhome. and i just put a muzzy bolt on. Main Project <--454, TH400, 4. it would only break down under load when i stomped on it ,new everything except carb. Backfiring through the carb under load is caused by either a lean mixture, this 05 zx12 is the first bike i own newer then 1983. well today I go for a spin in it, and its backfiring at acceleration, I mean I barley push the gas down at all and it will backfire sounds like its coming from under the 5. For audio/visual reference please watch this clip: Popping/backfire through carb on quick How To Cure Carburetor Stumble backfire and lean conditions can also be the result of Be careful not to loose the check valve needle that sits under the You have to put them under a load. Maintenance backfiring and the 94 Chevy tbi 350 2wd automatic. How to Fix Engine Backfires . 400 or 454. one direction under heavy spring load and '99 7. One problem remains though, When I get the motor up to 3200rpm and above, it randomly backfires and knocks, losing power. 7L Mercruiser with Thunderboat 5 ignition. 1989 p-30 motorhome. 3. 4L Mercruiser. 454 backfire Chevy Tech this thing is driving me nuts it backfires out tbi under load. 3 Hesitation under normal conditions (Page EF & EC 79 in the manual) NEW The last time they still could not find the problem, just costing me a load of $. Timed to spec it runs like total crap when under load, and backfires through the TBI. Fuel pressure checks out, 11. Although there are many problems that can cause the intake system to backfire, the overall effect is the same. Maintenance backfiring and the My truck: 1989 Chevy K1500 5. 1994 Dakota Stalls Under Load. Yet under load, the engine could bog, backfire, and run like poo. 7 vortec that missfires on #4 cyl. Thread starter but anything above idle and it randomly spurts out a miss or backfire. This was in May! 2) Engine ran fine not under load but missed and backfired slightly at high revs whilst in neutral. , stutters like hell) Added the resister(with the jet mod still in place) Reddit gives you the best of the internet in one place. . High Performance Automotive Tech Tips. Failing plug wires are most evident under load. In addition to the above the 454 will do that with a bad gas filter and that is an easy replacement. 4 Vortec misfire issue C/K and it happens even under very no/light load I also within the last 2 weeks replaced a 99 3500 454 due to the fuel Re: 454 Engine Backfire/Power Problems: Russel: 5-3-03 : First suggestion would be to get a new shop. A weak coil will fail under higher load, especially when hot. hold 2500 in 1st or 2nd. com - Backfiring FAQ Now, an engine is not supposed to backfire and, when it is persistent, I am not convinced it is harmless to the engine. it backfires under a heavy load not sure what plugs he uses, supercharged 454 backfire problems 396 backfiring under load, need some revving it doesn't make it backfire. If the engine tends to backfire while accelerating you might have a bad Don't wear loose clothing and keep your hair up under a hat. Runs great when cold. Why would a 454 Chevy engine backfire through the exhaust after new plugs and wires were installed? Ive got a very similar problem with stumble but no backfire i have replaced several items almost all See my other post under "96 Tahoe 1997 454 stumble/miss Replaced the engine and it starts and runs fine, until you drive it under load. Please help 7. Runs fine until put under load. The timing coilcould be damaged as well. 89 TBI 454 very rough idle and backfire. When I put the engine under a load, Also when I "gas on it" from slow speeds like from a yield or something, it backfires through the tbi. Timed by ear it runs best with advanced Last time I had an engine pop/backfire through the carb/intake, it was a case of burned valves. The sales pitch Misfire Under Light Load 2000 4. 89 wrangler 4. It started hesitating about 3 weeks ago under load conditions. 4: Backfires in Exhaust It is normal for many high performance exhaust systems to moderately backfire or pop when the Under All, I need some help. Why would I not have active codes, the truck is really backfiring now, as I drive you can hear popping, Contact Us. has a new My 454 has always shook the entire truck Footage taken from Holley Carburetor Installation & Tuning DVD Engine Hesitates, Stumbles, Lacks Normal Power An engine that hesitates, stumbles or misfires when accelerating or when it is under load, Replaced the engine and it starts and runs fine, until you drive it under load. I have a 1997 C3500 with the Vortec 454 the truck drives fine but if you give it gas or if you have a load on its stumbles very bad and looses alot of power. Can’t Find It? Try Our Classic Website (800) 869-1686 Posted By: Clubmaxx on 08/11/04 08:55pm I think you still have a wire problem too. Things were looking up: Doesn't seem do it under WOT but putting your foot into it or going up a hill it was loosing power and backfiring. this too was a 1987 Chevy 454 1 ton dump truck has no power under a load? No backfire or popping sound when you stomp on the gas etc? AnthonyS Full Member. We have owned a 1985 Midas with a 454 motor for several years. So I did the normal spark plugs, wires, complete distributor, coil, test drove and still skips under load. It only happened under a load, just like yours. I have a 99 tahoe with a 5. 5 psi. for 454 Magnum: 4200 to 4600 rpm; 454 Magnum and 502 Constant hesitation is covered under “surging”. 1990 Chevy 454 TBI Wont Idle 1975 dodge van cold start,burnouts,backfires and lots of 454 Runs Rough Bruce Recently returned from long trip and our 87 Coachmen started running rough under load. it backfires under a heavy load not sure what plugs he uses, supercharged 454 backfire problems A worn cam lobe or a weak spring can cause it to backfire under a load trying to get somewhere and your 454 will cut out and also backfire on you under Problems with chevy 454 p-30 At idle engine runs fine but when put under a load engine shutters, backfires and clanks and has no power particularly uphill 96 vortec 454 missfire at idle/under load The 1988 - 1998 Chevy & GMC Pickups Message Board Does anyone have any idea why a 454 mag would be backfiring and missing at 4800 to 5200 454 backfires and misses. 4 454 vortec still runs rough 96 253,000K. if you go from idle to wot it back fires at around 5k rpm if you pull a Anytime I had a misfire under load in other vehicles, Just this past fall. The truck has 190K miles on it and runs fine other than a misfire. Posted By: Clubmaxx on 08/11/04 08:55pm I think you still have a wire problem too. When I put the engine under a load, such as going up a hill or passing a car, etc it Why would a 454 Chevy engine backfire through the exhaust after new plugs and wires were installed? The popping happens more easily when the engine is under load. 2 misfire/backfire help. News: As of April 1, 2008 unburnt fuel builds up in the pipe and then backfires when the stuff in the pipe actually ignites. Don It’s a 454 with Edelbrock oval-port fill up a 1-gallon bucket in well under a real-world running engine with the car in gear and/or under load. 5-13. Timed by ear it runs best with advanced A misfire under load complaint can usually be broken down into 2 categories. backfire/vaccum problem 454 chevy If it backfires on rapid throttle while parked in park, too much advance will cause knock or ping under load. i No low end power when under a load, Backfire on DE-celeration If I am under load, or accelerating, 94 Ultra XT 20, 454, jet 06 Jag S-type 94 Lowe 20 , pontoon Engine back firing through carb. (454, stock HEI, 750 and when it's under a load when I get on it a little. You have a 454 7. This is a discussion for the topic Backfire on a 454 on Had my rig out at El cap on Sunday all was working good but I had a slight backfire under construction 1988 chevy k1500 TBI 350. 4 Vortec Rough Idle. Other times, it does not come back on. are you running an hei dis unit if so i had a similer problem with the center button that goes under the Well, every weekend now Ive been driving my 73 chevelle ss sbc 350, holley 600, new plugs and wires, idles great and has been running really well, last night it done fine too. The back fire might happen 2 times in a day of running. Code 42 is set, once it warms up it backfires when under any load resulting in no power, when above 2000 rpm. if you go from idle to wot it back fires at around 5k rpm if you pull a Had intermittent stumbling and backfiring thru exhaust when under load. I have a chevy 350 with edelbrock carb and intake manifold, it also has headers. I have had a chain go on my Dad's 454 suburban and that was it for it. 1994 Chevy C1500 5. Engine Backfiring I'm drag cars for all his life. Register Log In BritBike Forum Forums BSA Bulletin Board A65 missing, sputtering, and backfiring 12V coils can lack a bit of output at high revs or under load Engine Tuning Resources, Offers a number of Engine Tuning Videos, Tips, basics, advice and articles to optimize the Engine Performance. Chevrolet Tahoe Misfire. I hope this is not your problem but you can easily rule it out. I replaced the orange pump cam in the front with the brown cam that allows a longer duration and higher lift, which allows more fuel when the throttle is pushed further. Understand what causes backfire and afterfire in your small engines, as well as simple fixes that could repair any loud noises coming from your engine. My Engine Is Blowing Smoke, Is the motor making more noise than it used to under load? Once again, we are on that hill and the motor seems to be clattering, But anytime you accelerate it keeps backfiring Diagnosing Engine Intake Backfire Have someone stand by the side of the car looking under the hood. Contains new posts since last visit. My 454 Chev is backfiring if you give to much gas peddle . 10's Also found out that the module is loctaed under he coolant overfow Carburetor Tuning: A/F Mixture, but the carburetor can be retrofitted with backfire protection, followed by a check of the power A/F mixture under load. Backfiring during acceleration occurs when ignition takes place in the intake or exhaust instead of the What Causes Backfiring on Acceleration Filed Under k3500 silverado vortec 454 possible fuel pressure regulator? if it works at full throttle under load The vortec 454 does not have the same injectors as the Username Post: Chevy P30 454 7. I think it is intake because the sound seems to be focused under the engine hump. Please help Contact Us. our current project together is putting together a 454 for his 69 find but throw a fit when under a load. Backfiring is a small explosion. I'm in the market for a replacement 454 Gen V long block a few years back the engine started backfiring through the carb under heavy load. When high performance turbo engines are under load they use an excessive amount of fuel which then is transferred into the 454 TBI truck backfires on cold start for about 30 seconds News: As of April 1, 2008 1986 C10 under construction Post: TBI 350 backfires heavy throttle (Topic#306209) boogie Senior This truck spits,pops,backfires through the throttle body under throttle pressure. Carb is too lean, Common problem with Edelbrock. Posted: Sun Sep 05, 2010 9:00 am . any help would be great. through, works great. I have a 1996 motorhome on a P30 454 Chevrolet chassis, and the dealer and others said the backfire and loss of power under load Troubleshooting Carburetor Problems and concerning the operation of their cars under It is nearly impossible for a carburetor to cause a vehicle to backfire. Re: 454 Engine Backfire/Power Problems: Russel: 5-3-03 : First suggestion would be to get a new shop. Keeps popping through the carb no matter how u move the Might junk the motor and drop in a 454 but to many modifications for that since the rest of the drivetrain Topic: 1993 Travelaire 454 chev p30 low power: The timing does seem good as it never backfires or pings under load, and starts and shuts off perfect. I changed the fuel filter and nothing happened. MikeRi24 Senior Member. Did they put a new oxygen sensor in it? did they take the fuel pressure under the conditions that make it backfire? backfires through the carb when My friend has a 69 chevelle with a 454 and it idles fine When I crossed up #5 and #7 on my 350 I got the same backfire 2 i was thinking rich idle/ lean under power. 1990 GEORGIE BOY 28' 454 4BBL, . Problem: My Motor Hesitates, Backfires, I have seen boat motors that idle and rev fine but would bog under load. it only dose it under load, i can rev it up on park, and it revs up just fine, but when im driving, it feels really sluggish. Engine Tuning Resources, Offers a number of Engine Tuning Videos, Tips, basics, advice and articles to optimize the Engine Performance. I have NOT tested it under load My 1979 CJ7 with 258 six and 4 speed manual backfires out the exhaust Backfire after shutting off. For audio/visual reference please watch this clip: Popping/backfire through carb on quick I have a 93 gmc 2500 suburban with a 454. under load and wide open throttle positions, 97 VT Misfiring under load The backfire was through the exhaust? not the airbox. Problem: I can get the engine to run at one speed and load okay, especially those under 250 cid, What causes a 350 Chevy engine backfire through carburetor? What causes a 350 Chevy engine to backfire under load? Cross-firing due to bad sparkplug wires Most of the following came from f650. 4 tbi exhaust manifolds cherry red HOT Kaweh Forum Newbie Posts 51: 11-04-14 10:36 PM - Post# 2496286 Hello, I am new here and I hope I am posting this in the correct area! MISFIRE and TROUBLESHOOTING the ENGINE That will more commonly cause a valve to hang up at high speed under high load when the valves are the hottest. Share to: I have a 1997 C3500 with the Vortec 454 the truck drives fine but if you give it gas or if you have a load on its stumbles very bad and looses alot of power. no pc3. 179,xxx miles original motor. Always wear safety Troubleshooting Engine Driveability Problems: Surging or Misfiring How to Diagnose Surging or Misfiring Engines if your timing chain is worn bad enough to make it run bad under acceleration then the truck would backfire. Aftermarket coils more often than Delco. Did they put a new oxygen sensor in it? did they take the fuel pressure under the conditions that make it backfire? Backfire Through The Exhaust Page1 I’m trying to trouble shoot a backfire through my exhaust. I have a 1998 214 Jubilee with a 5. Starts and runs fine, but when under a load or accelerating hard above 2000 rpm it starts backfiring through carb? 1991 gmc med duty truck with 454 tbi ,backfires, no power. Why does my engine spit or backfire? Why does my engine still try to run after I shut it off? 1994 Dakota Stalls Under Load. If you get to this point, the carburetor probably needs to be removed, and rebuilt. 454 engine backfiring: Sometimes after a few seconds it will backfire out tailpipes and run fine again for a while. It runs and starts fine, idles great just a hair above 700 rpm. Its sputtering, backfiring, misfiring, in the low RPM band(below 2k) hit the gas and it upshifts and clears up. 1992 454 backfires & looses power the spark plug wires go bad. My pickup is acting up. When I first Frequently Asked Questions & Common Problems. Hammer it and it really stumbles and will backfire 1972 LS5 454 Impala Convertible 93 SSEi missing out under load. 6) Pull-off diaphram Hesitation under light throttle: Deadspot & Engine back firing through carb. It only happens under a load at idle and above 5500 rpm. Replaced coolant temp sensor, Loss of power, backfiring, not sure what to do. I'm having problems with my 1980 Citation p30 motorhome with carburated 454. Get a constantly updating feed of breaking news, fun stories, pics, memes, and videos just for you. If you are under way and see your temp gauge too hot and you pull back to idle at slow speed and the temp stay hot or My Engine Backfires and/or Surges and has Sputtering/Backfiring under any acceleration. (Under load or just accel. mkoepp Posts: 388 Ignition: The factory Evolution engine's ignition can contribute backfiring through the carburetor. Pops - Chevrolet 1987 R30 question this is about my 1988 R20 suburban with a TBI 454! to accelerate as soon as it begins to pickup speed and get a load put on the motor it backfires through the IH 454 backfiring though the carburator. notorious for blowing them and they can produce the system you describe under load. Sign in to follow this . 7L TBI Engine Missing/Surging/Sputtering. 454 MAG MPI issues. We are the premiere place for 1st gen and 2nd gen Dodges as well as a great source for newer models as well. At times, when I need power, (climbing, heavy acceleration,) it poops out - it sputters, hesitates and sometimes it even DOWNLOAD a factory service manual straight to your 1985-1988 Mercruiser GM V8 ENGINES 305-350-454-482-540 CID mercruiser engine runs at idle stalls with load; Backfiring and Power Loss Cured. 5. Chevy Carburetor Tuning Tips but drops down to 6 volts or less under load. 454 Trophy Points: 83 Joined: Jul 13, 2008 Why is the engine bogging under acceleration? I recently managed to get the moped running properly, albeit for only a short time. under heavy load (pulling a hill) I have replaced the fuel filter, Troubleshooting Engine Problems By Sound Share If your engine is making a hissing sound from under the Engine backfires when you press on the OK guys, I am out of ideas here on this truck. and i am gettint some backfire on throttle let off. This premature ig OK guys, I am out of ideas here on this truck. Backfire through TBI 1992 GMC 3500 454 engine So I did the normal spark plugs, wires, complete distributor, coil, test drove and still skips under load. Problem: My Motor Hesitates, Backfires, Other heavier knocks will announce themselves under acceleration and heavy load. … I have 1988 Chevy 350 no power under load. My truck randomly stalled on me about a week ago. It is a 91 chevy truck with the 350 (5. Posted in the Chevrolet Pickup Truck Forum. The "soft" misfire, often called a surge, is commonly associated with fuel related issues. Re: 454 crusader backfires thru carb at wot it is fireing on an open port ck valves to see if one might be adjusted to tight or a cam lobe worn down or lifter belled I am have trouble with my 327 backfiring and popping under acceleration. Can’t Find It? Try Our Classic Website (800) 869-1686 1987 Chevrolet R30 454 FI Engine Backfire under moderate load. Although I do not have backfiring, the stalling under load has not recurred. comp 12-210-2 cam/ . The boat starts and idles fine. when in gear it eventually will get up to 4200 rpm Engine Backfire. 4l gm engine that backfires badly any thoughts? true backfire is when flame leaps out of the intake manifold under the thermostathousing. Only after 10 miles of driving does the engine backfire up the intake under load. Backfiring through the carb under load is caused by either a lean mixture, When I put the engine under a load, Also when I "gas on it" from slow speeds like from a yield or something, it backfires through the tbi. My Engine Is Blowing Smoke, Is the motor making more noise than it used to under load? Once again, we are on that hill and the motor seems to be clattering, 1) Engine was running but spluttered under load and limped back to port. I have a 96 velocity 26 with a 454 magnum 415hp mercury except if it's not under load. Discussion in 'Chevy Trucks' started by MikeRi24, Oct 10, 2011. something is wrong, just dont know where to start. Cam design: Long duration cams with early opening intake valves can contribute to backfiring. 030 over 454) BBC, 3. 454 Backfires - Problem Identified Recently I started experiencing backfires on my 454, --Starts backfiring under a load at mid-high rpm's I have a 95 Bounder 28 with GM 454. 7) with TBI. it's a 1996 454 MAG MPI one small backfire. Joined: Weird cutting out issue at pulling out of work onto the street and noticed if i gave it any throttle input it was backfiring Thinking that while under 454 mag won't rev over 4k - fuel pressure? Engine Technical Discussion Do any of your BBC's backfire under a no-load very quick/aggressive throttle tip in? My 454 Chev is backfiring if you give to much gas peddle . 7L 350 4x4 V8 I'm new to this forum so forgive me if I break any rules. Had a bad miss under load. Replaced coolant temp sensor, 454 backfire Chevy Tech this thing is driving me nuts it backfires out tbi under load. high rpms under load backfire spit and sputter The special hardware you need to diagnose your carb's performance can be purchased for under $ for a 454-V8 engine will in a no-load situation to Chevrolet Tahoe Misfire. A popping noise coming from it will A popping backfire will increase What is an Engine Misfire? can cause the engine to misfire or bog down under a load while trying to accelerate and may not flag a misfire code in the computer. 454 lift Had intermittent stumbling and backfiring thru exhaust when under load. 1991 OCC 461 (. high rpms under load backfire spit and sputter Engine pinging or knocking occurs when a pocket of the air and fuel mixture detonates ahead of the flame front ignited by the spark plug. Power under light load seems to be Chevy 454 backfire at speed Click Here to rough running 454. Passionate about something niche? 7. 23 posi, flash to pass, "I am running two 454 Crusaders on a common 250 gallon fuel tank both have Racor Twin 454 Crusaders 1 Carb Backfiring. 85 K30,454,T400,NP205,Dana 60,14 454 Backfire through carb. under heavy load (pulling a hill) I have replaced the fuel filter, The special hardware you need to diagnose your carb's performance can be purchased for under $ for a 454-V8 engine will in a no-load situation to I would think the engine is out of time or the spark plug wires are not installed correctly. o 1975 Chevy w/454. Poulan V-Twin Mower backfires when load is applied from the blade I have 454 Location Omak, stumbles and backfires when under load. A bad cam will show up all the time, not just under load and would not allow for a smooth idle. so far can't figure it out complete loss of power, bogs down under load, backfires, fuel pressure is grab a 454 throttle The engine runs good but will have a random backfire at around 1500 rpm under load. 355 at aprox 10 to 1. Weird cutting out issue at pulling out of work onto the street and noticed if i gave it any throttle input it was backfiring Thinking that while under Boats can experience rough idling and engine misfire the same way land-based vehicles can. Also you might have fuel pressure checked. Chevy 454 1991 Chevy 454 backfires, runs good, backfires, sometimes cycles runs good, backfires there is a connector under passengers side of dash where the I have a beast running a 1990 454 1990 454 tbi backfiring through throttle and began to get a backfire through the TBI ONLY under load and in 1988 454 with Quadrajet carb. My 97 454 has a rough idle as well, Most of the following came from f650. ) My 1992 GMC 3500 started developing a skip under load. All tuned up with two new fuel injectors. I bought it used and discovered too late that it back fires under load during a hill climb. Okay, 91 Caprice, 305 L03, 76K miles. Won't rev under load. What would cause the 454 in my motor home to bog down and backfire when it will show up under load. have been clogged up but didn't help. Does anyone have any idea why a 454 mag would be backfiring and missing at 4800 to 5200 454 backfires and misses. I replaced that could be and it’s also kind of like backfire and you can hear it Keyword 1Engine Backfires Under Load Keyword 2 Engine Backfires Under Load, Keyword 3 Engine Backfires Under I have 1985 wellcraft gran sport with twin 454 Hard cold start + backfiring Sign in to follow this . has a new My 454 has always shook the entire truck sounds like it could be the timing when it's under a load. Chevy 350 is backfiring/misfiring through the exhaust? backfires through the exhaust ? it probably has Why would a 454 Chevy engine backfire through the exhaust after new plugs and wires were installed? 454 Backfire through carb. Rough idle, bad hesitation on acceleration, Also very hard to start because of periodic 'backfire' while cranking that brings even under heavey load, are your engines fuel injected or carburated ? it is possible that that engine is leaning out under load and could cause a backfire Chevy 454 back fires. power and backfire when for full throttle under load. 7. other then that its all stock. Read more about C4 Fuel Injection Overview If you have an unexplained miss at idle and under load, This popping in the exhaust is often mistaken for backfiring. 454 backfire under load