454 tbi backfiring under load Also check the injector for proper flow. Turned out to be arcing between plug wires. 0 5. Sometimes, locating the … Discussion Starter · #1 · Jul 24, 2005. 10,000ish miles on it. There is No true ECM on the 1993 454. Unplug mass air flow sensor restart truck and drive to see if . 882 heads. The fuel pump is not coming on when I first turn the key on. As mentioned above backfires can be caused by faulty spark wires and this is a cheap easy fix. Comp roller tip 1. 4. If it is too high or … Turns out there are two very common and easily correctable problems with tbi motors. The engine may be running too hot. Backfire through TBI 1992 GMC 3500 454 engine. Reconnect EST by-pass connector and clear ECM trouble code. / 256,000 mi… Answered in 2 hours by: Bart, GM Master tech 136 Satisfied Customers Generally, a backfire is caused by an imbalance in the air to fuel ratio. Discussion Starter · #1 · Sep 5 . 1991 gmc med duty truck with 454 tbi ,backfires, no power. have replaced; ECM (mechanic shop placed 30A fuse in the 10A ECM panel) It started back firing at 44,000 miles so I changed the standard wires to high temperature wires and at least 3 of old wires were burned. - idle to WOT the engine will backfire, hesitate, and usually stall - running at 3000 rpms, upon hard throttle advance (to WOT) the engine stutters and backfires, nearly stalling - at WOT, the engine will sporadically stutter at about 4200-4400 rpms (acts like it is running out of fuel, can't exceed this rpm) A pop through the TBI is equivalent to a backfire through TBI. When I got the rig, it ran pretty good but with high idle. When in park I can give it some throttle and it will miss and stumble at around 1200-2000 rpm. #1. April 11, 2017; My 1992 GMC 3500 started developing a skip under load. 5. This goes for all vortec 4. Also, unless the engine system has been updated; there is a vacuum advance unit … If it backfires when you let off the gas peddle it has air getting into the exhaust, either an exhaust gasket or cracked manifold before the catalytic converter or the emission … This is a 1989 454 in a motor home. I have a '78 2F freshly rebuilt with fuel injection from Affordable Fuel Injection. Frank, Expert 98 had fuel injection-87 had fuel injection. problems in the ignition system. The problem with the distributor cap caused the engine to kick back against the starter & backfire through the TBI unit. First, the fuel pumps are extremely picky and prone to fail if run out of fuel. seems to do it the best when in 3rd gear and u press the pedal to the floor to make it down shift and it back fires. 90 and older is particularly bad and that is largely due to NO OVERDRIVE. The transition from the lean idle mixture to the normal mixture as the . 3 5. Oops. Plug … There are a number of different things that cause backfires on the 454. 7. Also the idle would be erratic. comp 12-210-2 cam/ . Engine backfires can be produced by: a vacuum leak. When the engine is cold the timing does not vary. throttle body intake from my 1990 engine. Now this can be from pour timing or an open valve. 55 rockers on press in studs. I've replaced the following:. 1 spark plug wire. an exhaust leak. remove the dist cap with a socket on a breaker bar connected to the crank shaft front bolt turn it backwards a little when the second guy sees the rotor turn you can stop mark the balancer with a reference point on the timing mark. Is it a backfire or more of a popping out the exhaust. Misfire under load is almost always related to ignition secondary components. About 45 minutes into the cruise home running between 3000-3150 the motor seemed to stumble. 7 hesitates under load. I slowed down and the re-accelerated all seemed fine. I am getting a sag when I accelerate. lost power going home one day, very rough idle, dies when placed under load if you are lucky enough to get it to run long enough. See if any of your header tubes are colder than the others by … Open the throttle and the timing should advance even more, then "tap" the intake manifold with the handle of a screwdriver. Egr clean, egr solenoid valve working, fuel filter clear, getting good spray in injectors. Take put the front O2 sensors and run it like that to see if the problem improves. Has new plugs, wires, fuel pump, fuel filter and fuel pressure regulator. That means that the timing is too far advanced . If you're using the intank pump there needs to be a bypassing regulator in the system to reduce pressure at the carb to 4-6psi and provide a return flow to the tank so the electric pump doesn't dead head as it would against a non-bypass regulator. 1995 S-10 4. Stock TBI 454 makes 230hp and 380tq so stock fuel pump is maxed out right off and a typical 454 will run better with a fuel pump upgrade even with stock chip. Backfires occur in engines with severe malfunctions, such as those with diverter valve issues, exhaust leaks and faulty catalytic converters. My engine takes longer to start than I think it should. For various reasons like leaking fuel injectors or a clogged engine air filter . -Joe Joel Bos Category: RV Satisfied Customers: 998 Experience: dasdasd … What did you do about the fuel supply the TBI uses a lot more pressure than a carb. RPM air gap intake with a 1405 edelbrock and stock . Did not dump into glass to check for water. Always a big complaint with 454 TBI trucks. The fuel pressure regulator may be operating at low pressure. 8L TBI. So like SC DIVER suggested -- I advanced the timing little by little and take it for a ride till it runs the best. Re: 454 Mag Performance Issues - Hesitation/Backfire/Stumble on Takeoff and WOT My first reaction is Accelerator Pump. Discussion Starter · #1 · Oct 2, 2010. The fix: Check and repair the cooling system. 90% of TBI issues are the fuel pump or the ICM. It has been running great until a couple of weeks ago. Joined Aug 20, 2010. It goes from like 3" to about 2" with a small-car sized muffler. i was leaving a bonfire and one … In a situation where the ignition timing is retarded too far, the plugs ignite the fuel too late, allowing it insufficient time to burn completely. One of the TBI injectors may be sticking or not working (wiring or computer problem), or fuel pressure could be low. #3 · Aug 3, 2011. This will tell you if the ignition is behaving correctly. Your … for an engine to backfire through the throttle body means that the inlet valve is still open when spark occurs . 99% of the time it runs amazing. … This leads to increased combustion chamber temperatures that can cause the fuel/air mixture to ignite before the correct time, while the intake valve is still open. If you have access to the top of the engine … 2,868 Posts. They could have been damaged when the engine overheated. Check timing and adjust if necessary Timing should be 0 degrees BTDC @ Idle. About 6 weeks ago it started missing under load. The most that happens is under a load on a hot engine you might get a little spark knock because the PCM throws the timing out when the EGR is supposed to be open and leans the mixture a little. After test return timing to the most advanced position without spark knock under load for … ignition module, map, IAC, engine coolant temp sensor, rebuilt fuel pressure regulator and new alternator. Has all the signs of going lean under load to me. Found and fixed all the vacuum leaks (including replacing TBI baseplate gasket) 4. Pull the plug and see if it's oil fouled. On deceleration, there is a miss. code 42 is set, once it warms up it backfires when under - GMC 1991 K2500 question. I would think that a 454 should do better than that even with 116000 miles on it in good shape. The timing should retard momentarily. Location: Preston, England. When vehicle is cold and idle is high, it is very smooth. I have a 1992 Itasca Sunrise with a chevy 454 tbi. then look and … Backfire under load. 86 s-10 Blazer 2. So I did the normal spark plugs, wires, complete … An intake back-fire explosion can be caused by the fuel air mixture being to lean when the engine is demanding power. If it doesn’t, and you find no other issues such as fuel starvation or exhaust restrictions, your camshaft could be excessively worn. -Vinny. Vacum leaks will make it backfire through tbi on accelleration, not make it miss on decelleration. The lean condition in my case was caused by a bad pcv valve which resulted in a high idle around 1200 rpm & a nitrous oxide smell from the exhaust. The fix: Check the choke plate and make sure it is opening completely. Cold Air Intake And Mass Airflow Sensor I'm Interested In Buying A Cold Air Intake For My 4. Chevy silverado 5. reaches. Since your truck has 8 coils on it, it makes it really inconvenient to replace all of the coils, but I would definitely replace all of the wires, and if you didn't use AC Delco plugs, I would install those as well. 3L V-6, no emission air pump, A/C, TBI, all stock. People pass me on the freeway going up hill unless I really put my foot into it, & i'm only talking 55 to 65 mph & then they still fly by me. Your sensors could have been damaged also. There is a mechanical advance spring set up under the distributor cap. I have a beast running a 1990 454 with TBI. a faulty sensor. Under load it won't accelerated past 3000 rpm, really falls on its face from 1800 rpms up. Go to Napa and get part number 2-18421 or 2-18422 (can't remember whicho ne it is but I think it is the 2-18421) and it plugs in the supply line AT the trhottle … Re: 454 Mag Performance Issues - Hesitation/Backfire/Stumble on Takeoff and WOT My first reaction is Accelerator Pump. It could be running too lean. That would explain it worsening when going to WOT when allready at cruising speed. Anytime an engine backfires through the intake it is from spark occurring while an intake valve is still open. or some other system fault. Chevy 454 back fire Ignition timing is set by the computer as long as the distributor pickup point is within reason. Incorrect Timing 2. Please understand that I don't know your skill level or tools you have to assist us. If it's more of a popping it could be a burnt valve. now turn it back the other way slowly and when the other guy sees the rotor start to move stop . 2. My motor seems to be missing/backfiring once it warms up (about 10 minutes) and I go from an idle to accelerate. If it's a stock motor with high miles the rockers will … Accelerating it has no miss. There are a few different issues that can create this situation. RPM air gap intake with a 1405 edelbrock and stock type hei dist. The engine is a reman 454 TBI that was replaced in 09. If I accelerate normally or if I … Check the back fuel bowl and see if its getting gas in the bowl at all. Hesitation and backfiring will accompany the loss of power causing the plugs to foul leaving them with a black “sooty” appearance. Replaced the Coolant Temp Sensor. T. Another possible cause of backfires is engine timing. Check the fuel pressure and compare it to the manufacturer’s specifications. Posts . Either the engine is not getting enough fuel, which is also called running lean, or the engine is getting too much fuel, which is also called running rich. IT may … 1 Answer 1991 gmc med duty truck with 454 tbi ,backfires, no power. This may help your lack of power issue. Here is what has been done by me and the non-volvo mechanic at the marina: 1. It starts and idles fine but when I'm on the road at 55-60 mph and try to accelerate it has a very noticeable hesitation and occasionally backfires. The symptoms include a very rich running condition, a rough idle only in park or neutral, and the scanner shows a more rich condition on bank 2, and upon acceleration or any application of the gas pedal my bank 1 knock sensor is retarding timing by 6-7 degrees and 3-4 degrees when cruising. 3L TBI . sounds like its running on bad gas , so i'd check the timing as was mentioned. A leaky exhaust manifold gasket can cause running problems by burning the spark plug wires , but it can also allow air to be drawn into the exhaust system which can throw off the oxygen sensors. Check down the venturi and pump the … Throttle Actuator Bore Service The throttle bore or throttle actuator as they are called on newer cars is used to meter the engine air intake thus controlling the engine RPM and power output via the gas. Plug wires on the Chevy 454 are another common cause of backfiring. I do not seem to have as much power as I should. Engine specifics are: 355 at aprox 10 to 1. See if any of your header tubes are colder than the others by pouring some water on each tube. No known head or intake work. That is, plugs, plug wires, and coils. Check down the venturi and pump the carb. Runs great cold. This improved the condition but did not cure it. Every internal combustion engine runs on a … When this happens, the air/fuel mixture in the exhaust or the intake can combust, leading to a backfire. Your timing should be set around 8 degrees BTDC at idle with the vacuum advance disconnected and plugged. Connect a fuel pressure gauge to the fuel rail and start the engine. Any acceleration causes sputtering and backfire through intake. It seems to be an ignition problem. motor is an 86 reman converted to the TBI setup with about 40,000 on it. By the way, congratulations on the correct use … 1994 454 TBI runs rough, misfires, backfires, dark exhaust Classic Winnebagos & Vintage RVs Forum Topic Boards Chevy - GMC Chassis 1994 454 TBI … 1992 454 TBI Timing - iRV2 Forums iRV2 Forums > THE CHASSIS CLUB FORUMS > Workhorse and Chevrolet Chassis Motorhome Forum Page 1 of 2 1 2 > This discussion is proudly sponsored by: Please support our sponsors and let them know you heard about their products on iRV2 Thread Tools Search this Thread Display Modes Truck runs great in regular traffic, it just seems to lack power under minimal load conditions. Search Fixya . Double checked that the EGR valve is working correctly. 1,322 Posts. Dr Floyd: Don't suppose you have any idea what the damn thing is, huh? B 4. The fix: Check fuel pressure with a fuel pressure gauge. Something to note is that the previous owner had a tiny tubing exhaust welded on behind the cat. EVERTHING is new (except heads and block). #9 · May 12, 2010. then look and … Freeborn. We are at a total loss! Aug 10, 2011. Senior Member . The motor starts up the following morning to head back home with no sign of concern. Backfires can also be caused by timing too far advanced, also as mentioned above sticking valves, vacuum leak, or carbon deposits in … Is it a backfire or more of a popping out the exhaust. Engine bucks and backfires through throttle body under acceleration Only happens when engine is at normal operating temp while accelerating or under load. Code 42 is set, once it warms up it backfires when under any load resulting in no power, when above 2000 rpm. lean or rich air/fuel mixture. widmayer123 said: 99% of the time when it runs fine except under a load it is electrical!! Wrong. 3. has new plugs, wires, and a fairly new distributor. The electical portion of EFI has no idea what load the engine is under, except for timing which the OP stated was normal. She planed off as normal and we're on our way. When I cranked it down to "0" it runs like a dog and backfires under load. 3l V6 C1500. The egr being carboned up, will throw a code. . Build has aprox 50 miles on it other than break in time. Changed fuel-water separator. Seems to be running rough at idle but in neutral, can rev engine to 3k+ with no backfire and engine "sounds" good. Jump to Latest Follow 1 - 10 of 10 Posts. If it never had a computer the motor homes would vapor lock and starve and the … Inspected all the vacuum lines off the TBI. GAS MILEAGE. That would be my first suspicion. Every now and then (and there's no real pattern), when I start to accelerate from an idle, it hesitates and backfires through the throttle body. Nova NEWBEE said: I have a 71 Chevy Nova with a 350 motor. Page 2 of 2 < 1 2 This discussion is proudly sponsored by: Please support our sponsors and let them know you heard about their products on iRV2 Thread Tools My 454 backfired and shut down and will not start. have replaced; ECM (mechanic shop placed 30A fuse in the 10A ECM panel) Under load at about 1500 rpm backfires and no power. Given below are the top reasons why a Chevy truck could lose power while accelerating along with the symptoms you need to look out for and the solution to the issue: 1. A month before all this we put in a new battery, cat converter, o2 sensor, radiator and new head gasket. Check vacuum for broken, disconnected or loose connections, a vacuum leak will affect the timing. in may 2006 i put this engine in and i put a new double roller timing Ask an Expert Car Questions Chevrolet Repair This answer was rated: ★★★★★ timing chain. If I accelerate easy it doesn't miss. My engine is running to lean, or is backfiring on acceleration. Check the vacuum advance unit and vacuum lines as these are common causes. Replaced it, and began to get a … You should have at least 15 psi fuel pressure with the engine under load. It will be loud, but this is a test. Seems to miss with no load on the motor, during high vac conditions. Joined Sep 5, 2013 · 39 Posts. These wires sit right near the exhaust and often run into problems. Old plugs were white when removed indicating a lean mixture correct? The most common causes for backfiring during acceleration include an incorrect fuel-to-air ratio, a faulty ignition and bad wiring. I have a 1990 GMC TBI 454. Chevy Mechanic: rpmdiag Check for an exhaust restriction such as the CAT. Found the CTS to be bad. 140,000 MILES My truck has a Z-code 4. Here is a list of what I have done: 1. Checked timing (bypass wire unplugged) and found it was set at 0 BTDC. This causes a loss of power and poor fuel economy. Since the spark timing in a modern car is computer controlled, this is a problem that'll need to be addressed by a trained technician. 3l into a 2001 jimmy, engines starts fine and idles fine (650 rpm). 454 TBI won’t start when engine hot FAQ Mark Forums Read Mission Statement: Supporting thoughtful exchange of knowledge, values and experience among RV enthusiasts. An engine backfires through the intake from spark occurring while an intake valve is open . 8. throttle. 10 Posts. Next I installed new spark plugs again improved but did not cure. 454 lift 268 duration. If you get one that dosen't sizzle that's the cylinder giving you problems. My engine is running rich. Its not throwing a code or SES light. backfire. Code 42 is set, once it warms up it backfires when under any load resulting in no power, when above 2000 … Joined Aug 20, 2010. bad timing. have replaced; ECM (mechanic shop placed 30A fuse in the 10A ECM panel) There are a number of different things that cause backfires on the 454. seems to do it the best when in 3rd gear and u press the pedal to the floor to make it down shift and it . If it sounds good at idle , but not under load , thats usually fuel delivery , or … I've experienced the same thing with the 454 in both a P30 chassis and a boat. 7 liter vortecs. I have checked my timing when warm, and when I am at idle, the timing is varying plus minus 4 or 5 degrees. 1992 Pace Arrow 30E Chevy 454 TBI 4L80E 08-28-2016, 01:57 AM #17: kennyrodgers. 1 Answer 1991 gmc med duty truck with 454 tbi ,backfires, no power. Bad Fuel Pump Your Chevy Truck engine comes with a fuel pump that takes the gasoline from the fuel tank and transfers it to your truck’s engine. Rich Air/Fuel Mixture. In contrast, The fuel system is sensitive to engine load variations. Tags backfire ignition failure. Easy to replace, any junkyard with chevy/gmc trucks has a dozen of them. Took it to the local Chevy dealer and they said it was the EGR valve so they replaced it. May 21, 2009 • 1995 Chevrolet C/K 3500 Not finding what you are looking for? Connect timing light to No. the garaje · Registered. . I have replaced the wires, plugs, distributor cap & rotor, fuel filter, TPI, idle air control valve, carb gasket to … As mentioned above backfires can be caused by faulty spark wires and this is a cheap easy fix. Join Date: Jul 2015. I was worried about back pressure but the truck seems to have as much or more power than my 95 with open exhaust (it fell off due to rust). 3l backfires through throttle body Just installed a 2005 4. Joined Mar 6, 2008. Sometimes it is no big thing, sometimes pressure/volume problems arise. 6. the truck started to backfire pretty good only when at WOT just recently. Specifically my TBI kit includes their coil and ECM-controlled distributor.


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