1986 2.8, backfires under light acceleration when cold.
Thread Starter
Joined: Jul 2011
Posts: 695
Likes: 73
From: New York
Car: 86 Sport Coupe
Engine: 5.3 LM7
Transmission: T56
Axle/Gears: 4th gen 3.42 posi
Re: 1986 2.8, backfires under light acceleration when cold.
Thanks, i picked up a set of o rings today and put my original injectors back in for the time being. It's not that bad taking the rail out, so i dont mind doing it again when i get yours. Everything is sealed up and shes not leaking any more oil, and the rockers are nice and quiet. Still pops when cold somtimes, so im glad i got the new injectors on the way.
Spent the day wetsanding and buffing the paint. Shines really nice for original 27 year old paint. Hopefully shell soon run and nice as she looks
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Spent the day wetsanding and buffing the paint. Shines really nice for original 27 year old paint. Hopefully shell soon run and nice as she looks
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Joined: Mar 2011
Posts: 6,287
Likes: 41
From: Northwest Ohio
Car: 1991 Camaro RS
Engine: Lq4 6.0 SBE s485 turbo E85
Transmission: Fsi th400 stage 4. TSI 5500 st
Axle/Gears: Strange S60 4:10s
Re: 1986 2.8, backfires under light acceleration when cold.
Bud that cars in really good shape
Thread Starter
Joined: Jul 2011
Posts: 695
Likes: 73
From: New York
Car: 86 Sport Coupe
Engine: 5.3 LM7
Transmission: T56
Axle/Gears: 4th gen 3.42 posi
Re: 1986 2.8, backfires under light acceleration when cold.
Got the injectors from fasteddi and i hope to put them in once the weather gets a little better. The above pics were taken less than a week ago, and here she is now
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Supreme Member
Joined: Oct 2001
Posts: 8,113
Likes: 6
From: NWOhioToledoArea
Car: 86-FireBird
Engine: -MPFI
Transmission: T5
Axle/Gears: 3:42
Re: 1986 2.8, backfires under light acceleration when cold.
Every time I see one that color it makes me think of one a guy had in HS, all it had was some simple pin stripes like you would see on any car of that time, but it they really drew in the eye, shocking part was once close enough you could see the thinner of the two was pink, yea pink, but you couldn't tell till real close.
Thread Starter
Joined: Jul 2011
Posts: 695
Likes: 73
From: New York
Car: 86 Sport Coupe
Engine: 5.3 LM7
Transmission: T56
Axle/Gears: 4th gen 3.42 posi
Re: 1986 2.8, backfires under light acceleration when cold.
I just put the injectors and took it for a drive. Didnt stumble or pop. Im gonna see what happens when i leave work later today, but right now it feels good and it seems like the injectors were the problem.
Joined: Mar 2011
Posts: 6,287
Likes: 41
From: Northwest Ohio
Car: 1991 Camaro RS
Engine: Lq4 6.0 SBE s485 turbo E85
Transmission: Fsi th400 stage 4. TSI 5500 st
Axle/Gears: Strange S60 4:10s
Re: 1986 2.8, backfires under light acceleration when cold.
Awsome that is exactly what I wanted to hear. Take her for a good beating and make sure they are ok, and let up know.
Thread Starter
Joined: Jul 2011
Posts: 695
Likes: 73
From: New York
Car: 86 Sport Coupe
Engine: 5.3 LM7
Transmission: T56
Axle/Gears: 4th gen 3.42 posi
Re: 1986 2.8, backfires under light acceleration when cold.
Drove home from work with the car cold and had no issues. Started right up, had absoulty no hesiation or popping at any rpm. Looks like the injectors did the trick. Ill post another update some time next week to let everyone know how shes running. Thanks again for the help and injectors
Joined: Mar 2011
Posts: 6,287
Likes: 41
From: Northwest Ohio
Car: 1991 Camaro RS
Engine: Lq4 6.0 SBE s485 turbo E85
Transmission: Fsi th400 stage 4. TSI 5500 st
Axle/Gears: Strange S60 4:10s
Re: 1986 2.8, backfires under light acceleration when cold.
Drove home from work with the car cold and had no issues. Started right up, had absoulty no hesiation or popping at any rpm. Looks like the injectors did the trick. Ill post another update some time next week to let everyone know how shes running. Thanks again for the help and injectors

Thread Starter
Joined: Jul 2011
Posts: 695
Likes: 73
From: New York
Car: 86 Sport Coupe
Engine: 5.3 LM7
Transmission: T56
Axle/Gears: 4th gen 3.42 posi
Re: 1986 2.8, backfires under light acceleration when cold.
Well shes been running great, no popping or anything... Until tonight😭. Tried to leave work, but the car is revving very slow and has no power. It doesnt feel like its misfiring, as it idles in park alright. Just when you give it gas its very very slow, almost like the converter is clogged. I removed the o2 sensor, and it ran the same. Theres also good pressure at the tailpipes, so i dont think its clogged.
Checked the timing and its perfect, the advance is also working no problem. Did a compression test on all cylinders and there all between 140 and 165. Not sure where to go next. Smells very rich, and some of the plugs were completly black with soot when i pulled them.
Checked the timing and its perfect, the advance is also working no problem. Did a compression test on all cylinders and there all between 140 and 165. Not sure where to go next. Smells very rich, and some of the plugs were completly black with soot when i pulled them.
Thread Starter
Joined: Jul 2011
Posts: 695
Likes: 73
From: New York
Car: 86 Sport Coupe
Engine: 5.3 LM7
Transmission: T56
Axle/Gears: 4th gen 3.42 posi
Re: 1986 2.8, backfires under light acceleration when cold.
I was thinking fuel pressure reg too. I dont have a pressure regulator, but im gonna pick one up tomorrow.
Joined: Mar 2011
Posts: 6,287
Likes: 41
From: Northwest Ohio
Car: 1991 Camaro RS
Engine: Lq4 6.0 SBE s485 turbo E85
Transmission: Fsi th400 stage 4. TSI 5500 st
Axle/Gears: Strange S60 4:10s
Re: 1986 2.8, backfires under light acceleration when cold.
Hope that fixes it. Sounds like the diaphram is bad
Thread Starter
Joined: Jul 2011
Posts: 695
Likes: 73
From: New York
Car: 86 Sport Coupe
Engine: 5.3 LM7
Transmission: T56
Axle/Gears: 4th gen 3.42 posi
Re: 1986 2.8, backfires under light acceleration when cold.
Meant to say pressure tester. Gonna pick one up and test it. Ill let you know where its at.
Thread Starter
Joined: Jul 2011
Posts: 695
Likes: 73
From: New York
Car: 86 Sport Coupe
Engine: 5.3 LM7
Transmission: T56
Axle/Gears: 4th gen 3.42 posi
Re: 1986 2.8, backfires under light acceleration when cold.
Fuel pressure is at 42 key on engine off, and 40psi running. It junps to 45psi at WOT. Not sure what to check next.
Thread Starter
Joined: Jul 2011
Posts: 695
Likes: 73
From: New York
Car: 86 Sport Coupe
Engine: 5.3 LM7
Transmission: T56
Axle/Gears: 4th gen 3.42 posi
Re: 1986 2.8, backfires under light acceleration when cold.
Just scanned it, has a code 22.
Re: 1986 2.8, backfires under light acceleration when cold.
Thats a throttle postion code, do you have a service manual? Check for proper voltage at closed throttle, it should go smoothly to 4.5 volts at wot.
Thread Starter
Joined: Jul 2011
Posts: 695
Likes: 73
From: New York
Car: 86 Sport Coupe
Engine: 5.3 LM7
Transmission: T56
Axle/Gears: 4th gen 3.42 posi
Re: 1986 2.8, backfires under light acceleration when cold.
Dont have a service manual, but the middle pin on the tps connector was bent. I fixed it and the code went away, but its still running the same.
Joined: Mar 2011
Posts: 6,287
Likes: 41
From: Northwest Ohio
Car: 1991 Camaro RS
Engine: Lq4 6.0 SBE s485 turbo E85
Transmission: Fsi th400 stage 4. TSI 5500 st
Axle/Gears: Strange S60 4:10s
Re: 1986 2.8, backfires under light acceleration when cold.
Awsome. I was going to say if theres anything wrong with those inject make sure you pm me.
Thread Starter
Joined: Jul 2011
Posts: 695
Likes: 73
From: New York
Car: 86 Sport Coupe
Engine: 5.3 LM7
Transmission: T56
Axle/Gears: 4th gen 3.42 posi
Re: 1986 2.8, backfires under light acceleration when cold.
Everything is good now, just wanted to know, what exactly does the INJI fuse control? Because the car was still running without it, so it couldnt have been controlling the injectors.
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