Backfire on the Vette

[kingjason]

OK yes I am still fing with the crossfire on the vette. Did all the damn brakes last week and now she runs and drives. OK so I set the timing to right at about 6 and then tried 8 degrees, it has a hypertec in it, new cap, wires, and plugs gapped properly. Fuel pressure appears to be a steady 13psi on the guage while running and blips of the throttle. TPS is in check and operating properly and the injectors and TBI's are all fresh and clean.

Ok if I hold the throttle open at say 3k or so it will just randomly back fire through the TBI's and exhaust. The exhaust is just straight exhaust no mufflers and probably a hollowed cat. I tried the factory chip that was installed backwards at one time and its fried and just runs like hell.I put the hypertec back in and it idles fine and I get no check engine light either. It idles like it has a cam also but I am not sure. When I drive it I can punch it from a stop and it will launch but then quickly falls on its face and backfires thru the exhaust. There are two pedal positions where it runs fine sorta. I can drive at about 35 mph and hold it steady no issues except for an occasional sputter when it shifts. At wide open it acts like a litmiter or something is kicking in and then when I back off say a 1/4 pedal it just takes off and hauls ass. I actually had it on the highway running 65 with no issues but could add no throttle or it would start backfiring. Any ideas?? When I set the timing there was no jumping on the timing mark. If I unplug the distributor from the computer it does not back fire when I give it gas and idles kinda high but will not drive that way either.

[BP]

Make sure the TPS doesn't have a dead spot and I think your fuel pressure is probably a little high actually. What year Vette?

[46Tbird]

Those are all classic symptoms of a vaccum leak.

And really, the '82-84 CrossFire was just awful. Yes, it is fuel injection. But compared to modern EFI, it is akin to pouring gas down the intake and throttling with your hand.

Stash the CrossFire setup in the garage and get a nice aluminum intake and four barrel for it. You missed the Decatur swap meet last weekend, could have had it running like a champ for a hundred bucks.

[Whiteboy]

Those are all classic symptoms of a vaccum leak.

And really, the '82-84 CrossFire was just awful. Yes, it is fuel injection. But compared to modern EFI, it is akin to pouring gas down the intake and throttling with your hand.

Stash the CrossFire setup in the garage and get a nice aluminum intake and four barrel for it. You missed the Decatur swap meet last weekend, could have had it running like a champ for a hundred bucks.

Throw a carb on it!


lol I agree with Danny.

[kingjason]

Throw a carb on it!


lol I agree with Danny.

Very Very tempting but trying not to go that route. I may block off everything vacuum related and try it again today. I would think if it had a vacuum leak it would idle high though.

[YALE]

You should go carb, and H/C/I. I have nothing against GenII generous motors small blocks, but that induction system was an insult to the legacy of the fuelie small block 'vettes of old. The heads suck, the cam sucks, and the intake sucks. What's the next swap meet? The Pate? Take $300, and cleanup that mess under the hood. That place should be swarming with SBC parts.

[Lason]

You should go carb, and H/C/I. I have nothing against GenII generous motors small blocks, but that induction system was an insult to the legacy of the fuelie small block 'vettes of old. The heads suck, the cam sucks, and the intake sucks. What's the next swap meet? The Pate? Take $300, and cleanup that mess under the hood. That place should be swarming with SBC parts.

This is still a Gen I motor, Gen II was the awful LT1 of the 90's.

I agree 110% though, ditch that glorified TBI and either go real EFI or just carb it.

[kingjason]

Yes I would love to long tube it, heads, cam, intake, carb., and vacuum dizzy. Then throw all this fan shroud BS off of it and do a custom griffin with electric fans buttttt not sure what I am going to do with it so dont want to spend the cash right now. Was hoping for an easy fix so I can piddle with it and drive it if it stays. LOL

[shumpertdavid]

1 make sure you unplug the tan\black wire when setting the timing, this will put it in base timing mode.
2 if it's popping back through the intake on acceleration it may be running lean, you need to check the fuel pump volume, this is just as important as pressure, and you can have one and not the other. the pump should free flow a minimum of a pint in 30 seconds of cranking. Most will make a pint in 15 sec.
3 I always heard that syncing the throttle bodies was a pain, but you'll need to make sure that is good.

[kingjason]

1 make sure you unplug the tan\black wire when setting the timing, this will put it in base timing mode.
2 if it's popping back through the intake on acceleration it may be running lean, you need to check the fuel pump volume, this is just as important as pressure, and you can have one and not the other. the pump should free flow a minimum of a pint in 30 seconds of cranking. Most will make a pint in 15 sec.
3 I always heard that syncing the throttle bodies was a pain, but you'll need to make sure that is good.

Check on pulling the wire for the timing and it is set right. I had a 79 TA that backfired like crazy after you drove it a while and it was the sock in the tank fuel of crud. It acts alot like that but not really. LOL

[kingjason]

You know I had the Accel super coil off the dizzy the other day and didnt even think about how it rattled around in the cap. It was like the the center part of the coil was loose from the surrounding metal rings. Now I can not remember the last time I have messed with HEI but I am pretty sure this should be solid right?

[shumpertdavid]

The carbon button with spring goes in first, dielectric grease on the silicone washer/seal next, then the coil last. The ground strap goes into the cap before the coil. best I remember, haven't had one apart in a while. I had the carbon button wear completely off before and give some goofy runnin problems.

[kingjason]

It has a new cap and Rotors but the coil is what looks suspect. It just rattles in the cap between the metal square outer ring.