I have yet another problem that seems to evade me. I just put in a new distributor. Before I needed the new one everything ran pretty good. I installed it correctly and it's not 180 off. The engine idles fine up to 1700 rpms and then it starts to stumble and backfire. It won't go past 2000 rpm due to the backfiring. There is A LOT of backfiring through the exhaust and intake at 2000rpm. It also seems to me that there is a large pump shot when I step on the gas and I think this extremely rich condition is causing my problem, but why is it doing this just after replacing the distributor? My TPS voltage checks out OK. And yes, the plugs are on in the right order.

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88 firebird formula
350 Vortec TBI
214int/224exh, .471int/.491exh
Edelbrock headers
SIX-speed
Eats LS1's with a 2.73 open rear and 2 1/4 stock catback

My Formula

 

Ran pretty good BEFORE you changed the distributor and now won't go past 2,000 rpm - backfiring etc? Sounds like the source of your problem. DOUBLE check your distributor, all connectors, the base timing AND the spark plug wires individually from the cap to the plug. You wouldn't be the first person to cross up the spark plug wires. Swapping # 5 and 7 is really common.

Also check any electrical connectors you have disconnected and are located in the vicinity of where you where working. I have occasionally not pushed an electrical connector to some sensor "not quite in enoough" to make my car run crappy until I pushed it in "all the way". Sometimes I got the SES light, sometimes I didn't. An SES light would indicate a sensor not properly connected.

But do your basics. Re-check EVERYTHING involved in the disassembly. Given everything ran fine BEFORE you changed the distributor suggests something you did is not exactly as it should be when you put it back together.

[This message has been edited by Glenn91L98GTA (edited October 27, 2000).]

 

Sounds like the dist shaft is one tooth too far CW on the cam gear. This will cause the rotor to be too far away from the correct contact, in the direction of being closer to the contact belonging to the cylinder that is next in the firing order; so you will have anything from misfires to spit back through the intake as the mech advance does its thing.

Take the dist outjust far enough to clear the cam gear, rotate the shaft slowly CCW until it will drop back in, and re-time it.

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"So many Mustangs, so little time..."

 

Hey guys. Thanks for the help. I am sooooo frustrated with this engine. Ever since my motor swap it's been nothing but problems. And of course they are the wierd ones. I checked the timing connections and everything again and it has gotten better, but it still backfires from everywhere. I can get up to about 3000 rpms and it will give some pops and when I let off it it will pop through the intake. Some of the pops sound like they are coming from the headers though. Is it possible a header leak can cause this?? Thanks.

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88 firebird formula
350 Vortec TBI
214int/224exh, .471int/.491exh
Edelbrock headers
SIX-speed
Eats LS1's with a 2.73 open rear and 2 1/4 stock catback

My Formula

 

If it ran good before the distributer swap then odds are something went wrong. Before you try to lay the blame somewhere else, verify that distributer... are you sure its not 180* off like you say? Have you actually pulled it out and rotated it all the way around?

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Mark Lock
- 86 IROC-Z - My car, mods and ET's
- -= IROC Online =- - The site dedicated to the IROC-Z

 

Yup. I've done that LITERALLY 10-15 times with no improvement. It's almost like I'm not getting any advance in my timing. I took the distributor back today and got a refund even though I don't think the distrib. has anything to do with the advance. It was nice because they had already sent my core out and they had to give me a full refund as if I had paid the whole price initially. So basically they paid me $50 for my core!!!! Cool huh!?!? I think I need to get a brass gear anyways. Is this true?? I have a crane cam .471int./ .491exh, 214/224. I would think that it's steel. Why is the brass gear needed??

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88 firebird formula
350 Vortec TBI
214int/224exh, .471int/.491exh
Edelbrock headers
SIX-speed
Eats LS1's with a 2.73 open rear and 2 1/4 stock catback

My Formula

 

when you say the engine pops, and backfires alot it kinda reminds me of a problem i had when i repalced my engine. is your car a fuel injected or carb'd?

when my car popped and backfired i tried everything. it turns out that the number
2 and 4 (i think, i really cant remember the excact numbers) wires were switched around. once i put them back to where they were supposed to be and it didnt backfire.

daniel

 

The way your are describing it, it almost sounds like your timing set is off by one tooth. But I think it would be an incredible coincidence that your timing set jumps one tooth when you work on the distributor.

I like RB83L69's suggestion, distributor installed one tooth off. Makes perfect sense and it would explain your problem AFTER you have verified that everything else with the ignition system is fine.