00transamramair

I have a 2000 Trans Am that is stuttering on acceleration. Scanner shows 70psi fuel pressure and 9.1 hg of vacuum at idle(can't find vacuum spec but looks low to me) sometimes it will come out of it and run normally other times it just random misfires across multiple cylinders. The car only has 56,000 miles on it and about two months ago I added a BBBK intake manifold. I have checked my TPS. My MAF tested a little low at 2500 rpm but I don't think it was to bad. The fuel trim is trying to pull back fuel. I am running out of ideas and am considering bringing it to the dealership which sucks since I work at a shop where we have an amazing success rate on all makes, kinda ego bruising. Any ideas or suggestions are appreciated.

WS64Mula

iTrader: (1)

Any codes other than a random misfire? I know you checked your tps, but what did you check on your tps? It needs to bet set to a certain point. I don't have the info on that, but if you did set it....try a tps reset. If you have access to a known good Maf you could try that. Check the connection that goes to the valve cover for the coils. could be loose or not seated all the way.

roninsonic

iTrader: (3)

that fuel pressure is WAY high... Check it at the rail by hooking up to the shrader valve. If it's reading 70 on a mechanical gauge at the rail, that's probably your problem right there. fuel pressure should be 40-45psi at idle. That much pressure, your injectors are flowing a LOT more fuel than designed and it's running super rich. Your 02's are seeing this in the AFR and the ECU is trying to trim it back. I doubt the trims can pull back that much fuel to begin with, and it's definitely not helping. Your AFR is probably pig-rich, causing poor, incomplete combustion and probably fouling out the plugs, which would cause the misfires. The fpr may be taking a **** on you.

00transamramair

I found out my E3 spark plugs were cooked after reading a lot about them causing this problem so I installed some OE delcos and it ran great till last night. Its been about a month and a half and suddenly last night I could feel the early stages of the stutter at low rpm again! Can the intake manifold I put on in July be cooking my plugs? Do I need to change the heat range , gap, or type? Any ideas?

00transamramair

There were no codes but it was misfiring due to the cooked plugs.Sorry I didn't answer your post to help me, been a crazy few months but thank you.

00transamramair

Found that the psi gauge was faulty and my psi was in spec, traced to cooked plugs. Changed and car ran much better till top end which traced to a bad maf a few weeks later. Ran great till last night now acting like cooked plugs again. Wondering if I need different plugs with my aftermarket intake manifold which is when this all started.Sorry not no answer you earlier, crazy few months. Thank you for posting.

sjdf10112

I'm having similar issue except. My misfires are specifically 6 and 8. I don't think I have a blown head gasket. I replaced my wires plugs andswapped coils and still hhave same issue

alex722607

iTrader: (4)

Perhaps something is up with the coil packs? I havent done much troubleshooting with LS series engines, but if it was me I would see if there is a way to test the coil packs. This could also be a PCM problem or wiring related.

roninsonic

iTrader: (3)

It's all good, man.

Throw in a set of NGK TR55's, reset the ecu, and start it from cold and let it complete a heat cycle or two, then go drive around for 15 minutes. Hopefully it'll relearn it's fuel trims and you'll stop cooking plugs.

FU_I_AM_UltraZ

iTrader: (20)

are you making sure that the wires click all the way on the coil pack? for plugs, buy copper core ones. they don't last long vx plat plugs, but performance wise way better. I've seen plat plugs cause misfires on the dyno particularly this one LT1 Z28. Felt like it was running on half the cylinders, made like 160whp on dyno, but after switching to cheap copper core autolites, made 250ish whp... just changing plugs.