OK, I have an 87 GTA, L98 350, TPI, all that good stuff. Ok, here's my problem. I think it might involve those 3 letters we all knwo and love. MAF. OK, when I'm at idle, the car runs smoothly, but as soon as I hit the gas, it stumbles, and stutters hard. If I mash the gas, it will stumble a bit more, but will eventually catch and launch, but it's still weak. At speed, I will occasionally get an irregular miss, but nothing as dramatic as the miss on launch. OK, now the catch for everyone screaming "change your cap moron". It will only do this on hot humid days. If it's 60 degrees or so, it runs smooth as ever, and quick as hell. I figured it was probably the maf, so i tried just unhooking it, taking it out of the equasion. The problems exist in the EXACT SAME WAY. Removing the MAF from the equasion changed absolutely nothing. Now I'm confused as to, does that mean the MAF is toast? or does that mean that it's not the problem. It doesnt throw a code on it, thow last year when this all started, it threw the MAF code a couple of times. Does anyone have any ideas on how to further diagnosew this? I'm lost, and I havent been able to race yet this summer!!!! I figured if anyone would have a clue, it would be this message board. =) Thanks much.

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'87 GTA
Automatic 350 TPI
2 3/4" Flowmasters
K&N filtercharger
4 3/4" Glasstech Cowl induction hood
TPI intake air foil

'82 Transam,
A huge work in progress...

System:
Panasonic DFX-99
2 12" RF DVC's
RF 250.2 (Custom
RF 200.4 Painted)
Sony 10 disc changer
Clarion Pro Audio 4x6's

 

if you took off the MAF and it still ran like crap then that is not your problem. i would look at replacing the fuel filter or possibly the fuel pump. you might also look at replacing the ignition module. does the computer have any codes stored?

 

I agree, it sounds like a fuel problem. Get the fuel pressure reading and change the fuel filter (before you take the fuel pressure reading). I doubt it's going to end up being the 3 lettered word that we're not supposed to say in church. Sounds exactly like my car when the fuel pump went out.

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89 IROC-Z 350 TPI

-Flowmaster Catback
-Performance Resource Chip
-700R4 (Rebuilt) Too much done to actually list
-K&N Airfilters
-Ported Plenum
-2.77 Gears (not much to brag about but eh, its there)
-MSD 8.5 mm plug wires
-Gutted cat
-!AIR
-Gutted Air Boxes

 

Sounds fuel related to me as well.

Try the fuel filter. if that doesnt fix it, see if you can spare the time to do a pump.

good luck.

 

Well, here's what I got. I changed my fuel filter. Problem still exists. So I borrow a fuel pressure guage from a friend of mine and measure the fuel pressure. According to the haynes manual, the fuel pressure should be somewhere between 34 and 40psi. well the guage kind of bounced between 36 and 30 psi. Now 30 is lower than it should be, but is 4 psi going to kill acceleration that hard? Also, there was no conspicuous drop in fuel pressure when it would stall out on the rev. So now I'm even more confused. Frustrations are mounting quickly...I'm a bit lost on the next step to take. Would 4psi kill it that bad????
Thanks

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'87 GTA
Automatic 350 TPI
2 3/4" Flowmasters
K&N filtercharger
4 3/4" Glasstech Cowl induction hood
TPI intake air foil

'82 Transam,
A huge work in progress...

System:
Panasonic DFX-99
2 12" RF DVC's
RF 250.2 (Custom
RF 200.4 Painted)
Sony 10 disc changer
Clarion Pro Audio 4x6's

 

yes. stock at WOT you should be around 42, 37 at idle. this is what is causing your problem. did you tape the gauge to the dash and go do a WOT run? this is how you tell what your WOT pressure is, when the injectors are firing the most fuel, pressure will drop if your pump isnt strong enough to keep it up. i bet it drops low to around 25.

 

Your fuel pump is on its deathbed. Your pressure should be steady at around 37lbs at idle, with the vacuum line hooked up. If the gauge is bouncing around, your pump is getting ready to die. If you are reasonably comfortable working on your car, go ahead and swap the pump on a saturday. A lift, or a pit, are almost required for this. You can do it in the driveway, but you need to get the back end of the car pretty far up to drop the axle far enough to get the tank out.

If you don't want to go that route, you can prolly get it changed for you for around 400 bux at some reputable shop.

Good luck

 

Velocity: Your problems sounds much like the problem I'm having with mine now. It went in the shop yesterday and I expect to hear back this afternoon. I will post back here when I get the results.



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1987 Camaro IROC-Z
350 TPI (L98), HyperTech Airfoil, K&N Filters and modified airboxes, modified MAF, AC Delco RapidFires, Taylor SpiroPro 8mm wires, Energy Suspension polyurethane bushings for LCA and sway bars, KYB struts and shocks, BFG g-Force Z-rated tires, STB, JET low temp stat, CarSound Hi-flow Cat, DynoMax 3" Mandrel-bent pipes, Flowmaster muffler, 3" chrome tailpipes, T-tops, and White exterior with red leather interior.

2001 Sunfire GT
Bone stock 2.4L, 5-speed, 200W Monsoon Sound System (8 speakers), Silver Metallic exterior with grey interior.

Web: http://www.angelfire.com/on3/whitelightening

 

Well, I was looking to drop a new rear end in the car (brake drum to brake drum), so i guess, what better time to get all of this done at once right? I was hoping it wasn't the pump. there goes this weekend. =) Thankyou much to all who answered, it is beyond appreciated.