Well my 86 trans am is a 305 TPI,and it was running perfectly fine.Im not getting any trouble codes,but heres the problem,the car sometimes wants to stall,and runs real rough.Then a minute later it will clear up and be perfectly fine and sit there and idle perfect.The car had the following new parts:

plugs
wires
cap,coil and rotor
oxygen sensor
IAC motor
new fuel filter

The IAC had been correctly adjusted,and ive tried playing with the timing and it dont seem to help.I was thinking maybe i have clogged injectors,and it could be causing this.Or could it be the MAF burn off relay,MAF power relay,or the fuel pump relay???I need help bad,this cars gotten the best of me.And how canyou test for clogged fuel injectors???

 

You didnt mention if you were getting any trouble codes. You could have low fuel pressure, or a leaking injector, or a completely unrelated electrical issue. I have never seen a completely clogged injector...just poorly performing one. You could also have an ignition problem...with the parts you listed that were changed, you hit almost everything. Other electrical items you could look at: Ignition module, fuel pump relay, MAF relay.

To rule out your fuel pump, check your fuel pressure. When at idle, your vacuum is highest, which makes your fuel pressure the lowest. If your fuel pump is weak, it may not be supplying enough fuel or enough pressure for the fuel to atomize. Check at the fuel rail with the vacuum line off of the regulator and plugged.

Also try a leakdown test (I believe the procedure is in the technical articles).

A look at your spark plugs may also help narrow down your problem. Since each cylinder is fed by it's own injector...checking the plugs can indicate which injector is either not flowing, or leaking.

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Mike Metzler (Desert86Roc)[*] Check Out:SpeedWorldMotorplex.com[*] Check Out:Chevrolet F-Body Online Part & Illustration Manual[*] My 86 IROC 305 TPI Page (406 build in progress)

ET's @ 1250 ft[*] 14.28 @ 95.461 mph (uncorrected, NOS, no headers)[*] 15.362 @ 88.238 mph (uncorrected, headers, no NOS)
<><

 

ok thanks a lot man.

OK im not getting any trouble codes.I have changed the Ignition module,sorry i forgot to mention that.Allthough i did get a code for the MAF burnoff relay before i beleive.Then its went away and never came back.Im thinking for 12 bucks a relay im gona go to the store tomorrow and get the burn off,MAF power,and fuel pump relays anyways.Unless someone knows a way to test these relays with a volt meter.And where should the stock fuel pressure be at?

Hey desert,thanks im gona go look at my plugs if is not raining and then ill be back and tell you what i find.Thanks

 

Stock fuel pressure should be around 43psi with the vacuum line disconnected. When you rev the motor, it should not drop.

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Mike Metzler (Desert86Roc)[*] Check Out:SpeedWorldMotorplex.com[*] Check Out:Chevrolet F-Body Online Part & Illustration Manual[*] My 86 IROC 305 TPI Page (406 build in progress)

ET's @ 1250 ft[*] 14.28 @ 95.461 mph (uncorrected, NOS, no headers)[*] 15.362 @ 88.238 mph (uncorrected, headers, no NOS)
<><

 

thanks a lot man.Oh yea,and this is very important and i dont know how i forgot about it.When i try to start the car it just cranks and cranks and cranks and wont start,not usually till i turn my distributor a lil bit,and when it does start i have to turn the distributor back to where i had it so timing is on and so that its not detonating.

 

I am having the same problem, with having to turn the distribitor, on my 92. I have put on: Cap, rotor, plugs, ignition module, different set of used good (I thought where) wires (getting new ones today, light show under the hood.) good 43lbs of fuel pressure, injectors tested good, and tons of cursing. I am going to follow this thread, very close, to try to figure out my problem, I just thought that I would let you know what I did and have the same thing.
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Well, I feel stupid.... I just looked at the date....

 

hey lol i didnt notice the dates either. have you found anything on your problem? i think im having a similar problem. I've replaced all the same parts, AND MORE. while the car is running, with the timing all the way up it runs rough and idles like crap. than i turn the timing down real low until the idle becomes nice and steady. then, i turn the car off and crank her back up and it barely starts, struggles to stay on. is this similar to your problem or is mine doing the opposite of yours?

 

That is what mine would do. Mine ended being the distributor.

 

i had a real inconsistent idle problem on my 85 iroc (tpi). sometimes it would run perfect, sometimes it wouldnt run, sometimes it would sputter and stall. i replaced all of the normal stuff, plugs wires ignition module 02 sensor etc etc, and eventually i gave up and took it to a shop (i know, im ashamed) of course, my car being a stuck up bitch it ran just fine for them. they said they wanted to keep it over night and check it in the morning. sure enough it ran like crap and they took it in, traced the ignition wiring back to the ecm and there was a broken pin on the computer that controlled the esc. sometimes the wire would make contact and it would run perfect, other times it would make some contact, and still others none at all. never gave me any codes at all. anywho, put the new computer in (only $105 + labor which i thought was super fair) and i tell you what that is the strongest that car has ever pulled in the two years ive owned it. im in love all over again. anywho, short story long, if you guys are having an idle problem check your computer and esc module and all the wiring that goes to it, because it WILL NOT run without it!

 

i had similar prob, turned out to be 5 bad injectors

 

5 bad injectors??! holy $hit i hope thats not it! I already had one replaced a couple months ago. I dont see how your car ran at all! mine would shut down after it warmed up and would rarely start again. Thats been fixed though. Now, I've already replaced my distributor and the computer, and more of course. My problem seems to be getting worse though. When the car is in motion, while in neutral and whenever I put my foot on the clutch, the Idle hangs up around 2000 RPMs. the only way it goes down is if the car is sitting still or when im in a gear. The car tends to surge when its in RPMs below 1200...runs rich and idles like crap. i don't have much trouble starting it though. After the car Idles for a while, the temp goes up pretty high, almost in the red (just a lil over half way up the gauge). could it be fuel pressure? if anyone has a clue please let me know, this car is driving me crazy!

 

Hey there
I have a similar problem. I just bought an 87 that the previous owner said was running perfect then all the sudden has similar symptoms. I can only start it if i hold the pedal to the floor once it starts it will only stay running if i message the gas pedal and i mean it barely runs and spits spudders and stunbles. He mentioned it to NAPA and they sold him a maf sensor. No luck. He took it to the dealership and they said they would have to swap out sensors until it ran right possibly running a 1000 bucks, he opted to sell it to me. I checked for codes (NONE) fuel pressure 42-43 PSi, TPS adjustment is good, injector impedance correct and all within .01 of each other has new wires, firing order is correct,cap and rotor look new, i swapped ignition modules , maf and esc with working units from my S-10 350 TPI no luck I'm leaning towards leaking injectors.

 

check those injectors and see if they are the problem. if not, then check your spark plugs and wires. maybe if most of them are bad it may not run hardly. I believe I have bad spark plugs (that I havent gotten to replace yet) and it seems the car runs worse as each day goes by and I assume that it could eventually lead to your problem. just a suggestion, but its possible to be something else.