I have a '91 T/A with 305 and peanut cam. At higher rpms (3-4 K), I've recently seen stumbling or the engine falling flat (after using fuel injector cleaner). Spark plugs and cap and rotor were recently replaced, and I installed an Accell coil a while back. The idle of the car is rougher than it used to be. I think its due to faulty injectors. This I will replace. My question is: besides the coil, cap, rotor, plugs and wires that I've replaced, what else in the ignition could cause this problem at higher rpms?

Thanks, Dave

 

Could be the ignition module which is found on the base of your distributor under the cap. If i remember correctly it was about 10 too 20 dollars at auto zone, although they carry Wells brand which i have heard bad things about.

just a thought, plus you'd probably want to replace this sometime anyway from what i'ver heard.

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1986 Trans Am
305 TPI
"If it's not one thing, it's another!"
http://www2.hanover.edu/hierlmeier

 

Sounds like you have bad injectors. I recently went through the same ordeal with mine. I learned that the Multek design injectors 89-92 are cars defective.

Basically, they burn out like light bulbs. You can test the injectors by mearuring their resistance with an ometer. The variances should not be greater than .5 of each other. A healthy injector should read 16.0 to 16.5.

The Multek injector is easily identified by its sliver and grey housing. Take your time and be careful when removing the clips. If you need more advice feel free to e-mail me.

 

Another possibility is the pickup coil in the distributor. If this hasn't been changed you might want to do that. It only cost about $4 and you will at least know your ignition is OK

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Hank
87'IROC Z28
Hanks 87 IROC

 

I was having similiar problems. I borrowed a snap on scan tool which revealed an extremely lean running engine- 650 mv at WOT. Turned out my fuel pump was faulty.

Also, I ve had esc circuit problems in the past that were a result of a failing ignition module one time, and a failing ignition coil (accel after 1 year).

 

How can you tell it it is the fuel pump or injectors that are at fault?

 

You can start by doing a fuel pressure test. Get you a gauge, it hooks up on the shraeder valve on the fuel rail...

 

I just had my fuel pump replaced, and havent driven it yet (im at school) and i can tell you the symptoms i had before the pump went out....For about a year the car would buck at low rpms (less then 2000) as soon as id accerate hard or get about 2000 the jerking would stop. Then just recently the car would not want to start, it would turn over just like normal but would just not catch. I thought this was weird because when it finally did start it had 42 psi just like normal. I fugured if the pump is going out it should drop off. But anyway, finally i was sitting at a stop light and went to take off and just like always it jerked at the low rpms but then just never caushgt up and died, couldn't restart. took it to the mechanic, and then took it from the mechanic, so to speak.

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1986 Trans Am
305 TPI
"If it's not one thing, it's another!"
http://www2.hanover.edu/hierlmeier

 

HEY-
I'd bet its the injectors! I've been through it twice now and on the 2nd time I'm getting rid of my 140k mile LB9 and putting in a slightly modded 350. Check resistance as stated above and it chould be 16 ohms plus/minus 1 ohm. Mine are at about 13-14.5 right now and I have a bad idle and a "temporary" 3500 rev limiter. haha Hope this helps

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'91 GTA:5.0-5-spd, chip, K&N,Flows,Coil,Air Foil, 350 soon to come!
'39 Chevy coupe
'52 Chevy p/u

 

That is exactly what is happening with mine. It doesn't want to reve past 3500 rpm. I received my Walbro 255 ltr/hr pump yesterday and will be installing it tomorrow. If that doesn't fix it, its time for new injectors.