so i have a 86 fiero gt 2.8 4speed the idle is all over the place from 500-2500 rpm and when it is under load in gear it wants to backfire through the throttle body and sometimes seems like its pre detonating

Does the check engine light come on when you turn the key to start? Is your check engine light on at any other times?

check engine light acts normal. no major changes, daily driver.

Check the timing. Check for vacuum leaks.

Any idea when its going to idle fast or slow? does it go back and forth? Does it idle fine at times?

Do you have an ALDL tester or cable?

I have tested for vaccume leaks and the idle is sometimes consistant but not nesseraly at the correct rpm. Massive hessitation sometimes if I'm on the throttle at les then 3500rpm

Have you checked your fuel pressure?

No ALDL right?

Also. Checked the timing its st about 9 degrees adavanced I know its suppost to be at 10. But I had to check it at a slight angle so I'm assuming its at 10

You checked it with the jumper in correct?


All I can think it sensors.

Anyone else?

yes with the jumper in

K - I had to ask.

TPS?

MAP?

but no codes so idk?

it gives me a code 22 that should be the map sensor but i have replaced it and it makes no difference and still gives me the same code

Oh - thats what i meant way back when I asked about the light - I just was asking it in 'dumb mode' because I didn't know if you even knew codes.

Code 22 is on also eh?


hmm

yes replaced the TPS also replaced the EGR, PCV, MAP, bolth temp sensors and, IAC. i love my fiero so ill do almost anything to fix it ha

You have no code saying you EGR control valve is bad. I have a used one available here that works, but yours is OK.

I am wondering if you have a bad EGR valve (Not EGR tube btw)

If you think your egr control is messing up on controlling your egr valve you can just pull the vacuum line from the EGR valve and plug the line. This disables the EGR valve. You should get no codes by doing this.

id check that ignition module...
that and the voltage that the tps is putting out (use a good quality digital voltmeter if you have one)
pop the distributor cap off...(no need to remove plug wires.) see if the heat sink grease is under the ignition module. if not it may have burned up.
also what type of plugs are you running?

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1985 gt notchie auto (pic)
1986 se notchie standard 4spd

I have ngk v-power plugs and I just replaced the ignision module(I have a few on hand due to the frequency of malfunction) but yeah ill have to check out the tps voltage and a few other ideas

check the fuel pressure
mine is backfiring under load and losing power
i still need to get my fuel gauge but the symptoms point to low fuel pressure and bad or weak fuel pump...
will know more when i get my fuel pressure gauge when i get my paycheck