chrkevjac09

My 1988 Iroc-z has a reving problem when I touch the gas pedal. It bogs out after it reaches 3000 rpm when i push the gas pedal but when i release it runs fine and shifts fine. If I push the pedal to the floor and hold it, it revs up to 2500 rpm and then acts as if it wants to shut off. It back fires through the intake and looses all power. Can someone please help, I've had this problem for 3 months and really just want to drive my car but can't. Thanks.

iroc stangs

dirty throttle body or clogged cat?

chrkevjac09

I removed the cat beacause alot of people was telling me that was the pproblem and it didnt make a difference at all and i also cleaned the throttle body. i know its small i just haven't caught it yet. Im at a loss.

88gta3508

did you check normal tune up cap, rotor, coil, wires,
timing @ Spec? fuel Pressure 36 -40 PSI??? no codes ??

sharkbait

What voltage do you have at the TPS at closed throttle and at WOT?

https://www.thirdgen.org/tpimod2

chrkevjac09

I changed all of those things spark plugs, wire, cap, rotor, coil, i have not checked the fuel pressure but I just put a new fuel pump in the car cause i thought it would help but didnt i will check the fuel pressure and see what it is around......and I dont know how to check the tps. How would i do that?

sharkbait

Click on the link I provided above for detailed instructions on checking/setting the TPS.

chrkevjac09

Hey I just tried adjusting the idle speed and did everything right and when i plugged the idle air control valve back up the idle didn't change at all from when it wasn't plugged in it just stayed at 450 rpm at idle in gear the car wouldnt even idle it would just die out. Does this indicate that i have a bad idle air control valve?

88gta3508

that is a indication your IAC is not working.. check with a Ohm meter across A&B / C&D
should read above 20 Ohms if not replace.....

a scan tool is the best way to check your TPS!!!!
you can use a volt meter DC volts.. factory spec 0.54v +/- 0.08v or 0.46 - 0.62
this method you will need to make jumpers

chrkevjac09

I did tried A&B but not C&D do you think this will make a difference?....and i also did a scan and the only code i got is that the car is running very lean.Thanks everyone..!

ATX-Iroc

I had a similar problem turned out to be a pin hole in the hose to the FP regulator

chrkevjac09

Yeah alot of people tell me the FP regulator would yours backfire through the intake? ill probably try this after the IACV.

chrkevjac09

So I replaced the Idle air control valve and it did not fix the idle problem...
Im starting to think it might be a bad ECU..

9manastacio

iTrader: (4)

whats your base timing, any vacuum leaks, mismatched spark plug wires, double check they are in the right spot, dont assume it is right, double check everything. have you checked your fuel pressure? probably not an ecu problem. Unplug your MAF sensor, and start it, does it run better? When does it backfire through the intake?

J91

Possible faulty ignition module, i've seen this before...

chrkevjac09

i just replaced the MAF sensor yesterday it didnt make a difference i got the timming checked its at 6 degrees advanced .... It only backfires through the intake if I put the petal to the floor even if its in park it just jumps up to 2500 rpm and then looses power and begins to backfire through the intake until i let go of the gas ....it's weird because one day i got in the car to drive it around and warm it up and it drove perfect i raced and had a good time I thought it had gone away and then later that night it began to do it again and hasn't ran good since that day im really confused and wish i could drive this thing but i cant figure this out.

sharkbait

Is your timing advancing as give it throttle? What is the timing at 2500 rpm?

88gta3508

I would check your coil, PU coil & Control module

solaris_vii

iTrader: (3)

i had a similar problem in my 85 iroc, took forever to diagnose but turned out to be a corroded connector on the ecu, specifically where the ignition wires connected. i know you already suspected the ecu, so if i could find a known working ecu and try that in your car that might be a good starting point

chrkevjac09

yeah ill check it out and i did change the coil but where is the pu coil?

88gta3508

it's under the rotor.. to replace the P.U. coil ... you need to take the distributor Completely apart it looks like this Pic
I hope you are testing!!! all of the Components ??? and not just replacing
that will cost you Mucho Bucks...
we are suppling the Most probable solution...
ask or borrow a GM book for Testing Diagnostics

ruben0227jr

just installed a ramjet cam in my 1988 iroc with a 350 tpi and now it wont rev past 3000 rpm by the way what helped the most with your problem?

Kblakney

iTrader: (2)

i know this is an old post but did anyone come up with a solution to this? my 91 Z28 is doing this exact same thing today.

thanks

TecknoMike

I used to have a bog at WOT problem a few years ago. I even had the backfire through the intake problem as the original poster of this thread too. At first I thought it was that Granatelli adjustable MAF that I had. I went back to stock rebuilt MAF and it helped my issues somewhat but I had strongly suspected my original injectors were shot. Are you still using the original fuel injectors? I finally got rid of all of my fuel mixture and power issues after replacing mine with some stock rebuilt injectors from fuelinjectionconnection.

Kblakney

iTrader: (2)

OK, after doing a lot of checking here are a few things i found.

tested all the injectors, 1 OHMed 0, 1 @ 3, and 2@ 13. replacing them with a set that all OHM out at 16.5

while the plenum and runners are off i found the EGR was bad, replacing that.

i took the vacuum line off the Adj Fuel Press Reg and found that it is leaking vacuum. the diaphragm is good so i put the factory cover back on and rececked and now it is sealed up.

also while the plenum and throttle body is off i did the coolant bypass. i am in the middle of puting back together. i will update when done to see if all of this solves the problem.

TecknoMike

Did replacing the FPR and EGR fix your problem?

Kblakney

iTrader: (2)

Yes TechnoMike, after replacing FPR cover back to the stock one and replacing EGR and half of the injectors with a set that tested out the same (16.5 Ohms) the car runs great once again. my 13 yr old has been drag racing it at the local strip in the teen 1/8 mile class and running 9.3 @ 78mph with a set of drag radials on it. i took it down the 1/4 on a test run and it ran 9.24 1/8 and 14.50 1/4. not bad for a car with 145,000 miles and all original suspension with all wore out bushings everywhere (this will be the next upgrade now that running good again).

TecknoMike

That's good to hear! I'm glad that you replied, since it should be helpful to somebody in the future searching the forums (and you said you would lol).