i tried searching, sorry if i missed it. '89 350 with 100k. Will be idling fine at a light, then instantly idle rough, then smooth out again, then get rough. usually each one lasts about 10-20 seconds, then it goes back to the other one, very quick when it changes back and forth. im going out to check my TPS/IAC today, my dad said egr, and i wanted to know what you all had to say.

Thanks
Josh

 

Pull the codes. Scan it if you have access to one.

 

I had a similiar problem with my '89 firebird, turned out to be a bad oil pressure switch.

 

Probably not the EGR. Could be switching open to closed loop and back. Maybe a timing deal or even a MAF sensor going bad. Really need to scan and see what's going on there.

 

don't have a scanner, which sucks, so i guess i'll just live with it for now, i cleaned the IAC and the voltage at the tps was within the tech articles specs, would an o2 sensor lead to somethin like this? i haven't changed that since i bought the car, and i don't know when it was replaced before that, i've been driving it for roughly 25,000miles. Should i try that, gas mileage seems worse as well so i have been thinking of getting a fresh o2 and doing plugs/wires cap rotor soon.

josh

 

Have you tried pulling the codes (if any) yet? Fuel press.? State of tune?

 

There is no service engine light, so i would assume no codes right? fuel pressure ill double check, but i think i had it at like 46 or 48 psi (have afpr) state of tune? like when it was last tuned up? maybe 15k ago i put moroso wires on it, new plugs, new cap, new rotor, new coil. it didn't run much this summer because i rode a motorcycle most of the summer, but every time i did drive it it seemed fine, and now that im driving it more i've noticed this idle thing, maybe a fresh tune up will help it out again. also i put in a new fuel filter 8-10k ago, as well as stupid stuff like a pcv valve i put injector cleaner in it every oil change so in theory the car should run a little better than it has been

 

I would say your maf is going bad. If you know anyone with another maf just swap it out for a few minutes.

If this problem is happening when the car is not warmed up it is not a o2 sensor problem. Hope this helps.

 

the car behaves like this when is warm when it is cold it has always fealt like it had a cam, but now it just idles bad even when fully warmed up

 

i really would like to know what is wrong to because my car is doing the same exact thing?

 

Rough idles are one of the hardest things to diagnose on these old tpi's. As mentioned above, the first step in diagnoseing most anything on one of these cars should be pulling the codes because of how easy it is to do and how much it can tell you. Just because your SES light isn't on doesn't mean you don't have a soft code stored in the ecm that can get you headed in the right direction. I agree with No. 5, it's most likely not related to the O2, but I'd change yours out anyways if you got the loot/time. Better safe than sorry, a bad 02 puts out little to no signs of not working correctly and can really screw with your ecm. I think the MAF is a good avenue to explore for this problem. Try lightly tapping on the outside of the sensor while this problem is and isn't happening. If your tapping has any effect on the condition of the idle than I would seriously think about replacing it.

 

MAF's typically don't go bad. It's usually the relay switch or the other dohickey next to the relay. Vaccum issues will cause the rough idle as well as a bad pickup on your dist. I agree that it's probably not the O2...just my 2 cents...

Stan

 

Well i just started at Napa about a month ago and can get my hands on stuff real cheap in a little bit so even a new MAF is not going to hurt that bad.

Another thing i have noticed now is how horrible the gas mileage has gotten. In less than 60 miles i've burned a good 6-7 gallons of gas usually the car has gotten me about 15-16 mpg. I guess if this doesn't help anyone in their diagnosis i'll just let this thread die until i start plugging in new parts, and i will try tapping the sensor while it is running, as well as looking for some vacuum leaks...thanks for all the helps guys

josh

 

Did you ever get the problem resolved?

 

no actually, it didn't get worse so i just said that it's a 16 year old car and i can deal with a slightly rough idle, plus in the summer its not my primary transportation so it's still a mystery, though i did have someone offer to pull the codes because my light flashed on on the highway the other day, but never since so there is still something not right, but nothing major...yet.

 

... as the guy with the apparel that just can't resist a magnet says...

 

thanks for that...it's a code 32

for what its worth on reading other posts..this code came on on the highway, i have an adjustable fuel pressure regulator, and sometimes i can smell fuel when i a park my car... should i turn down the fuel pressure a few psi?

 

Sometimes the AFPR's start leaking fuel out back through the vacuum hose. Pull it off when the car is running. If fuel comes out, your AFPR is shot. Be careful when you try this.

If fuel poors into intake it will affect idle.

 

Code 32 points to the EGR system, either your EGR solonoid is shot and the valve is not getting the signal to open, or the passageway in the manifold or valve itself is plugged up with crud, or it could just be a bad sensor on the egr valve. If it were my car, this is where I would start looking.


John

 

Hey John, have you seen a vacuum selenoid go bad personally? I have some idle issues as well and think it may be this. I don't know how to check to see if mine is good or not.

 

If the search feels like working you could try and find the troubleshooting chart Trickster has posted a few times for a code 32. If not maybe PM him with a link to this thread and he may post it again for all.