tpi305

Hey everyone, this is a long one but I can't figure this out so I could really use any help you can give me.

Ever since I have purchased the car, its always had a weird idle problem. I'll come to a stop, but the idle won't go to the 750 area like it should, it'll just go to 1000 or even 1500. Basically it won't really drop to idle speed. Sometimes it will, but most of the time it likes to stay in high idle. The only way to get it to where its suppose to be is to tap the gas (I can do it just very lightly like maybe not even move the pedal more than 1/16). For some reason, that brings it back to where its suppose to be. Sometimes itll go back and forth between 500 and 700 like its going to die until I give it gas. Its always done this.

Next thing- it liked to stall. It would stall after slowing down for a sharp turn or after making a stop and taking back off. I thought I somehow solved this, but now its starting up again. I come around a turn where cars are and it stalls in the middle of the lane. This pretty much stopped until I removed the battery so I could reinstall the nose after I repainted it a couple weeks or so ago.

Ok and finally, the charging system. Sometimes at night I'll notice the voltage will be all the way down into the 11 range and sometimes it will be around 12.5 to 13.3 but it'll jump around a lot. It doesnt "jump around" a lot on the gauge, but I have a radar detector that displays voltage and its always bouncing around by at least .2v or so. The other day the rpm gauge went all crazy and it started cutting out under heavy acceleration. The check engine light started flashing a couple flashes at a time and the radar detector started beeping saying "hi voltage" as it was at 15.9 to 16v plus. So I pulled over, turned off the car, and fired it back up and everything was fine . It also had started losing power from the battery at times (car would just die and not re-start). So, I replaced the crummy positive connector because it was shot (it was some weird amp setup allowing another screw to screw into it) and I found lots of corrosion. I cleaned that up and the voltage stays at a steady 14.5 usually and it doesn't jump around. It ususally eventually goes to 13.8. Btw, when the charging system tweaked out, I couldn't get the idle to go down below 1500 for the life of me.

So, I thought I had the issue fixed, but It still stalls at times and the idle problem is still there. I don't know whats going on. Ive replaced the iac and I tried to adjust it, but the idle screw was already all the way back and the throttle couldn't be adjusted. That little thing over the screw didn't seem to have ever been touched either. I don't know if this is a tps issue, iac, or if my charging system has just been screwy since I bought it.

1986 Iroc-Z
305 TPI
Purchased with 106,000
Currently has 121,000

Thank you and I really appreciate your help. I don't have any clue whats going on and I'd rather not do unneccessary repairs, you know? Thanks everyone.

cIaRmOaCrZo

my car had the same problem with the idle and stalling. it was a bad tps sensor. but now mine has a slightly differant problem,, my car sometimes still idles high when im trying to stop or when im just sitting there in either park or drive. but now i figured its just my throttle blades sticking just a little, so i put my toe behind the gas pedle and pull it towards me and itll drop down. but yeah the tps caused the other problems u described.

tpi305

Thanks for your help! Yeah I've thought about replacing it but i never did so I'll either replace it or try adjusting it first. I think you have to adjust them even when you replace them?

smier

Before you start just replacing parts which gets expensive real quick, do some easy free checks first... Start with known issues first. Charging issue, find a local parts store, as much as I hate autozone my local one will test your battery and alternator for free, all you have to do is pull them out of the car and take them into the store. Also double check you battery cables, sometimes the corrosion gets inside the cable and will screw with your battery etc... Reason I say this is I had a yamaha motorcycle, in-line four cylinder with multiple coil packs for the ignition, my charging started going... Battery sitting @ 12.5 volts everytime I check it, but I'll be riding alon and it starts missing and idling weird, not revving right and occasionally losing power all together. I'm thinking fuel issues, spark issues, I couldn't figure it out. Finally one day the batteries down, it was older so I put a new one in. Ran great for 1 day!!! Next day batteries low again so I put my multimeter on it and realize is swinging from 11.3v to 14.75v, everytime the voltage would drop the bike would start to idle strange and miss. Fixed the charging issue and bike ran great no more problems... Now that was a fairly simple bike, imagine how much more complex our cars are and why effect voltage has on all of our sensors and computers?!?!
Next issue, your idles all out of whack, there's a lot of possibilities it could be. Bad sensors, or just out of adjustment. There are threads on here that go into great detail how to adjust you IAC (idle air control) and TPS (throttle position sensor) read them thoroughly and take your time, those things may be already working fine and you can mess their settings up!
When was the last time this car had a thorough tuneup? At least check the plugs and wires. Start simple, and verify what's working properly. I've thrown parts @ my cars, doesn't usually fix anything but make your wallet lighter!
Keep us posted what you find, always like to see what fixes a problem. I might have the same one someday...
Oh man, I almost forgot, SES light on? Have you pulled any codes yet? That would be a first thing to check.

tpi305

Thanks Smier, I appreciate the help. I'll look for some more ways to properly adjust the iac and the tps. I'll also get the alternator and battery checked as well. The check engine light isn't on, the only time it came on was when it flashed for the over voltage, but since then I've disconnected the battery to clean the corrosion. It has had a recent tune up. I put headers on it and I had to get shorty plugs and they kept burning the wires so it has new wires lol. Next time around Im gonna get msd stuff (if I can afford it that is). Thanks!

mreld3r

iTrader: (4)

try chevythunder.com Do it yourself information page

StevenB L98/LS1

I wouldnt waste time on getting it checked at a auto parts store, the way you described the problem sounds like an electrically short, or issue somewhere. You said it goes down, it goes up at levels i havent even seen a third gen reach, your alternator, and battery doesnt do that crap. If your alternator was bad it was always be low on voltage under or around 11 usually. You cleaned the battery terminals and it was at 14.5 again, no alternator issues, doesnt sound like a battery considering it cranking fine, i think you have an electrically issue somewhere.

And as far as your idle issue, change ur tps, and iac. If no go, change the distributor, its mostly probably bad. But to me it sounds like your tps is out of wack. Please dont buy one from autozone, im not racist against them even though i work for a parts store myself, but durlast electrically parts a just crap, buy BWD or acdelco parts from either advance or oreilys, or even napa.

y84pauloflondon

Start with the FREE checks first. Do not assume anything! Do not skip anything! Keep an open mind of what could be the cause of problem! Start from one end too another! Stay cool and take your Time. IMO, I think you have a loose/bad connection or wire! I would do a Continuity Test on all your wires, and check the connection to your ECM too.

BTW, are you getting any codes???

tpi305

Thanks so much for the help. Im gonna try and adjust the tps and the iac and see what that gets me. I think I'm having the same issue as cIaRmOaCrZo, because mine will stay high when I stop and if I just basically touch my foot to the pedal it'll go down. Its like somethings sticking. I can give it gas too while in park and sometimes itll stay up at 1500 or 1000 after I let off until I touch the pedal again.

So far I haven't been having any more issues with the charging system, so I'm hoping its ok for now. It usually ends up around 13.8-13.9 after a while, which seems to be normal for some cars (idk about ours).

Thanks for everything. Im just trying to get everything going correctly as this is my daily driver.

Thanks,
Danny

StevenB L98/LS1

As long as its high 13's thats normal charging for our cars.

tpi305

You were saying the distributor could be bad if it's not the tps or iac? I was planning on getting one of those pertronix hei upgrade kits (cap, rotor, 50k volt coil, 50k volt module, advance weights etc). Wouldn't that help? Im also wanting to get some spiral core wires as well as I have the cheapest wires Kragen sells on it presently. I put hooker 2055s on a bit back and it kept burning them so I wanted to make sure I get that taken care of before I put something decent on. Im gonna get some valve cover looms.

smier

" If your alternator was bad it was always be low on voltage under or around 11 usually."

It's not as common but do a google search and you will find lots of info on an alternator overcharging and the havoc it can create...

"And as far as your idle issue, change ur tps, and iac. If no go, change the distributor, its mostly probably bad. But to me it sounds like your tps is out of wack."

Not sure how we made the leap to a bad distributor, but I'd try checking a lot of other things out before I'd even consider a new distributor. $$$$

tpi305

Yeah changing the distributor would be a last resort for me. Im sure the kit would make a good difference. I wanted to get msd 8.5mm spiral core wires, but $70 plus for wires seems really steep to me. Jegs sells their name spirals for $39.99, but you get what you pay for so I'm not sure. My mileage has been lower too so I'm not sure whats going on.