Figure this out... When my car is cold, it runs like a dream. As soon as it gets up to operating temp, I have problems. Here is what happens---When I come to a stoplight, the car gets an erratic idle and then stalls. However it will start right back up.
Replaced: Prom, MAF & relays, Pickup coil, ignition mod., fuel pump relay, TPS and set voltage.
Took the car to Pontiac and they have no friggin clue. Tech1 cant detect anything because the ECM is so slow in the third gens. any clue?????


--------------
88 Formula, 305 TPI (engine code F), automatic trans, 91,000 miles, a real pain in the a**

 

It could be your ignition module i had problems with mine untill i switched from napa crapa brand to accel. Read your codes and see what it spits out.

 

I see you replaced the module, thats a tricky one. There should be someone on this board who can help you out.

 

perhaps they did not look at the data close. you cold be running rich and the comp. may not know it is.

 

Been there done that...Ignition Module HAS been replaced

 

yeah,but if it was running rich, wouldnt I have problems all of the time?

 

Man, I have been dealing with the same problem on mine ('90 IROC 350) for months and done a helluva lot to try and correct it. Nothing worse than a sorry idle and stalling. I even broke down after gutting it for 4 or 5 months and took it in...they couldn't find anything either (go figure).

Here's what I've done so maybe these things won't help you either: plugs, wires, cap, rotor, coil, ignition control module, pickup coil, fuel filter, valve stem seals, IAC, TPS, MAP, CTS, vacuum check, compression check, fuel pressure testing, alternator testing, new cat-back, air filters, PCV, O2 sensor, and probably a bunch of other s@#t I can't remember right now. Nothing changed a thing and all tests were fine. The thing gets 24MPG on the interstate at 90MPH.

I'm thinking it's either the EGR open at idle, clogged fuel injectors, plugged cats or the damn computer itself. Probably just some electrical gremlin I'll never track down until an engine swap sometime in the future.

What kind of cap and rotor are you running? The reason I ask is because mine is an Accel and I haven't heard many good things about them lately. Have you tried cleaning the injectors? Maybe between what I've done and what you've done we can narrow it down to one or two suspects. Your problem sounds similar to mine, does it run rough up to about 2200RPM if you rev it in park?

 

sounds like a vacuum leak. When the engine is cold it runs fine because the cold start cicuit provides enough fuel for it to run. However when the engine is warm and doesn't receive the extra fuel, then the mixture is to lean and that could cause the problems you describe. I know there is a way to use a vacuum gauge to check for leaks but I'm not sure how to do it. You could also try spraying wd-40 anywhere that an air leak into the engine is possible while it's running. If the idles changes while you spray a spot, there's your leak.

 

There are several things you can use to pin point a vacuum leak. Propane torch (unlit), water, carb cleaner, etc.

Hook up your vacuum guage to the plenum; reading should be relatively steady unless you've installed a performance cam.

Be sure to squirt around where the injectors enter the manifold, I found mine there.

IAC, IAC passages, back side of the butterflies carboned up, vacuum hose off or cracked from age. Make sure the polarity of the coil and pick-up coil match.

Just my thoughts.

Jake



------------------
1986 Corvette Coupe, 415 CID, Edelbrock 6073s, ZZ9

 

I couldn't help but notice that you didn't mention replacing the IAC or setting it along with the TPS... might want to try that too.

Here's a great set of instructions on how to do it: https://www.thirdgen.org/newdesign/tech/tpimod2.shtml

------------------
Kevin Irving
85 Trans Am WS-6, 305 TPI, custom burned '86 PROM with '87 "165"ECM, Accel Supercoil & 8.8 Wires, MSD 6AL, Aluminum Driveshaft, TB Coolant Bypass, Ported Plenum, Modified MAF, Syclone Fuel Pump, JET Airfoil

15.556 @ 86.65mph, Nov 10, 2000.... I know it sucks.. but it will get better!

http://www.geocities.com/transam85tpi/

 

Thanks for the advice, but Ihave set the IAC. I am running stock Delco rotor and cap.
I do agree that it is more than likely an electrical gremlin that I may never be able to trace. Thanks for all of the info Jethro. I am going to have ANOTHER buddy of mine look at the POS today and I will let you know if he finds anything. (he is a GM tech)
thanks again for the help and if anyone else has ANY ideas please post 'em

 

fuel pump or injectors cloged or maybe its the cam that went

 

Did you ever change the fuel filter and check the pressure (while driving?)?

 

sounds like how my iroc runs... it started with a choppy idle, than I started to go through oil quick and loose power. After checking and/or replaceing everything cheap, which I wanted the fix to be, I took it to my local gm dealer, they had no idea. Then I took it to reputable gm dealer, berger out of grand rapids michigan, and they told me what no one wants to hear, shatered piston rings requireing a total rebuild; their quote 3,700 bucks. I decided to do it myself this spring, I love excuses for more hp! Lets just hope yhou get off easier than I did, but you never know, big problems could show small simptoms. Good Luck

 

Ryan - I did a cylinder balance test on mine today by pulling the injector connectors while the engine was idling. Most of them only made it shake worse than it already does and only three of them or so caused the idle to drop. So I'm pretty sure now that my problem is clogged injectors since the entire ignition system is new, and you may want to try the same test I did and see what happens. Hope this helps.

 

Well, I went to my buddy (the GM tech) and he took a phillips drill bit and jammed it in the line that runs to the EGR, (to test it???) so far, so good. I will keep everyone updated on the progress. Keep the advice a-coming, 57 heads are better than one

 

I agree with NUN.. Sounds like a bad fuel pump maybe. If you consider how old that pump is if its the original, shouldn't it be replaced anyways? Auto performance engineering sells Walbro pumps for unbeatable prices. I think its autoperformanceengeneering.com... A vaccum leak is also a good guess too. Did you try the trick with propane or starting fluid yet?

------------------
Mike C
88 Iroc 5spd
355 TPI, AFR 190s and lotsa other mods
86 Iroc in pieces!

 

Yeah Mike I tried the propane trick. thanks for the tipon the fuel pump though.

 

Someone get VADER's opinion on this pls.

 

I'm not Vader, but if you haven't tried the cylinder balance test yet I would do it since your problem sounds just like mine and I've got the injectors in my crosshairs now. I'll be putting in new ones, new EGR, MAT and AFPR while I'm in there next week so I'll let you know if that clears it up. I'm sure it will, and when it does the Police will be on the chase .

 

This happened to my buddy's IROC. Turned out to be tired injectors. They would work fine at WOT, but down low they weren't performing fully.

------------------
'88 IROC TPI 355, fully balanced, 9.75:1 compression, fully ported '70 truck heads(for now), Harland Sharp Roller Rockers, Comp Cams TPI cam, fully ported '90 speed density TPI with '86 base so it fits older style heads, Crane AFPR, Flowmaster 3in. exhaust, Edelbrock TES headers, all emissions equipment is still intact, plan on burning my own chips, many more mods and parts on the way as time and money permits =(
Best E.T. with TBI 305: 16.11 @ 82mph
Haven't been to track with new motor
Won bracket races at Numidia Raceway with my '70 Nova
In memory of Dale Earnhardt, I'll miss cheering for that black #3 on raceday!!!

 

Injectors for sure. My 91 was doing the exact same sh*t.

 

My cavalier had a problem kinda like that, it drove me crazy. It would do alright until it got hot, then it would die at stoplights and such.

Turns out it was the torque conveter lockup solinoid. The converter was staying locked and I was stalling out when i came to a stop. I don't know if that could be your problem or not. I have my cavalier's lockup wires unplugged right now, runs fine now.

------------------
1989 Pontiac Firebird Formula LO3 Auto
-180 degree stat
-Hooker Cat-Back
-vinyl security shade, velcro t-top bag
*****Possible summer '01 mods*****
Dual Snorkle, Auburn Posi, Keyless Entry, Wonder Bar from my IROC, 4th gen seats, T/A tail lights

http://www.geocities.com/krt80/

 

Hey-
I've been having similar problems. I have a ton of other posts on here right now. I've replaced/checked:
-checked TPS
-checked MAP
-IAC
-new fuel filter
-new Holley AFPR
-new Holley 255lph Fuel Pump
-checked injectors(ohm test and leakdown)
-new o2 sensor
-new cap/rotor
-new Taylor 8mm's
-new plugs
-new coil/wire
Possibly a few others.

*It still is doing it though. We hooked up a scanner last night and really couldn't find anything though. We think its the HEI module, pickup coil, ECM, or ignition short. I have a spare ECM on the way and we may replace the PROM too. I also am thinking about replacing the 2 distributor parts I talked about above. Well, I'll keep ya all posted and keep me posted too!

*I'm thinking its the D#! ECM though. Later
-

------------------
'91 GTA:
www.fbody.com/members/91WS6GTA

[This message has been edited by GTA91 (edited March 14, 2001).]

 

IROCZ28-
Tired injectors? How do you check for these? I already did a leakdown and ohm test on them and they seem fine by that. I'm still wondering if they are bad though? How can I tell if they are weak? TIA

------------------
'91 GTA:
www.fbody.com/members/91WS6GTA

 

Hey, had a similiar problem real intermitent like every other day it would stutter for a while and the first thing to look at if nothing appears wrong is the ECM.
Im not saying rreplace it, but drop it down start the car and give it a few whacks. If the car stumbles it could very well be a crappy ECM.


------------------
355 10:1 , AFR 190 heads, LT4 HOT cam w/ 1.6 roller rockers, complete Superram intake, 58mm BBK TB, 24# injectors, screens out of MAF, MAT relocated, March underdrive pulleys, Streetdampner, Crane HI-6 ignition, 160 thermostat, K&Ns, TES headers(Jet hot coated), Mufflex 4' cat back, B&M shift Kit, 2500 converter, and 3.27s.

 

WOW thank you all for the advice. I am going to try the advice on for size, but keep it coming. No suggestion too far fetched at this point.

-----ryan

 

you check the o2 sensor?? it may be clogged and when the car heats up and goes to read the sensor it cant.. its a possibility and real easy to check..
good luck

 

I'll bet you that your fuel injectors are getting weak. I have a 1989 cavelier and my car would run great until it warmed up and it would be fine while i was driving. Then every once in awhile it would stall when I came to a stop. I was told by a trust worthy mechanic that there are springs in the fuel injectors and when it warms up the springs get warm and stretch (not sure if that is exactly how it works, but its close). Well I replaced my injectors and the problem was fixed. you can get your injectors tested, but beware that there might be a couple that are weak and a couple that are fine. (just replace them all.

 

Ryan,

I think your first idea was a good one - sell it.

I'll give you a couple of Hamiltons for it. AFter I get it, I'll do the power balance test on the injectors, probably realize that they aren't all flowing the same, and send them off to Cruzin' Performance for cleaning and flow matching. After they come back with excellent spray patterns and flowing within 3% of one another, I'll reinstall them, then sell you the car back for a few thousand - running good as new for $120.00 of gaskets and injector work, and a little of my time. I might even throw in some new floor mats.

Yeah, I think that's a good idea....

------------------
Later,
Vader
------------------
"I'm'a do Things My Way - It's My way or the Highway."
Adobe Acrobat Reader

 

HAHA really funny Vader...I will look into the friggin injectors this weekend. It is my B-day, so maybe it will be a present to me.

Thanks again guys for all of the help.

 

Everything seems more influential coming from Vader .

------------------
1990 IROC 350
Mods: Too busy trying to make it run right to mod it.
Airfoil, Dynomax cat-back, Accel coil, 180 t-stat, Bald Eagle tires
Hypertech fan switch, hot wife, new oil filter, thick rubber floormats.
18.0 @ 85MPH since I'm one big-a$$ MF
"It's better to have and not need than to need and not have."

 

I'm telling you an easy test for the torque convter lockup malfunction is to just unplug it. I did that on my cavalier and it hasn't stalled since. Gonna get that fixed this summer, but it runs fine for now, just no lockup.

 

Okay Okay Keith I will try your idea today. just chill man.

 

OH one more thing, I checked the website for Cruzin' Performance, and that is great if you are in MI, but I am in OHIO. Anyone know who can provide the same services near me?????

 

I've replaced my pickup coil and module and stil ldoes it. I'm thinking weak injectors or ECM, but not sure. Oh well, keep me updated on yours. Thanks

------------------
'91 GTA:
www.fbody.com/members/91WS6GTA

 

the way you are supposed to check the torque lockup is get on the highway get up to 70 in overdrive, with one foot on the gas press the brake down with the other about 1 inch just enough to get the brake lights to come on you should feel the converter unlock let off the brake and within about 5-10 secs it should rengauge and listen for a chattering or vibrations. hope this helps

 

And I'm on the Illinois/Wisconsin border, but I use them anyway. That's what UPS and FedEx are for...

------------------
Later,
Vader
------------------
"I'm'a do Things My Way - It's My way or the Highway."
Adobe Acrobat Reader

 

Thanks again Vader

 

Or you can just unplug the pigtail. Remember this is a intermittent problem, mine worked sometimes, sometimes it didn't. If you unplug it then you drive around for a few days like that so see if it messes up.

If it does then that's one more thing that it isn't.

 

Replace your o2 sensor and check your timing. Be sure to check it with the computer bypassed. Also could be water in the fuel. Try getting 93 octane + octane booster. Try replacing the knock sensor. It could also be an intake manifold leak.
--just a few ideas--

------------------
1985 TransAm BLK/GLD Stock
1985 TransAm BLK/BLK
305HO (soon as it is put in) 5-speed, 3.27 posi, WS6, power everthing.
http://www.geocities.com/bullfrawgs

[This message has been edited by bullfrawg (edited March 15, 2001).]

 

Vader's right, I'm all the way down here in podunk Tennessee and Rich at Cruzin is getting new injectors from Accel to me in a matter of a couple days. Ahhhh, the beauty of USPS express shipping.

 

I don't know if you've already got it running right or not, but mine was doing the same exact thing. I had tons of bad vaccum lines that were replaced or fixed and i put a new egr valve in and it worked fine after that. MAF sensor is another good place to look, good luck with it.
Bryan

------------------
86 Irocz, 305 bored 40 over, 211/221 comp cam,paw rocker arms 1.5,10:1 comp., stock heads, 100 shot of nitrous,

soon to be airflow research 190 cc heads, 373 gears to replace 273, and induction work

 

Hey bryan...I am leaning your way, ever since my buddy rigged that erg line, it has been acting up alot less. But did your car only act up intermitently???

 

Yeah sometimes I could start it up and I wouldn't have a problem with it, but then after letting it sit for a little while i would start it up and it would start to die and I would turn the idle up, then it would stop the next crank. It would do it sometimes alot then sometimes hardly ever. All I did was get a egr and put it on, and got some rubber hoses to cover up the bad vaccum lines and it hasn't done it again yet. I was also always getting code 32 too. If you can't get a good egr like from chevrolet or ac/delco or one of the top brands just block it off because that pos I have on mine is cramed in there.
let me know how it all works out and good luck let me know if you need anymore help i'll try all i can.
Bryan

 

I had this problem on my 91 305 TPI, and it took over a year to find what was wrong. Turns out the problem was the PROM. I know you already replaced it, but what did you replace it with? This is important because GM puts out PROM updates as service bulletins. I didn't quite understand this but the mechanic said that as the car gets older and wears, it's specs that are controlled by the PROM can sometimes change. So they reprogram a new PROM to fix the problem. So what I'm saying is that if you replaced the PROM with the exact same part number that came out, you won't have fixed the problem. However, if the dealership recommended the new PROM then chances are you have the most up-to-date version.
But for everyone else out there who's reading this and has the same problem, it's something to look into. There's no way to test for a bad PROM, the only way is to throw a new one in and see how it does. It's kinda guesswork, so I'd only recommend it if you've checked everything. I don't know about the rest of the thirdgens, but I know there's a service bulletin for all 91 305s, both TPI and TBI. Just thought I'd share the info and save some of you the headache because I'm sure my car isn't the only one with an outdated PROM.

[This message has been edited by ViciousZ (edited March 18, 2001).]

 

Hey V, thanks for the input...That GM tech said the same thing about the prom, so I am going to look into an EGR and then maybe the PROM. Another problem has arisen though...I was leaving my grandmothers house after an ice storm, and a fire hydrant jumped out in front of my passengers side fender and bumper cover. so that comes first because I cannot stand to see my poor car that way. OH WELL, just another trip to the local pick-a-part. (they love me there)
thanks again guys.

---ryan

 

Ryan, one thing about the EGR, don't forget about the solenoid that controls it. This could cause your problem just as easily as the EGR valve itself. But the solenoid is a lot cheaper to replace, and easier too. I suppose there's a way you can test the solenoid, but I don't know how.
That sucks about your fender. Those fire hydrants really oughta learn to behave themselves.

[This message has been edited by ViciousZ (edited March 19, 2001).]

 

As for turn-around with Cruzin' Performance, I had my injectors back the same week I sent them out to Rich- and I'm from New Jersey.

------------------
-Tom P (Hot rodded 1986 Firebird 2.8l) from http://www.f-body.net/mailbag/3rd/3rd_mailbag.html message boards
---Think your car could be pic of the week? Visit http://www.f-body.net for details!

 

Ok Ryan ,, I would have to say try either cleaning or replacing the IAC and see if that works , my dads car did the same thing and for years i couldnt figure it out not even GM certified technicians could do it,, but it sounds like the exact same thing .