'89 Grand Prix 3.1 - Need Help Please...

[Toxie]

Ok guys, this is going to be long and I apologize beforehand for that. I am running out of ideas of what to do here and need some ideas.

 

This is what I have… '89 Grand Prix 3.1 non turbo

 

This is what I replaced last year on a seperate issue that was resolved… I found out that I had a bad ICM and a blown fuse. After that it ran like a champ until now.

 

Crankshaft Position Sensor

Spark Plugs

Plug Wires

Ignition Control Module

ECM (Computer)

 

This is what I replaced last week trying to fix the current issue…

Ignition Coil Packs (3)

 

I have had this car for over 10 years and it always ran super great. I do all my own work and know just about every nut ,bolt, squeak, and part on a first name basis.

 

About 200 miles ago the car was acting like it does when you have a bad ignition coil pack… AutoZone tested them all out along with the ICM and said they tested fine but I thought for sure that I had a bad coil pack because I had that happen before about 98,000 miles ago. I replaced all three coil packs anyway. It ran fine for a week (200 miles) problem solved… for awhile until below…

 

It’s acting up again now. I tested the new coil packs with only 200 miles but they all test out ok (tested several times by AutoZone and myself). The ICM was tested by AutoZone again too.

 

Like I said, after I replaced the coil packs it ran fine for about a week until this next little episode.

 

I had my AC unit charged last weekend and the guy said that I should hose out my radiator as it looked like it may be dirty. So I took the garden hose and very carefully hosed from the engine side out to the front. I was very careful not to get water around the motor. After I did that I started it up and it was missing bad and would cut out all together… Sh!t!! This was acting very different than when the coil pack was going out… that was like running on half a motor and very low on power. This was an obvious miss and cut out.

 

I couldn’t figure out how that happened because I was very careful and the motor didn’t look wet. Anyway I left the hood up and let the sun dry it out and the next day took off the coil packs and ICM to make sure all was dry. I took them to AutoZone to test just in case, and they tested fine. The plugs on the ICM and packs looked very bone dry without a hint of moisture. Anyway I put it all back together and it ran fine for a 10-15 mile test drive. Fixed... or so I thought.

 

Later it acted up again and i had to limp back home… not a miss or cut out but now back to acting like a bad coil pack… WTF!

 

So… I take the coil packs and ICM off and test them again while it was in the acting up stage... all tested fine. I check the wires thinking there may be a fray someplace and did find a bare spot on both wires going into the little plug on the ICM on the side where there are two plugs. I put some plastic shrink tubing around the wires to separate them and covered it all with liquid tape thinking that I found the issue because water would surely have hit there and maybe that is why the issue was coming and going… Nope… as soon as I fired it up the next day to do the idle re-learn it idled rough as hell and was running like crap. I let it go through the re-learn process but that made no difference.

 

Now the car is running as bad as ever and idles very rough. I can smell gas in the exhaust and it has no power so I’m pretty sure that it is not firing on all cylinders for some reason. It is not an obvious miss or cut out just a very bad idle and no power… like when you lose a coil pack but those have been tested, replaced, and tested again several times.

 

This is where I am at now and really do need some help as I an running out of ideas… Hell, actually I have ran out of ideas…

 

Thanks Guys!

Toxie

Edited June 26, 2010 by Toxie

[BXX]

Check your injectors, pull the upper plenum and ohm them and post the results. Should be around 12.2-12.6 IIRC. You may have one or multiples stuck open or leaking pretty good.

 

Also, look at the vacuum line going from the FPR (fuel pressure regulator) it should be bone dry. if its wet with fuel, the the FPR has failed and must be replaced.

[jtwmechanic]

yeah, it sounds like it is getting to much fuel instead of not enough spark. to much fuel can cause a cylinder to misfire. what codes are stored in the ecm? always check fuses then pull the codes. make sure the car has run long enough since last time bat was unhooked so that it can trip the check engine light again.

[Toxie]

Thanks for the help guys, I do appreciate it.

 

Here is an update...

 

Taking Bob's advice I tested all my injectors. According to my GM manual these should be 12.2 OHM + - .2 OHM

 

Mine were:

Cylinder/OHM's

 

1 = 12.4

2 = 12.4

3 = 11.5

4 = 12.4

5 = 12.4

6 = 12.3

 

Cylinder 3 injector was out of range so I replaced it. When I pulled the plenum I saw where cylinder 5 had lots of residue on the intake.... this had to be coming from the EGR valve and was causing that cylinder to misfire. This car has 220,000 miles and it's 21 years old and this EGR valve is the original so I didnt even try to clean it I just replaced it. Knowing that the #5 cylinder had been getting crap in it from the bad EGR valve I went ahead and changed all the plugs, that plug was wet with gas. I went ahead and replaced the plug wires also. I also found a small vacuum leak and replaced that line. The vacuum line to the fuel pressure regulator is dry.

 

so.... now I think that it will run fine and it does during most of the idle re-learn until about mid way though. it stumbled and died. I restarted and it idled rough, I pulled the vacuum line housing on top of the throttle body and plugged it back in and it ran fine again... today when the engine was cool again I pulled the battery cable to re-learn again and it is running/idling rough again from the start.

 

I'm thinking that maybe I have a vacuum leak someplace now. Is all five of the ports on the throttle body supposed to pull a vacuum?? I get great vacuum from the first and second port, some from the large middle one and nothing from the last two ports. Is my throttle body clogged partially blocking the last three vacuum ports?

 

I'll pull out the battery and check for leaks around the vacuum canister and see if I can find a broken line someplace.

 

Again... when I fired it up after putting it all back together it ran super smooth, better than ever. Then at about 150ish engine temp it started to studder and stall, pulled the vacuum line and when replugged them in it seemed to come out of it. When I started it this afternoon when cold to do an idle re-learn it started off with that same studder/rough idle. Not a miss but like a vacuum leak someplace. No CES lights either.

 

Any more ideas???

 

Thanks again!

-Toxie

[Addicted To Boost]

How are your vents inside the car working? Will air come out of the instrument panel vents, or are they stuck on defrost? Also, is your cruise working? If either of these aren't working, you have a vacuum leak somewhere.

[jtwmechanic]

most vac leaks will cause a high idle, and do not come and go. bad temp sender maybe? at this point i would run a scanner in streamimg data to see what is going on when the temp hits 150ish. get a vacum schematic and verify you have everything routed to its proper location. vac line is cheap so if in doubt just replace it.

[AL]

Im thinking 02 sensor if its only happening at 150 or higher... Also, I have had it where the ICM tested good, but wasnt good.

[Toxie]

Thanks again everyone, I do appreciate it.

 

Here's an update...

 

I cleaned the throttle body, checked the vacuum lines, and replaced the IAC valve. I don't have cruise control, that stopped working about 6 months ago, but the air vents inside the car are working fine.

 

The vacuum canister holds vacuum fine, the lines going to the plenum are holding vacuum also. when you rev up the engine all 4 throttle body vacuum ports are pulling vacuum also.

 

After I did all this I disconnected the battery and went through the re-learn process again. It was silky smooth until around 130 degrees and then it started the jerking and stumbling again, so bad I thought it was going to jump off the wheel blocks. I turned it off and later took it for a ride, it ran fine on a 15 mile ride but the jerking on re-learn had me thinking the problem was still there.. it is...

 

Today i started it up cold and it ran ok until the temp got up to 150ish and again it is jerking really bad and has a hesitation when you give it the gas.

 

Could a bad MAP or MAF sensor cause this?

 

Thanks again... I'll keep trying...

[jtwmechanic]

you really need to watch this thing in streaming data to see what is going on when temp rises and check for stored trouble codes or you can speculate and replace every sensor on the car eventually you will find the problem

[Toxie]

Thanks jtwmechanic... your suggestion is just about the only option I have left at this point.

 

I tested out the MAP sensor tonight and it's good. Was told I didn't have a MAF sensor.

I picked up another O2 sensor as mine had 40,000 miles on it and I'll put that in tomorrow...

 

Thanks again

-Toxie

[alec_b]

Sure sounds like an O2 sensor issue... there was someone else here who had trouble with his TGP when it got warm, and while watching the scan data as soon as the PCM started watching the O2 sensor it started running like crap. Strong bet if you replace it you'll see good results.

[GOT2B GM]

A scenario I ran into with my old 93 3.1 vert sounds similar to this. Ran like an absolute pile. Could smell fuel like crazy. Turns out the coolant temp sensor in the LIM under the TB had gone bad and was telling the car that the coolant temp was -40 degrees, causing the ECM to dump WAAYY more fuel than needed.

[jtwmechanic]

bad coolant temp will make your car run as though it is getting to much fuel because in a sense it is constantly thinking it is in a cold start scenario. to the pcm it is like it never warms up even though it is. really screws with the air fuel ratio. still run a scan before you spend any more cash on parts.

[tornado_735]

...the coolant temp sensor in the LIM under the TB had gone bad and was telling the car that the coolant temp was -40 degrees...

 

Jesus Christ!

[Toxie]

Thanks for the help guys, I really do appreciate it.

 

This is really kicking my butt...

 

I replaced the O2 sensor, throttle position sensor, and the coolant temp sensor... still running like crap when going into closed loop. The crazy thing, after I replaced the TPS it ran super great all the way through the idle re-learn and I thought I had it. Hell it ran better than ever... But the next day it ran like crap as soon as it got into a closed loop again.. go figure..

 

I recorded this streaming data while it was running bad as soon as getting into the closed loop tonight.... does anybody see anything here that could point me into some direction? It says it's running rich but I pretty much already knew that...

 

1989 Grand Prix

T=3.1L PFI SD

Vehicle Data List

 

CODES PRESENT NO

2ND GEAR SW OFF

3RD GEAR SW OFF

4TH GEAR SW OFF

A/F DESIRED 74

AC CLUTCH OFF

AC REQUEST OFF

AIR SW SOL CONV

BARO("HG) 29.21

BARO(V) 4.71

BATTERY(V) 13.5

BLM 117

BLM CELL 0

CCP DUTY(%) 0

CCP SOLENOID OFF

CLNT STRT(øF) 91

COOLANT(øF) 175

EGR DUTY(%) 0

EGR SOL 1 OFF

EGR VLVPOS(%) 19

ENGINE RPM 625

ESC COUNTER 0

EXHAUST 02 RICH

FUEL PUMP(V) 13.6

IAC POSITION 18

IDLE REQ RPM 638

INJ PW(mS) 2.6

INTEGRATOR 125

KNOCK RET(ø) 0

LOOP STATUS CLSD

MAF(gr/S) 17

MAP("HG) 18.31

MAP(V) 2.75

MAT(øF) 97

O2S(mV) 413

O2S CROSSCNTS 131

P/N SWITCH R/DL

PROM ID 8461

RUN TIME 06:50

SPARK ADV(ø) 27

TCC LOCKUP NO

TCC SOLENOID OFF

THROTTLE(%) 0

TPS SENSOR(V) 0.69

VATS STATUS OK

VEHSPEED(MPH) 0

 

 

Thanks again...

Toxie

Edited June 25, 2010 by Toxie

[AL]

If its running rich, there is a good chance of a vacuum leak because there is unmonitored air getting into the intake

[Toxie]

I checked all the lines I could find and the vacuum canister. The canister held a vacuum fine and the lines running from it toward the cruise and climate control held vacuum too. I replaced any lines that seemed questionable. Is there another way to check for vacuum leaks? When I unplug the canister purge and MAP sensor there is vacuum there. If there was a leak would it run bad all the time or only when in closed loop? Before closed loop it idles fine, it’s just once it goes into closed and the ECM starts monitoring things that it starts to get the loping idle.

Thanks,

Toxie

[GutlessSupreme]

Sorry, I read the whole thing but could you make just a summary of parts replaced?

 

In my experience, this sounds like either a bad ICM or bad coolant temp sensor (LIM is for ECM, single wire one on rear head is for cluster, correct?). But from what I remember reading it sounds like you replaced both.. and it looks like you're getting a reading from the coolant temp sensor so I'd rule that out, but keep monitoring the readings to make sure it's not cutting in and out due to a broken wire or something.

 

It's tough diagnosing this. My ICM didn't act up until it got warm, and my coolant temp sensor didn't show problems until in closed loop, so even though they would potentially trigger at the same time, they were technically for different reasons. When my ICM was bad I thought I had a cracked block for two weeks, because I had rushed fixed a coolant problem a few weeks before and only added water.. then it hit below freezing one night and I thought the worst had happened.

 

I should add that in my case with the coolant temp sensor, I believe it was actually caused by slightly broken wires at the sensor connector itself, cause they make that awkward 90* bend upwards towards the fuel rails. Do a continuity test or try wiggling the temp sensor wires when the car's in closed loop to see if it makes a difference. I actually got by for at least 3 weeks using a zip-tie to hold tension on the wires to keep the circuit from breaking before I finally had to make time to really fix it.

Edited June 28, 2010 by GutlessSupreme

[Toxie]

Thanks GutlessSupreme,

 

These items were replaced…

 

Plugs and wires

Idle air control valve

One bad injector (others tested within specs)

EGR valve

O2 sensor

Coolant temp sensor

Throttle position sensor

Coil packs

 

 

The ICM has been checked at AutoZone three different times and tested ok each time. MAP was tested also and checked out ok. I checked vacuum lines again tonight. While running I sprayed starting fluid around all the connections and the plenum, everything seems fine.

[jtwmechanic]

ran in to a similar issue, replaced coolant sender and problem persisted. upon further inspection while running i wiggled the coolant sender plug and the idle changed. turned out to be a bad plug. just somethimng else to consider.

[Toxie]

Thanks again everyone...

 

I checked the coolant temp plug and watched my scanner for temp changes and it was steady all the way up, no issues there. I did find out a couple things though I dont know if it will help or not.

 

This does happen both in closed loop or open loop, it does not matter.

It happens when hot or cold

It could be running bad and then you turn off the ignition, restart, and it fine... or vice versa

 

If it was a vacuum leak why would it run fine sometimes and others not?

 

Below was a good run datastream and a bad run side by side to compare.

 

Scans.pdf

 

The good run went all the way through idle relearn to max temp, it was fine all the way. The bad run was like that from the start before closed loop. Once it got into closed loop it didnt matter, it still ran bad. When it is running bad the O2 reading stays on Rich. When it runs good it runs perfect... it just won't stay there.

 

Thanks again,

Toxie

[Jonpro03]

Im leaning toward ecm/wiring problems. Check all of the wiring to see if anything got pinched. Check the sensor grounds on the back of the engine. Make sure your alternator is putting out good voltage. If you can get a ecm at a j/y for cheap or have one laying around, I would swap it in.

[Toxie]

The saga continues...

 

I took the car to the Pontiac dealer garage to have the "professionals" finally get to the bottom of my problem. That was a story in itself but I won't go into that here now...

 

I gave them a list of what had been replaced, they took it in and did whatever on it and they told me ECM, no questions... I asked what plan "B" would be and they didn't have one... ECM for sure. They wanted over $300 to replace it. I did it myself for less than $100.

 

So, driving it home from the dealer it ran like crap for the first 10 miles or so then came out of it and ran perfect for about 5 miles. Once home, I replaced the ECM and it ran 20 miles perfect and I parked it in the garage thinking I finally had it. Since it was warm when I replaced the ECM I wanted to do a proper idle re-learn when it was cold the next day. It started off just fine and then started running like crap again... I didn't even move the stupid car since it was running ok and now it running bad again!

 

I pulled the ECM power and started it again this morning cold and it runs bad right off the start. Pull battery power to reset everything, same deal... runs rich and runs like when you have a coil pack going out.

 

I dont know how much more of this I can take..

[Garrett Powered]

all you gotta do to reset the ecm is pull the fuse for it by the fuel pump relay, it will save you a bit of time at least... sorry you have these problems, I am having all the same crap right now too. not sure what it is yet. I took my red tgp to this one shop when I got desperate and not sure how he fixed it. he just said it runs now, and I gave him a hundred bucks. I said the same thing today, I don't know how much more of this I can take.

 

If I remember right though, he did say something about messing with a ICM plug. it had new ICM and coils and coolant sensor though. and more including all thats on your list.

 

the 88 is running on 8F and it has the same problem, but it just stalls in busy intersections during the hottest part of the day. usually it starts a few minutes later. I broke down today as I rolled in the driveway. put in coils and ICM yesterday brand new. so yeah, dont feel bad because you are not the only one.

 

I heard lately that my buddy Jim in town here had gotten his more severely stalling tgp fixed by a new IAC motor. hell, I am willing to try anything right now as long as I can get over this stress and not bash the car.

 

I wish I could be more help.

[mra32]

im looking at this thread to try to solve my poor idle issues shown here:

 

http://www.w-body.com/showthread.php/47214-Is-this-a-burnt-valve

 

I'm going to try to look at the coolant temperature sensor before it rains real quick and maybe think about replacing the ICM. I know my coils are not in the best of shape because sometimes when its humid/rainy for a few days, my car will have a misfire until it gets warm.

 

Sorry I couldnt add more.