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1989 Regal 3.1 stalling issue


Sigurd Jarlson

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Sigurd Jarlson

For some background I've recently got my Regal on the road after sitting a while. It has been driving perfectly fine for a few weeks of intermittent driving. It's not my daily driver so I was using it for local errands. The other day it stalled as I was going up a hill and I was able to coast into a parking lot. I kept trying to restart it and it would catch and then quickly die. After about 15 minutes and multiple tries it finally started again. I chocked it up to old fuel and I topped off the tank with premium and was able to make my way home no problem. The other day I started it and it idled fine but as soon as I left the driveway it died. I rolled it back, and it's doing the same thing where it catches for a second but then stalls, but hasn't "woken up" again like last time.
I have good fuel pressure at the rail, about 40 psi, and as a quick remedy I tried throwing in in a new IAC valve, but that didn't help. I'm not super familiar with the 3.1 engine, as my area of expertise is the 3.8 that was in my two Cieras.
It's a super low mileage (less than 70k w/ a broken odometer) engine and pretty clean.
Are there any common issues that would cause this?
Thanks for any help.

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One needs to rule out if the issue is either ign or fuel related. . Pick up a can of ether, if the issue is still present (the engine will not fire) disconnect the fuel pump relay, one individual

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This is usually caused by the injectors starting to fail and bringing down the entire injector bank. Ohm out all 6 injectors and make sure they're within range of each other. It's likely that one will be nearing a short. Multitecs are pretty notorious for this once they get old.

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Thats a good thought, Shaun. In my experience, 2 were shorting and the third (the kicker that left made it stall) was shorting when the engine was at running temp.

Since the early injectors had inherent issues, I converted 1 of my 3.1s to the injectors from the 94+ 3100s. They were proven more reliable and interchanged with fuel flow being within 4% of OE spec on the 3.1 LHOs.



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One needs to rule out if the issue is either ign or fuel related. .

Pick up a can of ether, if the issue is still present (the engine will not fire) disconnect the fuel pump relay, one individual at the key, you under the hood, as the engine is cranking spray a LIGHT to moderate amount of ether directly into the *open* throttle body.

does the engine try to fire at all?

If it doesn't then the issue may be on the ign side.

Check the entire ign system, do you have spark at the plugs?, a spark plug tester will let you know, plug one into each spark plug circuit & look for irregularities in the pulses as the engine is being cranked. Each of the 3 coils fires 2 cylinders (1-4, 2-5, 3-6), look for an issue related to just 1 coil, look for an issue related to all coils (ICM board issue). Look for any chafed wiring going all the way back to the CPS, it may be something as simple as a bared conductor grounding which is causing the issue.

   

 

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pontiac6ksteawd

If it has a MAF, unplug it, and see if the issue continues. It will set a SES light, but it would rule that out. This is what the problem sounds like to me.

 

If it does have a MAF, it may be worth calling a local dealer, and see if they can program it with the speed density software that eliminates the MAF function, but keeps the MAT that the MAF also does.

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On the sensor side of the equation MAP, Coolant temp & the IAT all required for the ECM to have correct barometric pressure  & coolant temp info for the ECM to correctly calculate the fuel mixture to fire the engine. 2 of the 3 of these each or together missing & the ECM cannot fire the engine properly and will set a code immediately, the 3rd (the IAT) will set a code within 50 secs of the engine initially firing as long as it stays running. 

A scanner would be needed to read the actual display readings in realtime..

Edited by 55trucker
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pontiac6ksteawd
5 hours ago, digitaloutsider said:

I'm *fairly* sure the MAF was relegated to only the '88 2.8Ls. I believe all '89s were speed density, especially a 3.1.

You are correct...... For the most part. I have seen it both ways. A 88 2.8 without a MAF (I owned a 88 Pontiac 6000 LE 2.8 without MAF), and a 89 3.1 with MAF. Sometimes you wonder what kind of drugs these guys were on back in the 80's.

I will also admit, the 88 2.8 was a weird one. It had the MAF wiring, but there was a short 3 inch adapter plug on the end of the harness where the MAF would normally plug in, and it went to a MAT on the air filter housing. No stickers or anything for speed density software installed.

But back to the topic...

Edited by pontiac6ksteawd
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Sigurd Jarlson
7 hours ago, 55trucker said:

One needs to rule out if the issue is either ign or fuel related. .

Pick up a can of ether, if the issue is still present (the engine will not fire) disconnect the fuel pump relay, one individual at the key, you under the hood, as the engine is cranking spray a LIGHT to moderate amount of ether directly into the *open* throttle body.

does the engine try to fire at all?

If it doesn't then the issue may be on the ign side.

Check the entire ign system, do you have spark at the plugs?, a spark plug tester will let you know, plug one into each spark plug circuit & look for irregularities in the pulses as the engine is being cranked. Each of the 3 coils fires 2 cylinders (1-4, 2-5, 3-6), look for an issue related to just 1 coil, look for an issue related to all coils (ICM board issue). Look for any chafed wiring going all the way back to the CPS, it may be something as simple as a bared conductor grounding which is causing the issue.

   

 

Update. It starts and runs as I spray ether into the throttle body. Ignition doesn't seem to be the issue. Even without the ether, it starts for a second or two and then dies.

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Sigurd Jarlson
35 minutes ago, pontiac6ksteawd said:

You are correct...... For the most part. I have seen it both ways. A 88 2.8 without a MAF (I owned a 88 Pontiac 6000 LE 2.8 without MAF), and a 89 3.1 with MAF. Sometimes you wonder what kind of drugs these guys were on back in the 80's.

I will also admit, the 88 2.8 was a weird one. It had the MAF wiring, but there was a short 3 inch adapter plug on the end of the harness where the MAF would normally plug in, and it went to a MAT on the air filter housing. No stickers or anything for speed density software installed.

But back to the topic...

Yes, no MAF sensor, which is what I thought the problem may be since I had a similar issue with one of my 1988 3.8L Cieras

Edited by Sigurd Jarlson
changed 2.8 to 3.8
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Sigurd Jarlson
3 hours ago, 55trucker said:

On the sensor side of the equation MAP, Coolant temp & the IAT all required for the ECM to have correct barometric pressure  & coolant temp info for the ECM to correctly calculate the fuel mixture to fire the engine. 2 of the 3 of these each or together missing & the ECM cannot fire the engine properly and will set a code immediately, the 3rd (the IAT) will set a code within 50 secs of the engine initially firing as long as it stays running. 

A scanner would be needed to read the actual display readings in realtime..

I forgot to mention in my original write up that there wasn't an active SES light.

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Sigurd Jarlson
18 hours ago, digitaloutsider said:

This is usually caused by the injectors starting to fail and bringing down the entire injector bank. Ohm out all 6 injectors and make sure they're within range of each other. It's likely that one will be nearing a short. Multitecs are pretty notorious for this once they get old.

It appears that unlike the 3.8 SFI injectors I'm familiar with that the ones on my 3.1 are buried under the upper intake manifold and I would have to pull that to Ohm them. Is that correct?

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You can get to like one of them without pulling the manifold, maybe 2. If you use a noid light (or straighten out the "legs" on a 194 bulb and stick it in the plug) , you can test to see if it's even firing that bank.

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15 hours ago, Sigurd Jarlson said:

I forgot to mention in my original write up that there wasn't an active SES light.

Meaning that the check engine is not functioning or there are no codes stored?

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Sigurd Jarlson

Checking the codes a 3-3 and 3-4 both came up, which for 1989 is the MAP sensor, but I did unplug it and try to start it yesterday with it unplugged, but I don't know if that would have triggered that code automatically. 

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Sigurd Jarlson

Video of it trying to start. I wish it would "wake up" like it did the first time this happened so I could move it to it's correct spot in the driveway.....

 

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1 hour ago, Sigurd Jarlson said:

Checking the codes a 3-3 and 3-4 both came up, which for 1989 is the MAP sensor, but I did unplug it and try to start it yesterday with it unplugged, but I don't know if that would have triggered that code automatically. 

If one unplugs the MAP then the ECM cannot calibrate fuel mixture, little wonder the engine would not/could not run.

 

33 is high voltage (low vacuum) & 34 is low voltage (high vacuum), disconnect the harness & both will set seeing as the ECM doesn't know what's going on.

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Sigurd Jarlson
2 minutes ago, 55trucker said:

If one unplugs the MAP then the ECM cannot calibrate fuel mixture, little wonder the engine would not/could not run.

 

33 is high voltage (low vacuum) & 34 is low voltage (high vacuum), disconnect the harness & both will set seeing as the ECM doesn't know what's going on.

I only unplugged it it briefly yesterday. It was plugged in when the problem arose and and is currently plugged in as the problem persists.  

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Sigurd Jarlson

So I tried to start it today and it ran for about 10 seconds, allowing me to move it closer to it's spot in the driveway. Then back to the almost catch and then die as seen in the video. I got in a new MAP sensor, swapped it out with the old one and nothing changed.
So I have:
Fuel at the rail. I even purged an 8 oz bottle of fuel from the schrader fitting just in case there was a bit of dodgy fuel in there.
Spark. It runs on ether and also run for a few seconds occasionally.
A new AIC and new MAP.

I haven't had a chance to do a check on the two injectors that are accessible without pulling the upper intake manifold.

Would bad injector(s) fail intermittently like this?
 

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You mentioned earlier that you had 40psi at the rail.....I take it that you have a fuel pressure gauge? Is the rail holding 40psi even after the 2 sec pre pressure cycle?.......injectors leaking or not leaking, FPR is possibly faulty?.....

Can you get your hands on a scanner?

One wants to be able to see what the MAP reading is, what the coolant sensor reading is, a possible  out-of-scale high TPS reading. Any one of these three items being faulty will cause a hard start/no start situation/shortly after die. 

Where the MAP is concerned if there is a vacuum leak to the MAP it cannot function properly, one needs to ensure that there is not a vacuum leak involved. Are ALL the vacuum hoses original? The MAP reference voltage is 5v, with the key on the voltage should approx .5v less than reference. One needs a vacuum pump to test the MAP & read the change on the scanner in real time as one applies progressive vacuum to the MAP. Similar same with the coolant sensor, with the key on the coolant display (engine cold) should correspond with the ambient temp outside, a -40 is an indication that there is an issue with the CTS or CTS circuit.  The TPS should read between .3 & .9v with the key on engine off throttle closed.

 

Edited by 55trucker
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Sigurd Jarlson
1 hour ago, 55trucker said:

You mentioned earlier that you had 40psi at the rail.....I take it that you have a fuel pressure gauge? Is the rail holding 40psi even after the 2 sec pre pressure cycle?.......injectors leaking or not leaking, FPR is possibly faulty?.....

Can you get your hands on a scanner?

One wants to be able to see what the MAP reading is, what the coolant sensor reading is, a possible  out-of-scale high TPS reading. Any one of these three items being faulty will cause a hard start/no start situation/shortly after die. 

Where the MAP is concerned if there is a vacuum leak to the MAP it cannot function properly, one needs to ensure that there is not a vacuum leak involved. Are ALL the vacuum hoses original? The MAP reference voltage is 5v, with the key on the voltage should approx .5v less than reference. One needs a vacuum pump to test the MAP & read the change on the scanner in real time as one applies progressive vacuum to the MAP. Similar same with the coolant sensor, with the key on the coolant display (engine cold) should correspond with the ambient temp outside, a -40 is an indication that there is an issue with the CTS or CTS circuit.  The TPS should read between .3 & .9v with the key on engine off throttle closed.

 

I'll check the fuel pressure more in depth tomorrow. 
I only have an OBDII scan tool. I probably can't get a scanner that would work with a 1989.
Where is the coolant temperature sensor on this engine?

Thanks

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2 hours ago, Sigurd Jarlson said:

I only have an OBDII scan tool. I probably can't get a scanner that would work with a 1989.
 

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https://www.amazon.com/INNOVA-3123-OBD1-Code-Reader/dp/B000EVU8C0/
~$30
https://csr.innova.com/Content/Manual/Innova/010412_3123_93-0102_RevD_Manual_English_Final_downloadable.pdf

 

https://www.amazon.com/Actron-CP9001-GM-Code-Scanner/dp/B0006V2BHI
~$30
https://actron.com/sites/default/files/chart_16152.pdf

 

Btw, the following may also work, the manual isn't clear.
https://www.amazon.com/Actron-CP9690-AutoScanner-Enhanced-vehicles/dp/B011ICD2WQ
 

And, there's always the China clone GM TECH-II Scanner for (~$300-$500).
https://www.ebay.com/sch/i.html?_from=R40&_nkw=GM+TECH-II+Scanner
 

 

Good Luck!

 

Edited by Cutlass350
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12 hours ago, Sigurd Jarlson said:


Where is the coolant temperature sensor on this engine?

Thanks

The CTS sensor for the ECM is located on the thermostat end of the intake manifold, the sensor is screwed into the bottomside of the manifold under the thermostat somewhat out of sight.

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Sigurd Jarlson
4 minutes ago, 55trucker said:

The CTS sensor for the ECM is located on the thermostat end of the intake manifold, the sensor is screwed into the bottomside of the manifold under the thermostat somewhat out of sight.

OK Thanks.

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