3800 intermittent slow cranking when warm after ICM replacement

[mbook]

Weirdest problem ever. I have a 2003 Buick Regal 3800 engine with 130,000 miles that has always been well maintained. A few months ago it died on the road and a nearby shop (I was almost out of town and didn't want to have to it towed a distance to my regular mechanic) promptly diagnosed it as a failed coil pack and said it needed replaced, and they also recommended changing plugs and wires (they were original). I didn't realize they'd replace the ignition control module too.

So it had coil pack, ICM, and plugs/wires replaced. I was back on the road and it ran good as new, like always. But 30 minutes later when I stopped at a store I noticed it slowly cranked, though it started. In all the years I've had it it's never slow cranked anytime unless the battery or starter was failing. The starter was replaced 6 months before, and the battery is only 2 years old.

It's weird behavior but it never fails to start as long as I keep the key turned until it pushes through the slowness (and virtual stoppage) of rotation and starts up. You can't replicate the problem on demand, because it is intermittent (though only when warm). You can start it 10 times when warm and it won't do it, but you forget about it and just drive it will happen occasionally.

So my regular mechanic can't replicate it and he's never seen this behavior. He's tested the starter and battery and says they're fine, and my experience says they're fine. I'm confident it will always start, but it's annoying and if I have passengers and it slow cranks it makes the car feel junky. I like the car and it's useful and has sentimental value as well.

I'm tempted just to replace the ICM and see if the problem goes away. It almost certainly seems like an engine timing issue when it happens, but it runs perfectly fine.

Anyone ever heard of such a thing?

 

[Mad_Coachman]

At nearly 20 years old other items may be on their way out like the fuel pump. Did your mechanic check fuel pressure with a gauge? You could also turn the ignition to ON but not start twice for about 3 seconds each time and then START on the third time. A faulty fuel pressure regulator is also suspect.

Another scenario is the parts that the repair shop used to get you back on the road were of sub-standard quality and are starting to fail prematurely such as the ICM and/or the coils.

 

[HotZ28]

Has the UIM Or the LIM (gaskets) ever been replaced? The symptoms you mentioned sound like coolant in the combustion chamber. In addition, if the battery has never been load tested, now may be the time to have that test performed.

 

[ulycyc]

Slow cranking (rpm's) has nothing with ignition unless you hear popping and backfiring. A weak or bad cell in a battery can cause it. Also anything with battery cables, connections and starter. If thats ok then as said a bad intake or head gasket letting coolant into the cylinders can cause hydro static locking.

 

[mbook]

Has the UIM Or the LIM (gaskets) ever been replaced? The symptoms you mentioned sound like coolant in the combustion chamber. In addition, if the battery has never been load tested, now may be the time to have that test performed.

I had most of the gaskets replaced a few years ago. It began to leak oil onto the garage from the top end. Mechanic recommended replacing intake gaskets because he said he thought it would soon need it in addition to valve cover gaskets. Hasn't leaked a drop since. So at least the UIM has been replaced. Not sure if LIM gasket would have been replaced at the same time or not. But oil and radiator fluids look great. The battery was load tested.

 

[Globetrot1]

Weirdest problem ever. I have a 2003 Buick Regal 3800 engine with 130,000 miles that has always been well maintained. A few months ago it died on the road and a nearby shop (I was almost out of town and didn't want to have to it towed a distance to my regular mechanic) promptly diagnosed it as a failed coil pack and said it needed replaced, and they also recommended changing plugs and wires (they were original). I didn't realize they'd replace the ignition control module too.

So it had coil pack, ICM, and plugs/wires replaced. I was back on the road and it ran good as new, like always. But 30 minutes later when I stopped at a store I noticed it slowly cranked, though it started. In all the years I've had it it's never slow cranked anytime unless the battery or starter was failing. The starter was replaced 6 months before, and the battery is only 2 years old.

It's weird behavior but it never fails to start as long as I keep the key turned until it pushes through the slowness (and virtual stoppage) of rotation and starts up. You can't replicate the problem on demand, because it is intermittent (though only when warm). You can start it 10 times when warm and it won't do it, but you forget about it and just drive it will happen occasionally.

So my regular mechanic can't replicate it and he's never seen this behavior. He's tested the starter and battery and says they're fine, and my experience says they're fine. I'm confident it will always start, but it's annoying and if I have passengers and it slow cranks it makes the car feel junky. I like the car and it's useful and has sentimental value as well.

I'm tempted just to replace the ICM and see if the problem goes away. It almost certainly seems like an engine timing issue when it happens, but it runs perfectly fine.

Anyone ever heard of such a thing?

Thank you for this post. I have had this exact same problem with mine (a 3800 V6 in a LaCrosse, so same chassis) and experienced it yesterday. I made a thread about it.

Everything was fine and then the ICM failed and stranded me. They put in the new ICM as well as did its first tune up (plugs and wires).

When it cranks over, it cranks over better than before the repair. But, randomly, I will get a slow turn for half a second, like it may not start. It always still starts. Low 30s mpg on highway. And it started just fine, without the pause, about being away for 3 weeks in February! It's a head scratcher.

I see what you're trying to stress. It's like an ON-OFF switch. It never happened before the repair ... but it began to happen right after the repair. Nothing else appears to be wrong with my car, either. And, if you were to take it in, it wouldn't do it for the mechanic.

If you found the solution, please let us know. Or if folks have other ideas.

 

[mbook]

Thank you for this post. I have had this exact same problem with mine (a 3800 V6 in a LaCrosse, so same chassis) and experienced it yesterday. I made a thread about it.

Everything was fine and then the ICM failed and stranded me. They put in the new ICM as well as did its first tune up (plugs and wires).

When it cranks over, it cranks over better than before the repair. But, randomly, I will get a slow turn for half a second, like it may not start. It always still starts. Low 30s mpg on highway. And it started just fine, without the pause, about being away for 3 weeks in February! It's a head scratcher.

I see what you're trying to stress. It's like an ON-OFF switch. It never happened before the repair ... but it began to happen right after the repair. Nothing else appears to be wrong with my car, either. And, if you were to take it in, it wouldn't do it for the mechanic.

If you found the solution, please let us know. Or if folks have other ideas.

Oh, thank you for your post! You gotta love the internet. How you can find others who've experienced rare things. Yep, same car different styled body. Well I haven't found the answer, but I may make an attempt sooner or later, and if so I'll most certainly post here.

Your description is perfectly concise: "randomly, I will get a slow turn for half a second, like it may not start. It always still starts." Exactly. Mine did it the first time I shut if off after the repair. In fact it surprised me so I backed off the key since I expected it to start faster and it didn't start. I turn key again only hold it down longer, and after slow crank it starts. Now that I know to hold it down until it starts (even though slow crank random and rare, I'm habituated to it anyway) it always starts. The one thing I've learned over last few months is that when it happens it's always when warm, never when cold. Sometimes after setting for 3 hours in a parking lot, but still with a little warmth at least on a warm day I guess. So I think I'd add to your description: "randomly when at least slightly warm, I will get a slow turn for half a second, like it may not start. It always still starts."

I'm not a mechanic, but I do troubleshoot things a lot for my work. Here's how I see it.

1) It's improbable that an electronic component (ICM) would cause a failure of this type. Yet, the ICM does control ignition timing, so it's possible. And of course electronic stuff is sort of like magic and could cause about anything, however rare it might be. I think I've even heard it said (other Internet forums) that "if all other troubleshooting or diagnosis fails, suspect the ICM". So maybe improbable, but certainly possible.

2) Though laypeople (those who never troubleshoot anything) are over quick to say "can't be a coincidence" that x started happening immediately after y service or component replacement, such coincidences happen much more often than they suppose. And yet, when all else fails, the coincidence can't be dismissed as a clue either. So maybe probable it's the ICM, but also possible it isn't just the ICM.

So basically dealing with two improbable things, along with 3rd possibility it could be replacement of ICM may have caused the issue (rather than just coincident with issue) but replacing it with another might not solve it since there's no guarantee it's a simple matter of a single bad component, however unlikely that might be.

The ICM is brand of replacement is 'Standard', and I think those are supposed to be of reasonable quality. But I wonder if Delco still makes them. Don't know, and perhaps they farm them out to same company even if so.

I was miffed that the mechanic who did the work, not my normal local one who is really inquisitive and flexible, wasn't interested in an intermittent problem at all. If it were me I'd have been intrigued, and sympathetic, and offered to replace the ICM under parts warranty and see if that fixed it. I've learned it's a good policy to trust people's observations unless I think it's unwise or I shouldn't for some reason. I'd have paid him for his time, but I prefer not to deal with people in service businesses with a "didn't see it, not my problem" attitude. I've talked it over with my regular mechanic, and he's not heard of it either, but when I take it in next time for rear brakes and oil change I'll ask him what he thinks about swapping ICM just to see if it fixes it. If it doesn't, I don't suppose I want to keep chasing the problem and might just have to think of it as the quirks of an older car, but if I'm lucky that won't happen. I really love these old cars.

 

[century61]

If it was hydro locking a bit you might see white exhaust out the back end when it finally starts after a slow crank. I would watch for that if you can. Kinda doubt it though.

You can always just put another ICM in and test it for a bit. If you still have the issue then return the new one you bought (ask them their return policy). After that I would inspect the power and grounds to the starter. Also, Inspect the starter relay.

On the starter is a short cable - I think its a ground strap for the motor - I have heard those get corroded and cause issues. Take a look at that.

 

[mbook]

Never see any smoke or anything. Thanks for the advice. I'll talk it over with mechanic on next visit, but it may be a few months since I'm not in a hurry.

 

[Globetrot1]

Your description is perfectly concise: "randomly, I will get a slow turn for half a second, like it may not start. It always still starts." Exactly. Mine did it the first time I shut if off after the repair. In fact it surprised me so I backed off the key since I expected it to start faster and it didn't start. I turn key again only hold it down longer, and after slow crank it starts. Now that I know to hold it down until it starts (even though slow crank random and rare, I'm habituated to it anyway) it always starts. The one thing I've learned over last few months is that when it happens it's always when warm, never when cold. Sometimes after setting for 3 hours in a parking lot, but still with a little warmth at least on a warm day I guess. So I think I'd add to your description: "randomly when at least slightly warm, I will get a slow turn for half a second, like it may not start. It always still starts."

1) It's improbable that an electronic component (ICM) would cause a failure of this type. Yet, the ICM does control ignition timing, so it's possible. And of course electronic stuff is sort of like magic and could cause about anything, however rare it might be. I think I've even heard it said (other Internet forums) that "if all other troubleshooting or diagnosis fails, suspect the ICM". So maybe improbable, but certainly possible.

2) Though laypeople (those who never troubleshoot anything) are over quick to say "can't be a coincidence" that x started happening immediately after y service or component replacement, such coincidences happen much more often than they suppose. And yet, when all else fails, the coincidence can't be dismissed as a clue either. So maybe probable it's the ICM, but also possible it isn't just the ICM.

So basically dealing with two improbable things, along with 3rd possibility it could be replacement of ICM may have caused the issue (rather than just coincident with issue) but replacing it with another might not solve it since there's no guarantee it's a simple matter of a single bad component, however unlikely that might be.

The ICM is brand of replacement is 'Standard', and I think those are supposed to be of reasonable quality. But I wonder if Delco still makes them. Don't know, and perhaps they farm them out to same company even if so.

Thanks for chiming in! I'm "cherry picking" some key points.

Yes, also when warm. Crazy. But it started just fine after being in Europe for a few weeks. Stone cold. Go figure. The repair was done last summer, so I've been living with this.

I also think the ICM is the culprit with mine. The only new parts that went in were 6 plugs, 6 plug wires, and an ICM module. Plug wires are typically squirrely under load when failing. I've had that with my previous Regal.

Right. The ICM gets changed ... and it begins. Coils are easy to replace, per YouTube. It just makes me wonder if the ICM is also easy to replace and if it has to "relearn" anything or if it's plug and play.

My new plugs were Delco. The ICM and plug wires were Standard. I don't know much about them. I find this coincidence interesting.

The weirdest thing is that, when it cranks over cold, it's more seamless than before the new ICM. There's not even a minimal amount of "shudder."

(I will also consider the starter relay and the general attachment of the charging system.)

As a general comment, it's far easier to conceptualize mechanical issues. I usually can identify those. And I can zero in on some issues to some degree via my cheap code reader, like the P0128 code I had a few years ago and with which the car ran fine. But, while some members understand the electrical system of a car well, some who understand mechanical issues may not be good at electrical diagnostics. And electrical issues are the most frustrating gremlins of all.

 

[mbook]

Interesting that the repair on your car slightly improved the startup experience except for the intermittent issue we've been discussing. I think mine usually has a shudder feel when cranking, but I supposed that was normal for 3800 since it seems to me it's done as long as I can remember. At least the ICM swap didn't change anything in that regard.

I think it goes way back that spark plugs should be oem, so few would put anything other than delco plugs in a GM car, or autolite in a Ford for that matter. I don't know if it's a general recommendation, but some say to replace the ICM when the coil packs are replaced. I assume that's the only reason my ICM was replaced. I wonder about that now. If that is recommended, I can't think of a reason other than that they must be considered to have a similar mean time between failure. I've seen yt videos showing how to replace ICM and it looks pretty simple.

I don't think ICM itself learns anything. I looked it up once and if memory serves it alone controls spark timing while cranking or under a certain rpm or whatever until the engine starts and then it can take input from the ECM. Reminds me of when a friend's 3800 a few years back had an issue with low idle and dying occasionally after startup. Turns out it was a carboned up throttle body, which can occur in 3800s after high mileage and is fixed by simple cleaning. Same deal, it was a matter of sensors in throttle body doing the fuel inputs for first few seconds after startup until the ECM jumps in. Mechanic said dirty throttle body can prevent that initial period from working correctly until ECM takes over and car sometimes his car would die.

I think the ECM does learn stuff. Once I replaced the battery and the car was without power for awhile because I stopped to do something else. After that it cranked longer than normal when starting, so I called my mechanic and he said just drive it and it will relearn stuff. Sure enough, after a few starts and driving it it began to start as it always had.

 

[Mad_Coachman]

Has fuel pressure ever been checked?
BTW there is no relearn for the ICM. It gets it's marching orders from the crank sensor (CPS).

 

[century61]

It just makes me wonder if the ICM is also easy to replace and if it has to "relearn" anything or if it's plug and play.

I did the ICM in my Lucerne 3800 and it seems just plug and play. That certainly is a weird issue. The only thing I can think of is perhaps the ICM is drawing too many amps when starting warm. Some kind of anomaly with it.

 

[Globetrot1]

Based on my battery comment today, something might have come into play. Today, my battery tested out fine. Last week, not so much. The negative connector to the negative post has been changed in the meantime and I've driven it some ways without stopping.

The guy who did this test for me heard it crank over in a split second. I shut it off. Then, as I cranked it over again, he heard the half a second pause.

He said that what it "COULD" be is that the other connector - the positive one - that has not been messed with in over 14 years, other than changing the battery twice, should probably be replaced and cleaned ... and the battery properly charged.

The car runs too good at highway speeds and gets too good of gas mileage for me to suspect a finicky ICM. I will attend to getting this smaller task done and am hoping the pause goes away. It is infrequent as it is. However, I don't want issues with starting and the battery because I haven't had the positive connection taken care of to the level it may require at this point in its "long in the tooth" life.

 

[Globetrot1]

@mbook

Yes, the ICM replacement looks simple enough per YT. If I keep the car for much longer and the ICM lasts a fair bit, I may put in an AC Delco one next time just because.

Also, I just had my accelerator pedal replaced last week after a couple years of randomly throwing out some APP codes. The car just feels a little more connected from pedal to the throttle response. I also had him put in a new PCV valve, which is location under the MAP.

I was going to have him look at the inside of the throttle body flap, since I don't want to mess with a "snapping turtle." But I will save that for another day before winter.

On my last car, which also had a 3800 V6, the throttle body was not messed with in almost 300,000 miles. I am curious to see what the inside of the flap looks like on my current 3800 engine and want to be there when he tilts it open.

 

[Jason06lucerne]

Weirdest problem ever. I have a 2003 Buick Regal 3800 engine with 130,000 miles that has always been well maintained. A few months ago it died on the road and a nearby shop (I was almost out of town and didn't want to have to it towed a distance to my regular mechanic) promptly diagnosed it as a failed coil pack and said it needed replaced, and they also recommended changing plugs and wires (they were original). I didn't realize they'd replace the ignition control module too.

So it had coil pack, ICM, and plugs/wires replaced. I was back on the road and it ran good as new, like always. But 30 minutes later when I stopped at a store I noticed it slowly cranked, though it started. In all the years I've had it it's never slow cranked anytime unless the battery or starter was failing. The starter was replaced 6 months before, and the battery is only 2 years old.

It's weird behavior but it never fails to start as long as I keep the key turned until it pushes through the slowness (and virtual stoppage) of rotation and starts up. You can't replicate the problem on demand, because it is intermittent (though only when warm). You can start it 10 times when warm and it won't do it, but you forget about it and just drive it will happen occasionally.

So my regular mechanic can't replicate it and he's never seen this behavior. He's tested the starter and battery and says they're fine, and my experience says they're fine. I'm confident it will always start, but it's annoying and if I have passengers and it slow cranks it makes the car feel junky. I like the car and it's useful and has sentimental value as well.

I'm tempted just to replace the ICM and see if the problem goes away. It almost certainly seems like an engine timing issue when it happens, but it runs perfectly fine.

Anyone ever heard of such a thing?

Did you find your issue im having the same exact problem after replacing my icm

 

[HotZ28]

Did you find your issue im having the same exact problem after replacing my icm

mbook, has not been seen here in the past year, so I doubt you will get a reply. 🙁
https://buickforums.com/forums/members/mbook.74066/

 

[Jason06lucerne]

mbook, has not been seen here in the past year, so I doubt you will get a reply. 🙁
https://buickforums.com/forums/members/mbook.74066/

Thanks I really need help lol

 

[Jason06lucerne]

Thanks I really need help lol

Well guys idk if anyone still reads this but I may have found our problem there is a wire harness that runs behind the icm module to the cam and crank sensors that wire was excessively heat damaged I replaced that harness from the icm to the sensors and replaced the crank sensor no more slow cranking or uneven acceleration also keep in mind I replaced all coil packs plugs and wires with new icm this may be a place to look if your having this issue if you remove harmonic balancer make sure to realign it’s as you removed it or it will compromise the timing and not start hope this helps someone god bless you Buick Geeks 🙏❤️

 

[Globetrot1]

Well guys idk if anyone still reads this but I may have found our problem there is a wire harness that runs behind the icm module to the cam and crank sensors that wire was excessively heat damaged I replaced that harness from the icm to the sensors and replaced the crank sensor no more slow cranking or uneven acceleration also keep in mind I replaced all coil packs plugs and wires with new icm this may be a place to look if your having this issue if you remove harmonic balancer make sure to realign it’s as you removed it or it will compromise the timing and not start hope this helps someone god bless you Buick Geeks 🙏❤️

This issue still continues with my car.

I now have 2 things to take away from this thread:

1. Check the grounding of the starter and the solenoid.

2. Check the wiring harness from the ICM to the cam and crank sensors.

A year or so later, my car continues to start, with good performance per the voltmeter, and does this every now and then.