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Rough idle and rough cruising, especially with light acceleration. E042 Code


sarookha

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Posted (edited)

I'd been having intermittent issues with rough idle, and rough running.  I've cleaned the MAF sensor, I've cleaned the IAC, I've replaced the crank position sensor.  No change.  I was on the verge of replacing the ECM.  But while I was under the car replacing the crank sensor, I noticed a foul viscous sticky goo on the frame, that seemed to have come from above.  The slime was beige, with a greenish tint to it, really nasty looking, very sticky, and impervious to WD-40 and Goo-Gone.  When I traced it uphill, it was leaking from the seam between the coil pack (Motorola) and the ignition module.  I removed the coil pack, and sure enough, there was a crack on the bottom side with this gross slime oozing out.  I had to clean a lot of slime off the wiring that connects the coil pack to the Ignition module.

 

But replacing the obviously failing coil pack didn't change anything, which really surprised me. 

 

Inspired by Daves89 post about the ignition harness on his '99 Regal having been the problem, I thought I'd take a look at my Reatta's ignition harness.  First step was unplugging the ignition harness from its socket on the ignition module, and that's when I discovered that the wiring harness connector and socket on the ignition module were both fouled with the slime that had leaked out of the old cracked coil.  I tried electronic parts cleaner, but the slime was unimpressed.  Lots of scraping and digging with tweezers and tiny screwdrivers got much of the goo off of the connector, but there was still plenty of sticky residue on everything.  

 

I was concerned that something as aggressive as carb cleaner might soften the wiring harness connector, but as it was useless anyway, unless I could get the slime off, I gave it a try.  Carb cleaner did the trick.  I wrapped a rag around the connector to keep the cleaner from removing paint or anything else important in the vicinity, and cleaned the socket on the ignition module the same way.  Finally, I sprayed off all the goo that had embedded itself into the wiring bundle, hoping that carb cleaner doesn't soften wiring insulation either.

 

After putting it all back together, she started right up and idled smoothly.  A short test drive was similarly uneventful.  As the problem has been somewhat intermittent, I'm hesitant to say I'm home clear, but it does look like the slime was actually the culprit.

 

 

Edited by sarookha
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Alas, after about 30 miles of trouble-free cruising, I'm right back where I started.  Lots of rough idle, sometimes it's hard to keep her running.  When driving, there is such a stutter that I'm afraid the transmission is going to be damaged.

 

Swapped in a known-good ignition module and coil pack, no change...

 

Threw two codes, which is new, as before even with being barely drive-able, there had been no codes.  So today, E041 and E042 popped up.  Cam sensor and ignition module.

 

Swapped in a known-good ignition module and coil pack, no change...

 

Looks like I'll be swapping in a known-good cam sensor as well.  Along with checking on the magnet that activates the sensor.  But I'm assuming that the magnet would have a hard time being intermittent.  If it falls out, it's gone. 

 

Any thoughts?

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The cam sensor won't cause the problem you are having. Even if you unplug the sensor the engine will run smoothly. It just won't be as efficient due to the injectors not opening at the optimum time which is determined by the cam sensor. Bad spark plug wires might be a possibility, especially in damp conditions..

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042 puts the spark timing in bypass or limp home mode. Have a look at ED08, spark timing and see if it looks normal or stable. It should be 20+ degrees at warm idle or a little more. It should increase with rpm as well. I suspect the connecting harness is still an issue.

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  • sarookha changed the title to Rough idle and rough cruising, especially with light acceleration.

ED08, while running, was unstable, but hard to tell if that was simply because the idle (or faster, if I gave it a bit more gas) was also unstable.  Clearly not operating in Module Mode, as the spark advance should be fixed at 10 BDC in that case.

 

What was interesting was ED11, RPM, which, like the instrument panel tach, would bounce around with the rough idle, but every few seconds, would read 9999, though the engine's real rpm didn't rev up a bit. 

 

I also got the car to cooperate with a smooth idle for a few minutes, and ran the same diagnostics.  ED08 was smooth, increasing with RPM if I gave it some gas as expected..  ED11 read steady, realistic RPMs.

 

It is still giving codes E041 and E042.  Also some kind of blinking code from the SES light.

 

I checked, cleaned and tightened all of the grounds, as detailed in this site's How-To.  They all looked clean and were tight to start with, and no change after reassembly.

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All of those things are interconnected but which one is causing another item to react, or vice versa may be a head scratcher. The timing table is based on load and rpm but it is fairly coarse so the timing should be stable at idle or any fixed rpm and load without any real deviation. The rpm signal comes from the ICM too, so an unstable rpm will make the timing react, sort of self propagating.

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  • 3 weeks later...

Back to messing with this issue again, after a few weeks out of country.  Just for reference, intermittent rough running, both at idle and at speed.  Code E042 may or may not show.  Cleaning IAC, MAF, replacing coil pack, Crank position sensor, swapping in a known-good ICM all have no impact.

 

Pulled the ECM connectors off and plugged them back in, in case a loose or oxidized connection was at play.  Everything looked nice and clean.  After getting it all buttoned back up, I got about 30 miles of trouble-free driving.   Before the symptoms listed above started up again.  Oddly, they were less pronounced this time around, nowhere near causing a stall.  It puzzles me that after I replaced the coil and cleaned up the connectors, it ran fine for about 30 miles.  Now, I unplug and reconnect the ECM, and get about 30 miles of trouble-free driving. 

 

Probably coincidence, but what if there is a clue here that I'm not recognizing?  Like maybe just disconnecting the battery for an hour and reconnecting might be giving me another 30 miles of function, before it all starts sliding south again?  Or something else?

 

Or what if this has nothing to do at all with the ECM and various control modules and sensors.  Could ethanol in the gas cause problems with the fuel system that could lead to these symptoms?  The 1990 Riviera/Reatta Factory Service Manual specifically states that contamination of gas with ethanol can cause problems throughout the fuel delivery system.  They even have a test procedure to determine whether there is alcohol in the gas tank, and how to drain and clean the tank if the gas is determined to have had alcohol in it.

 

If swapping in a known-good ECM doesn't solve my problem, I may start looking into replacing the in-tank and in-line fuel filters, servicing the fuel injectors, and using only ethanol-free gas.

 

I see other posts here where folks are pointing out the lower gas mileage they get using E10, but I haven't found anyone saying that using E10 has messed with their driveablity.

 

Thoughts?

 

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I'm sort of ignoring the connecting harness approach, since it looks like a bear to get access to.  But I can practice with the parts car, and see how that goes...

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Try NOT putting the ECM back in place and leave it out on the floor. Maybe for some reason it's overheating.

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42 minutes ago, DAVES89 said:

Try NOT putting the ECM back in place and leave it out on the floor. Maybe for some reason it's overheating.

Interesting approach, I'll give it a try.  I should clarify that it doesn't always run well for awhile, before going nuts.  I just noted that after some repairs, I think all is well, until it crops up again.  But more commonly it is hard to get her started and backed out of the garage without dying.

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Maybe check your gap on the crank sensor a well and if the bolt is tight on the adjustment screw. You might be able to do both without removing the balancer. If the crank sensor moves at all you will have the exact same symptoms. I had the exact same issue, even had 2seater come over and help troubleshoot. After trying everything I crawled under the car and checked my crank sensor. The adjusting screw was loose allowing the sensor to move in and out taking me from a perfect running car to one that would barely start and run.

Edited by DAVES89
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Posted (edited)
On 6/16/2024 at 8:05 PM, DAVES89 said:

Maybe check your gap on the crank sensor a well and if the bolt is tight on the adjustment screw.

I checked the crank sensor, feels tight and aligned.  Today I plan to implement the E042 Diagnostics procedure (pg 8D1-52, 53 in the FSM).  Looks like it will point to a bad connection, or a faulty ECM (since I've already ruled out a faulty ICM).

Edited by sarookha
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If nothing else turns up, that front engine harness may be to blame. The wiring scheme is different between the 88-89 and the 90 and up. Operationally they are the same but that big silver wrapped harness across the firewall on the early models is not there, or at least greatly reduced on the later ones. While that front engine harness has some convenience to it, it seems to suffer more heat related problems, probably due to the intertwined routing under and around everything as noted. All three I have opened up had some amount of defects inside.

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i have had similar issues with going from a perfect running car to suddenly stalling, and that bucking lik you had before it died then later restart, almost perfect for a bit then not., , i have not yet checked the crank sensor , but that seems possible along with either ECU or harness issue. the plugs and coils are new, so next up for me is checking for codes. Should have done this sooner but didnt know it had that. 

where is the ECU located on these cars?

 

any progress for you since your last post?

 

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Posted (edited)

Well, as 2seater and Daves89 suggested, it seems to have been the wiring harness?  I ran a pair of bypass wires (20ga, silicone insulation), for circuits 432 WHT and 424 TAN/BLK that run between the ICM and the ECM.  I cut the white and tan/black wires about 4 inches from the ICM and ECM connectors on each end, and spliced in the new pair.  Test drive was clean and hesitation free.  As have been several other previous test drives.  And then back to the original hesitation and dying.

 

If you've read the entire thread, you'll know that I first checked the connection at the ICM.  It was really gunked up with goo leaking from a cracked coil module, so thought that was the issue.  But alas, no change with a new coil.  Swapping in a known-good ICM didn't help either.  Initially, this problem was not throwing any codes at all, which made it hard to know where else to look.  Cleaning the IAC and MAF sensor, and replacing the crank position sensor were all reasonable things to try.  But no change.

 

When the system finally began to throw the E042 code, at least that gave me some indication of where to look.  The 1990 Buick Reatta/Riviera Factory Service Manual has two pages just for the diagnosis of this code, pages 8D1-52 and 8D1-53.  The flow chart on the second page led me to "Check CKT 423 for open or CKT 424 for a short to voltage."  The intermittent nature of the problem made that hard to do reliably, so I just bypassed both circuits.  But after about 30 miles of trouble free cruising, she's back to shuddering and shaking, with the dash tach jumping around like crazy. 

 

Question for the experts out there:  Is there a pass-through in the firewall anywhere, that I can fish this new pair of wires through?  Right now I've just draped them unceremoniously across the top of the engine, wrapped them around the rear hood stop, and fished them through the passenger door into the passenger footwell.  That is not what I think of a a long-term solution.

 

Edited by sarookha
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On 6/27/2024 at 12:59 PM, radride90 said:

where is the ECU located on these cars?

For the 1990, the ECU is behind the glovebox, but you access it by removing passenger footwell "roof".  Just four small torx bolts and two wing nuts, all easy to reach.  Well, if you are limber and don't mind working upside down and partly folded in half...

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  • sarookha changed the title to Solved: Rough idle and rough cruising, especially with light acceleration. E042 Code
44 minutes ago, sarookha said:

Is there a pass-through in the firewall anywhere, that I can fish this new pair of wires through? 

I had to run a wire from the engine compartment into the inside of the car to a toggle switch. I didn't do it the expert way. I did it the easy way. 🙂 

 

If you look at the base of the steering column where it goes through the firewall you will find a rubber bellows like seal around the steering column. You can use a sharp pointed awl or similar tool to pierce a small hole in the rubber seal (smaller than the wire) and then force the wire through it. That will give a good seal around the wire and you won't have to drill any holes.

 

Someone may have a different idea on how to do it but that worked for me without doing much damage to the car.

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  • sarookha changed the title to Rough idle and rough cruising, especially with light acceleration. E042 Code

So, here we go again.  Finally swapped in a known good ECM (from the White 1990), and again, my test loop around the county was smooth.  Had I known how easy it is to drop the ECM, I would have tried this earlier.  We'll see if this fix finally holds.  Of course the White 1990 needs her ECM back, but if I can at least clearly identify the problem, then at least I'll not be throwing new parts at the problem just hoping something works.

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And after another 300 miles, looks like we're good to go.

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