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Discussion Starter · #1 ·
My 98 PAU now has 163k miles on it, but recently it started acting up. A few weeks ago while I was cruising at 30-35mph, the engine just died on me. The tach and speedo were still working, but the engine itself had cut out totally. I manhandled it into a parking lot, put it in park, turned the key off and then back on and it fired up without a hitch.

I drove it to my mechanics to tell him what happened, I was thinking I had lost fuel (pump is going) or spark (lose wire somewhere). He told me I probably just needed to clean my throttle body with the right cleaner and a toothbrush, so I followed his advice and cleaned it as best I could in my driveway.

The car was fine for about two weeks when one night while going about 40mph I saw my tach had dropped to zero. The engine was still running and the transmission was shifting fine, but the tach was dead. This problem also corrected itself after a stop and restart. This happened to me a few more times and I wasn't sure what to make of it.

Then on Monday, again while going 30-35mph, the engine died and so did the tach.

My mechanic has been doing research while I've been doing google searches, and from what I can tell, it sounds like it's most likely the fault of my CPS, but there are no trouble codes in the computer pointing at it. I've read stories of others having the same problems with their 3800 (stalling with no idiot lights/codes) and replacing the CPS did the trick for them.

So what do you guys think, am I on the right path or am I barking up the wrong tree?
 

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It's always tough to troubleshoot an intermittent issue but the CPS is a likely suspect.
The tach dropping out is one sign of a bad CPS or its wiring--either at the CPS or at the ICM connector.
Usually it is noticed when the car fails to start and the tach sits still when cranking.

GM service manuals state that a sudden failure of a component will often not set a code.
 

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Many times the Crank Position Sensor will fail when it gets hot.
After the engine cools, the car will start, That is classic.

Another telltale sign is that the tach cuts to ZERO. If the engine cuts out more often after it is plenty warm, the sensor may be failing.

Now is a good time to clean all your engine grounds and battery connections.
Make certain they are definitely tight. Electronics get flaky with an intermittent loss of ground.

Best of luck
Cheers
 

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Discussion Starter · #4 ·
It's always happened when the engine is relatively cold. It will have been running for maybe 5-7 minutes depending, so with the exception of the first time the tach dropped out, this has all happened to me on the same stretch of road not too far from my house around the same point.

That is the only real consistent thing. I don't have a problem after I start the car back up.
 

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Is the car only run on short trips?
Perhaps the CPS reaches the failure threshold at a relatively low temperature.

I would carefully check the connections and wiring at the CPS, the ICM and the ECM and ground wires.

Corrosion, a loose or partly backed out connecter or wiring insulation that has rubbed off are not uncommon as cars age.

Part 1 -How to Test the 3.8L GM Crank Sensor With a Multimeter

Read through this article, as it shows which wires the tach signal travels through.

You might find its "Real Life Case Study 1" at the end interesting.
 

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Crank sensor diagnosis

I have had some results with "tap testing" the crank sensor bracket. I use a long extension and barely thump the mounting bracket while the engine is running and sometimes if the sensor or connectors are bad, the engine will die.

The connector terminals get collapsed easily after pulling and unplugging numerous times. The female terminals (chassis side) shouldn't have more than .035" opening. If they are collapsed you can get a pigtail for the wiring harness. Be sure to solder, shrink tube, and wrap any wiring splices.

Sounds like a crank sensor to me. Keep an eye on that tach. If the tach drops, then the sensor is the likely culprit.
 

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Discussion Starter · #7 ·
I had the CPS replaced yesterday, and so far the problem hasn't returned, but all I can do is keep driving it to see if that really was the cause. Also something I want to note, the old sensor was actually cracked near where one of the mounting ears meets the main sensor area. It was barely noticeable and wasn't till I pointed it out to my mechanic that he saw it as well.

When I tried to pull it apart a bit so I could get a picture of it, the ear broke right off, so clearly the crack went deeper and further than it first appeared. I don't know if that was the main cause, maybe the crack was causing it get just slightly out of alignment, I'm just spitballing here.

Thanks for the help guys, it's appreciated.
 

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Discussion Starter · #14 ·
Just checking back in after several more months and the problem still has yet to return. My butt still clinches anytime I drive past that stretch of road where the car kept crapping out, but it's been golden since the new sensor went in.
 

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It's always tough to troubleshoot an intermittent issue but the CPS is a likely suspect.
The tach dropping out is one sign of a bad CPS or its wiring--either at the CPS or at the ICM connector.
Usually it is noticed when the car fails to start and the tach sits still when cranking.

GM service manuals state that a sudden failure of a component will often not set a code.
Hi MikeK not sure if you are still posting on this site and I have never used one of these before but need to find out where I can locate a GM service manual that states 'a sudden failure of a component will often not set a code'. I was in an accident nearly died due to Holden Commodore stopping dead no power no brakes no steering and am suffering consequences of that accident. However, the car had done that several times and I returned it to Holden Service Centre and they refused to check the crank auto sensor because it would cost $300-400 and the code did not indicate a problem!!!! They just 'wiggled and crimped a wire' returned car to me after 4 times in their centre and unfortunately the fifth time I was on a major road and got smashed. Fortunately no one else on the road at the time was injured just me and the car a write off. Life has not been the same since but I am determined to make these ignorant, arrogant, incompetent and disgusting people accountable as their actions put every road user at risk.
Any information would be greatly appreciated. Stay safe BD
 

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BD, not sure if you'll find that exact phrasing (you won't), but the GM manuals will list the timeline of when each DTC will get triggered and set a light. Not sure if it'll help your situation, but try getting your hands on a used set of the book manuals from your exact vehicle, and read the articles for the specific components you're concerned with.
 

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Dear dezldave961 Thank you for your courteous and polite response and information. Apparently on another site I have no right to ask questions and response was extremely rude and after the first one I then received the second stating I was obviously taking Holden to task and apparently according to those 'gentlemen' that is not acceptable. In my world putting a car back on the road 5 times which stops suddenly in heavy traffic with potential to cause an horrific accident endangering the lives of every person on the road is unacceptable. Thank you again for your civil response and will check out the information - greatly appreciated.
 

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Hi MikeK not sure if you are still posting on this site and I have never used one of these before but need to find out where I can locate a GM service manual that states 'a sudden failure of a component will often not set a code'. I was in an accident nearly died due to Holden Commodore stopping dead no power no brakes no steering and am suffering consequences of that accident. However, the car had done that several times and I returned it to Holden Service Centre and they refused to check the crank auto sensor because it would cost $300-400 and the code did not indicate a problem!!!! They just 'wiggled and crimped a wire' returned car to me after 4 times in their centre and unfortunately the fifth time I was on a major road and got smashed. Fortunately no one else on the road at the time was injured just me and the car a write off. Life has not been the same since but I am determined to make these ignorant, arrogant, incompetent and disgusting people accountable as their actions put every road user at risk.
Any information would be greatly appreciated. Stay safe BD
Hi MikeK thank you for responding and for your information, greatly appreciated. Every mechanic I spoke to said this service centre should check the crank auto sensor but the manager refused each time I asked for that to happen and excuse was 'too expensive'! Nothing is 'too expensive' if it is going to save lives. Thanks again.
Stay safe
BD
 

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Dude, who are you replying to? Have the bots gotten this good? Dang, I might have to shift my filter ideas closer to human.
 
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