98 Malibu stalls hot won't start


ShadeTreeJack
07-06-2012, 06:47 PM
My 1998 Malibu starts and runs good. I hear a misfire but doesn't set a code. When it was 103 degrees last week, the car drove fine. I stopped for a few minutes then it would not start. soon it started but stalled and would not start until it had a chance to cool. it has been hot out everyday since then and I have the problem every time I drive it. most times it sets a P0341 DTC along the way, but usually can keep driving. Then It 'skips' like it going to quit, then goes for a few more seconds, then dies. The I need to open the hood and wait 45 minutes.Now every time I drive it, I need to open the hood or let it sit for an hour.
If I don't stop, I can keep driving.

I have replaced the Cam Position sensor. cleaned and added fresh thermal grease. swapped the ICM from the old engine(long story), swapped the coil packs from same. checked and moved the crank postiion sensor harness away from the exhaust - it was touching. moved the plugwires away from the CPS harness. cleaned the IAC and intake, MAF.
I have same fuel pressure when it wont start as when iot does: 40-42 psi. I have no spark when it wont start. I replaced the Crank sensor last year when I replaced the engine. I have a basic scanner and can read a few parameters. tps, and maf, map all seem to be working OK.

based on all the things replaced/swapped what could this be?

I replaced the head gaskets about two months ago. it was running great. Now it runs great, but has that slight misfire when idling.

Tech II
07-08-2012, 03:39 PM
3.4?

ShadeTreeJack
07-09-2012, 02:04 AM
3100. there wasn't a 3.4L in 98, not in the 'bu anyway. the 3.4 and 3.1l have the same controls.
when it died yesterday, I did more testing: the CAM position sensor harness from the pcm had 12V, and the crank position sensor in the block had the correct ohms. Today I replaced the crank position sensor behind the balancer. Although this is the exact symptom that has led the crankPosSens on two of my 3800's, I resisted replacing this one because it was only 18 months old, not 13 years old like the 3800's ( 92 bonneville, 98 Camaro). I found a groove cut into it as if a piece of debris got caught in there. but not deep enough to go through the plastic casing. We'll see tomorrow: I know I can drive it to work and back, The test comes after a drive + a 20 minute 'soak'..

ShadeTreeJack
07-09-2012, 11:33 AM
Car died on the way to work. Since I had my VOM with me, I did a few tests while waiting for the cool down. The Crank Position Sensor (CKP) that is installed in he block had 25 - 60 ohms when it wouldn't start and 1260 ohms when it did. happened twice. Coincidence? I think not. Sensor is only 18 months old, so again, I was looking elsewhere. AZ has one on hold, 20 bucks. I'll update to let you know. Hope this helps someone else root cause.

Tech II
07-09-2012, 06:01 PM
Your vehicle has two crank sensors....usually when it won't start and has no spark, it's the one in the back of the block.....

ShadeTreeJack
07-10-2012, 01:50 PM
Yes, that was it. The resistance would drop to 25 ohms when it stalled, slowly climb to 50 or 60 then jumped to 1260 at which time it would start. Between the fact that the sensor was new 18 months ago and the ohms checked ok the first time I check it, I was thrown off. I MUSt have checked the ohms after it had time to cool. Thanks for your help. Please look for my 98 Buick 3800 Smokes BAD! post I am about to start.

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