Stupid Car

THought I finally had my intermittent problems fixed.......BZZZT

Have been driving the car around the neighborhood and taking longer and longer jaunts in it as my faith was slowly being restored. Last 2 weeks have driven it about 8 times and put about 130ish miles on it.

Ran flawlessly until this evening. Got home from work and hopped it in and it fired right up. Headed over to West Marine but they closed at 6 (was 6:10). So I just drove through the parking lot and back out towards Home Depot.

The check engine light popped on for a second and went out and the engine didn't hiccup. A couple blocks from Home Depot it died at a stop sign and tried 2x and crank, no start. Busy intersection so I jumped out and pushed it off the road. 15 seconds later it started but roughly then raced for 3 seconds and settled down. I turned off the AC and drove to HD.

Went inside and bought my silicone and 5 min later came out and it wouldn't start. I tried all the tricks I used before and nothing. Walked 10 min home and got a tow strap and went back (now 25 min later) and still no start so dragged it home and pushed it into its spot before the trick or treaters started showing up.....

Car is pissing me off! A couple weeks it the INC picnic in Orlando (200 miles) and I want to go with a wagon full of parts to sell. (clean out the garage).

John

I'm sure you have, but have you checked the grounds on the thermostat housing?

Tom

The LT1 doesn't have any grounds on the Thermostat Housing.

94Woody wrote:

The LT1 doesn't have any grounds on the Thermostat Housing.

??? My 94 Caprice does.

have you checked the coil and or the ICM?

goldwolfnhn wrote:

have you checked the coil and or the ICM?

replaced the coil, egr, fuel pump and sending unit as well. opti vent harness is new (PO put it on, but youu can tell its new as it's still bright and shiny lol

replaced water pump temp sensor and cleaned up the connector there as well.

Crazy part is it'll run fine then take a ****, so I doubt it is fuel or spark related. Has something to do with the computer (removed it and made sure all connections were clean and tight) or sensors feeding it.

Didn't have time look at it tonight.

Tom, I will check all my grounds as well, but don't think that's it either.

well on my 89 crew cab after my brother shorted out the electrical the truck would crank but not start after we put a new positive battery cable to replace the melted one, I put a ICM on from one of my surburbans and the truck started right up, that's why I also asked about the ICM as if the ICM is going out it can't control when the spark goes out so the car won't start. I've also heard from others that had intermitten issues that for some of them it was the ICM starting to fail.

sadly if it's the factory ICM it's riveted in so the rivets have to be drilled out before it could be replaced if it turns out that's the problem

Sprocket wrote:

Tom,  I will check all my grounds as well, but don't think that's it either.

John, it probably isn't it, but who knows.  On my tan Caprice wagon, I had occasionally hard time starting and running rough.  I checked those grounds, which have about 4 ring terminals under the bolt.  One of them was held on by a thread, redid it, and it cured all ills.  Pretty rinky dinky system for grounding.

Good Luck

Tom

I have a wifi transmitter that plugs into the OBD2 port (OBDLink MX) and will compile a continuous log of all engine sensors on my phone while I'm driving.  Neat device, and not expensive ($79).  At least you'd know what the PCM is seeing leading up to, and during the car taking a ****.

See: https://www.scantool.net/obdlink-mxp/?gclid=EAIaIQobChMI8ufM0aHL5QIVy56zCh2HGwB3EAQYAiABEgKi-PD_BwE 

Ya gotta catch 'em in the act.

Coil
coil wire
ICM
ICM grounds (little brittle wires, just like Tom said)

silverfox103 wrote:

94Woody wrote:

The LT1 doesn't have any grounds on the Thermostat Housing.

???  My 94 Caprice does.

Interesting. My 94 didn't and my current 95 also only has bolts on the Thermostat housing on the water pump.





My LT1 ground wires have always been on the driver side front corner beside the coil setup.

Well after talking to Sherlock9C1 he is convinced its my ICM, so I sucked it up and just bought on on Rock Auto. Also bought a spare Serp belt tensioner for $9 on closeout. I think there is one left.

Figured it'd be good to have a New spare as they have gone on several other cars I've had.

Fingers croseed this is it. Went out tonight and it fired right up.

94Woody wrote:

My LT1 ground wires have always been on the driver side front corner beside the coil setup.

That could be correct, I had the issue about 8 years ago and went by memory, but John got the idea.

Tom

Jury is still out, as I only drove it about a mile since swapping ot the ICM on Sunday morning (before breakfast no less). Rained on Sat and got the old one off, then the rain came, so Sunday I woke up at 7 and it was sunny and nice so I got right on it.

Family stuff and etc all day and worked today. Took to Home Depot and Target, but it never got warm. Ran fine. Will start venturing further.

found out, it's easy to remove the ICM while the heat sink is on the block, but damn near impossible to put it back on (had to pull the whole heat sink off then it was cake).

kinda wondering if the issue was that one of the screws holding it on the heat sink was loose and it just overheated. I put the new one on anyway and used thread locker on the screws.

You used thermal paste like Arctic Silver under the ICM, correct? Not dilectric grease (the FSM is wrong, btw)?

jayoldschool wrote:

You used thermal paste like Arctic Silver under the ICM, correct?  Not dilectric grease (the FSM is wrong, btw)?

Yes, this. Dielectric grease is an INSULATOR used primarily for sealing out moisture. thermal paste is completely different.

ICMs will run very hot without proper conductive cooling... but they'll degrade faster. If you want to experiment, take one to an auto parts store and have them test it, then feel how hot it is. That's why bolting it to the front of the cylinder head actually COOLS it. Air cooling is insufficient for this part.