1992 LQ1 Intermittent failure to run

[Schurkey]

1992 Lumina Euro 3.4, about 130K miles.  Have owned car since nearly-new, never any real problems besides the friggin' alternator and brake shudder.

 

Visiting a town about 120 miles away, mostly Interstate highway but some secondary highway.  Engine ran flawlessly on a day in the hottest week all summer.  Shut off engine, re-started fine after about 1/2 hour.  Returned to the first major city, got gas (shut off and re-started fine)  Visited the pawn shop next-door to the gas station (shut off and re-started fine.)  Ordered a pizza, went back to the car.  Started fine, backed-up out of the parking place about eighteen inches...engine stalls.  Won't re-start, but cranks like normal--not faster, not slower.  Various combinations of throttle position resulted in no difference.

 

I had fuel at the Schrader valve.  Sprayed all over me.

 

Attempted to pull a plug wire and watch for spark as I cranked.  No visible spark, but the test was poorly done.  Inconclusive.

 

Waited in the car for three hours (cranking the engine about every 15 minutes with no satisfaction) while a friend calls a friend and arranges for a flat-bed trailer so I can yank the car back home the remaining 80 miles.  Get car loaded on trailer, (trailer problems) get pickup truck sorted-out (pickup-truck problems) and I finally get the pickup, trailer, and my Lumina stuffed into my driveway.  Set up battery charger on trailer battery for the hydraulic lift and the electric winch  Go to bed, it's one in the morning.

 

Nine the next morning, I get the trailer tilted, offload my Lumina.  Climb into the driver's seat, turn the key, the thing starts like there was nothing wrong.  Has re-started every time since then, but hasn't moved from the driveway, and I haven't run it long enough to get up to normal temperature.

 

WHAT goes intermittent on a hot day, after hours of 80 mph and in-town driving along with heat-soak?

 

I'm figuring ignition module or crank sensor, since I had fuel pressure and the thing runs great now--therefore compression and cam timing etc. is fine.  Either all three coils went intermittent at the same time, or it's not the coils.  I lean towards ignition but really, it could be a failure to fire the injectors.  Maybe, it's not even heat-related.

 

I haven't heard of intermittent ICMs or crank position sensors.  Seems like they're generally reliable until they croak for real.  Suggestions???

[Psych0matt]

On my old Grand Prix I had a similar issue when one of the injectors would get hot it would stop firing. Although it kind of sounds like a heatsoaked ICM possibly, or one of the coils

 

Mine actually died on my way to look at a new truck a few years ago, and so I parked it at a restaurant and then came back the next day and drove it home

[Schurkey]

Ran the car today.  It cranked and ran just fine.  Left the car running while I worked on my friends' pickup.  In truth, I forgot that I left it running.  Came back an hour later, it had stalled.  It cranked but wouldn't start--same symptoms as previously.

[Psych0matt]

I would test the injector ohms, and possibly pull off the cooils and Icm and test those, im thinking it's one of those

[snippits]

Crank sensors will do exactly like you are describing.  The last crank sensor problem I had was on a 4.0 Jeep, and it was intermittent.  Just stall out, and it would crank right back up.  Then it changed to stalling, and having to wait a minute to a few minutes before it would crank.  Bought a crank sensor on Ebay for $8.99 shipped, and that took care of the problem ever since.

[Galaxie500XL]

Most likely crank sensor, a scantool is your friend here.

 

Not the most fun thing to replace, it sits at the bottom of the block, between the block and right transaxle housing. Be careful, they tend to break when removing, which pretty much means pulling the engine to fish out the broken piece.

[tsilney]

If you give it gas does it start while cranking?..my bet is a failing fpr....it's loading the engine with gas after it runs, in the morning it's fine after it sits..I had that issue on my 95..

[Schurkey]

If you give it gas does it start while cranking?..my bet is a failing fpr....it's loading the engine with gas after it runs, in the morning it's fine after it sits..I had that issue on my 95..

No combination of throttle position would get the engine to start and run...until it had cooled-off overnight, at which point it fired up like there was never any problem.

 

When it runs, it runs good.  Therefore not likely to be FPR, or individual injectors, or one--two ignition coils.  I'm now half-a-continent away from the car, so all diagnosis/repairs/fruitless parts replacement will have to wait for several weeks to a month.

 

I have ignition modules scavenged from other vehicles, and I can probably scare-up a CPS as well.  I'll look on the scan tool to see what my cranking RPM is, replace ICM or CPS, and see what happens.  That's my plan of attack when I get home.

[primergray]

Sounds Ignition Module-y to me.

[GabsOlds]

So, what happened? 

[Schurkey]

So, what happened? 

Put car on ramps, looked at crank sensor.  No f'n way I can get it out from below--and no longer motivated to try.  WTF were those "engineers" thinking?  They need a hearty bitch-slap.

 

Dealing with health-care issues with Dear Old Dad; when life settles-down, the heads come off and I'll pop in a new crank sensor from over-the-top of the engine instead of from below.  Probably drop an ignition module in there while the front head and exhaust manifold is off, also.

 

Fresh valve-job, fresh head gaskets, fresh alternator, install block heater, perform camshaft oil passage re-routing all at the same time.  Probably install upper and lower rad hoses and fresh coolant (the coolant isn't all that old, but the hoses are original.)  May do a cam-belt job while I'm in there, but the belt on the engine only has about 20K miles on it, if that.

[White93z34]

You can get at the cranksensor from the passenger side, but the alternator has to come out first. There is even room to get a dremel tool back in there - should the old sensor be stuck in. That was a fun job on my old Euro 3.4

 

Since you already verified fuel, you can try the next steps:

 

Check for spark when it is doing this If you don't have spark it should be one of 2 things - ICM or CPS. *USUALLY* if you have the tach reading during cranking it can be narrowed down to ICM. If you have a Tech1 or other scan tool you should be able to check for that in those places as well.

 

So assuming you have spark next step is to check for injector pulse. One failed injector is enough to take out all 6. I've had it happen. I've just used a 194 lamp on the injector connector in the past but they sell special lights for cheap if you are so inclined.

 

To be quite honest I've seen both injectors and ICMs cause what you describe.

[Galaxie500XL]

I'm a bit confused...the LQ1 has two crank sensors, right?  There's one just above the oil pan, between the engine block and transaxle on the passenger side, which didn't require pulling the alternator, and the 24x sensor that would require the alternator to be pulled....right?

 

I might be remembering this wrong, but the one above the oil pan will prevent the car from starting at all, but a bad 24X will generally allow the car to run, but poorly.

 

I seem to recall it took me about 20 minutes to pull the one above the oil pan and replace it, once I had the car on ramps.

 

 

[White93z34]

The second one you describe was new for 94-97 engines 91-93 only had the one in the block.

 

Likewise the 91-93's had no cam sensor

[carkhz316]

Sooo, any verdict. (I could bet money on a fuel injector, and since these are batch fired from one driver, a shorted injector would shut down all 6 as mentioned above).

[GabsOlds]

Thanks for the update, Schurkey! Hope your dad gets well. Let us know how this gets resolved, once you get to it.

[Schurkey]

Thanks for the update, Schurkey! Hope your dad gets well. Let us know how this gets resolved, once you get to it.

Spent a month in California getting his house ready for sale.

 

Dad is now resting peacefully underground.

 

Another couple of weeks or so, and I think I'll be ready to rip the heads off.  When the rear head comes off, the crank sensor should be easy.  Replace sensor, replace alternator, install block heater...all before the head is reinstalled.  Similarly, when the front head is gone, the ICM and coils will be easy.  I'll swap the Lumina ICM 'n' coils for Dad's 3.1 Monte Carlo's ICM 'n' coils.  If the Monte becomes temperature sensitive, I know it was the ICM.  If it doesn't, I know it was the crank sensor.

 

Yes, I'll update this when I have results.  Photos, too.

[Schurkey]

Sooo, any verdict. (I could bet money on a fuel injector, and since these are batch fired from one driver, a shorted injector would shut down all 6 as mentioned above).

I thought they were fired in two groups, not one.  Am I wrong?

[RobertISaar]

they use two pins on the ECM connectors, but internally they're connected to the same driver. the 16149396 only has one actual injector driver populated(though the board traces do still exist to add in a second driver).