94 4.6L Northstar stalls after warmup

[AlanK]

Hi Folks,
I have recently taken on my dad's 94 Eldorado. It is a wonderful car and a joy to drive. However, it has a problem that I can't seem to fix. I've been searching the forums and seen lot's of different suggestions - I'm hoping someone can give me some direction on what I've missed.

1994 Eldorado Touring Coupe 4.6L N*
P032 Current
P071 History
P095 History

The car starts and drives normally while warming up. The problem occurs when I stop somewhere for a few minutes. When I come back out and drive off, the engine will die. Sometimes the PCM is able to rev the engine up to ~1500 rpm and keep it from dying (up down up down etc.), other times it will rev up momentarily before dying, but most of the time it just quits as if I turned off the key. Once this happens it is very difficult to get the car to start, even harder to keep it running for more than a second. The motor can then sit for 30 minutes and then will run normally again. These problems also manifest after about 20 minutes of highway driving, though it is not as prone to dying because of the higher engine revs, it will just jerk and sputter for a while.

Map sensor has been replaced along with fuel pump, FPR, plugs, plug wires (non-oem), coils, ICM, fuel filter & TPS. EGR has been cleaned. I'm out of ideas (and money) so if anyone has a suggestion I would really appreciate the help.

[Ranger]

P032 (E032) ................................................. Open MAP Sensor Signal
P072 (E072) ..................... MAP sensor signal change without TPS signal change
P095 (E095) .................................................. Engine Stall Detected

Sure looks like a bad MAP sensor. Have you checked the wiring? How about the manifold gasket? Cleaned the TB and the EGR "mouse holes" in the manifold?

[AlanK]

Thanks for the reply Ranger. The TB is clean. I'll have a look at the wiring and gaskets.

[roger greeb]

odd..i came here for similar prob. my 97 seville sls has been runnin like a top..finally...last nite driving normally to work not a lead foot anymore..it was raining and around 45 degrees outside..coldest day here so far..anyway car ran fine thru the city as normal..about three miles and stop lites..came to stop lite rolled to stop for rite turn on red...without warning the car just STOPPED ..odd..it started rite up...proceeded about a mile to work..no missfire..nothing..pulled into a parkin place..still in "D" and for about 5 secs. a small surge, then car died again..started rite up..ran...then again..it died..after work of 5 hours..no rain car started and ran fine all the way home and back again no prob. what in the world would cause such a problem..lack of fuel i would figure it would loose power or missfire in driving..is there a sensor or some item i should look for on this caddy with a mind of its own?

[Ranger]

The fuel pump could be failing intermittently, but start by pulling the DTC's.

[AlanK]

Hi Ranger,
From what I can tell, the plenum gasket/plastic spacer on top of the engine may not be sealing properly, the thin rubber gasket has some flat spots in it. The symptoms have gotten slightly worse since my inspection and causes me to think that this is the problem. Do you know if this is a dealer only item and what the official name might be? I've looked on-line but can't seem to find any references to what this gasket is called.

[Ranger]

I'm just guessing here, but I'd call it the intake manifold cover gasket. I would think you could find it anyplace that sells engine gaskets.

[AlanK]

Update & solved:
Be warned about the troubles that an intermittent sensor failure can cause!

My MAP sensor, less than a year old, had a bad connection inside which would cause it to behave erratically. It would output a steady signal with a hand-held vacuum pump and over a range of pressures. However, if you were to lightly tap on the sensor (on one side only), the signal would fluctuate, sometimes shorting out entirely.

A secondary issue was the intake gasket around the decorative plenum. It was not sealing due to some flat spots in the gasket. The gasket is molded into the plastic plate holding the fuel injectors, map sensor and FPR. Unfortunately I could not find anyone local who could get it. The Caddy dealer wanted $190, the Chevy dealer cut me a break and I got it for $155.

Final question: Does anyone have any experience with non-OEM MAP sensors? Am I better off ordering an AC-Delco MAP or continue to use the new one I bought this morning (it's manuf. by Wells Manufacturing) as it seems to be working OK.

[Necrosan]

Don't replace it again if the problem seems to be gone. Just more money down the drain for a fixed problem..

[AlanK]

OK - Thx.