97 SE in the shop.... mechanic stumped *updated* - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


1992-1999 Series I L27 (1992-1994 SE,SLE, SSE) & Series II L36 (1995-1999 SE, SSE, SLE) and common problems for the Series I and II L67 (all supercharged models 92-99) Including Olds 88's, Olds LSS's and Buick Lesabres Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

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Old 10-28-2006, 08:28 PM   #1
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Default 97 SE in the shop.... mechanic stumped *updated*

Car runs OK till it gets hot then starts hesitating big time. That lasts for a few seconds then the car idles down and just dies. Starts up no problem but only for a second or two then dies again. Funny thing tho, it makes a weird scraping sound when it dies as if the engine is being turned in the opposite direction. After it cools down again it runs fine but eventually acts the same as it heats up. THe whole time there is a funny whirring noise coming from the airbox area. Brand new fuel pump, filter, strainer, wires, LIM, UIM. THe car is showing codes for MAP and crank sensor. ??????? vacuum leak perhaps. Will a scanner pick that up?
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Old 10-28-2006, 08:56 PM   #2
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are you sure you mean MAP and not MAF? just making sure you mean Manifold Absolute Pressure sensor or do you mean Mass Air Flow sensor? I am wondering because you said near the airbox area, and that would mean MAF to me, but then again the MAF is not a mechanical sensor, so that is a little odd.

but MAP does sound possibly right. it could be that the MAP sensor is acting up when its hot and not reading the vacuum pressure correctly? this sounds...kinda right, being that the MAP does control fuel flow and could be causing the engine to stall.

although I do know the crank sensor can act up when the engine is hot when it starts to fail, and the MAP would control fuel flow in conjunction with other sensors...so I would say replace both if its giving you a code.
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Old 10-28-2006, 09:05 PM   #3
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Here are the part links from Checker just to save you some time.

I personally have heard some problems and have experienced problems with the GP Sorensen sensors from checker/advance so I gave yah the links to the Niehoff ones instead.

MAP SENSOR

CRANK SENSOR
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Old 10-29-2006, 01:32 AM   #4
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Quote:
Originally Posted by wjcollier07

....this sounds...kinda right, being that the MAP does control fuel flow and could be causing the engine to stall.
The MAP sensor does not control fuel flow; the PCM does. The PCM receives data from the MAP sensor along with the other sensors in the loop. Based on this information, it makes the final decision on spark timing and fuel flow. Kind of like the president and his top advisors.
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Old 10-29-2006, 02:12 AM   #5
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Please give us the number designators of the actual codes being pulled from the PCM. That would help narrow things down.

I think if there were a vacuum leak the car would be hard to start. Has your mechanic tried swapping a known good MAP sensor onto the car? Honestly, I don't know how much the MAP figures into the PCM equation for fuel, timing, etc. In general, though, it sounds like the car might be running fine in open loop (when the PCM uses preset data), then having trouble in closed loop (when the PCM bases engine operation on sensor input). I would suspect some kind of sensor failure in this case.
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Old 10-30-2006, 09:09 PM   #6
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this sounds like something similar to what was wrong with my z24, cept my z24 wasnt throwing codes, it had a bad o2 sensor
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Old 10-30-2006, 09:12 PM   #7
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You said the engine is making a weird noise. Have you checked out the harmonic balancer?
And to rule out the maf, unplug it and see if it runs better. It will just use the map.
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Old 11-17-2006, 04:17 PM   #8
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According to the mechanic it was the MAF sensor that caused the car to break down. The MAP was bad too, and there was a vacuum leak somewhere. Car runs better than ever. Much much faster than it ever has been.

About the MAF... mine was bad for months I was just too lazy to replace it. Then I bought one on ebay that was bad as well. According to the mechanic there are degrees of 'bad' so the badder MAF coused the car to break down.... ....whatever... car runs awesome now.
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Old 11-17-2006, 05:32 PM   #9
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Glad you got that figured out. It almost had to be a sensor, based on the fact that it was having trouble when it went into closed loop. Good deal.
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