Oldsmobile Silhouette Electrical / Computer Problem

Tiny
ABE_ROBINSON
  • MEMBER
  • 1998 OLDSMOBILE SILHOUETTE
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 160,000 MILES
I have a 98 silhouette with 160K miles on it. The trans was rebuilt last year by a shop that I have used for years and trust, it jost got new tires, outer tie rod ends, alignment, brakes, I replaced the A/C compresoor and accumulator this past summed using A/C delco genuine parts, it has new rear shocks, and is in real nice shape over all. The intake gasket has also been done. The problem I am having now is that the van overheats. When it overheats the guage goes all the way up to the "hot" and the light comes on. If I leave it running and immediately raise the hood, I find that the cooling fans are not running. If I shut the key off for a minute and then restart the van, the cooling fans come on at high speed and cool it down. If I drive it after that, it may work fine, or it may over heat and do the same thing again. Other problems I have noticed that seem to have something to do with this problem is that the engine surges at idle, and the transmission does not shift well. The computer set a code for "fuel system lean", I do not remeber the code number. I thought there was a aproblem with the computer and replaced it with a factory AC/Delco reman, went through the expense of having it flashed, but the problem is 100% the same or maybe a little worse. The thermostat was replaced with a Stant, by the way. I Know jumping on replacing the computer may have been a little premature, but with all the other new parts on the van, and the fact that I need it for work, I would really like this van fixed. The local mechanic shop can't figure it out either. They tell me to take it to the dealer, but my experience in the past of taking any older car to the dealer has not been good. They usually tell me a bunch of stuff is wrong with it like oil pan gasket or valve cover gasket, but can't solve my actual problem, and charge me money that I don't have. PLEASE HELP.
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Wednesday, December 29th, 2010 AT 12:10 AM

8 Replies

Tiny
JACOBANDNICKOLAS
  • EXPERT
Does the engine ever overheat when driving at highway speed? Has the temp sensor and fan relay been checked?
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Wednesday, December 29th, 2010 AT 12:20 AM
Tiny
ABE_ROBINSON
  • MEMBER
The van doesn't overheat at highway speed. I will check the relay by substituting one off of my Park Avenue, if that is possible. I have scan tool that can read live data, can I rely on that to determine if the temperature sensor is working properly?
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Wednesday, December 29th, 2010 AT 1:43 AM
Tiny
JACOBANDNICKOLAS
  • EXPERT
If you have a scanner, yes. As far as the relay, make sure the part number is the same. If it is, it will work.

Let me know what you find.

Joe
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Wednesday, December 29th, 2010 AT 6:03 PM
Tiny
ABE_ROBINSON
  • MEMBER
I "borrowed" from my local auto parts store two new relays. I still have the same symptoms. Also reading the live data it seems that the temp sensor is working fine.
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Wednesday, December 29th, 2010 AT 6:35 PM
Tiny
ABE_ROBINSON
  • MEMBER
I "borrowed" two new fan relays from the local auto parts store. Still have the same symptom. Also, the temperature sensor seems to be working fine. I took it for a long drive on the highway today. It does not overheat, but the temperature guage goes up to about 3/4, and then it drops back down to about 1/4, then slowly heats up again to 3/4, and the cycle continues. I'm not sure what is going on really.
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Wednesday, December 29th, 2010 AT 6:38 PM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Based on that, it sounds like the thermostat is reacting slowly. Have you replaced it? Now for the fans, here is how it works. The PCM monitors the temp sensor. Once a certain amount of resistance is recognized from the sensor, the PCM sends a signal to the relay which in turn sends power to the fan motors. It isn't a difficult system. Since you have replaced basically everything and have the same problem, I'm starting to question the PCM. Before doing anything with that, however, replace the thermostat. It's much cheaper.

One other question. Has there been any coolant consumption?
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Wednesday, December 29th, 2010 AT 10:23 PM
Tiny
ABE_ROBINSON
  • MEMBER
No coolant consumtion, no water in the oil, and the pressure test was good. The thermostat was just replaced, the local shop charged me $125.00 to do it, since the throttle body has to come off. They told me that they used a Stant thermostat, so it should be good, and I just replaced the PCM, but I also do wonder if it was possibly defective. It was a reman unit from A/C Delco, so it should be good.
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Thursday, December 30th, 2010 AT 1:18 AM
Tiny
JACOBANDNICKOLAS
  • EXPERT
It should be. Something tells me there is a wiring issue. The stant is one the best thermostats, and since you got PCM from Delco, I feel it should be good too. I hate to say it, but I think you partially broken wire somewhere in the system. It makes contact at times and not others.
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Thursday, December 30th, 2010 AT 6:30 AM

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