1994 Oldsmobile 88 Engine problems

Tiny
MADSMARTDUDE
  • MEMBER
  • 1994 OLDSMOBILE 88
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 170,000 MILES
Hello,

My engine lopes/hesistates at high RPMs. Runs fine at idle and low rpms. The longer I drive it the worse it gets, it will start to lope at low rpms after a while and eventually cut off all together. This is after like 45 mins of driving. If I have less than half a tank o f gas then it takes about 20-30 mins a full tank it will run longer. Ive dumped a ton of money into this trying to figure out what the problem is. Ive replaced the spark plugs, wires, coils, ignition module, egr valve, air filter, fuel filter, fuel pressure regulator. I recently took it to the dealership and had them diagnose it. They told me that the engine wasnt getting enough gas caused by a failed fuel pump. I got that replaced along with the strainer and fuel filter. After testing the car out it still did the same thing. I unhooked the fuel line before the fuel filter to see if it was pumping and it was. I checked the pressure at the engine and it was where it should be. So now im at a stalemate. Do you guys have any idea what the problem could be?
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Monday, February 23rd, 2009 AT 10:04 AM

5 Replies

Tiny
MERLIN2021
  • EXPERT
Have you had the service engine light come on? Read the codes? If it is a fuel problem, the 02 sensors might be part of it, but the MAF and TPS can aslo give these symptoms. Also ckeck the PCM grounds. Thats the black and white wire under the ignition module. Where it seems temperature related, check the engine coolant temp sensor. VIN L its on the top left of the engine VIN 1 its under the throttlebody.
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Monday, February 23rd, 2009 AT 2:57 PM
Tiny
MADSMARTDUDE
  • MEMBER
Yes I forgot to mention the service engine light did come on. It was the EGR valvle, that was replaced and the light didnt come on since. Changing the EGR valve helped it takes slighty longer for the symptoms to stop me from driving all together. I will try the other things you mentioned, is it possible that codes will still show up on a code reader even if the check engine light isnt on?
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Monday, February 23rd, 2009 AT 3:29 PM
Tiny
MERLIN2021
  • EXPERT
Not likly, but the TPS and MAF and even the ECT can be out of range, and the ECM doesnt store a codes all the time.
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Monday, February 23rd, 2009 AT 4:13 PM
Tiny
MADSMARTDUDE
  • MEMBER
Update:
I took the car to this shop that had this advanced diagnostic system that pin pointed the problem. The MAF sensor was failing, they cleaned it off and now ti runs as good as new. I wish I would have found these guys 1800 dollars ago. But on the bright side looks like im going to have this car for a while as I have replaced just about every part under the hood this past year minus the engine and transmission. Thanks for your help guys
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Wednesday, March 4th, 2009 AT 5:50 PM
Tiny
MERLIN2021
  • EXPERT
Your welcome.
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Thursday, March 5th, 2009 AT 5:21 PM

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