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2002 Chevy Trailblazer Gauge malfunction & engine light

Tiny
FRAN PARK
  • MEMBER
  • 2002 CHEVROLET TRAILBLAZER
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 160,000 MILES
I started having a problem a year ago with the oil pressure gauge dropping to "0" when at a stop, and them going back to normal when I accelerate. The Service Engine light also came on and stayed on. I had it looked at and was told "get another car." That wasn't an option, so I took it somewhere else. They put a used motor in it, and it was okay for about a week, and then the oil pressure gauge started doing the same thing again. Then two weeks later, the Service Engine light came on again.
So $2500 later, I have the same problem I had before.
What's going on? A different motor, a new oil pressure switch, and nothing's changed. Is this a computer issue?
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Monday, August 30th, 2010 AT 8:41 AM

8 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,179 POSTS
Well first of all. I really question why the first engine was replaced. When the oil pressure gauge drops, do you ever hear a knocking or ticking from the engine this one or the old one?

Joe
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Monday, August 30th, 2010 AT 9:23 PM
Tiny
FRAN PARK
  • MEMBER
  • 5 POSTS
The old engine had other problems. The lifters were very loud, the car was starting to stall out while I was driving it, it idled very rough at a stop. I had three different mechanics look at it and put it on the diagnostic machine, and they all said it had a timing chain problem. The first mechanic's solution was to "get another car." The other two said it would be just as cheap to replace the engine as it would be to fix the timing chain.
Since I didn't want to buy another car, I decided to try a different engine. Yesterday the engine light went off. The oil pressure gauge stiil drops to zero when idling, but not all the time, and not every time I stop.
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Tuesday, August 31st, 2010 AT 7:52 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,179 POSTS
Wow! A timing chain is about 50.00 plus labor. REgardless, when the pressure gauge drops, do you hear any ticking or knocking from the engine?
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Wednesday, September 1st, 2010 AT 8:06 AM
Tiny
FRAN PARK
  • MEMBER
  • 5 POSTS
I'm not talking about timing belt, I'm talking about a timing chain, that requires tearing the engine down to get to. There is no ticking or knocking when the gauge drops.
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Wednesday, September 1st, 2010 AT 10:51 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,179 POSTS
The chain is about the same cost for the part. If you are not getting any noise when it drops, that is a good thing. I would recommend replacing the oil sending unit to see if that takes care of it.

Let me know.

Joe
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Wednesday, September 1st, 2010 AT 11:20 AM
Tiny
FRAN PARK
  • MEMBER
  • 5 POSTS
Is the oil pressure sending unit different from the oil pressure switch? The mechanic replaced a part that wasn't very big, and had a wire connected to it. Where is the oil pressure sending unit?

I keep getting the feeling that when this is all said and done, I will be replacing the computer. Please tell me it ain't so.
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Wednesday, September 1st, 2010 AT 12:39 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,179 POSTS
They are the same part. AS far as a computer is concerned, the only one that could have an affect on this is the body control module. AS far as the gauge, if the sending switch is new, my guess is the gauge itself is bad. However, before I would replace the cluster, I would recommend checking wiring from the oil switch. Remember, if you don't hear knocking or ticking, there isn't an oil pressure problem.
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Wednesday, September 1st, 2010 AT 12:51 PM
Tiny
FRAN PARK
  • MEMBER
  • 5 POSTS
Seems to me that whether its the gauge or the wire, I'm getting bad information. There is no difference in the engine idling no matter what the gauge is reading. Like I said, it hasn't blown up yet. I think you have told me what I wanted to know. Seems like a lot of work to have to replace the whole cluster for one bad gauge. I'll get the wiring checked first. Thanks.
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Wednesday, September 1st, 2010 AT 1:23 PM

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