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Discussion Starter · #1 ·
91 trooper, 2.8

A few nagging issues...wondering if any are related...and what you'd try first.

1. My oil gauge used to always read around 55...now it's consistently 30 (could be the guage, seems to be running fine)
2. My mpg used to be consistently around 18...now it's consistently 15
3. Any time it's humid and cool and I run at a consistent 2nd or 3rd gear speed...my check engine light comes on...stays on for a minute and seems that pushing the pedal, changing up the speed helps it go off.

I don't notice any loss of power. It doesn't seem to be using an unusual amount of oil. I haven't replaced MAP, EGR. I've tried to get the codes read...but I'm told at every place I go that they don't have the computer for my age vehicle. What would you try first?
 

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#3 is most likely a bad vacuum hose somewhere that will be next to impossible to find, buried under tons of other stuff.
#2... Ethanol! Everybody's mileage has gone to crap since they forced that junk on us.
#1 I'll let the experts speak here. My first thought is a bad sending unit to the gauge.
 

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When my oil pressure gauge goes down from where it normally sits I check the oil...typically its a half quart low, must be a really sensitive system. When I put a half quart it in, goes right back to where it normally sits. Check oil level!
 

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my 99 was doing something similar to yours, egr was the culprit, not only the valve but the tube was clogged too, a valve and tubes cleaning took care of it
 

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Hey man nice trooper!! I am in the Maryville area and I am looking for a nice first gen pretty soon. It is nice to see other people with similar interests locally. We have a 1998 trooper that we love and want another one. Maybe once I get one we can wheel a little together.. Peace

Pete
 

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You don't need anything more then a paper clip or jumper wire to read your codes. Do a search on here and I'm sure you'll find it, just running a jumper in to a plug that's located in your center council beneath the tray. You then count the flashes of your cel to determine the code. On the cel, my first guess (and only a guess until you read the code) is your VSS, mine does it too.
Here's a link to one thread, there are others if this one doesn't do it for you.
viewtopic.php?t=47126
 

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Its just like described above, I used a short chunk of wire myself. Remember is going to flash 12 three times. Its like saying hello to the system components. When you get the stored codes then post them and about anyone will be able to tell you what it means. My old Chiltons has a section telling what the codes are, Like above I usually get one for the VSS and have just ignored it. Gonna have to address it someday.
 

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Discussion Starter · #8 ·
Thanks to all...what a cool tip about checking codes...never knew. I'll post when I find.
 

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Try changing your oil to a heavier weight and see how the pressure behaves. If it stays the same, I would say something is wrong with the sending unit, if it changes and gets higher, I would look at possibly replacing your oil pump at some point.

Bart
 
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