gmc jimmy

[g19m99c]

for some reason, my oil pressure gage was at 1/2 of what it usually is. Its usually at 40, now its a lil below 20. my check engine light just came on. i changed the oil like 650 miles ago. and doing 70mph, (dont tell the popos i was speeding), on the highway, at like 2500 rpm it felt like every second or so it would back down a lil and the rpm would lower for about 1/2 a second then go back to normal. the rpm was only droping a small amount. anyone have any input on this. its a 99 gmc jimmy.

o, and its going through gas like a mofo

[02CHEV]

check the egr valve for the gas prob, might have a pice of carbon stuck in the egr.
you might have a bad rear seal for the oil prob.

[g19m99c]

thanks for your help, ill check it out tomorow

[txarkitekt]

<div class='quotetop'>QUOTE(g19m99c &#064; Apr 23 2007, 08&#58;14 PM) [snapback]91119[/snapback]</div>

for some reason, my oil pressure gage was at 1/2 of what it usually is. Its usually at 40, now its a lil below 20. my check engine light just came on. i changed the oil like 650 miles ago. and doing 70mph, (dont tell the popos i was speeding), on the highway, at like 2500 rpm it felt like every second or so it would back down a lil and the rpm would lower for about 1/2 a second then go back to normal. the rpm was only droping a small amount. anyone have any input on this. its a 99 gmc jimmy.

o, and its going through gas like a mofo
[/b]

How many miles on it? Several things can attribute to bad gas mileage---missions related, egr, spark plugs, dirty intake, fuel filter, carbon deposits, etc.

When it comes to the oil pressure problem, there are also several factors involved---Oil sending unit, the gauge on the dash, oil pump, bad electrical connections... See? You may want to take it to a shop where they can run diagonstics. Any oil leaks?

[g19m99c]

i went to my mechanic today, and he believes the oil pressure and possible gas milage thing has to do with a bad/broken speed sensor in the trans. i guess it controles how much gas is fed into the engine at different speeds. i had my trans rebuilt, after i blew it showing off when this kid almost kicked my truck. i believer it has around 135,000 miles. last summer i had the spark plugs replaced. the air filter was a lil dirty, i got a new one today just incase. it passes state inspection in december, but that was before i put my exhaust on. he said possibly the fuel filter, i havent changed or looked at that yet since iver owned the truck. im gonna check out this trans shop maybe tomorow, because of a hard first shift after i drive for a while.
thanks for all of your help

[txarkitekt]

<div class='quotetop'>QUOTE(g19m99c &#064; Apr 24 2007, 08&#58;59 PM) [snapback]91303[/snapback]</div>

i went to my mechanic today, and he believes the oil pressure and possible gas milage thing has to do with a bad/broken speed sensor in the trans. i guess it controles how much gas is fed into the engine at different speeds.
[/b]

I am no mechanic, but I think the only "speed" sensor in the tranny is the VSS. And that really doesn&#39;t control the amount of fuel---the PCM does that by monitoring many other methods, i.e. engine load, engine rpms, air-to-fuel ratio, etc.

The VSS pretty much just tells the gauge on the dash how fast you are going (m.p.h.) and when for the tranny to shift... I would consider the other methods...fuel filter, oil sending unit, oil pump, etc.