When I put my tracker in park or neutral, the engine surges or lopes.

Asked by Mar 26, 2013 at 10:47 PM about the 1994 Geo Tracker 2 Dr LSi 4WD SUV

Question type: Maintenance & Repair

Just got my tracker and it runs fine until I put it in park or neutral, then the engine lopes from high rims back to
regular rpm's. seems to do this more when the engine is warm.

22 Answers

Let's start with the PVC valve, it is connected from the valve cover to the intake tube...pull it and jiggle it like a maracas, should be nice and wiggly, if it makes no noise it is plugged with oil residue and should be replaced. They are usually about seven bucks~ try n see if your positive crankcase ventillation valve PCV valve is all that...thanks, post again when you find out----thanks...judge

1994...rubber can degrade and leave us with an assortment of vacuum operated equipment failures...be expectin' a few dooozies~

Best Answer

if we get around to it, the EGR valve (exhaust gas return) causes the engine to inhale exhaust on de-celeration...on DECEL...if it ain't flappin right, cause the vacuum has been comprimized or is buggered up with carbon will cause surging and ill-performance....the MAP sensor checks the state of the combustion gasses to see if it's pollutin' right.

I changed the PCV and there was no change. While in park or neutral, it still lopes from 1500 rpm to 2000 rpm.

2 of 2 people found this helpful.

can you find the EGR valve? some of them are behind the motor, yet in front of the transmission...there will be an exhaust connection and a intake manifold connection and a vacuum hose connection.

no CEL (check engine light)? someone suggested rather rudely that it was the catalytic converter what was plugged, and I thought there would have to be a CEL if this were the case~

1 of 1 people found this helpful.

No check engine light.

1 of 1 people found this helpful.

I'll check the ERG next.

1 of 1 people found this helpful.

Yay, there is a vacuum hose to it, see if it's still holding vacuum.

1 of 1 people found this helpful.

Still looking for that darned vacuum leak

1 of 1 people found this helpful.

you could take a propane cylinder and run the engine, wave the cylinder across all the vacuum lines, when you get a sudden acceleration there's the culprit....unlit...of course!


If you cant find a vacuum leak check the TPS (throttle position sensor) I had the same issue with a vehicle I owned and thats what I found to be the problem there. Same symptoms as you are having. Good luck

when I say cylinder, yes a cylinder with an unlit propane torch on the end of it....you probably knew what I was talkin' about anyways...this is an old trick we'd do at the shop to find a vacuum leak and feel honored to be able to share this diagnostic 'cheat' :)

remember boost in acceleration = suckin' propane instead of ambient atmosphere~

let's take a look at how to test the TPS, kudos Patroler16...happy to learn something new everyday, this might be a challenge to find this kind of info~

My son told me to use break cleaner to locate a vacuum leak.i do have the small propane tank. I'll use that.

no ignitors nearby, you probably do value your eyebrows~

brake cleaner is probably the green can and not flammible, if you're gonna go this route gotta use the expensive stuff. Propane gas is hella cheap, yes, I'd take the chance just be well ventillated there, we don't wanna blow up. propane is heavier than air!

the tps is a tempting offer, but looks like a variable resistor type endeavor, no trouble codes with this is excluding this in a big hurry.

That did cross my mind, but didn't want to rule out anything.


1 of 1 people found this helpful.

that wasn't too helpful. will have to do more~

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