having problems with 94 Geo Tracker.....

[DJAthens]

I had the same mysterious bucking problem and tried many of the fixes listed on this thread to no avail. I tested the TPS and found that it wasn't working correctly around 2200 RPM, so I got it replaced and it worked great for a while, then the bucking came back, at first softly, then noticeably stronger. We took the truck back to the dealership who installed the TPS and they had it for three days scratching their heads until they found the problem.

It was the wire that leaves the TPS and goes to the ECU. It travels in a wiring harness under the throttle body towards the front of the vehicle, then turns downwards and goes under the intake manifold and back to the firewall. What had happened was the TPS wire insulation broke down and was grounding against the intake manifold. This over time "burned" a patch on the TPS sensor at the most common RPM we drove at, and eventually that area was so damaged that it didn't send information back the ECU, causing the bucking problem.

The dealer simply spliced a new wire and ran it directly to the firewall, outside of the harness it usually goes through. We've driven it for two months now with no problem at all!!!

To all of our credit, they had their top service tech (reportedly one of the top techs on the whole west coast) on our Tracker for three days before he tracked it down, it was even stumping him!

I know this thread is kind of old, but I promised myself that I would post this information in the hopes that it helps someone out. We lived with this problem for eight months, and it truly sucked. Glad to have the Tracker running strong again.

Cheers,
DJAthens

[Casey6602]

To "94Twacker"!
I have been having the exact same problem as you did except I have an automatic '94 Tracker. I tried disconnecting some of the wires to the computer under the dashboard yesterday but nothing changed. Is there any wire in particular that you feel is the "main" connection to the computer? I'd be grateful for any particulars you can offer on what your mechanic did to fix your problem. I love my car and when it runs, it runs GREAT. This has been a real stinker to figure out but your posts here have really helped. Thanks for sharing your information!

[Sgt Mack]

As questioned by a previous poster, if the Tracker stalls at stops and especially if it has been running for about an hour, you might check the coolant sensor for the injectors. $15 dollar part cured my problem.
Sgt Mack

[byrddog]

Originally Posted by 94twacker

Oh, heres the story, my girlfriend has had this 94 tracker since probably march and it has been a very good vehicle, basically trouble free. Well the service engine light has been on since she bought it, and finally I figured out how to check the codes. I had to use the "california" port and according to everything Ive read hers must be a california one because she has the mfi 1.6 liter, not the throttle body injected one, and I read that was only available in a California tracker in 94, and not in federal ones until 95. Anyways the codes that I got were code 13, oxygen sensor no signal change, and a code 51, egr valve. So first thing I did was disconnect the battery, took out what I thought was the EGR valve, its down at the bottom of the motor in the back, actually in the block held in by two bolts, I took that off, cleaned the valve itself the best I could, and the ports in the motor with a q-tip, replace the gasket and put it back together. Well the light is now back on with the same codes again. Also she has started having troubles with it. While driving, especially when accelerating up a hill and such it will be just fine then all of the sudden shake and shutter really bad, then go back to normal. I mean its pretty violent like someone trying to start out in a standard vehicle for the first time, it really shakes and hesitates. It seems like it is either A) losing fuel or B) losing spark. It doesnt really seem to be rpm related, nor gear related or anything. It happens in the city sometimes as well, but worse when like going up a hill and giving it more gas to accelerate, it just jolts and shakes for like 2 seconds then goes back to normal. I dont really know for sure if this is related to the two codes that I got from it, I dont think the egr would have anything to do with it, but I suppose its possible the oxygen sensor would. I just dont understand why the light has been on this entire time, and it just NOW starts to have driveability issues. I think Im going to change the fuel filter and see if that helps at all, and I may also put a timing light on it and check that, but I really dont think that is what it is. It idles smooth as can be, and otherwise runs great. It is a 4 wheel drive 5 speed just to let you guys know. I really appreciate any advice I can get, I am more of a gm man myself and dont know too much about these cars. Oh by the way, I tried running some seafoam through it but it didnt seem to make a difference. Thanks again guys and I look forward to reading your responses!

When you get your timing done. Check and see how much if any play is in the distributor itself. These things do wear out and have to be rebuilt. they normally lockdown fist, but i have heard of guys having to have the rebuilt because they are worn out and wont hold the correct timing