having problems with 94 Geo Tracker.....

well, after the recent problems with the temp guage and such, we took it back to the mechanic that told us to bring it back if it starts getting worse. It got worse, alot worse. The bucking was awful and uncontrolable. Well, he looked at it and said that he got a wiring diagram for it and got under the dash and unplugged and plugged back in a couple of plugs and it seemed to fix the problem. Well, so far so good, and it has been a few days now. It hasnt bucked at all, the temp guage hasnt acted up, and all is good. All except ever since we took off the tps and tested it its acting up a little, as soon as you let off the gas while driving it starts slowing down real quick, I think it may just need to be adjusted properly, or replaced. Either was I am just thrilled this seems to be fixed, it has been a LONG time now. So to anyone else having simular problems, try something really easy and just get under the dash and unplug and plug some plugs in, one may be slightly loose or dirty, you never know but it has seemed to solve a problem that has been very bad and serious for some time now, so it cant hurt to try!

He probably unplugged the ECU then pluged it back in.. You can accomplish the same thing by un hooking the battery and turning the key to on and in 30 min come back out turn the key to off and try starting it up. It seriously sounds to me like he reset the ECU.

well we tested the tps as well and it came back bad, it has a bad spot in it and its very intermitten. I got a new tps from a junkyard and havent had time to put it in yet, but it seems like this is a seperate problem. If you hold the throttle in a certain position it fluctuates 500 rpm's up and down, and when driving as soon as you let off the throttle it slows down instantly, and then when you give it gas again it jerks, because the tps. Its very wierd because the problem this tps is having seems like it couild have been the problem the entire time, but his unplugging and plugging wires back in obviously fixed something and it wouldnt effect the tps, the CEL is still on and never went off, so I dont think he reset the computer. I will get the tps on as soon as I can and let you know the verditct, but so far so good when it comes to the bucking.

well we tested the tps as well and it came back bad, it has a bad spot in it and its very intermitten.

If I may ask - did you take the TPS apart?

Is the TPS a wire wound potentiometer or is it a graphite POT like
in electron equipment - radio volume control, etc.?

I have a Geo Metro with some strange problem and I have not
checked the TPS yet.

But I was wondering how they work. If a graphite POT is in them,
then Hell!, they'd wear out fairly quickly moving back and forth
with each throttle movement - Gozillions of times a year!

DoctorBill

If I may ask - did you take the TPS apart?

Is the TPS a wire wound potentiometer or is it a graphite POT like
in electron equipment - radio volume control, etc.?

I have a Geo Metro with some strange problem and I have not
checked the TPS yet.

But I was wondering how they work. If a graphite POT is in them,
then Hell!, they'd wear out fairly quickly moving back and forth
with each throttle movement - Gozillions of times a year!

DoctorBill
Well in the 2-3k range it just bogged down now it is doing the violent stuff yours is doing. It was fine untill I unplugged the O2 sensor and plugged it back in. When It jerks the check engine light comes one but then turns itself off.. its really wierd. I have a rebuilt ECU.. I'm probably going to change the tps and o2 sensor and see if that helps. Or just take it to the dealership.. :uhoh:

problem is back and strong as ever, I dont know anymore....I just give up. She is planning to hopefully sell it soon..

problem is back and strong as ever, I dont know anymore....I just give up. She is planning to hopefully sell it soon..
Somewhere in this list lies the problem because my tracker doesn't bog down anymore.
I had a small exhaust leak I fixed it.
I checked the timing it was retarded 20+ degrees. (Used an Inductive timing light.)
Timing is now at +5
Replaced the distributor cap, spark plug wires, and spark plugs.
Replaced the O2 sensor.
I did all that at once cranked her over and she hasn't sputtered, stalled, or felt like it has hit a brick wall yet and I've been driving it for a couple of weeks.

Try spending less than $10, change your pcv valve, add a litre of methyl hydrate to your gas tank on your next fill up and keep your tank above 3/4 full for the next 10 fill ups. Good luck.

So Whats the verdict?

replace the egr valve and the egr valve sensor cleaning it does not work replace the 02 sensor while your at it

Mine just started having the bucking problem about 4 weeks ago. Took it to the garage and they did tune up (plugs wires and all), did nothing. My mechanic (small town guy) had to farm it out to another garage and it turned out to be the computer. They put a new (used) computer in and now it's running wonderful.

Check the points on the distributor cap and the rotor. It sounds like it is misfiring. Also if you have the chance check the teeth on the distributor.

I've seen in here, or somewhere, that the crank/timing belt sprocket can slip, or be broken from it's mount if not put on correctly (or just age). Then timing problems can result, and you can be out of time even when you set it according to the +5 mark.
It's in Viper's list above, he reset timing as part of the cure. Maybe you could pull the timing cover and belt, so you can remove that pulley and check. The cure was to drill and put pins into the crank and pulley. There were two people there, who had that problem and solution. They both did the drill/pin technique, maybe because the crank was also damaged, or because the pulley was costly.
One other thing, maybe your Cat.

you can send me the ecm no charge if if is not the problem. just shipping.
[email protected]

parts for sale list on a thread. questions on a part email me.
[email protected].

i have a 95 tracker with 215k on it and having the same problem! Idles great and runs super except for cutting out some times, and it mainly happens when the AC is on. Changed dist.cap,plugs and wires, didn't fix a thing. Also cleaned Throtle body which helped it Idle much better and helped mileage. I have no codes, I think I have narrowed problem down to the ICM(ignition control module), ECM(computer)or Pick-up coil in Distributor. The ICM will not put a code in system where the ECM will. Also The ICM will check out fine when at idle because it is not breaking down. Going to try ICM first, and get one from junk yard, new one is 80 to 100 dollars, might be able to get one from yard for 1/2 that.

I have a 95 geo tracker, and i can drive it all day long without any problems and then run the ac and i lose power and drop from 75mph to 45mph...idles great, but i lose power when i take turns and when i run the ac. i have changed the spark plugs, and wires, i had an oil leak because we changed the oil pan gasket and my friend didnt tighten it up enough so we redid that. and no more leak, still losing power though, so we changed the fuel filter,and put a new battery in. i was wondering when you changed the icm did it work? mine is an automatic...and it is strange but one day i was doing alot of driving and it was hot outside, and after driving all day, it just lost power completly. it would drive at 45mph in the beggining and then not go anywhere.. i let it sit over night and the next day it was fine. it acted like it over heated, but the temp. gage never got hot, and i know it works, because it got hot when my serpentine belt broke, in fact i never had this problem till i replaced the belt. please help...as for now i am checking the computer...

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

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!

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

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