1997 Geo Tracker Idles Badly, Won't Accelerate

[lewis(mistreated)]

Got a 1997 Geo Tracker LSI with 70K miles that's run fine for a couple years now, until suddenly there was no acceleration and then couldn't get it to start.

I've been fighting this one for over a month now and have gotten it to start but now it idles very poorly and stepping on the gas seems to have little effect. Here's the list of things I've done/checked:

-Replaced distributor and spark plugs/wires
-Replaced throttle position sensor
-Verified proper pressure on the fuel rail
-Checked Air Filter

In addition I've used the OBDII interface to check for DTCs and there are none. If I remove the O2 sensor or MAF sensor then a DTC IS set so it appears that all inputs are working properly. I can also verify the Throttle Sensor value over OBDII so I know the new sensor is working properly.

I've also checked the signal from the ECM to one of the fuel injectors with a scope and the signal is toggling from Vbatt to GND at a (slow) frequency, which seems to tell me that the ECM is controlling the fuel injectors OK.

Any ideas as to why it may be idling so poorly? Cranking up the throttle results in no or very little change in engine rpm. It's like the engine is not getting enough fuel but I'm out of ideas of what to check.

Please, any ideas will be much appreciated!

[jjb1702]

Sounds like your cam drive belt (or chain - whatever it uses) has slipped a notch or two.

[crazyinkc]

I just had a 96 Tracker do the same thing. I found the crank bolt loose and it let the crank gear work back and forth on the crank and chewed up the gear and the crank. I found this out by lining up the timing marks and saw it was 2 teeth off and the belt was loose. I hope this is not the same problem.