Trooper Lacks Power

Last post on Oct 26, 2009 at 5:54 PM

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#1 of 1 1998 Trooper Lacks Power by icanoutfishyou Oct 26, 2009 (5:54 pm)
I have thouroughly searched for information on this topic, and have found nothing which begins to describe what problems are being presented with my vehicle. 1998 Trooper, 102k miles, periodic maintenance. Here's the problem (problems?) The truck starts right up, but idles super rough. It refuses to run above 2000 rpm's, and when I attempt to get it there it just bogs down completely. I ran an OBD II scan, and initially came up with code p0120 - throttle pedal position sensor faulty. I ran the scan 3 more times, and it came up with p0120 the second time as well, but on the two subsequent scans the tool read p0300 - Random/Multiple cylinder misfire detected. During the OBD II test, the throttle position sensor was showing 0% regardless of whether the gas pedal was depressed or not. RPM's at idle fluctuated between 550 - 850 rpm's. At this time I'll reinforce that the engine sounds very rough. Replaced the inital stuff that would cause minor problems; the PCV valve, fuel filter, and air filter. When I checked the underhood fuses, an O2 sensor fuse was blown; I replaced it and it's still fine but made no difference in the engine's idle. None of the three fixes above have changed the quality of the idle. It's still super rough. If I am able to get it to 2000 rpms, when I let off the gas pedal it sounds like it backfires once or twice; some kind of popping sound. But the whole way to 2000 rpms it just bogs down completely like it's under some kind of heavy load. The vehicle will shift into gears and would drive if the engine wouldn't stall/bog. Any help would be much appreciated, and I've tried to include all of the pertinent information in this post. Thanks in advance! Forgot to add; ignition advance at idle fluctuated between 15 and 18 degrees, around 2000 rpms advance was 20 degrees.

#1 of 1: 1998 Trooper Lacks Power by icanoutfishyou; Oct 26, 2009 (5:54 pm)

I have thouroughly searched for information on this topic, and have found nothing which begins to describe what problems are being presented with my vehicle.

1998 Trooper, 102k miles, periodic maintenance.

Here's the problem (problems?)
     The truck starts right up, but idles super rough. It refuses to run above 2000 rpm's, and when I attempt to get it there it just bogs down completely.

      I ran an OBD II scan, and initially came up with code p0120 - throttle pedal position sensor faulty. I ran the scan 3 more times, and it came up with p0120 the second time as well, but on the two subsequent scans the tool read p0300 - Random/Multiple cylinder misfire detected.

     During the OBD II test, the throttle position sensor was showing 0% regardless of whether the gas pedal was depressed or not. RPM's at idle fluctuated between 550 - 850 rpm's. At this time I'll reinforce that the engine sounds very rough.

     Replaced the inital stuff that would cause minor problems; the PCV valve, fuel filter, and air filter. When I checked the underhood fuses, an O2 sensor fuse was blown; I replaced it and it's still fine but made no difference in the engine's idle. None of the three fixes above have changed the quality of the idle. It's still super rough.

     If I am able to get it to 2000 rpms, when I let off the gas pedal it sounds like it backfires once or twice; some kind of popping sound. But the whole way to 2000 rpms it just bogs down completely like it's under some kind of heavy load. The vehicle will shift into gears and would drive if the engine wouldn't stall/bog.

    Any help would be much appreciated, and I've tried to include all of the pertinent information in this post. Thanks in advance!

Forgot to add; ignition advance at idle fluctuated between 15 and 18 degrees, around 2000 rpms advance was 20 degrees.