lofreqjeff

Yesterday morning my truck decided to take a dump on me about 150 miles into a 420 mile round trip snowboarding from Chandler Az to Sunrise Ski park in Show Low Az. I am not sure where to begin with fixing it, or what really needs to be fixed/replaced.

I know the first thing everyone wants/needs to know is the truck specs:
1st Gen 89 4Runner
3.0 with manual tranny
@ 186K miles.

The check CEL light came on about 100 miles after leaving my place yet it seemed to be running just fine. Then, about 50 miles later, it started to loose power and run rough. It almost felt like I lost on of my cylinders. We struggled to get to our destination, parked and boarded for about 8 hours. Then, when we left to drive the 210 miles home, it seemed to be driving just fine for about the first 30-50 miles the CEL came on and it started that shuttering agian, and that same feeling as if 1 of the cylinders was misfiring, or not firing at all. There are some very steep mountain passes we had to go through and at times I didn't think it had enough power to make it. On more than 1 occasion, I ended up having to downshift to 3rd and floor it just to maintain 45-50 mph at about 3500-3800 rpms. I have made this trip probably 10 times in the past 2 years with this truck and never hand any issues like this before.

The codes it gave are:

12 - Engine Speed (RMP) Sensor circuit

21 - HO2S front circuit

41 - TPS circuit

51 - A/C switch ON during code retrieval/Closed throttle position switch OFF during code retrieval.

I have checked all my wires and plugs, checked the distributor cap and rotor (all of which are less than 6 months old) and everything seems to be fine.
This morning I took it for a short drive to my office and it seemed to be running just fine again, but I am very concerned about this happening again.

I'm am just not sure where to begin.

I will be doing a compression test this evening.

Any help is greatly appreciated!

Thanks!!

1994runner

Check wiring between igniter and distributor. If you can get your hands on a used test distributor I would try that.

lofreqjeff

Thanks I'll give it a whirl that and see what I happens. Right about now I'm willing to try anything right about now.

Thanks 1994runner!!

Anybody else have any additional suggestions??

1994runner

No problem... Also check to make sure the o2 sensor wires are not shorted to ground. I have seen some that melted against the exhaust. with wind and vibration it would ground intermittently.

fthertime666

check the wiring diagram to see if these components share a ground..

lofreqjeff

It seems to be an intermittent problem. I was out for a test drive yesterday it seemed ok - for the first 2 or 3 miles, then all of a sudden...bam it was running like crap again. I didn't do anything to provoke it, no bumps, sudden stops or turns. Same feeling as before, as if one of the cylinders wasn't working. So I pulled over and checked all the connections - the plug wires to the distributor, the coil/ingitor wire to the distributor, all the plug wires to the plugs and they were all fine.

This morning on my way to the office it was running just fine. I have NO idea what is going on.

I will check the manual and see if there are any common grounds.

Thanks for your help guys!!

1994runner

This may sound strange... but did you check the oxygen sensor wires? I have seen them ground out on the exhaust. As the exhaust got hot, ran like crap, cold it was ok... Worth a shot

Targetnut

code 12 RPM sensor code should make the engine just cut off.

code 21 though would be somthing to make it run like you've described. As was mentioned before check the wiring to the O2 sensor because that is the source of many peoples problems with that circuit. Another possibility is that the O2 sensor is shorted internally allowing voltage from the heater circuit ot "leak" onto the sensor side. This higher sensor voltage will cause the ECM to make an unecessary lean correction and cause you to lose power in a big way.

You can check the voltage at the OXY terminal in you diagnostic connector. It should fluctuate back and forth between about 0.2V and 0.8V. If the voltage is staying higher that 0.8V or 0.9V then you may have a bad O2 sensor.

Of course there are other things that can cause you truck to run like crap, but this is at least easy to check.

lofreqjeff

Thanks for the replys.

It doesn't just shut down though, and it starts right up everytime. So, you guys have me convinced that its a short somewhere cuz these symptoms come and go.

I will check all the O2sensor wiring and test the OXY terminal in the OBD.

Thank you for all your help!

4Crawler

iTrader: (3)

Check the TPS IDLe contacts as well:
- http://www.4crawler.com/4x4/CheapTri...#TPSAdjustment

lofreqjeff

Well, the mystery has been solved!

it was a bad fuel injector. But, we replaced the TPS before we knew it was the injector.

littlyota

What did you do to diagnose the injector?