Power Loss in an '89 4Runner


toyotatech89
07-29-2009, 10:09 PM
I've got an 89 4-runner with a 3.0L V6 engine. About a month ago I had the timing belt replaced and ever since I have had a noticeable loss of power. The idle is smooth, so I don't think the cams were misaligned. However, the loss of power has been accompanied by a varying idle, where it slowly climbs a few hundred RPM then drops. I pulled the cat and drove around the block, but it ran worse with an open exhaust! I'd appreciate any advice!

Brian R.
07-30-2009, 01:19 AM
Pull the codes if any and see if it points you in any particular direction. There is a good chance one of your sensor connectors is no longer connected or loose.

toyotatech89
08-04-2009, 10:55 AM
Unfortunately I don't have a code reader capable of reading my 4Runner, but I used the self-diagnosis method which showed code 51: "Switch Signal." The problem, according to a Haynes manual, is somewhere in the A/C switch circuit or the throttle position sensor circuit. I kind of doubt it's the A/C, but how do I go about checking the throttle position sensor?

Brian R.
08-04-2009, 01:55 PM
Download the user manual from the sticky post at the top of this forum and find the troubleshooting procedure in there. Basically, you check the resistance of the TPS at various throttle postitions.

toyotatech89
08-05-2009, 11:33 PM
Well, the TPS checks out with the ohm meter. I've also been doing some research online, and there are a few references to an idle switch somewhere in the TPS circuit. Do you know what this is?

And by the way, thanks for the help so far! I'm sorry about the delays between posts though. Work has been getting a little crazy!

toyotatech89
08-06-2009, 11:24 AM
Ok, well here's another bit of information: The thing stalled on me this morning!! It was a cool morning, about 40*, and the engine started just fine but slowly lost power over the course of 30 seconds until it died. I couldn't get it started right away, but after letting it sit for a while it started right up again. I'm personally wondering if my PCV is clogged... Any suggestions?

toyotatech89
08-07-2009, 02:23 PM
Got it! Turns out it WAS the TPS! I only checked the VTA tab, which ohmed out correctly. However the IDL tab was open at all throttle positions. Turns out I just had to recalibrate it and re-adjust the timing and I'm off and runnin! Thanks again for the help!

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