My '89 Pickup (3.0 V6) has been idling rough as of late and right now I'm trying to pinpoint the source of the problem. It's going in on St. Pat's day for a tune up, but I'm curious as to what might be causing the problem as to give the mechanics some idea of what to look at.

The problem is that sporadically the motor gets very bad fluctuations in idle speed. It seems to be worse when the clutch is in, but occurs with it in and out. I don't really notice any difference in acceleration or anything, it's just extremely annoying and seems to be getting worse. Recently I cleaned the throttle body out and put some Outlaw fuel system cleaner in the gas tank. I stupidly did not take off the TPS when I cleaned, so I will have them look at that. Anyway, here are my actual questions...

If the TPS is damaged, will it necessarily trigger a code if I try to pull them? Is there a chance the ECU may not know it's malfunctioning?

Is there a chance the fuel system got clogged by a deposit being knocked loose, perhaps clogging an injector? Would this trigger an error code?

I guess I'm just curious as to whether or not there is a good chance the problem would trigger an error. I am between classes right now and wondering if it's worth my time to check it on my own tonight, or if I should just wait for Toyota to try and pull codes. :

 

when my TPS was bad there was no code.. just had to use an ohm meter to check resistance. My truck would just catch at a higher idle when pressing the clutch in to stop though, that's how I found out it was bad.

also make sure there are no tears in your intake tubing, there was one in mine on the bottom near the tb and it was really easy to miss.

 

Thanks for the response. I haven't had time to check the TPS myself completely, though I did measure it with no feeler gauge in the stop screw and the continuity was normal. Is there an easy way to get the feeler gauge between the stop screw without taking the throttle body off, or is that an absolute must in order to test and respec it?

I'm good with wiring and electricity, but motors and mechanics confound me.

 

Check the timing, I had the same problem. My TPS was off by just a hair and causing the timing to read at 30 degrees BTDC at idle. If I would bump the throttle a few times it would settle down to 10 deg BTDC, my TPS was ok, just needed about 2 degrees of rotation

 

I had to bend the two that I used for the throttle, but it's possible... just a very tight fit. good luck

 

Never thought of bending the feeler gauge. Thanks!

The TPS tested out just fine. I am thinking more and more that perhaps I just got some bad fuel or the cleaner I put in the tank is fouling things up, but I will also attempt to check the timing before Thursday. If I can resolve this on my own and save some money that is fine by me.

I've also been listening for air leaks and I'm pretty certain I have none. I'm going out right now to see if there are any codes stored in the computer...

 

I feel like a moron now. The idle speed was too high after the cleaning. I need to get myself a tachometer. :pat: