OldSven

I have an (89' pickup, 22re, 5sp, 181k) that is having a few issues. I have searched now for about 3 weeks and have come across a few issues that have been worked out but these two just haven't popped up yet.

I have owned it for about a year now and have done all of the maintenance, timing chain, water/oil pumps, etc.

After cleaning the TB and IACV it was finally able to get up to normal temp, normally only going to 1/4. I also installed a 192 tstat, now it will get up to normal temp but once the tstat opens up the temp drops back to 1/4.

Also the other issue which seems to be tied in with this is when at 1/4 temp the idle is rough and even if I adjust the idle in all the way there still seems to be to much air getting in like the truck thinks it is cold. Have checked, no vacuum leaks either.

Anybody that knows what it is or knows a few fixes to try would be great, thanks!

OldSven

Once the tstat opens up and coolant starts flowing could a bad sensor be why the temp drops? Seems like the gauge and ECU have different temp sensors so I can't see why the gauge would drop and then the idle would start having issues, it has to be one in the same.

96vettelt4

could be a defective gauge..

OldSven

Thought about that, but why would when the tstat opens the temp drops and the idle starts acting up? Its looking like it is one issue that is causing two different problems.

Gamefreakgc

There are several things that can cause a bad idle. Here's what I've learned based off the FSM and my experience (mind you I have a 3VZ-E, but the system is the same).

There are three sensors that monitor the temperature of your coolant. I'm not sure of their specific location on the 22RE, but they are all located on the water bypass section near the back of your engine. On a 22RE they are right to left, on a 3VZ-E they are left to right:

Cold Start Injector Switch - Sends temperature reading to the Cold Start Injector for startups with a cold engine.
Engine Coolant Temperature Sensor - Sends temperature reading to the ECU and the Throttle Position Sensor.
Engine Coolant Temperature Sender Switch - Sends temperature reading to the gauge cluster on your dash.

Another part of the system is:

Throttle Position Sensor - Monitors the position of the "butterfly valve" that allows air into the engine. Electronically adjusts fuel based off readings received by ECU. It also switches the engine from open and closed loop based off butterfly valve position (switches the engine to idle and normal function, in other words).

Here's how I would check and the order in which I would check:

The ECT sensor and the ECT sender switch are both cheap and easy to replace. Just locate them on the back of your engine and replace as needed if they don't match up with the FSM readings: http://personal.utulsa.edu/~nathan-b...40engineco.pdf. You'll need a multi-meter to measure ohms to do this right. Or you can do a visual inspection for rust, corrosion or if it just snaps in two like mine did. Neither of these sensor trip a check engine light when broken (the sendor is obvious though).

Take note that the sensor has an offset groove pattern for the connector and the sendor switch is a "clip-on" tip (no specs on how to measure this one, it either works or it doesn't). Just seal the top threads with some RTV sealant so they don't leak. The sender switch is a last resort since it doesn't affect the engine performance at all.

The next easiest thing to check is your Cold Start Injector Switch. If it's malfunctioning it could be supplying fuel when the engine is warm, bogging down the engine. Mine was broken for two years and I didn't know it (P/O ripped the thing in half and stuffed it back in! ). Once again, check it with a multi-meter using the following instructions: http://personal.utulsa.edu/~nathan-b...ne/39colds.pdf. If you need to replace, just be sure to coat the top threads with RTV sealant again to prevent leaks. The CSIS also does not throw a check engine light.

If that doesn't work, the last culprit is your Throttle Postion Sensor (TPS). This may be your most likely cause (by removing and cleaning the TB you may have changed the position of the butteryfly valve, causing the TPS to be out of spec) but it's a very tedious job , which is why I saved it for last. I had a bad TPS that would idle very low when the engine was warm, similar to what you are experiencing. No matter how I high I adjusted the idle screw, it would idle really low when warm. You can test your TPS using a multi-meter that measures ohms and using a feeler gauge (very thin blades with measurements) with instructions here: http://personal.utulsa.edu/~nathan-b...34throttle.pdf. Basically you are testing to see if it switches to idle when closed and then when opened .85 mm it switches to normal when open. If you need to adjust it, it is done by rotating the TPS on the throttle body, reducing or increasing tension. Note this is easier with two people where one person rotates the TPS and the other steadies the multi-meter on the two prongs, makes it go WAY faster and easier. If you can't get all the reading within spec no matter how much you adjust it, your TPS needs to be replaced. The TPS is SUPPOSED to throw a check engine light if it completely fried, but mine was only half-fried so it didn't.

You can run these tests without having to purchase any parts and it will tell you if any of these need to be replaced. It'll take some time but save you money in the long run. An ECT sensor costs about $20, ECT sendor $20, TPS (Denso only, cheap knock offs don't work well) $100, CSIS $7 - $200 depending if you can find a good one to pull from the junkyard or not!