Hugh_Mann

So today I decided I'd clean out the the throttle body in my 22re with a rag and some throttle body cleaner. I sprayed some directly inside and on the rag and wiped it out real nice, and then I sprayed a couple drops of penetrating lube where the throttle plate hinge meets the TB. Now it idles like ˟˟˟˟. Before it would settle between 750-900 rpm, and now it bounces between 1000-1250 constantly.

My first thought was a vacuum leak or the TPS. All the vacuum lines are routed and connected properly, so I really doubt it's vacuum related. As for the TPS, I didn't think it would be that sensitive to TB cleaner, but now I'm thinking that's the culprit. Has anyone had a similar experience?

Badger62811

My dad did the same thing to my 94 shortly after I got it. Had the same problem except it would also idle higher and higher till it hit about 5k and I turned it off. Fairly certain a sensor was the culprit. Eventually it stopped and i was able to adjust the idle down. From what I've heard from other guys it's real easy to fry a few of the sensors on these engines. I'd start with TPS.

Hugh_Mann

So I tested the TPS as per 4Crawler's instructions and everything was within factory spec! I can't see what else could be causing my problems Before I cleaned the throttle body it idled fine, and since only two vacuum hoses were disconnected to do so, it can't plausibly be a vacuum leak.

I also noticed another symptom: when I slowly rev the engine up to 3000+ rpm, it surges up faster than I'm pressing the accelerator in a couple spots. This again seems like a malfunctioning TPS. It's like the ECU isn't getting the correct throttle position.

Despite the passing test of the TPS, I'm still thinking it's the culprit. I would appreciate input from anyone with experience in this area.

Hugh_Mann

Here's an update... In order to see if the idle circuit of my TPS is functioning, I jumpered the timing test contacts. The idle lowered about 100rpm as you would expect, so the ECU thinks it's in stable idle according to the TPS. Not what I was hoping!

I also tested how smoothly the resistance rose between the VTA-E2 contacts and found a dead spot between 1.9k and 2.3k. This may simply be incidental? Not too sure if this is the root of my problem. For what it's worth, the TPS is faulty, and the used unit I picked up doesn't have any dead spots.

Thus far the TPS has passed all 4Crawler's tests (except for the dead spot), as well as the timing jumper test. I'm starting to think the TPS may not be causing my idle issue, but I'm stumped as to what it might be. For the sake of discussion, here's the resistance values I recorded from the tests, correct numbers in parentheses:

• 1. 808 (470-6100)
• 2. 113 (<2.3k)
• 3. Infinite (Open/Infinite)
• 4. 4.78k (3.1k - 12.1k)
• 5. 6.14k (3.9k - 9.0k)

Maybe if I tear off my throttle body, give it a good cleaning, hook up the used TPS I picked up, the issue will disappear!! Or so I hope

hiluxhack

It may have idled up because you cleaned out the crap. If it's hunting, make sure the intake hose is tight and not cracked on the bottom. Look for other vacuum leaks. It's best to clean it with a small brush and sensor safe TB cleaner. Good hunting ( no pun intended )

mct75

What if you put all the dirt back in the TB?

Old_ blue

take the battery connectors off the battery posts. Take the positive and negative clamps and touch them together(dont touch the battery posts) this will reset all the learned memory your truck has had while it was running with a dirty throttle body

Valvoman

What's the update? Fixed?

Hugh_Mann

Alright, I took off the throttle body and cleaned it (TPS removed this time), installed and adjusted my used replacement TPS, re-installed the TB with a fresh gasket, and fired her up. Same issue: high and hunting idle. At least I got rid of the old TPS with the dead spot, and eliminated it as the cause, too.

After accepting that the problem persisted, I took her for a test drive. Then it hit me. When I applied the brakes, the idle jumped rhythmically between 900-1100rpm, and when I let off it settled at around 1400rpm. I think this indicates a vacuum issue after all!

The first thing I did was plug the brake booster vacuum line downstream of the white backcheck valve thingy, which surprisingly did nothing. Pressing on the brake still produced hunting and high idle (wtf?).

Then my bro-in-law pinched off random vacuum lines while I pressed on the brake to see if there was any effect. When he pinched the line going to the power steering pump idle-up device, the idle settled at about 1100rpm. When he let go, it resumed hunting 900-1100rpm.

This just seems bizarre, and it's getting late so I'm going to bed!

Edit: Oh yeah, I checked the intake for cracks and disconnected the battery as per hilux_hack and old_blue, to no effect. Thanks all for the input!

Valvoman

Ok. I just did mine, but mine is a '93 3.0. However, it did the same thing, idled up and down.

So, I resprayed the throttle plate lightly and cleaned a little more black stuff. Use a quality T-body cleaner like a Valvoline product.

Then I drove it. For over 30 miles. I found that the jumping idle stopped, but it sounded like too many rpms to my ears. So I backed it down. Seems good now.


Cheers!

Hugh_Mann

SUCCESS! Sweet, sweet success. It turns out it was just a mis-adjusted idle the whole time. I gave the idle air screw a couple turns in and she's purring at 900rpm and no more hunting.

I did some research last night and I learned that our trucks actually cut fuel when braking with the engine above ~1100rpm. That accounts for the hunting idle. Since my idle was about 1400rpm, the ECU cut fuel, the idle then dropped below 1100rpm, the fuel returned, the idle rose, and so on.

Thanks everyone for your help!

punks_is_4x4

Do u know what the screw should be set at stock?

Hugh_Mann

Hmm, not too sure. Just make sure if you decide to adjust the screw that you're not compensating for a vacuum leak or malfunctioning sensor/idle-affecting device. I think if you had to have it all the way in or out, that it would be a sign that something else is amiss.

Bottom line: make sure everything else is adjusted and functioning properly before messing with the screw.

punks_is_4x4

Well here's the problem as I mess with it the idle still is rough not high I'm thinking it's something with my coolant I found a bunch of coolant around the thermostat housing I hope there's no crack or anything