I've been having the infamous surging idle on my '94 22RE pickup for the last couple of months, so today I pulled the TB and cleaned it out. There was quite a bit of carbon buildup, but with a little elbow grease and a lot of TB/Intake cleaner, she was looking like new. When I blew compressed air through the vacuum ports some gunk came out too. I reinstalled the TB with a new gasket, topped off my coolant and fired up the truck. Well, the surging idle problem is gone but now it idles very rough (sounds like a Harley). It also sounds like there is a hissing sound over near the TB now, which I don't remember being there before (vacuum leak?). I've checked and re-check that I reconnected everything, and was wondering if you guys had any suggestions? <img src="/forums/images/graemlins/angry.gif" alt="" />

I think you answered your own question there.

Double check:

Vacuum lines
TB gasket
Big intake elbow clamps
Idle air valve

You can always spray carb cleaner or similar around the area, and when the RPMS change, you found your leak.

Iinterestingly I don't get any vacuum from the P port on top of the TB (3rd down) at 3500 RPMs like I am supposed to. I sprayed compressed air through that port just to be sure that something hadn't gotten in there when I was cleaning, but the rough idle persists. At idle there is a strong exhaust smell as if it is running too rich.

Is the vacuum line to the fuel pressure regulator still connected?
http://www.4crawler.com/4x4/CheapTricks/22RE_Engine_Pix/9.html

The vacuum line leading to the fuel pressure regulator is still connected.

I tested the resistance across terminals on my TPS and this is what I got:

0 mm clearance VTA-E2 - 0.49 K Ohms (Ref Range .47-8.1 K Ohms)

.57 mm clearance IDL-E2 - 0.01 K Ohms (Ref Range < 2.3 K Ohms)

.85 mm clearance IDL-E2 - Infinity (Ref Range Infinity)

Wide open throttle VTA-E2 - 2.92 K Ohms (Ref Range 3.1-12.1 K Ohms)

0 mm clearance Vcc-E2 - 3.66 K Ohms (Ref Range 3.9-9.4 K Ohms)

While the last two resistances are slightly outside of the reference ranges, the first 3 look pretty good. Could a small change in resistance like this in the TPS cause such a rough idle? Interestingly when I spray the junction between my TB and intake with TB cleaner the engine revs up, which leads me to believe there is a leak there. I installed a new gasket when I reinstalled the TB (which is paper thin), but just tightened down the bolts and didn't torque them to factory specs (14 ft/lb). I think I'll reinstall it and see if that fixes the problem.....does it sound like I'm on the right track here?

The IDL-E2 setting is what matters at idle:
http://www.4crawler.com/4x4/CheapTricks/TPS/index.shtml#TPSAdjustment

Sounds like you have located where the vacuum leak is, I would look into that first.

Well I removed the TB again, reseated the gasket and reinstalled the TB, torquing the bolts down to 14 ft. lbs.....fire it up and....same rough idle. I sprayed the junction between the TB and intake with TB cleaner again and the RPMS still jump up. Has anyone had issues with aftermarket TB gaskets creating a good seal? Do you think a factory gasket would make any difference?

Update: I replaced the TB Base seal with a factory seal and the rough idle disappeared. However, two days later my head gasket decided to blow while I was driving down to Oregon <img src="/forums/images/graemlins/angry.gif" alt="" />

Good, and DANGIT for you.

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