Hey,

Greetings from Fort Collins. I'm new to this board and look forward to some good advice!

Anyway, I've got an 88 4runner, 22re, MT that's having some idle issues. It seems to idle really low, and the idle is unsteady. Generally pulling up to a light it will be real low, and then slowly, over like 10-15 seconds it will increase. Sometimes it will get to a high point and then suddenly drop back down, like the ECU is cutting fuel or something. It doesn't matter if my foot is on the brake or not.

Truck runs pretty well off idle. Good throttle response and decent mileage (22 highway) It will surge a little if I hold the accelerator steady in second or third gear.

Here's what I've done so far:

-Adjusted TPS to specs
-Thoroughly cleaned out TB
-New plug wires
-Pulled plug wires at distributor - plug number one caused no change. Put a new spark plug in #1, this smoothed the idle and raised it a bit, but still idles rough. Now if I pull 1,2, or 4 while running the idle will drop a little, but if I pull #3 it will drop a lot (!)
-Applied vacuum to EGR at idle and truck almost dies
-Pulled vac hose to fuel pressure regulator - no change. Apply direct intake vacuum to this - no change.....could be bad??
-checked out coolant temp sender - within specs
-Diagnostic short doesn't change idle speed

I plan to: get OEM cap/rotor/plugs/wires when I get paid, valve clearance check, replace all vac hoses

I have a feeling there are a few things going on here. i.e. new #1 plug helped but didn't cure it... Perhaps since pulling #3 causes such a drastic change I have a bad cap/rotor?

Anymore stuff I should be looking at?


Thanks!
-andy

Need to re-check that TPS.

Otherwise you're on the right track, esp. with the valve adjust.

Before buying a lot of parts for nothing do a compression test. How many miles on your rig ? I'm kind of leaning toward a headgasket/valve problem.

It's 200k. I'm starting to fear the headgasket as well... I replaced the cap, rotor, and the rest of the plugs with no noticeable change in idle, though this may have fixed the surging with throttle steady. I then set the valves to .007/.011 (Engine was only warm at this point) and now the thing won't idle at all, even with the idle adjustment screw nearly all the way out. Disconnected EGR to make sure it wasn't pulling way more vacuum and opening that thing but no change. I'm gonna check the TPS again and then...???

But if the TPS is putting out the proper resistance (200-800 ohms) at idle shouldn't that be fine? Won't that at least put the computer in idle mode?

You need the IDL-E2 setting to be under 2300 ohms with the throttle closed, that is what the ECU looks at. In fact both unsteady idle speed and inablility to set base timing are two of the most common symptoms of a TPS out of adjustment:

http://www.4crawler.com/4x4/CheapTricks/TPS/index.shtml#Troubleshooting

my IDL-E2 is reading 14 ohms, and my VTA-E2 is showing around 600 ohms with the throttle closed

Measured at the TPS connector I assume? If so, it might be that signal is not making it back to the ECU. You could check the resistance at the ECU connector.

I saw that on your page, but how do I connect to the E2 at the computer? I onle see Vcc, VTA and IDL

Never mind... it just isn't in bold like the others are.

I'm guessing that is the one TPS wire (White w/ black) that connects to ground, per the FSM wiring diagram.