87 4Runner 22re cold start issue and rough idle cold and warm. (1 Viewer)

[Seadoobie]

Hey everyone, I’m stumped on a rough idle issue with my 1987 4Runner 22RE. Cold start idle is 600 RPM (should be 1200–1500), rough at 1500 RPM, with a stutter and rich smell. Here’s what I’ve tested and the results—any ideas on what to check next?

• Cold start injector: Sprays a nice conical mist, 3 ohms (in spec). Time switch 30–52 ohms (in spec).

• Throttle body: Clean, butterfly moves freely.

• IAC: Cleaned, pintle moves freely, solenoid flap stiff, 52 ohms (in spec). No idle change when unplugged (cold or warm). Direct power test (battery + to brown pin, - to blue pin): no response—likely bad, new IAC on the way.

• Wiring: IAC connector (brown power, blue control) shows 30mV on both pins (should be 12V on brown). Continuity from IGN fuse to both pins (short in harness?). No continuity from blue wire to ECU E2 pin 3 (green/yellow)—break in control wire?. Planning to run new wires (IGN fuse to brown, ECU pin 3 to blue).

• Fuel pressure: Ruled out (engine runs, injectors firing).

• ECT: 1.4 kΩ at room temp (in spec).

• EGR: Holds vacuum, not leaking. PCV: Rattles, good.

• Vacuum leaks: No change with booster line plugged or starter fluid spray.

• Compression: 145–155 psi (low but consistent).

• Plugs: Healthy, no fouling yet. New cap/rotor/wires, no change.

• O2 sensor: One-wire (turbo 22R-TE style), ECU (89661-35070) matches turbo model—suspect turbo truck with 22R-E swap?

• EFI relay: Hot with key on. Tested coil: ~80 ohms (good), clicks when powered, but heat suggests harness short?

• Air intake hose: Not checked yet.

New IAC coming—considered running new wires to bypass harness issues. But the rich smell, stutter, and rough idle might be something else (turbo ECU/non-turbo engine mismatch?). What am I missing? Thanks!

 

[gnob]

id start with checking the ect sensor VOLTAGE during cold start issue.
i would also check/disco fuel injectors to check for function while cold. check injector resistance cold and hot. check the injector resistor (if the 87 has it idr)

i had a similar situation on cold starts at one point and it turned out to be a bad injector.

iac probably isn't going to cause a rough idle, just a low idle.

also make sure the o2 sensor is sweeping correctly and its not shorted or grounded.
make sure you don't have an exhaust leak at the header or sensor.

 

[Seadoobie]

Thank you! Do you happen to know about testing the electrical connection to the iac? If it’s shorted I don’t want to get a new iac and it gets fried again. I have the two wire connector to the iac mounted down lower under the throttle body. Not the one attached to the throttle body. It has a brown and a blue wire. They both read only 30mV with the key on. Shouldn’t the brown wire be power and measure 12v? It seems like there might be a short between the two. But I’m struggle to make sense out of the wiring diagram because the blue wire makes so many stops before the ecu and the brown wire makes so many stops along the way to the ign power.

 

[gnob]

so the air valve (iac) under the tb should get key on 12v from the circuit opening relay only when the vehicle is running. or you can move the flap in the afm to test while key on but not running.
not sure what you're saying about a pintle because this is a heated element air flap.

the blue wire is the power side. brown wire or white/black is always ground

and if your resistance spec is good, unless it's physically broken, the iac is fine.

you can take the cover off to inspect/adjust. note the flap position. put it in the freezer to make sure it moves. or heat depending on the ambient temperature.

 

[Seadoobie]

so the air valve (iac) under the tb should get key on 12v from the circuit opening relay only when the vehicle is running. or you can move the flap in the afm to test while key on but not running.
not sure what you're saying about a pintle because this is a heated element air flap.

the blue wire is the power side. brown wire or white/black is always ground

That’s what grok called so I just went with that. lol but it’s the flat plate with the teardrop shaped hole in it. It moves freely. But this it’s its “resting” position with no power applied. If I supply power straight from battery should it move? Because it does nothing. Thank you again.

 

[gnob]

yes it should move but not immediately. its a heated coil.
so if it's warm out, put it in the freezer and see if position changes

 

[gnob]

fsm

 

[Seadoobie]

yes it should move but not immediately. its a heated coil.
so if it's warm out, put it in the freezer and see if position changes

Thank you. Ok we froze it. But at rest it was barely half open. Not much more than the picture I posted above. But it did close down slowly but surely when we applied electricity to it. But shouldn’t it be wide open at rest when cold?

 

[Seadoobie]

Also I should mention that it bogs down and almost dies when shifting into drive with the brake applied. Warm or cold.

 

[gnob]

the air valve can be adjusted. that's what the stud and nut is for.

what's the idle like at full temp?

 

[Seadoobie]

It’s still rough. And bogs down when sitting at a red light. Have to keep foot on gas. Ordering the injector rebuild kit.

 

[Seadoobie]

We adjusted it as far as we could. This is the furthest it will open. In freezer.

 

[gnob]

im sure that should make a difference.
do a good inspection on the intake boots as well.
idle should be smooth and correct at temp so im pretty certain this isn't an iac issue.
double check tps settings and afm voltage values