Hello yotatech.

Bought an '87 4runner about a year ago that was probably one of the cleanest most intact ones I've seen in a long time. It never quite seemed to run right but I figured I'd be able to sort it out.

It's always had an issue that occurs after you turn the A/C off. The A/C will engage and turn on fine and idle up a bit. Once the A/C turns the Idle will go to about 1200 rpms and stay there until I turn the car off and then on and it seems to reset.

I never got around to figuring it because it had a couple bigger issues. One, I had a bad misfire on cylinder three and two I had no cold idle... At all.

So I ordered an engnbldr head and while it was off was able to adjust the IACV. Put it all back together, made sure the timing was set up right, changed plugs, dist cap, plug wires, 02 sensor (denso), changed the oil and set the TPS as per 4crawlers website. Also re went over all my lines and can't find any vacuum leaks.

Cold idle works great, truck runs much smoother, but still seems a bit off. The idle also still goes up after turning the A/C off.

Checked the lines from my VSV and those seem to be routed appropriately.

Lost patience with it and took it to a mechanic. He told me it seemed to be very inconsistent with the fuel delivery and would often run rich. He seems to think it might be the AFM (?) and was going to test the voltages tonight. I'm trying to find the page that lists the voltages so I can cross reference it myself. (*edit* Found it! http://www.4crawler.com/4x4/CheapTricks/AFM/index.shtml thank you 4crawler!) I'll probably drive over to his shop tomorrow and see what he got.

Does anything think this could be the culprit or does it sound like it could cause that? Looks like there are separate parts numbers for AFMs, does it matter which one I find? Only place I've really been able to locate them is Ebay.

I also think I may be overlooking something silly... Anyone have any recommendations?

 

My 87 4Runner did that when the two vacuum lines to the A/C idle up VSV were swapped. Would idle low before switching on A/C, idle up with the A/C on, but not idle down after shutting the A/C off.

 

Idle connected to operating the A/C sure sounds like the A/C idle up valve is sticking open. http://web.archive.org/web/201102052...24vacuumsw.pdf Disconnect the vacuum line TO the plenum and plug it. If that makes the idle-up and idle-down stop (it should), then you know your problem is somewhere in that system. The manual has the tests for the VSV, and you could check the actuator by switching vacuum lines in and out.

 

Thank you for the pages! Sounds like I may have two separate problems still. One being the A/C idle issue and the other being possibly the MAF being bad.

I've printed out those pages and am gonna head over to the mechanic to see what he says.