lexruger

i have a turbo b16. I have been fighting a low/ rough idle issue for about a year now . it started happening with the stock block and even after i went ahead and built the block.

when i throw it into neutral the idle will dip real low then go up to normal (900) then dip low and then go up. It will eventually fix it self right after a few seconds and then idles perfectly. Car drives normal... no issuues and NO CEL, even jumped the service connector to double check.

things i have done recently include... plugs, wires, dizzy, rebuilt engine, checked mechanical timing

now i have cleaned the iacv valve twice with no change, also changed the pcv valve about 2 months ago with no change. Replaced pretty much all the vacuum lines.

I was told that i neededf to unplug the iacv valve while the car is running and then adjust the idle speed but every time i unplug the iacv the engine just dies which leads me to believe that the iacv is junk but at the same time it is not throwing a code. I am really stumped as what to do and dont really wanna send it to my mechanic for him to diagnose it for hours. im probably gonna go ahead and replace the iacv in the meantime but im open to any suggestions. Thanks and sorry for the novel

lexruger

also though it might not be pulling enough vacuum because the other day i added a Gm 3 bar map sensor and the idle issue has gotten worse. Ran it off my vacuum manifold which was added last month.

Former User

Your IACV seems fine. The idle speed should drop low when the IACV is unplugged. Adjust the idle speed as instructed in the B16 service manual.

Also try bleeding the cooling system.

lexruger

i understand the idle dips low but every time i unplug it the car shuts off so i am unable to adjust idle speed according to the manual. Also have bled coolant many times and have done a full system flush...

Former User

Feather the gas pedal to keep the engine alive after unplugging the IACV. Then adjust the idle screw. Get a buddy to help you. You need to hook up an external tach to do this right.

Also test the resistance of the ECT sensor and the voltage output from the TPS.

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Did you bleed like this:

This may take 20-30 minutes.

1) Park the car on an inclined driveway with the front end higher than the rear.

2) Push the dash heater lever/**** to MAX heat.

3) Follow the directions in the diagram below (hint: the bleed bolt is located where the upper radiator hose connects to the engine):

azandford

No i did not bleed it like that... i will try it that way though

also... i know the tps sensor is located in the throttle body but not sure about the ect sensor....

also i forgot to mention as soon as the idle issue started i began having issues at startup. The car would have to turn over a bunch to get it started if it was cold... warm start though it would fire right up. Not sure if the two are related but they began happening at the same time. Sometimes the idle issue seems better after driving the car for a bit but that might be just in my head

Former User

It's the 2-wire sensor located below the distributor. When the engine is fully warm, unplug it and measure resistance across the two sensor terminals. It should read 200-400 Ohms.

If you have a FITV, clean and adjust it, in addition to the other items.

lexruger

No FITV... idle issue only occurs after the car is fully warmed up

it will bounce around a bit then idle fine...then if you give it gas it will do the same thing. If you just let it sit and fix itself will idle fine no issues of course until you give it more gas..lol

can it possible that the sensor might be junk w/o throwing a code?

Former User

Yes. Test it. Don't just replace it.