I turned on my car and let it idle. I unplugged the wiring for the IAC and noticed no difference in the idle. Revved the throttle a couple of times and no difference. I also unplugged the TPS switch and again no difference in idle. Is this normal?

 

Yes,

When you unplugged the IAC, it stayed in the last position it was in and wouldn't move because there was no power to it. Again the TPS is preset when you adjust it and only sends a signal to the ECM. It also is not wise to disconnect and reconnect these components with engine running.

 

The IAC is a little survo motor and the only times it should move is when you turn the A/C on, put in gear and when it goes over from cold to warm and turns the idel down.
You might not want to mess with the TPS like that with the car running.

 

Hey oil pan 4,

How's the 432th or are you navy?

 

If i unplug my iac my idle goes up. If i plug it back in my idle is VERY low, like almost to cut off point.
I thought my iac was bad but if it is then why the faster idle when unpluged?

 

When you had the engine apart, Brobert, did you clean the IAC air passages in the throttle body? I know you have had the EGR disconnected for a while now, but there still might be junk in the air passages. Clean the air passages to the point you need to wear sunglasses they are so shiny. The carbon buildup in those passages is what is choking the engine when the ECM takes over idle control.

 

i wouldn't say to clean the air passageways until they're shiny... that's a waste of time. they'll get carboned up quick. the cleaning should just remove major high mileage buildup due to lack of maintenance, and the cleaning should be then made part of your tuneup/maintenance schedule.

ecm will use a "limp home" mode to compensate for a failed (and UNPLUGGED) sensor... does it for o2, tps, maf/map, cts, mat, and any others i missed. iac would stay where it was at when it was unplugged (as was said), so a smoother idle means the ecm was trying to adjust the idle to where it should have been- lower- and w/iac unplugged, ecm can't adjust=idle is high. Do a Major tuneup (when was the last time- do them yearly- the Entire list!!) & clean the iac system. seems like 99% of the driveability probs on this forum are due to an out-of-tune car.

 

just cleaned my IAC and the hole it goes in. Made no difference in my idle problem. I also now have a noticeable bogging when hitting the throttle. You hit the throttle and the car will kind of cough once and then kick in and start revving up. Funny how the car started running rougher after I relpaced the MAF sensor. Go figure.

Also got the Motorvac cleaning done. Didn't make any difference. Mechanic said it would take 100-300 kms before it goes through the whole system. We'll see.

 

When i had the motor apart i cleaned EVERYthing till it looked new.
Also My plugs, wires, cap, rotor, oil, oil filter are all new.

When i disconnect the iac my idle goes up much higher, too high for normal driving.

With it connected its way too low, cuts off sometimes.....

 

Anyone checked their TPS voltage lately? That could be a possibility....

 

I have not checked mine since i got the car.
It think its a bad iac because when its connected its too low(idle) when its connected its too high.
I dont have a volts tester so ill have to get one. Cant hurt to check the tps even if it isnt the problem.
Btw $49 here for the damn iac. That sucks!

 

NO way. 28.00$ I have the exact same problem. I was going to say clean it up. That could cure the problem. Go to advanced auto and they have it. Let me know how you make out. Thanks

 

i have cleaned mine, it looks chrome. Mine doesnt move either. I had it out and connected to the ecm and when i jumped the ad and turned on the key it didnt move at all.

 

When you cleaned the IAC, did you remove the conical portion of it and clean that? It gets really carboned up even though it is inside the stepper motor. Did you take the top off of the throttle body and clean inside there as well?

 

yep yep and yep. When i had the motor apart i cleaned everything. I took the tb apart and all. After i put the iac back together i noticed it didnt move. thats what made me think it was bad.

 

What do you mean it doesn't move? How are you testing it to see if it moves?

 

I do think you have to have the engine running so the ECM knows what position the IAC needs to be in to maintain a certain RPM range, and will adjust it accordingly to what the engine is doing at the time. When the engine is not running but the key is on, the ECM will close the IAC to let less air mix with the given amount of fuel so the engine can start easier, similar to a choke plate in a carb. If you have the IAC so that it is in the "closed" position (pintle as far out as it can go), you won't notice anything because the pintle is so far extended it doesn't need to extend any more for the ECM to think it's closed.

 

My iac doesnt move. Engine on or off. Key on off or in my pocket, it doesnt move. Also i have some small dents ontop of the iac housing like someone smacked it with a wrench. Maybe it was acting up on the previous owner.

 

I'm sure that someone has mentioned that unplugging the IAC with the engine running will throw it out of adjustment. Anyone know if that's true?

 

i doubt it.

I just unscrewed mine to see how clean it still was. Its still clean. I guess a blocked off egr keeps the inside of the plenum real clean.
I also plugged in the iac with it unscrewed from the plenum and jumped the adl and turned the key to see if the iac moved.

The pintel shot across the engine bay!

So iac is ok, i reinserted the iac and did the relearn again.
Car still idles real low so maybe my tps isnt adjusted correctly.

At least i know i dont need a new iac.

 

I listened to the tap/ticking more today since it was warm out and it seems to be louder under the car.
Doesnt seem right for a collapsed lifter to me
Its loudest right smack by the cat.
Also when i rev it up pretty high i have carbon smoke shooting from the tail pipes so i think the cat is trash.

Oh well if the tap/tick is still there after the cat hollowing ill try the lifters.

 

Brobert, you have yourself a leaking cat right there or one of the joints. Carbon smoke means you have too much gas or gas vapor going into the intake from who knows where (leaking injector is what I would look for since you don't have any more EEC canister), or that your TPS is misadjusted and has to be set differently according to the idle speed. Check your plugs. If they are not black then you can go ahead and do whatever with the cat. If they are black, the TPS is set too high according to the IAC setting, and is giving the engine too much gas to fire normally, hence the low idle.

 

plugs are fine, i think its the cat

 

Are you basing that statement on fact or the last time you seen any of the plugs?