Maury

iTrader: (1)

sorry if i'm becoming a pain. i'm trying to educate myself as fast and correct as i can, but i'm new to the whole idea of fixing my own car. i truly appreciate all of you for your patience with me.
now that i've fixed my mafs, the only problem is that my idle is very, very low ... any lower and the car will stall. i'm looking at my haynes manual all day & doing my best, but i hit a snag. i reset the idle speed via the adjustment screw, and now she's back to 700ish rpms... running great. my question is this; is it possible that by cleaning the throttle body (for the first time in 112,000 miles) and replacing the mafs, that i needed an idle adjustment? i did the check where you let it idle and throw the a/c to max - passed that test no problem. i get no codes now either. i'd really appreciate your opinion. i did a search here on "idle" and noticed that you had told someone else that adjutsing the idle may only mask other problems. i get no code, so i'm hoping it's just the recent change in my mafs and that "path". as always, thanks.
maury

emax02

iTrader: (1)

Your best bet whould be to check for air leaks after your MAFS.

Sonic

Idle Air Control Valve. Do a search for that inseatd.

Maury

iTrader: (1)

thanks guys. i did the "haynes" check on the iacv and it passed. i'm going to try and look for leaks, but so far i'm not sure how...visually all hoses look ok. i'll keep at it, and if either of you guys have another idea, it's definitely appreciated. you guys are really great to be so helpful. still no codes so far.
thanks

Daniel B. Martin

This kind of leak is called False Air and it results in a racing idle. Maury reports the opposite problem, a slow idle speed.

Daniel B. Martin

Here is some text copied from the factory service manual.

"Idle Air Control Valve (IACV) -- Auxiliary Air Control (AAC) Valve

This system automatically controls engine idle speed to a specified level.
Idle speed is controlled through fine adjustment of the amount of air which
bypasses the throttle valve via the IACV-AAC valve. The IACV-AAC valve
changes the opening of the air bypass passage to control the amount of
auxiliary air. ... "

The correct idle speed is...
- 700 +/- 50 (automatic transmission, in Neutral)
- 625 +/- 50 (5-speed)

Here's the factory service manual component inspection procedure for the IACV-AAC.

1) Make this test with the ignition key OFF. Disconnect the IACV-AAC valve harness connector.

2) Looking into the valve connector with the latch at the top, you will see two rows with three terminal positions in each. They are numbered 1-3 (top row, right to left) and 4-6 (bottom row, right to left). Check resistance between the following terminals.
2 and 1.
2 and 3.
5 and 4.
5 and 6.
At a temperature of 68 F, the reading for all measurements should be approximately 30 ohms.

3) Reconnect the IACV-AAC valve harness connector.

4) Remove the idle air adjusting unit assembly (IACV-AAC valve is built-in) from engine. The IACV-AAC valve harness connector should remain connected.

5) Turn ignition switch ON and OFF, and verify that the IACV-AAC valve shaft smoothly moves forward and backward. If NG, replace the IACV-AAC valve.


There are other engine parts which play a role in maintaining the right idle
speed, but the IACV-AAC is the first thing to look at. Good luck!

Maury

iTrader: (1)

thanks daniel. yeah, i just checked the resistance across the terminals and it passed... i haven't yet done the other test yet. i'll go and try that right now and post my results in a few minutes. also, is there any type of cleaner or "engine flush" i should do at this mileage (112k)... like something on the shelf at autozone, or a dealer service? thank you
maury

Daniel B. Martin

Replacing the Mass Air Flow Sensor should have no effect on the idle. Cleaning the throttle body... that might have an effect. Did you clean the TB by removing it and doing the cleaning "on the bench"? Did you clean it while still fastened to the upper intake manifold? If the latter, there is some small chance that the deposits which were loosened moved just two inches downstream and are now obstructing the Idle Air Control Valve.

I have learned more about the IACV and no longer recommend the A/C test. That is a good test for the A/C fast idle solenoid which is adjacent to the IACV, but is not a good test for the IACV itself.

No Codes means the problem is not one of the things the Engine Control Module tests. It is not surprising that you are getting no Codes.

IMHO the idle speed screw should never require adjustment. Solving an idle problem by adjusting that screw is not the right fix, it merely compensates for some other problem which remains unsolved.

Maury

iTrader: (1)

thanks daniel. i apologize for the delay... it's been a long day
yes, when i cleaned the throttle body it was still connected to the intake. since your last post, i took out the iacv housing & checked the black shaft for movement - it moved. i took the whole thing apart and i did find black gunk in there (not tons of it, but it was not clean.) so i cleaned in there with some throttle body spray, reassembled everything & took a test drive.
now it felt as though my idle was slightly too high, so i put the car in self-diagnostic mode & reset the idle screw to where it was originally. right away i got a code 0806 - fuel lean or rich in left bank. i thought "give me a break!" i cleared the code & took 2 test drives since and it feels like we're back to normal.
in summary, i cleaned the tb, changed the mafs, increased the idle speed via screw, cleaned the iacv, and lastly returned the idle to where it should be. thank you all for the help and with any luck, we're done here!
sorry for the long post, but i wanted you to have all the info.
good day,
maury