Intermittent low idle & stalling

[MH1]

Hello,
I have 1999 SR5 V6 with 240K miles which I bought new. I have maintained and service this truck myself and take care of it very well. Recently, I have been having intermittent low idle (450-500 RPM) and intermittent stalling, specially when truck is nice and hot with No ck engine light! I have read about the idle control valve and throtle body cleaning and did that last week. The throtle position sensor was replaced 3 years ago, the spark plug wires and plugs were replaced 25000 miles ago 4 years ago. I run fuel injection cleaner at every oil change and replace PCV valve. The fuel filter was replaced 20,000K ago . 3 of the 6 injectors on the driver side was replaced about 5 years ago. Air filter replaced every 15k.

The truck runs great and drives fine but the idle issue is driving me crazy!! Do you guys have any suggestions or experiences with this issue? I ordered the Blue driver OBD2 tool from Amazon yesterday and waiting to hook it up and see if it gives me any more information.

Thanks in advance!

 

[mtbtim]

Have you checked for vacuum leaks?

 

[jgue467]

So when cleaning the throttle body - was the flapper and its pivot points cleaned really well also?

Does the flapper sit ever so slightly open? It should.

Luck and enjoy your Runner.

 

[MH1]

Thanks for the reply guys....Yes, I have looked at all the hoses and I did not see an cracks or anything noticeable. I can only do a close visual inspection and and looking closley at all the hoses and did not see any cracks. Yes, the flap in the throttle body and it's pivot point were cleaned out and i didnt pay attention to any gaps when it closes shut. It looks like it closes shut , so not sure on that part. But this Idle has driving me crazy....I got the Blue driver scanner, going to scan this weekend and see if I notice anything strange.

If anyone fix this issue, I'm real curious as to what was the cause, it's got me stumped!!

Thanks again

 

[spartacus]

Test the iac, and clean the maf, check the engine grounds, long shot the engine coolant sensor.

 

[mtbtim]

Thanks for the reply guys....Yes, I have looked at all the hoses and I did not see an cracks or anything noticeable. I can only do a close visual inspection and and looking closley at all the hoses and did not see any cracks. Yes, the flap in the throttle body and it's pivot point were cleaned out and i didnt pay attention to any gaps when it closes shut. It looks like it closes shut , so not sure on that part. But this Idle has driving me crazy....I got the Blue driver scanner, going to scan this weekend and see if I notice anything strange.

If anyone fix this issue, I'm real curious as to what was the cause, it's got me stumped!!

Thanks again

I'm still not sure if you've ruled out the IAC as the culprit. This is sounding like an IAC problem. Did you happen to see if there was any issue with the Air Assist hose that connects to the IAC?

 

[SirWilliamGoes]

Id say try cleaning the MAF also the TPS you said you replaced, was it OEM or aftermarket? A good rule of thumb Ive always used is that if it has a wire, get it from dealer / OEM

 

[Spiker Engineering]

I'm also suspecting the IAC. When you use your scanner, see what the LTFT and STFT readings are.

 

[Hungryhawk]

I also think the IAC is part if the problem. If you take it off the intake system it will clean up with spray can of solvent cleaner and brushes Be careful not to get into your eyes. Have a water bottle handy in case you splash your skin. If lucky you might not damage gaskets and be able to bolt back.

 

[MH1]

Thanks so much guys......... the MAF has been cleaned out and the TPS which I replaced soem time ago had the check engine light but it was from Autozone not OEM. But after I replaced it, the Ck ENg light went off, so I assumed all is good. The dang Blue driver scanner, reports no trouble code, I looked thru it's menues but it does not show any alerts or problems. Not sure where the Air assist hose is, but when taking the throttle body out, you have to disconnect a small rubber hose and a thick rubber hose to remove the air intake and I looked closely and didn't see any cracks. I did not see any values for the LTFT or STFT , I will run the scanner again and see what it says, Thanks again!!

 

[phattyduck]

I did not see any values for the LTFT or STFT , I will run the scanner again and see what it says, Thanks again!!

LTFT and STFT are "live" data - and won't be on any reports/scans. Find the live data (it should support that?) and see what it says during various operating conditions.

A stock engine running well (no headers, intake, supercharger, stock injectors, etc.) should be within +/-5% basically everywhere.

-Charlie

 

[MH1]

Ah...got it, thanks very much. I will have to run the scanner and look for Live report and see the values and compare them!

 

[mtbtim]

Thanks so much guys......... the MAF has been cleaned out and the TPS which I replaced soem time ago had the check engine light but it was from Autozone not OEM. But after I replaced it, the Ck ENg light went off, so I assumed all is good. The dang Blue driver scanner, reports no trouble code, I looked thru it's menues but it does not show any alerts or problems. Not sure where the Air assist hose is, but when taking the throttle body out, you have to disconnect a small rubber hose and a thick rubber hose to remove the air intake and I looked closely and didn't see any cracks. I did not see any values for the LTFT or STFT , I will run the scanner again and see what it says, Thanks again!!

The air assist hose connects to the IAC. It's the one without a constant tension clamp on it. That hose leads to a plastic tee at the back of the intake manifold and then one rubber hose on each side connects to the tee and plugs into a metal port on each side of the intake manifold to feed air to the injectors.

 

[Spiker Engineering]

The air assist hose connects to the IAC. It's the one without a constant tension clamp on it. That hose leads to a plastic tee at the back of the intake manifold and then one rubber hose on each side connects to the tee and plugs into a metal port on each side of the intake manifold to feed air to the injectors.

 

[MH1]

Just wanted to give a quick update......after reviewing everything I have done and all the great helpfull information from everyone here, I ran the OBD scanner and I got P0171 system too lean Bank1. One thing that I did not do after I performed all the work and cleaning Idle control valve and throtle body was to disconect the battery for about 15-20 min and reconnect to clear the code. Well, I did that over the weekend and so far, so good!!! The idle issue seems like it has been resolved, atleast I am not noticing it drop to 500 at red light anymore. I may need a few more days to be sure but so far the idle looks normal. Thanks again to all of you for your help and sharing the knowledge, may we help others as well and god bless!