2003 Chevy Express Van 5.3 L Idle too Low

[Tbone]

OK, I know this a Buell site, but I have already checked on-line and with Chevy & GMC stealerships as well as an independent garage and I had no Luck. Anyways this van has 208,000 miles on it and I am the only owner so it has been maintained.
HISTORY: Initially the van Idled too high and had codes for too lean fuel bank(s) so I did the following:
Intake Manifold gasket.
Fuel Filter/pump
MAF Sensor
IAC/IAC connector kit ($18 part at NAPA) This fixed the high idle because broken wires at IAC connector.
CURRENTLY: Now the Van Idles too LOW during warm up with no CEL or codes. During warm up especially first thing in the morning, it will stall if you try to drive it before it reaches Operating Temp ~180 F. I usually let it warm up so it is not too big a deal, but my wife does not have the time, patience to let it warm up in the morning.
I have tried to do a couple things:
Clean the throttle body, IAC ports, MAF, etc...
Idle re-learn by disconnecting the battery for 20 minutes, starting, put in drive and let idle for 10 minutes, then neutral and idle another 5 minutes. Also other idle relearn procedures, seems to work until the next day & SSDD. I have temporarily resolved the issue by wrapping a cable tie around the idle stop on the butterfly cam and it idles pretty good at all times, seems like 600~700 rpms without stalling in all situations. The idle stop on the TB seems to have glue on it like maybe there was a rubber bushing or something there on top of the idle stop? Stealership wants $99 to diagnose and another $80 to clean the throttle body again and they say it might fix it? Cable tie is a lot cheaper so far, but want something more permanent for a fix.

 

[Theycallmecrash]

Quit being cheap and get it diagnosed.

 

[Cosworth]

Check the coolant temp sensor, at those miles they can be bad it controls the open closed loop transition and wont switch correctly if reporting faulty information.

 

[Tbone]

Yea, I have thrown a lot of cash at it already. Chevy diagnosed then replaced the Intake Manifold gasket for $1,000, also replaced the fuel pump for $800. as well as an Independent garage replaced the IAC for $180, MAF for $280 and it did not fix the high idle until I googled it down to a less than $20 replacement IAC connector from NAPA which I did myself. All the idle problems began after Chevy replaced the water pump, thermostat, hoses, flushed the radiator for $1200. Google says it is common for the wires to get broken at the IAC connector when having work done on front of the engine on the van. It became a DIY project because I spent all my money at Chevy trying to fix a high idle. Now I am having low idle issues and afraid to have more diagnosing and work done that will not fix the problem again, and might be something I can fix cheaply? I can't afford not to be cheap.

 

[Cosworth]

You should be able to unplug the coolant sensor on the drivers head behind the power steering pump reservoir and note any change in idle.

 

[lawdog]

Get a Bluetooth OBDII adapter, run about $10-20 on Ebay. Get Torque app and monitor all your engine data and sensors to troubleshoot. Best investment you can make to diagnose problems. Watch your coolant temperature sensor, iac commands, idle rpm, tps, etc.

 

[Tbone]

Thanks Cosworth, will check this on my way home from work.

 

[Cosworth]

^the torque app lawdog suggested is a great tool for diyers

 

[Spud]

Try a TPS reset

 

[Tbone]

I think a TPS reset consists of disconnecting the battery for a time, and there are a few different procedures on what to do after that? I also disconnected the connector to the TPS, flipped the throttle linkage a few times and reconnected the TPS. Both of these seemed to have only a temporary impact.
Well I replaced the ECT Sensor last night with the battery disconnected. Connected the battery this morning and drove to work. I did not let it warm up, not too cold this morning and it was a little shaky, but drove better. The ECTS was $23 at AutoZone and pretty easy to access except the lock clip was brittle and disintegrated when when I unlocked the plug from the sensor. I made a lock out of 3 zip ties. The temperature is now reading ~18 F lower than with the old sensor, I guess this sensor sends the temp to the computer then to the temp gauge. With the old sensor it was reading just above ~200 F, now it reads about ~184 F. Hopefully this indicates that it needed to be changed as I speculate the the old one was beginning to short, or closing it's connection too soon? Probably will know tomorrow morning after the engine cools down overnight. No problems after it is initially warmed up in the morning.

 

[Cosworth]

With vehicles you basically set the TPS to read what the computer wants to see which should show approx. .5 at idle and 4.9 at WOT. Stock TPS sensors are not slotted so cannot be adjusted unless you dremel a slot. Too many other things to account for if you try resetting the factory set blade such as IAC, etc.

To read/test the TPS voltage either use a scan tool or you can use a volt meter at the TPS and test the dark blue wire for the voltage as stated above approx .5-4.9