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Re: [GMCnet] Thanks for Help [message #308876] Mon, 17 October 2016 10:36 Go to next message
THOMAS R WHITTON is currently offline  THOMAS R WHITTON   United States
Messages: 47
Registered: September 2016
Karma: -1
Member
I want to thank three GMC owners who helped me diagnose a problem I had with my coach on the way home from the Mansfield rally:  Bob Stone, Bob Burkitt and Randy Van Winkle.
In Kentucky, forty miles or so south of Cincinnati on I-71 we pulled onto the front section of a gas station for a rest stop.  The coach wouldn't start when we were ready to leave. The starter turned the engine over but it wouldn't start.  Three construction workers in a diesel pickup truck offered to give me a jump.  I  didn't think it would help but accepted the offer.  The engine started but wouldn't idle.  As soon as I took my foot off the gas pedal it died.  After a few tries, I learned how to keep it running most of the time but didn't want to chance driving 300-miles like that.  It might have been okay on the interstate but might not restart if we stopped for any reason.  The good Samaritans in the pickup offered to lead me to the nearest campground, which turned out to be 8-10 miles away on narrow roads, up and down hills and around curves.  When we got to the campground the guys wouldn't take anything for their trouble.
The campground itself was fine but there was no AT&T cell service.  This was "Verizon only" country.  I had to ask the lady who runs the campground to use her phone.  I then called Bob Stone.  He suggested I call Bob Burkitt who lives in Cincinnati and Randy Van Winkle who is very knowledgeable on throttle body injection.  When I reached Randy and described the symptoms, he said it sounded like the Idle Air Control (IAC) was not retracting.  If not, it could be the Throttle Position Sensor or possibly the MAP sensor, in that order.  He told me I could tell if the IAC was retracting by looking at the pintle, the arrow head shaped end of the spring loaded rod on the end of the IAC.  If it visible inside the TBI, it probably wasn't retracted to allow air into the system for the next startup.  I checked.  The pintle was visible inside the TBI so I decided to  try to find a replacement.  About this time, my neighbor in the campground offered to give me a ride into Carrolton, a town of about 4,000 people.  It turned out that Carrolton had an AutoZone, Advance Auto NAPA and an independent parts store.  None had an IAC in stock but the AutoZone could get one from another store by 6:30 that evening.  It was about 2:30 in the afternoon.  I couldn't ask my campground neighbor to wait until 6:30 so we went back to the campground.  He told me on the way back that he had family coming in to visit and wouldn't be able to give me a ride back into town.  The lady manager of the campground offered to go into town after she closed and pick up the part.  At 9:30 PM she knocked on our door and handed me the part.  She wouldn't take anything for her trouble either.  I immediately put the new IAC on.  The engine started and idled down perfectly.  We stayed the night, unhooked and started the engine the next morning, ready to leave.  The engine wouldn't keep running.  As soon as I took my foot off the gas it died.  We were back to square one.  
My wife at this point was more than ready to get home.  I was trying to decide what to do next about the coach.  She was suggesting options for getting her out of there.  I called Bob Burkitt, he started looking for parts around Cincinnati, checking rental car and airline possibilities.  Randy Van Winkle again went through what the problem might be.  These included the O2 sensor and even the computer itself.  I carry a spare computer but it has never been tested.  I bought it at a junk yard a few years ago for $20 and stuck it under the seat in the coach.  I also carry a spare ignition module and rotor.  I tried all these parts without success.  Another campground neighbor came by and offered to take me into town.  I jumped at the chance.  It so happens there were two possibilities, the pintle diameter on one is slightly larger than the other.  AutoZone had gotten them both in from the other store.  This time we miked the pintle on my old IAC.  Sure enough, the diameter of the first replacement IAC was slightly smaller than the other one.  When I tried the second IAC the engine started, idled down correctly and restarted.  So, again we stayed the night.  The next morning the engine started, idled down correctly and restarted.  Three hundred interstate miles later we were home without a hitch.  

Here's what I learned:1. Never take a GMC trip without a tow car2. How to basically troubleshoot a TBI3. What spare parts to carry4. Keep the blacklist handy5. Return the favors 
Importantly, I was reminded of the goodness or people.  I had a lot of help from good people who saw that I needed help and from fellow GMC motorhome owners, namely Bob Stone, Bob Burkitt and Randy Van Winkle.   
Thanks to everyone,
Tom Whitton26 foot updated GMC (now with a new IAC)Paducah, KY










   



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Re: [GMCnet] Thanks for Help [message #318166 is a reply to message #308876] Mon, 29 May 2017 18:43 Go to previous messageGo to next message
larry.whisler is currently offline  larry.whisler   
Messages: 356
Registered: August 2005
Karma: 8
Senior Member
Tom & Netters,

Is there any way to test the IAC to see if it is working?

I removed it from the throttle body unit and plugged it in
and turned on the key to see if it would retract or move the pintle.

No activity so I am wondering if this is my problem. I am having
the same symptoms you describe.

larry
Re: [GMCnet] Thanks for Help [message #318173 is a reply to message #308876] Mon, 29 May 2017 19:33 Go to previous messageGo to next message
RF_Burns is currently offline  RF_Burns   Canada
Messages: 2277
Registered: June 2008
Location: S. Ontario, Canada
Karma: 3
Senior Member
Larry,
I can't remember what type of EFI you have (Howell, EBL etc). I have an EBL ECM, it moves the IAC each time I turn the key ON.

If you have a GM 7747 ECM, if you goto Bob Drewes TPS setup and follow the instructions for adding a jumper. The IAC will extend and re-tract.
http://www.gmcmi.com/wp-content/uploads/2013/02/Whats-Up-with-EFI.pdf
it starts on page 21

The IAC on my original Howell TBI (Holley TB) died after a couple of years. I have a GM Rochester TB now.


Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.
1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that
Re: [GMCnet] Thanks for Help [message #318174 is a reply to message #308876] Mon, 29 May 2017 19:35 Go to previous messageGo to next message
RF_Burns is currently offline  RF_Burns   Canada
Messages: 2277
Registered: June 2008
Location: S. Ontario, Canada
Karma: 3
Senior Member
Larry,
Don't power the IAC while you have it out. If you do it could eject the pintle, then after to find the pintle and spring, its hard to get back together.


Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.
1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that
Re: [GMCnet] Thanks for Help [message #318182 is a reply to message #308876] Mon, 29 May 2017 20:16 Go to previous messageGo to next message
jhbridges is currently offline  jhbridges   United States
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
Senior Member
I refer to the toad as a 'lifeboat'. I will bobtail my coach alone, but if wife and or dogs are present, so is the toad.

--johnny


Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons. Braselton, Ga. I forgive them all, save those who hurt the dogs. They must answer to me in hell
Re: [GMCnet] Thanks for Help [message #318187 is a reply to message #318182] Mon, 29 May 2017 20:44 Go to previous message
tphipps is currently offline  tphipps   United States
Messages: 3005
Registered: August 2004
Location: Spanish Fort, AL
Karma: 9
Senior Member
Towd=Escape Pod.
Tom, MS II


2012 Phoenix Cruiser model 2552 KA4CSG
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