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Pete, Auto Service Technician
Category: Chevy
Satisfied Customers: 28253
Experience:  14 years GM dealer Technician.
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03 gmc savanna 5.3 engine intermittent Low Idle. Changed

Customer Question

03 gmc savanna 5.3 engine intermittent Low Idle. Changed MFS, cleaned Low Idle Valve ( not avail - has be bought with Throttle Body assy = $ 500. GMC dealer could not duplicate failure? Thanks for any suggestions
JA: How many miles are on the car? What size is the engine?
Customer: 120K engine 5.3 ltr
JA: Are you fixing your Savana yourself? What have you tried so far?
Customer: Yes, due to dealer could not duplicate low idle issue. See first message as to items tried. Thx
JA: Anything else you want the mechanic to know before I connect you?
Customer: Usually occurs after driving awhile and engine is fully warmed up. VERY intermittent issue. Is there a temp sensor that may be involved?
Submitted: 3 months ago.
Category: Chevy
Expert:  Pete replied 3 months ago.

Hi my name is ***** ***** I will be happy to assist with this today.In some cases I may need more info to assist better.I apologize for any delay.

Did you already clean the throttle body at all?

Let me know so we can continue,thanks Pete.

Customer: replied 3 months ago.
Cleaned all areas I could see with Mas Air Flow Sensor Cleaner. Did not appear to be very dirty. Just some darkness around the edges of flapper ( for lack of a better disc. )
Expert:  Pete replied 3 months ago.

Did you spray the cleaner into the throttle body or use a shop rag with cleaner on it to wipe out the throttle body?

Customer: replied 3 months ago.
Just spray. Used a flash lite and sprayed all areas to include the 2 top recessed areas at top of body. Will start ok numerous times and then after driving awhile, will start the low idle issue. Frustrating.
Expert:  Pete replied 3 months ago.

O.k.,that was an issue on these.If you spray into the throttle body the fluid can work its way down the shaft of the throttle plate into the throttle control motor and throttle position sensor.The way that it needed to be cleaned is to spray onto a rag and take the rag and wipe out the throttle body bore opening the plate by hand carefully and wiping beyond the plate to clean out the carbon.

If you know for sure it is clean now most likely the throttle motor or throttle position sensor is at fault here with the throttle body needing replaced.It isnt allowing the throttle plate to stay open enough to allow it to idle properly when warm or intermittently.I have seen this occur before unfortunately and had to replace the throttle body for this issue here.

Once replaced you can relearn the idle position by key on for 10 seconds then key off for 10 seconds and repeat 2 more times then start the engine.

You can obtain a new throttle body from a dealer or local parts store ( as the local parts store may be cheaper) or even used for far less of a cost.I use for used parts and they can ship it to you.

But if no codes are set I do suspect throttle motor or throttle sensor in the throttle body at fault with the throttle body needing to be replaced.

If more help is needed, use the reply tab to continue our conversation. If no further assistance is needed, kindly rate my service,your 5 star rating is appreciated.You can rate at any time and we can continue to work on your question as this will not close out your question.Keep in mind in some cases it can be difficult to fully diagnose or help repair your vehicle without seeing it and I work on delivering the best possible answer from what I see to work with.

Thanks Pete