[anku94]

Hi all,

I have some questions around throttle body issues that my dad is facing with a 2008 Chevy Spark.

They're definitely solvable by replacing the whole assembly, for which the ASS is quoting 18k, and these questions are purely in the spirit of "hustling out" an alternative to spending that amount for a somewhat beaten down car.

Also, my understanding of some of the specifics may be hazy, they've been received from dad over phone, and I live too far off to be able to check it personally.

Problem: idling issues with the car. Dad has alternatively reported "car won't start" and "car would stall when I try to engage gear 1, but I was somehow able to manage by stepping on the gas heavily to get home".

So he called some local mechanic over, who pulled up the OBD codes on his phone, and a code for "Idle Speed Control" seems to have been triggered. The mechanic might have attempted some cleaning etc, after which he reset the code, and the car seems to work fine, but with the YMMV caveat.

My understanding is that when the ECU detects throttle body glitches, it switches to some failsafe mode, which might explain him finding the extra acceleration and all necessary. He got it cleaned, so if the issue was caused by some fluke, the reset should work (which it seems to).

1. If one were to hazard a guess from this limited diagnostic information, is there a good chance that the code was a fluke and the assembly should be fine?

2. It seems to me that the throttle body replacement is fairly DIY-able (with the help of say, a local mechanic), without needing fancy recalibration gizmos. You just remove and replace the wiring and throttle harnesses. Relearn procedure seems to be a simple start car, idle for 10 seconds, stop engine, wait 10 seconds. The throttle body seems to be 1/3rd the cost if one calls around and orders the part.

Is this line of reasoning err.. reasonable? I understand of course that any DIY will be fraught with some risk, just want opinions on whether it's something that's pretty hard to get right, or doable with some precautions.

Thank you!

[Jeroen]

Idle Speed Control is not necessarily related to the throttle body. So as always you have to ensure you get a proper diagnosis before doing anything!

Failsafe mode is something completely different from issues idling. Also failsafe mode can be triggered by a host of different issues, some of the throttle body, but not necessarily throttle body alone. (E.g. on Jaguar a wonky brake switch is a known cause for failsafe mode.

Best is to try and figure out what the real code was or is.

With the few symptoms you describe I would first check the idle air valve, check for air leaks, dirty electrical connections on various sensors. grounds straps etc.

But best is to get somebody reliable to hook up an OBD reader and get the codes. That will give a much better idea of what is going on.

Good luck

Jeroen

[nirmaljusdoit]

Can you please upload a copy/photo of the scan report ? It would help to give a proper guidance !

Has the issue gone after the throttle body cleaning ? How was it done ? What is YMMV caveat ?

[geekyengineer]

I own a 2013 Chevy Sail and had similar issue.

My FNG mechanic, takes out the valve from the throttle body and cleans it and that solves the issue. The valve requires the cleaning on yearly basis. If not cleaned, the car overshoots RPM in stop and go traffic.

He charges only some 200 bucks labor and add another 100 bucks for the WD40.

Try this once.

[anku94]

Originally Posted by Jeroen

Best is to try and figure out what the real code was or is.

With the few symptoms you describe I would first check the idle air valve, check for air leaks, dirty electrical connections on various sensors. grounds straps etc.

Originally Posted by nirmaljusdoit

Can you please upload a copy/photo of the scan report ? It would help to give a proper guidance !

Has the issue gone after the throttle body cleaning ? How was it done ? What is YMMV caveat ?

Originally Posted by geekyengineer

My FNG mechanic, takes out the valve from the throttle body and cleans it and that solves the issue. The valve requires the cleaning on yearly basis. If not cleaned, the car overshoots RPM in stop and go traffic.

So I called up dad for updates on all these issues, and here's what apparently happened.

1. The local mechanic did not really do anything - he reset the code, car seemed to work, he recommended an ASS visit ASAP

2. Dad went to ASS, and the mechanic there seems to have been diligent. He cleaned up the throttle body using some fluid (not necessarily a spray can cleaner meant for this purpose, could've been diesel, dad's not sure), found a puncture in some tubing (dad says it was 3/4" or so in diameter), did not have an OEM replacement but fashioned something out of something to replace it, also found an issue with some sensor that he then cleaned, and it seems to be fine now.

These line up with the possible culprits @Jeroen described, so I'm somewhat confident that the underlying issue has indeed been resolved. If it comes to it, the ASS mechanic also suggested salvaging a replacement throttle body from discarded vehicles in a junkhard he knows, which should be a fraction of the cost.

Just for the sake of completeness, I'm sharing a screenshot of the code from the local mechanic's app. Fingers crossed that the issue is indeed resolved - thanks for the inputs everyone!

[Jeroen]

Originally Posted by anku94

S
Just for the sake of completeness, I'm sharing a screenshot of the code from the local mechanic's app. Fingers crossed that the issue is indeed resolved - thanks for the inputs everyone!

When you google this DTC this is what you will find:

Possible causes:

• Faulty Throttle Actuator Control (TAC) module
• Throttle Actuator Control (TAC) module harness is open or shorted
• Throttle Actuator Control (TAC) module circuit poor electrical connection
• Throttle plate sticking due to carbon build-up
• Engine Control Module

So this code can be triggered by at least 5 different items, only one of which is the actual throttle body. If it was indeed the throttle plate sticking due to carbon build up, very likely the cleaning has resulted in solving the problem

Jeroen

[AntPaul]

Originally Posted by Jeroen

Possible causes:

• Faulty Throttle Actuator Control (TAC) module
• Throttle Actuator Control (TAC) module harness is open or shorted
• Throttle Actuator Control (TAC) module circuit poor electrical connection
• Throttle plate sticking due to carbon build-up
• Engine Control Module

Jeroen

The throttle should be simple mechanical one (I am assuming since Spark was a fairly economical car to purchase), so there should be no throttle actuator other than accelerator cable.

The throttle body houses the throttle plate, IAC, and throttle position sensor.
So chances are carbon/oil sludge build up due to PCV or dirt from leaky air intake plumbing. Cleaning these sensors, valves and throttle plate is fairly straight forward.

I wonder that the punctured 3/4 inch tube. Could it be the pipe from air filter to throttle?