NEED HELP Clean Throttle & MAF Sensor... Still Rough at Idle...

[AC75TB07]

I cleaned my throttle body which was FILTHY, could have used a chisel on the buildup, and gave the MAF a good clean too. Everything improved, but when I start up and let the truck idle for a few minutes, it goes sorta sputtery and rough until I hit the accelerator. It hesitates for a split second then takes off just fine...

I followed a few YouTube tutorials to do the cleaning, and pulled the PCM fuses rather than disconnecting the battery... I had the fuses out as long as it took me to dissasable, clean, and reassemble everything so that should have been long enough, surely? The clock and stereo etc. didn't reset though...

Did I miss anything important? Anything I should check? Anything else I should clean?

Thanks for advice...

 

[JayArr]

Do you have a Tech 2? Run the diagnostic to look for misfires. I've had coils go bad where the first indication is they miss at idle but run OK at speed. Later they fail altogether. The Tech 2 has the screen that tells you which cylinder is missing and how often, it's a real time saver.

 

[Mooseman]

First of all, do have a CEL and check for codes? One possibility is water in the gas. Seen that before

How's the maintenace? Plugs replaced lately? Maybe check the fuel pressure too.

 

[AC75TB07]

I do have a scanner but haven't checked yet because the weather is shite this week. Will do.

When I started up today everything was good at idle until I dropped into reverse. Then it just did a little sputtering and hesitated when I backed out. A little throttle and it was fine and drives fine. Stopped in traffic for a couple minutes and no problems there either.

I have no history records on the plugs or coils. I've got about 180,000 Kilometers on the clock.

 

[TequilaWarrior]

Which fuses did you pull, exactly? When I do mine I think I pull a total of 3 fuses... because I'm not sure which one it is exactly. Alternately, if you have a reader that can clear codes - I believe that clears the PCM's memory as well. It sure seems mine does and mines a cheap one. Also, are you sure you reinstalled the throttle body correctly? All hoses and cables, etc, in the right place? Check for vacuum leaks? Make sure everything is installed correctly...

 

[AC75TB07]

Which fuses did you pull, exactly? When I do mine I think I pull a total of 3 fuses... because I'm not sure which one it is exactly. Alternately, if you have a reader that can clear codes - I believe that clears the PCM's memory as well. It sure seems mine does and mines a cheap one. Also, are you sure you reinstalled the throttle body correctly? All hoses and cables, etc, in the right place? Check for vacuum leaks? Make sure everything is installed correctly...

I pulled fuses 10 and 28. PCM B & PCM 1. Should I have pulled some other fuse as well?

I'd say I'm pretty confident in the work and that I reinstalled everything OK. Checked it all over and the truck started right back up.

 

[Mooseman]

Alternately, if you have a reader that can clear codes - I believe that clears the PCM's memory as well.

No it doesn't. It's kept deeper and needs a full 30 minutes of no power to clear it. Here's an article that gives a procedure and which fuses to pull.

Throttle body (TB) relearn (4.2)

Hope it's not a re-post but here's what works. When you clean your TB generally you need to pull the wire harness but some may leave it attached. Either way, the PCM needs to re-establish the idle position after the gunk has been removed from the bore. This may or not be 100% accurate since...

gmtnation.com

 

[TequilaWarrior]

Mooseman would know better than I. Maybe try pulling fuse 10 for an hour and see what happens.

 

[mrrsm]

The crusty nature of the Throttle Body prior to getting a good cleaning might be tied to a particularly clogged Air Filter. And since you mentioned "...and gave the MAF a good clean too..." it follows that the MAF is a rather *Finicky* component that...if not cleaned with the recommended CRC MAF Cleaner versus a common Brake-Kleen Solvent might make things worse:

Amazon.com

Take a minute or two to observe how Paul "Scanner" Danner addresses the importance of the MAF's ability to correctly WEIGH the incoming Air Stream ... and what he does to Clean this Device in the following two videos. Otherwise... the PCM won't know precisely how much EFI Spray is required for a decent Air-Fuel Mixture... and a symptom of this discrepancy can be engine staggering and stalling. Ignore the Vehicle Make and Model...it is the PRINCIPLE here that is important:

If you are unlucky enough to have a Rodent Infestation Problem...they will tend to incessantly Gnaw away on Wiring Harnesses and Module Connectors. Check Out Paul's (and his son Caleb's) discovery of what the MAF failure in this GM Truck turned out to be and follow his model of Checking ALL your Engine Module Harnesses for any damage at the MAF, IAT and Throttle Body locations: