What's he done to my throttle

[bernhund]

Took my car to the local garage to look for a potential water leak & a general look over. He said he gave the throttle housing a clean, but now tick over from cold is around 1300 which drops to around 800/900 once warm. Occasionally the revs now bounce at tick over too. And I'm not sure if I'm imagining this, but I feel when driving the revs are slow to drop when I lift off. Any thoughts?

[AMG Merc]

Ah! Did he clean your butterfly plate? There was a trend here to clean our throttle butterfly's a few years ago. I followed the herd and wished I hadn't. I used the correct cleaning spray and immediately suffered what you now have. I never solved the issue - tried cleaning off with a lint free cloth. It took months to get back to normal - on its own. Bottom line, I will never clean one again.

[bernhund]

AMG Merc said:

Ah! Did he clean your butterfly plate? There was a trend here to clean our throttle butterfly's a few years ago. I followed the herd and wished I hadn't. I used the correct cleaning spray and immediately suffered what you now have. I never solved the issue - tried cleaning off with a lint free cloth. It took months to get back to normal - on its own. Bottom line, I will never clean one again.

That's interesting Rob. I wonder what it is about the butterfly cleaning that upsets things?

[Green3R]

wonder if it's worth resetting the adaptive maps? Though not sure they'd have any effect at tickover.

[Driven]

If your throttle body was cleaned, I'd disconnect the battery for a bit to let the ecu try to relearn.

Also, may have accidentally "adjusted" your throttle cable in the process, so maybe checking the jamb nuts on the throttle cable stay

[bernhund]

Driven said:

If your throttle body was cleaned, I'd disconnect the battery for a bit to let the ecu try to relearn.

Also, may have accidentally "adjusted" your throttle cable in the process, so maybe checking the jamb nuts on the throttle cable stay

Thanks for this, I'll try it out

[Jim O.]

Many times there's a slight air leak between the throttle shaft and the bearing that supports it. Oil and dirt residue in the throttle body will tend to seal this leak, so if you clean the throttle body, the leak opens up more. Also, this sort of leak tends to be larger when the throttle body is cold, and lessen as things warm up. I'd suggest having your intake system checked for leaks using a smoke machine.

Another issue could be if the shop removed the throttle position sensor when they cleaned the throttle body - if they did, and did not get it back on in exactly the same position, it may be throwing off the tune. Unfortunately, I can't think of a really good way to fix this, except by measuring the voltage coming off the TPS, and using that to adjust the sensor through trial and error...

[bernhund]

Jim O. said:

Many times there's a slight air leak between the throttle shaft and the bearing that supports it. Oil and dirt residue in the throttle body will tend to seal this leak, so if you clean the throttle body, the leak opens up more. Also, this sort of leak tends to be larger when the throttle body is cold, and lessen as things warm up. I'd suggest having your intake system checked for leaks using a smoke machine.

Another issue could be if the shop removed the throttle position sensor when they cleaned the throttle body - if they did, and did not get it back on in exactly the same position, it may be throwing off the tune. Unfortunately, I can't think of a really good way to fix this, except by measuring the voltage coming off the TPS, and using that to adjust the sensor through trial and error...

Cheers Jim. I'll ask him exactly what he did when cleaning it. You know I think he did the same to my 2.5 some years back and that too ended up with a similar issue!