Throttle body fault
Discussion
For years I've been trying to track down a random electrical fault that puts the car into limp-home mode. Always seems to happen when I sometimes stop for petrol and it did it again today. Tried stopping and restarting but no joy so I 'limped' at 25mph for a few miles before getting fed up and pulling in to call my wife to tell her where I was.
Sure enough, after a 10 minute break I tried again and same as always - car started and no further problem!
When I got home I did some investigation and noted the fans stay on for a good 5 minutes after the car has stopped and there's always a "click" when the car shuts off. By pulling off the intake pipe I could see the throttle blade is not completely shut until this point and the "click" is the blade closing.
So, the reason it sometimes throws a fit is because when the car does its start-up checks, the throttle is not where it expects it to be. I know this because the faults which I've had read says the ECU has lost contact with the throttle body. If you shut the car off, leave it for a good 10 mins and try again, it's always fine.
Any ideas why the throttle does this weird behaviour and doesn't shut properly when the ignition is switched off?
On the plus side, I got time to take a picture just to prove to you all that it does move under its own power (albeit intermittently)
Sure enough, after a 10 minute break I tried again and same as always - car started and no further problem!
When I got home I did some investigation and noted the fans stay on for a good 5 minutes after the car has stopped and there's always a "click" when the car shuts off. By pulling off the intake pipe I could see the throttle blade is not completely shut until this point and the "click" is the blade closing.
So, the reason it sometimes throws a fit is because when the car does its start-up checks, the throttle is not where it expects it to be. I know this because the faults which I've had read says the ECU has lost contact with the throttle body. If you shut the car off, leave it for a good 10 mins and try again, it's always fine.
Any ideas why the throttle does this weird behaviour and doesn't shut properly when the ignition is switched off?
On the plus side, I got time to take a picture just to prove to you all that it does move under its own power (albeit intermittently)
Maybe it's a sticky blade or something ?
Some cars will open/close the blade on key on to reset and confirm it's working which ensure's everything is ok before you actually start the engine.
So if somehow it is sticking when warm when you shut it down...the problem would only be detected on key on again.
Not sure if the GM ecu's do it or not ? Presumably it is bringing up some fault codes ? Read via a proper reader, what are they, as usually they're quite specific as to what it thinks the problem is
Have you asked on the HPT forum ?
Some cars will open/close the blade on key on to reset and confirm it's working which ensure's everything is ok before you actually start the engine.
So if somehow it is sticking when warm when you shut it down...the problem would only be detected on key on again.
Not sure if the GM ecu's do it or not ? Presumably it is bringing up some fault codes ? Read via a proper reader, what are they, as usually they're quite specific as to what it thinks the problem is
Have you asked on the HPT forum ?
stevieturbo said:
Have you asked on the HPT forum ?
Nope, haven't got that far yet. Don't think the blade is sticking, it always does it. I.e - ignition off, fans run, charge cooler pump runs, everything shuts off, "Click".It's reliably unreliable if you know what I mean, doesn't always do it and only happens if you shut the car off and try to start it when hot a few mins later. Leave it for 10 mins and it's never a problem.
wormus said:
Nope, haven't got that far yet. Don't think the blade is sticking, it always does it. I.e - ignition off, fans run, charge cooler pump runs, everything shuts off, "Click".
It's reliably unreliable if you know what I mean, doesn't always do it and only happens if you shut the car off and try to start it when hot a few mins later. Leave it for 10 mins and it's never a problem.
The fans staying on are more likely just a symptom of the limp mode because of the TB error.It's reliably unreliable if you know what I mean, doesn't always do it and only happens if you shut the car off and try to start it when hot a few mins later. Leave it for 10 mins and it's never a problem.
Are you saying when all is fine, and you key off, the fans or pumps etc do not run for a period ? whereas when you key off and this fault is present, they do ?
Unless perhaps the test cycle for the blade is on key off rather than key on ? if indeed it even performs this cycle.
Again, what fault codes have been showing ?
DRC72 said:
I have just replace 2 electric throttle bodies on Jeep Compass 2.4 petrol and a much older Dodge Caliber 2.0 petrol.
They both had the same fault code sets and it is due to oil mist getting into the electronic motor, this in turn causes high resistance putting the eml on.
Can the motor be easy to clean rather than buying new one every time?They both had the same fault code sets and it is due to oil mist getting into the electronic motor, this in turn causes high resistance putting the eml on.
Ade
I had a similar issue 4 years ago.
The car would randomly go into limp mode but would be fine after it was stopped and started again.
This happened a couple of times until one day the car wouldn't start at all. When you turned the electrics on it just threw up a message on the dash saying check engine.
Throttle body was replaced and it's been fine ever since.
The car would randomly go into limp mode but would be fine after it was stopped and started again.
This happened a couple of times until one day the car wouldn't start at all. When you turned the electrics on it just threw up a message on the dash saying check engine.
Throttle body was replaced and it's been fine ever since.
throwyourbike said:
I had a similar issue 4 years ago.
The car would randomly go into limp mode but would be fine after it was stopped and started again.
This happened a couple of times until one day the car wouldn't start at all. When you turned the electrics on it just threw up a message on the dash saying check engine.
Throttle body was replaced and it's been fine ever since.
Sadly mine does it rarely but when it does, it's always at a petrol station and no matter how many times you stop/start it, you get the same problem as soon as the ignition is switched on. Only cure is to leave it 10 mins until everything powers down and then try it again. It's never gone wrong whilst the car is running.The car would randomly go into limp mode but would be fine after it was stopped and started again.
This happened a couple of times until one day the car wouldn't start at all. When you turned the electrics on it just threw up a message on the dash saying check engine.
Throttle body was replaced and it's been fine ever since.
My main question is why does the throttle blade stay open a few degrees, closing when the rest of the car (e.g. fans/interior light) also power off?
wormus said:
Sadly mine does it rarely but when it does, it's always at a petrol station and no matter how many times you stop/start it, you get the same problem as soon as the ignition is switched on. Only cure is to leave it 10 mins until everything powers down and then try it again. It's never gone wrong whilst the car is running.
My main question is why does the throttle blade stay open a few degrees, closing when the rest of the car (e.g. fans/interior light) also power off?
The whole purpose if DBW is so the blade can do things independently of the actual pedal.My main question is why does the throttle blade stay open a few degrees, closing when the rest of the car (e.g. fans/interior light) also power off?
As to why it does certain thing at certain times, again it could be part of self test features to ensure it's working ok ( or not )
You'd need to look to see what the ecu is commanding for blade position and what the blade is actually doing, or any errors etc
But it could be as simple as a faulty unit.
stevieturbo said:
wormus said:
Sadly mine does it rarely but when it does, it's always at a petrol station and no matter how many times you stop/start it, you get the same problem as soon as the ignition is switched on. Only cure is to leave it 10 mins until everything powers down and then try it again. It's never gone wrong whilst the car is running.
My main question is why does the throttle blade stay open a few degrees, closing when the rest of the car (e.g. fans/interior light) also power off?
The whole purpose if DBW is so the blade can do things independently of the actual pedal.My main question is why does the throttle blade stay open a few degrees, closing when the rest of the car (e.g. fans/interior light) also power off?
As to why it does certain thing at certain times, again it could be part of self test features to ensure it's working ok ( or not )
You'd need to look to see what the ecu is commanding for blade position and what the blade is actually doing, or any errors etc
But it could be as simple as a faulty unit.
Ade
THUNDER STORM said:
Would disconnecting the battery for say 30 mins and then re apply power cause the car to go into relearn mode, and maybe this would sort problem? Any ideas.
Ade
If there is a fault, there is a fault. Disconnecting the battery wont fix it, but may make it go away for a short period.Ade
Really, the ecu needs interrogated and see what live data and codes etc are telling you about the blade/pedal relationship and blade targets etc.
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