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Engine light on after cleaning throttle body

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11K views 19 replies 7 participants last post by  Bones126 
#1 ·
Afternoon all. So I've just had the airbox out cleaning the throttle body. Managed to get everything out and back in ok without too much difficulty and felt quite pleased with myself for doing so only to find I now have an engine management warning light on. :surprise:

The car starts no problem and seems to drive ok after a quick test run around the block, pulls cleanly away with no apparent hesitation or stuttering like it was before cleaning. I'm not overly worried that its something majorly serious and I'm guessing that me rumaging around unplugging stuff has disturbed something but has anyone else ever had this happen.

I dont have an OBD tool to plug in (I do but with a different connector) so I cant read the fault code. Is there any other way to find out the fault, or can anyone offer up any other solutions before I have to start thinking about going to a garage.

Cheers.
 
#2 ·
OK quick update, I've managed to get an OBD reader and got two codes coming up.

P0113 Intake air temp sensor 1 circuit high
P0102 Mass or volume air flow A circuit low

I've cleared the codes to get rid of the engine light but what do these mean exactly and is it anything I need to be concerned with?

Cheers again.
 
#4 ·
I sometimes get codes because I’ve disconnected the wiring plugs/connectors, if you didn’t disconnect the battery. If you have cleared then, which is what I do, and they don’t come back then you should be ok.
 
#6 ·
Yeah I didn't disconnect the battery before unplugging the MAF sensor. Didn't think I'd need to being honest given that you need the ignition on to open the throttle butterfly, but that's most likely what caused the light to come on.
Hopefully the light will not come back now its been cleared.
 
#7 ·
I always clean my MAF sensor without having the engine light up and I never unplug the battery.
I believe the engine light up is due to cleaning of throttle body hence you need to just reset the battery after plugging back the shining clean throttle body.

Btw, which OBD2 model did you use to check the code?
Planning to buy a new unit for my FN2.
 
#8 ·
If the fault has been cleared a few ignition cycles seems to cure the light. Took my airbox off the other day and forgot to plug the MAF back in. Engine light cam on when I switched the ignition on, hadn't even started the car. Realise the issue, and plugged the MAF in but the light stayed on for a few cycles then went off.

Tried the disconnecting the battery for 30 minutes which didn't work.
 
#9 ·
So to follow up from cleaning the throttle body I now have the crappy idle problem which it seems a few others have also suffered. At slow speeds/low revs the car feels like the throttle is slightly stuck open which can cause sudden jerking/kangarooing. It's possible to drive around the issue to a degree but obviously not ideal.

Ever done a job then wish you hadn't bothered? yeah me too.


So I'm faced with the decision to either take it to a garage to sort, or buy a proper diagnostic tool (foxwell or similar) to try and sort it myself.
 
#11 ·
1) If you ever remove any plug from the engine bay, have your key off the ignition. That's the reason for the CEL. You don't have to disconnect the battery next time.

2) To fix your problem you have to do the "idle relearn" procedure. There are numerous ways to do that. But since you haven't got any dianostic tool the easiest one is to disconnect your battery for 1 minute and then reconnect it. Immediatelly after start the car and let it idle until you hear the radiator fan (this will take a while depending on your current engine temp). When you do, your are good to go.

Problem solved ;)
 
#15 ·
Well I tried the idle relearn procedure as per the above method and it made absolutely zero difference. After a bit of searching on youtube I found a slightly different method which involves disconnecting the battery and then touching the two battery leads together for about 10 seconds. This method made a very small difference but still hasn't completely cured the problem. Also the idle speed now fluctuates from about 800 to 1000rpm every few seconds but the car also now has a weird power drop whilst driving. It feels a bit like dabbing the brake for a couple of seconds even though the throttle is still on.

I've got a diagnostic tool coming this week which I'm hoping will help to remedy things back to how it was beforehand as the car has gone from being a nice place to be, to a pain in the arse and very irritating.

If anyone is thinking about cleaning their throttle body, do yourself a massive favour and leave it well alone.
 
#16 ·
Just to add to the list of bugs, I've noticed that the A/C now seems to be a bit temperamental. Sometimes it blows chilled cold air as expected, but other times when I put the A/C on it only blows the same temperature as if it was still off. I recently re-gassed the system (before I cleaned the throttle body) and it seemed all ok.

There's also an occasional loud juddering noise coming from underneath (cant be certain where from exactly) which comes on when sat stationary or very slow moving which is rather concerning. It only lasts a few seconds when it happens and doesn't seem to happen ( so far at least) when moving at normal speeds or higher.

I'm wondering whether this issue is related to the A/C being re-gassed as the car ran absolutely fine for well over 8 months before, without so much as a hint of any noises.
 
#17 ·
So hopefully, fingers crossed, I've sorted the crappy idling problem with the help of a Foxwell scanner tool. After reading up on other forums regarding idle problems after cleaning the throttle body it seems that you MUST reset the idle learning values stored in the ECU before doing any sort of idle relearn procedure and the only way to do this is with an appropriate scan tool. If you do not reset, doing the idle relearn alone will make very little or no difference. It seems that if you've done the idle relearn after cleaning the throttle body and thought the car was running ok then the chances are that the throttle body was not far out to begin with.

My car now idles around 700rpm once warmed up and no longer has that surging feeling when coasting down in the lower gears as if the gas pedal is being slightly pressed. As for the other issues I mentioned above I'm guessing they are only related to the A/C system which I will worry about another day. As for now I'm just happy to have sorted the idling. :smile3:
 
#18 ·
Glad you’ve got the idle situation sorted, I have a similar issue but was advised I have an air leak somewhere (need to check but don’t think I do). But the amount of times I’ve had the throttle body off over the last couple of weeks it may need resetting so same as you may need the tool to reset the TPS. Where did you get yours from?
Cheers
Dave.
 
#20 ·
Thanks for letting me know, glad it’s done the trick.
 
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