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Discussion Starter · #1 ·
Hi all!

This is my first post and I was just hoping for a bit of advice. I have just bought a 1999 1.8T Golf GTi and am really happy with it other than the idle not being quite right. It idles perfectly when you first start the engine (about 900 revs), but when you come off of the throttle when driving the idle usually comes straigth back to about 1200 revs then gradually creeps down to around a 1000 - sometimes it creeps back to about 1200 revs again on it's own. It seems to behave itself a lot better when the air-con is switched on!

It there a common cause for this such as an air leak, dodgy sensor or idle control needing to be adjusted somehow?

Thanks for any advice!

Dan
 

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It's a common fault usually caused by a dirty throttle body. There are several 'how to's' on the forum that detail how to clean the TB. It's an easy DIY job - try that first.

Hope it works!

Rick.
 

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Discussion Starter · #3 ·
Thanks for the reply Rick! I'll take a look at the 'how to's' section and clean the throttle body up then!

Cheers again

Dan
 

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Discussion Starter · #4 ·
Brilliant Rick, I found the DIY instructions for the throttle body cleaning!

One thing I'd just like to check with anybody on is the throttle body adjustment after re-fitting. I've seen mentions of resetting using VAG-COM - Is this VW's onboard diagnostics, or would I have to take the car to a main dealer to do this? I did see something about setting the ignition key to position 1 for the car to run it's own checks and reset!?

Cheers,

Dan
 

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Interesting one, this.

From what I can gather, many people on the forum seem to have good results using the door open, ignition on method. I don't, however! I've been told by a VAG technician that the only way to reset everything after the throttle body has been removed is by VAG themselves (or possibly VAG COM).

Not wishing to take over your post, Dan, but I was, today, going to post an entry on the forum myself to ask that very question. After cleaning the throttle body on my car at the weekend (that's the second time in a few months), the high-idle problem remains. Does anybody have any other clues, please?

Dan - it's still worth doing yours as most people get good results and a cure to the problem.

Rick.
 

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Try taking your car out for a long road test, bout half an hour; and at various speeds. High speed full throttle worls well, but try and stay within the law etc etc. The Engine Management system should eventually learn itself and re-set the throttle body settings for you.
 

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Thanks - I've tried all that and it hasn't made much difference. I think my only option left is to take it to a garage and get them to reset things. I'd also be interested to know whether any other fault codes show up while they're at it.

Anybody got any other ideas, please?
 

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Discussion Starter · #9 ·
I got round to taking the throttle body off of my 1.8t yesterday and cleaning it up - to be honest it looked pretty clean before I'd even started. Anyway, I put it back together and it doesn't seem any different. On first starting the car it usually idles perfectly, but when driving, when you come off the throttle it tends to drop straight to somewhere between 12 - 1400 revs before gradually dropping back to about 1000'ish revs - sometimes it creeps back up to about 1200 again of it's own accord.

Are there any usual suspect other than a dirty tb?

Cheers,

Dan
 

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I had a similar problem (70k) that turned out to be the coil packs, the idle speed would fluctuate slowly after short or long journeys between 800 and 1200 at the most. Eventually one of the cylinders stopped firing. The stealers told me that the coils put in my car (2001) are known to be faulty, they have since brought out new ones which no longer have this problem, so they had to replace all 4 with the new ones.

Just as a comparison my car idles at 1200 when I first switch on the engine with a few slight twitches at idle. After a short journey or a few minutes it drops to 800 and thats where it stays until I shut it off, I see the ocasional twitch at 800 (800-850 guessing).
 

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Hopefully mine's not coil-pack related - I think one or more would have given up the ghost by now.

I took Spudley's advice and did some more full-throttle runs. In the past I've always used 3rd gear, foot to the floor from low speed to 'red line'. This time I did the same in 1st and 2nd gears and it seems to have made a difference as for a few days now the idle has been quite stable at about 8-900 rpm. There's been the occasional blip but, in general, the problem has gone away - so thanks, Spudley.

Dan - the procedure I followed was to disconnect the battery for about 15 mins; re-connect; turned the ignition on with the driver's door open; left it like that for about 3 minutes (I'm sceptical that did anything); then drove the car, including full throttle in 3rd gear. I didn't do the full throttle in 1st and 2nd gear until a few days and a couple of hundred miles later but, as I said, it seems to have helped. It's worth a try!

Rick.
 

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Discussion Starter · #12 ·
Thanks for the advice guys, I'll be most pee'd off if I need to replace my coil-packs! I've foundout that a friend of a friend was a VW tech for 10 years and now works mobile - he's supposed to know his stuff and he's taking a look at the car tomorrow and plugging his code reader into it etc etc! I'm hoping it'll be something like a faulty air temp sensor or something else not too punishing on the wallet!!

Rick, re the reset precedure, I was thinking, would that only aplly to DBW cars? Mine's a 1999 model with cable throttle.

Dan
 

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Dan,

Mine's an AGU engine with cable throttle as well. Try disconnecting the battery, re-connecting and then a drive including full throttle in first and second gear. As I said, it worked for me.

I'll be interested to hear what, if anything, your friend comes up with. My car had a temperature sensor replaced about 14 months ago after it generated fault codes. It cost about ?25 from memory - didn't completely cure the high idle problem, though!

Rick.
 

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Discussion Starter · #14 ·
Well I had my Golf looked at on Thursday and the throttle control valve is faulty. After years of advising VW techs to spray cleaner into the throttle body to clean it, VW now tell them to dampen a cloth with the cleaner and clean the throttle body this way. If you get the throttle body too wet the cleaner travels down the spindle of the butterfly and into the throttle motor, and eventually knackers it!! The only solution is to buy a new complete throttle control valve - UK price is just shy of ?300 plus vat but my local VW specialist can import one from Germany for ?230... Still wouldn't mind getting it a bit cheaper than that!

Dan
 

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Bad news then, Dan.

I've a feeling that's what's wrong with my car but haven't had it confirmed. Did the problem generate a fault code of some kind?

Sounds like you'll have to bite the bullet and buy a new TB.

Rick.
 

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Discussion Starter · #16 ·
Hi Rick, yeah, bad news, but at least I know what it is now!!

I've got the print off of the 2 codes which were generated, I'll dig them out this evening and post a reply with each exactly what they were. Roughly, the first one was something like idle minimum speed not being reached, and the second one was throttle valve idle reset not being allowed.

Dan
 

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Discussion Starter · #17 ·
Ricke, the fault codes read off as follows:

2 faults recognised

17973 P1565 035

Throttle valve control unit-J338

lower stop is not reached

17967 P1559 035

Throttle valve control unit-J338

Fault in base setting

System in basic setting 98

4.420 V 3.740 V Idling ADP.runs
 

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Those codes look to me like a re-set issue. You need to get the correct diagnostic tool/machine on it really and get it re-set. Whilst you're there ask them to re-set the readiness codes as this can determine whether or not you really have a fault or not.
 

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Thanks for the comprehensive information, Dan.

I tend to agree with Spudley about your car - it must be worth a try before you splash out on a new throttle body.

Mine's been behaving reasonably over the past week or so with an occasional 'high idle' thrown in. Redlining in 1st and/or 2nd gear seems to cure it again.

Cheers

Rick.
 

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Interesting to see this is a common problem. I suffer from this too, albeit infrequently. Will set my skills to work during the week.
 
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