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View Full Version : Question why engine maintains its revs (for a 1-2 secs)after removing foot from gas pedal



dorame
10-03-2011, 01:50 PM
Hello all
I have been here before see thread ,
http://www.vwaudiforum.co.uk/forum/showthread.php?p=571814#post5well

Following on from that, I was lousing water but was unable to find the leak, also when I put my foot on the gas (stationary) just to raise it above 1000/ removing my foot, the revs kept increasing after I had removed my foot (almost to 2000) before dropping back. This was in December.
I then put a bit of dry cardboard under the engine and had it running for a while without detecting anything, maybe worth noting that the water cap was always tight and when released there would be quite a vacuum before it settled .
After I took the car back the garage said they removed the head again and said they found some small matter on the gasket which may have caused the water to get into the oil. and the over revving should be all ok, I had another water drop after that but after topping that problem may have sorted itself. its worth mentioning that I am a pensioner and don't do a lot of miles as when I use to work and any problems I think will take longer to appear, when we had very cold mornings i took a lot of trys before it would start, but as we havent had cold days as before pre Christmas so i am not having that at the mo.
Well up to date my car to my way of thinking is not running in the smooth way that I was accustomed to, before even on cold mornings the choke was much lower to the point where I sometimes wondered if the auto choke was on but I would always hear when the engine tone change as the auto choke was kicked off, now when i start the car I think the choke is too apparent with lumpy running and a flaffing sound.
Also when I press the gas now and take it off the engine revs does not change at the point where I remove my foot but stays for (not increasing)a second or more before dropping back to slighty above 1000 revs
this is really puzzling me, the garage has spent a lot of time on this car.
I very much hope some of the people here mechanic/engineers can educate me as to what's the problem is (if its getting another injector/ adjustments/head needs looking at again/or the problems are just in my head. car by the way is a VW Golf 1.8 Driver 1993 reg, sorry for long post

TIA
ps anyone knows of any vw specialist in london walthamstow/chingford area?

Housemaster300
13-03-2011, 10:29 AM
You know what mate, i have the same car with the same engine on the same year and have the same problem.
Ive tried alsorts using this site and others.
It seems to do it mainly when it is cold.Even if i tap the gas pedal a tiny amount it revs to 2k and then falls very slowly.Its very annoying.
Ive scanned it with no faults.Ive swapped the dizzy,changed the temp sensor replaced the big rubber throttle body gasket as these are a common problem,set the timing up using vag com and a strobe light.
No joy!
Im sure i have asked on here before but never got reply.

Crasher is the man and if he doesnt know then nobody will:p

Im in the process if building a vr6 turbo engine at the minute so ive decided to just live with it until that engine goes in.
However it drives me up the wall to know i cant suss the problem.

I will be watching this thread just incase the problem gets an answer.

Good luck mate.:D

kenney
13-03-2011, 01:51 PM
The mono motonic injection system has been one of the best systems VW have had,with very few problems.One problem i have encountered several times either the throttle valve positioner unit or its adjustment,which when faulty,results in various symptoms,among other unstable idle.The gasket and o ring on the intake air preheater element might be worth checking for leaks,as this will also affect the idling

dorame
13-03-2011, 02:24 PM
Thanks House
I could be checking with the mechanics, and maybe its not their fault but prior to the head gasket change I had no such problem, thats what I cant understand.
My wife's advice was to not spend money doing repairs as its an old car get another one. couldn't see it her way because being retired I dont do that much miles anymore, cheaper to repair and more logical and now the. refrain (I told you so) with a smirk.
This morning I checked my mpg and its crazy 16.4 mpg albiet tyres were all under inflated when I filled up yesterday, will check again with proper inflation, 40mpg I use to get with on long runs (40 miles)when working

thanks kenney just noted your post.
re unstable idle, when the engine walms up that lumpy idle goes but the (quote :Also when I press the gas now and take it off the engine revs does not change at the point where I remove my foot but stays for (not increasing)a second or more before dropping back to slighty above 1000 revs) remains

Housemaster300
13-03-2011, 02:46 PM
Yep.thats exactly what mine does lol.
Mine never used to do it till the engine blew up,replaced it with a good 86,000 one and then the problem started,mpg wise it was knocking about 20-25mpg which i just lived with.
Since the car is due to be my motor now instead of the missus ive done lots of work to it so it would be nice to get this sorted.
Ive got lots of ABS engine spares including a full head,inlet and exhaust manifold,various ancillaries etc,so if your stuck for parts give me a shout and you can come pick them up.I dont want anything for the head so your welcome to it.Its complete too.

kenney
13-03-2011, 02:56 PM
16.4 mpg that would indicate a lambda probe fault,which would also cause unstabel idling

dorame
13-03-2011, 03:04 PM
does that mean a computer resetup jobies or a replacement? what? the whole injection unit?
or the probe?

kenney
13-03-2011, 03:25 PM
there is no computer reseting on these engines.The lamba reading can be read in Vagcom in measured value blocks,or a quick reading of the exhaust gasses,will tell you a lot

dorame
13-03-2011, 03:30 PM
thanks for your kind offer House, but as I am not a mechanic apart from changing my brakepads I will pass on that, this knowledge that I am getting here will help when I get back to the garage I don't like to argue completely naked.

dorame
13-03-2011, 03:33 PM
i see
thanks

Housemaster300
13-03-2011, 05:22 PM
I stuck a new Bosch lambda in mine with no effect on the idle problem. It's reading right in vagcom too. Another £70 lol

dorame
13-03-2011, 05:51 PM
Another £70 lol
there must be a point where a car becomes a wife, do we get rid and buy another wife
lol*2

Housemaster300
13-03-2011, 06:15 PM
True lol
Having just stripped the car ready for a nearly £2000 spray job my missus is saying similar ha ha

dorame
13-03-2011, 06:38 PM
ouch
that cheered me up (but sorry to hear that), i now know that i have got off lightly
in comparison
lol
better not laughf too loud
half smile quietly
hsq

kenney
13-03-2011, 07:31 PM
I stuck a new Bosch lambda in mine with no effect on the idle problem. It's reading right in vagcom too. Another £70 lolHave you checked the pre heater element gasket???Have you had an analysis of the emission?

Housemaster300
13-03-2011, 09:14 PM
As it happens I havn't checked the hedgehog, only to see if it kicks in doing tests through vagcom.I havn't looked at the gasket though tbh.
Emissions are ok as it went through it's mot with the same problem. Hydrocarbon was borderline mind you.

dorame
13-03-2011, 09:21 PM
No I haven't kenney.
, This is all new information for me this w/e, when my tank runs down a bit will do another mpg check this time with tyres properly inflated then together with all your informative tips return to garage, this has been like research and I cant thank you guys enough, have been with this awhile hope there will soon be an end to my frustrations. and get my old boring trouble free VW driver back
time now to catch up on some telly

kenney
14-03-2011, 11:43 AM
As it happens I havn't checked the hedgehog, only to see if it kicks in doing tests through vagcom.I havn't looked at the gasket though tbh.
Emissions are ok as it went through it's mot with the same problem. Hydrocarbon was borderline mind you.you can check the gasket by spraying some easy start around that area,if it's leaking the revs will increase

Housemaster300
14-03-2011, 02:10 PM
Ive already done that(albeit with brake/clutch cleaner) and there was no surging at all.:(

kenney
14-03-2011, 03:06 PM
do you know how to check the throttle valve positioner unit?

Housemaster300
14-03-2011, 03:25 PM
Hmmm i remember looking on Elsawin about it but never actually got round to it.If i remember rightly its a case of measuring the resistance between 2 pins and setting a gap of about half a mm?

kenney
14-03-2011, 06:02 PM
Hmmm i remember looking on Elsawin about it but never actually got round to it.If i remember rightly its a case of measuring the resistance between 2 pins and setting a gap of about half a mm?I suggest you check it, as it plays a very important part in the idling

Housemaster300
14-03-2011, 06:51 PM
I will get on with it tomorrow and report back,it may be of some help to the op too.
Cheers for the help Kenney.