Volkswagen Mark IV Forum banner
1 - 15 of 15 Posts

·
Registered
Joined
·
1,669 Posts
Discussion Starter · #1 ·
Today I cleaned the throttle body on my 1998 1.4 Polo.

The car was running okay but it was sometimes a bit lumpy when idling with a cold engine.... either way being such high mileage I decided to give it a clean.

This was how dirty it was....

Posted Image


Anyway, since I've put the car back together it has'nt been running right.

If I pull up to a junction, the revs sit at about 2000 before slowly dropping down to between 1200 and 1400.... they used to be around 800.

When driving if I take my foot off the accelerator it takes a few seconds for the car to register, so say if I'm cruising at 30mph in 4th gear and take my foot off the pedal, the car continues to 'pull' at 30mph for a few seconds.

While driving, if I go to change gears, when I press the clutch the revs stay at around 2500.

Sooo....

Somebody suggested I disconnect the battery for 30 mins, then re-connect and let the car idle for 15 mins.

I did this, but the idle is still between 1200 and 1400.

I then took the car on a 20 mile drive, and red lined it in 2nd and 3rd while accelerating to 70.

Still the same.

While cleaning the throttle body I noticed a split in the breather hose that goes from the back of the engine block to the air box... apparently this hose vents oil vapours back into the engine?

Would this split cause the idle issues? I've got a new hose on order from VW but it wont be here till Saturday.

Or is it simply a case of me needing to sweet talk Chris. into re-setting the throttle body on his vag-com?

Anybody else had this issue who can advise?
 

·
Registered
Joined
·
1,403 Posts
You need the trottle body aligned. A simple procedure can be done at dealers or with VCDS.
aRd is local to you.
 

·
Like A Bawwsss
Joined
·
25,247 Posts
Simple procedure was not so simple.

Re-aligned it about 5 or 6 times with vagcom today and it never sorted it. All pipes going to the throttle body are ok.

When you unplug the multi-plug for the stepper motor, revs drop to about 700-750 bit lower than normal, which is expected.

Also get a 00533 Idle speed regulation - adaption exceeded (i think it was from memory) fault code which returns when car has been ran.

Im stuck for ideas.....something is telling me stepper motor is dodgy.
 

·
Registered
Joined
·
1,669 Posts
Discussion Starter · #8 ·
Its starting to get better [:)]

VW specialist has said I need to drive it for a week for it to 'learn' how to adjust itself or something like that.....

Either way apparently I've got to drive it like this for a week or so, and if it gets no better I will have to replace the throttle body.

Since my visit to Chris. at dinner time its got loads better. Its still not right, and it still idles at about 1200, but it does'nt rev as much when changing gears so fingers crossed it is juts a case of it having to 'learn'
 

·
Registered
Joined
·
1,669 Posts
Discussion Starter · #12 ·
Its starting to get better
and then it got worse.... much worse.

Car began idling at 1400 all the time, and as soon as i started to move the car wanted to idle at around 1800 meaning it was awkward driving at 30mph in 4th gear - as the car was idling so high it was constantly trying to go faster than 30mph even without me touching the pedal! It then became very jerky and generally awful to drive, juddering for no reason while cruising.

I went to VW to get the new oil breather pipe they had ordered, but when I went to fit it they had sent the wrong one [:mad:]

So I bandaged the old one and re-fitted it, hoping this would help. The car still ran exactly the same.

I spoke to a mechanic at VW while I was there, and he suggested I would need either a new throttle body or a new ECU!!

Then I had a brainwave

Thinking back, when Chris had the car plugged into his laptop, the laptop was saying the engine temp was in its 50's, but the needle on the dash was bang on 90.

Unsure if this was related, or even if this was normal, I thought 'what the hell' and while re-ordering the correct oil breather pipe I bought a new temp sensor, with the idea of replacing cheaper things before anything expensive!

As soon as I fitted the new temp sensor (something that took all of 30 seconds), the car ran perfectly!

It now idles between 800-900, when I pull up at a junction the revs instantly drop to 1000, before slowly dropping back to the 800ish mark.

No more idling at 1800-2000 at the traffic lights [<:eek:)]

Oh and you can REALLY tell the throttle body has been cleaned, it pulls so much better and is much more responsive! [au]
 

·
Registered
Joined
·
1,669 Posts
Discussion Starter · #13 ·
So... I'm wondering..... had the dirty throttle body been hiding the faulty temp sensor? Or had the old temp sensor broke at exactly the same time I cleaned the throttle body? hhhmmmmmm..... [:cool:]
 

·
Registered
Joined
·
1,669 Posts
Discussion Starter · #15 ·
BAHAHAHAHA

Its a little beast Chris!

Can't believe how much better it drives.

I dont know if had been the dirty throttle body or a faulty temp sensor hindering the performance but its never driven so good!

Like turbo charged shoot off a stick..... shoot being the operative word lmao

Picked up gearbox oil and new petrol filter from VW today.... they go in next week so cant wait.

MPG was 42 before all this.... I wonder if / how much higher it will go?
 
1 - 15 of 15 Posts
Top