please help diagnose my lumpy Pug

[nicklouse10]

Hi all,
I recently bought another 205 GTi after a 4 year break of not owning one, and I love it to bits, however, its running a bit rough and I was hoping someone may be able to help diagnose my problem. here are the details;

F Reg 1.9 Gti, with KnN induction kit fitted by previous owner.

Symptoms;
Car bunnyhopping at low revs and jerky to drive
Car stuttering through the rev range even with foot to the floor
Car wont idle when cold

What I have done so far;
Replaced split scavenge pipe
Replaced non existent Vacuum advance hose
Cleaned out MAF unit
Found that previous owner had blocked off the air hose that runs from the pipe between the MAF unit and throttle body, to the intake manifold, via a sensor (choke sensor?) I unblocked this hose and the car now idled at 2000RPM,
I adjusted the idle screw as far as it would go and now it idles at 850RPM, this didn’t seem right to me that the screw is as far down as it will possibly go……?

Symptoms now;
Car still wont idle when cold (stalls)
Car bunnyhopping at low revs and jerky to drive, especially when cold
Engine still hesitating when foot to the floor going up through the rev range, even when hot
Very strong smell of fuel when driving (and when driving behind the car)

Things I am going to try;
Change plugs
Give it some injector cleaner
Change auto choke
Change fuel filter
Check fuel pump

any other sugestions or ideas will be most welcome.
cheers
Nick

[Jon.Brook]

Hi, I also have a Pug 205 1.9 GTI. I am afraid I cannot help you with your problem, however, I thought you might be interested to know that I have similar problems. The only difference is that mine doesnt hesitate during full acceleration.

It runs very rough when cold (misfires and stalls) and is very jerky (bunny hops) when a small amount of throttle is applied, making it very hard to drive smoothly and a nightmare for traffic jams!

I have tried many things:
Different Airflow meters,
New Coil,
New HT Leads,
New Dissy Cap,
Different Distributor,
New Spark Plugs,
Different Injectors!

And I still cant get rid of the problems explained above. I sometimes wish I had a manual choke that I could leave on until the car was warm enough not to cut out!

I will keep checking this post for any help! Thanks and good luck!
Jon

[nicklouse10]

HI there,
I've been doing a bit of searching and have found that our problems may be caused by a faulty SAD device, which is basically the auto choke, and located under the dizzy in the airline that runs between the induction pipe and the intake manifold.
I'm going to remove mine, clean it and test it and I'll let you know if it helps
cheers
Nick

[Jon.Brook]

Hi Nick,

Fingers crossed that helps. I wondered what that device was when I tried a different distributor, so I guess it was the SAD (Supplementary Air Device).

My car does have a K&N filter on fitted by the previous owner...Im sure this doesnt help cold running, but I think it should still tick over and not just cut out!

Let me know how you get on,

thanks,

Jon

[Steven Grove]

Hi Nick,

I think I have the answer to all your questions! firstly the missfire you speak of during full acceleration will be from an incorrect or faulty hall sender (amp module) located on an aluminium plate bellow the coil on a pre 90 model or if the coil is mounted to the inlet manifold the module is located on the drivers side suspension turret just behind the cam belt cover. As for the lack of idle from cold, this is indeed a fault with the ecu supply to the SAD device. What has happened in your case is by reconecting this device you will find the car idles at 2000rpm when hot, this is because the device has no voltage supply to reduce the amount of supplied air to the engine as it warms up, you then turned the idle control screw in to compensate for this. what happens now is when you start the car from cold the SAD devise delievers the correct amount of air for a cold engine but because you have screwed in the idle screw so much it has counteracted the extra air supplied by the SAD device which is needed when the engine is cold. An inexpensive fix for this is to pull up the rear seat prise up the plastic fuel pump cover to access the petrol tank, then splice a wire from the fuel pump supply (white wire) and run this wire to the front or the car through the bulk head and to the SAD devise. Cut both wires to the SAD devise and connect the new wire to one of the wires on the SAD device and connect the other wire straight to vehicle ground or negative on the battery. then wind the idle screw out enough that it will idle when cold, once warm turn the idle screw back in till the car idles at 1000rpm and hey presto! job done at a cost of some wire and terminal blocks.