Golf Cabriolet acceleration problem

[willgt290]

I have a 1989 Golf Cab GTi. Recently, when going uphill, the car stutters when you change gear from 3rd to 4th, and likewise to 5th. This doesn't happen all the time, but occasionally it can almost feel like the car is going to stop completely. For a few seconds there seems to be no power/acceleration.

When I first bought the car it had a similar problem and I was told it was the pressure in the fuel injection pump which needed adjusting. Could it be the same problem again?

I have also noticed the car needing regular coolant top-ups recently but I'm not sure thats related. It has never ever over-heated.

Thanks

[Crasher]

The main system pressure of the injection pump should not be tampered with unless serious modifications are made to the engine and even then it has to be tied in with a reduction of the control pressure or else it has no effect. Your problem does sound like it is fuel pump related and is probably due to a corroded filler neck. Remove the filler cap and use a battery powered torch (no naked lights please!) to inspect the inside of the filler neck. If it is corroded or holed your fuel tank is full of debris and will need to be removed and cleaned plus the lift pump in the tank may have failed and the main system pressure pump possibly damaged. This problem can turn into a serious world of hurt should fuel lines start snapping as they are almost all obsolete.

[vince70]

I had a similar problem with my old 1987 gti cab a few years ago, sometimes it would just cut out and not restart for about 10 minutes, or do as you describe,it seemed like fuel starvation,
I took it to a garage I used at the time and I had the fuel pump changed, fuel tank taken off and cleaned, fuel filler neck renewed new inline filters, they also took off my thatcham immobiliser, renewed my relays and fuse box as they told me it was electrical and also they renewed something on the fuel injection system, it cost me a fortune.
Only for me to take it somewhere else, to find out it was only a kinked fuel line on the back of the car, it was because I had a steep drive and the fuel line would catch and kink when I went over it.
So its worth looking for the obvious first.
As for the loosing water check and see if you have any mayonnaise on the oil filler cap or in the expansion bottle, if you do it may be a head gasket on the way out, if you dont have a look for a leak or maybe you have an airlock.

[willgt290]

Thanks for that. I will check the filler neck today, and probably take it to a garage tomorrow and explain that I'm pretty sure its fuel pump/fuel line related.

Vince70, there is no gunk on the oil filler cap or in the expansion bottle, but I will get underneath and check for a leak today, but pretty sure there isn't any marks on my drive from it.

Someone else has mentioned that it might be a warm-up valve problem, i.e. it needs adjusting because the car is either running too hot or cold. What do you think of that idea? The temperature gauge barely ever reaches the middle even on long journeys, so perhaps its running too cold?

[vince70]

I wouldn't like to say as I'm not a mechanic, but it must be good news if your not getting any gunk on the filler cap, You may even find out the the misfire is due to something simple as a dodgy rotor arm or a hairline crack in the distributor or a ht lead breaking down.
I did have a water leak once on a polo I had and it ended up being a heater matrix so it may be worth feeling round the back of the dash and around the carpets.

[Crasher]

The fuelling warm up valve (the correct name for this part is the Control Pressure Regulator) is not adjustable in normal use, it should only be modified as required for enrichening the running mixture on a modified car. The two main adjustments are actually made by pressing in or pulling out two interference fit components on a factory test rig so adjustments are not easy to make and must be made with fuel pressure measuring equipment attached. If the hot and cold control pressures are not to specification (again this can only be ascertained with fuel pressure testing equipment) the CPR will have to be replaced. If the CPR does need replacing it is usually down to fuel system water contamination due to a failed filler neck, in normal use they are extremely reliable.

[willgt290]

The reason why I thought it may be the warm-up valve is because that is what I was told it was last time I had a similar misfire problem. I have since stopped using that garage because I found them unreliable so maybe they lied to me that time.

The filler neck is quite rusty, and I can see small areas where it has flaked away. Perhaps it is that.

Anyway, I am taking it to a reliable garage today armed with the info from this thread, so thanks for that.

[willgt290]

An update:

The garage fitted plugs, dizzy cap and rotor arm which certainly needed doing because they left the old ones for me to see and they were well worn. This had cured the misfire but the pinking on acceleration was still there, and they said I needed to take it to a VW specialist for tuning etc. This is what I did next.

Firstly, they did a diagnostic to see if there was electrical fault but there was none, and the suspected HT leads were operating fine. Then they adjusted the timing and CO mixture and said that had cured part of the problem and that I should test it for a day or two and see if it was better. It drove home ok, but the next day it drove awfully, so straight back it went.

This time they narrowed the problem down to lazy or non-working fuel injectors. These were removed, cleaned and refitted. I was advised to buy some injector cleaner to put into the petrol tank which I did. There was an advisory note about the possibility of water in the fuel tank or filter, which I wasn't too sure about. Anyway, it drove really nicely after that, and I drove it to Cornwall the following day (about 270miles from me) and it was faultless. No misfire, pinking or anything.

I had my weeks holiday, drove home, and it was fine again till I came off the motorway and the engine overheated. I noticed that it slightly misfired whilst overheating but I assumed that was related to the overheat. A water pipe had split, it was changed and new anti-freeze put in. And guess what, I noticed a slight judder whilst accelerating up a hill today!! A one off or another fault somewhere?

What do you guys think? Thanks for reading my longwinded story!

[vince70]

Well its not a good sign if your car is overheating have you cooked it, have you checked the oil filler cap and the expansion bottle for mayonnaise, if it was running lumpy after you overheated it, you may have done the headgasket.