Fuel Problem FIXED (I HOPE)

[JBOB 0]

Hi guys, Ive got a problem with my car and hoped you could help.

 

Ive made a list

 

1 - At idle revs jumps around from 1000-1500ish.

2 - Car is very jumpy at low revs/gears (like kangaroo petrol)

3 - Smell of fuel from exhaust but not all the time.

4 - MPG from MFA (I know its not gonna be 100% acc) at best driving like a 90 year old nun 24MPG.

 

I did buy a new rotor and dizzy cap last month and them were a bit smaller than the ones I took off but they fit on the dizzy so left them on (and cos I broke the orig rotor), but the black plastic cover for the cap wouldn’t fit so I left it off.

Should I replace them with ones the same as before, could it make a difference.

Ive got a new fuel filter cos the one on the car looks really old and battered and some rear bearings that im gonna fit tomorrow as I have the day off work so ill have a look at all the fuel pipes but they were fine at the MOT in September so im not expecting to find anything wrong there.

Ive had a look through 2500ish posts on a searchs and found one about turning the mixture down on the metering head as a quick fix should i do this as i cant get the car to my brother (Audi spanner monkey) til next month.

 

Thanks for your help in advance

J

 

Ive also just noticed that im a CF Enthusiast :D 8) :D

[aide 0]

basic question, but you did put the leads back on correctly when messin with the dizzy, and didn't mess with the hall sender or timing? assuming its a 16v?

[JBOB 0]

basic question, but you did put the leads back on correctly when messin with the dizzy, and didn't mess with the hall sender or timing? assuming its a 16v?

 

Yes sorry its a valver.

I just swaped the leads over one by one being very carfull so that they were in the right places.

 

Ive put a new fuel filter and wheel bearings on today but havent started it yet as it got dark so its still on the stands till morning. I didnt see anything wrong with fuel pipes or anything else and as the MOT guy said everything is perfect under the car.

[stevemac 0]

Sounds like your engine is dragging air in from somewhere - check your inlet manifold & gasket.

[JBOB 0]

Sounds like your engine is dragging air in from somewhere - check your inlet manifold & gasket.

 

:( Not what i wanted to hear but thanks Steve, im gonna get my brother to look at it asap.

[JBOB 0]

Yesterday i had a go at resetting the idle via the screw on the throttle body with instructions that Gavin had posted on another thread and i noticed that the rubber washer on the screw was a bit loose/tatty. What effect could this have on the engine ? also where can i get a new one.

 

I took the car to Leeds and back this morning and it drove/pulled fine with the same power that ive always had but everytime i stopped at lights etc i noticed that there is a very slight backfire type noise from the exhaust. any ideas?

[stevemac 0]

As above.. :wink:

[JBOB 0]

As above.. :wink:

 

:lol:

[JBOB 0]

I was driving to work this morning and spend the usual time stuck on the M62 and the engines backfire at idle was getting worse, every time i turned something electrical on like the wipers/heater the revs would jump to 2000 and then go back down to 1100 and start to backfire again.

So i took it to a garage that’s just behind where i work ive never used them but a guy at work recommended them.

I told him what was wrong and suggested that i could be the inlet manifold/gaskets as Steve has said. I picked it up this evening and was told that it was all sorted and it was the running valve :? and the bolts on the upper inlet manifold joint were in bad shape so they fitted new ones.

So i paid them and went out to the car and guess what its still as bad :( but now its idle is at 1500 most of the time and will get down to just over 1000 when its idled for a while, the backfire is still there and seems to be getting worse.

The garage are having it back tomorrow morning and will try again for free :D but im not sure i want to use them again but want to get something for the money ive already spent.

 

Ive had a look and they have replaced the bolts and a new gasket on the manifold so i don’t think its that.

[aide 0]

AFAIK, and please correct but I think backfires are caused by mixture being too weak (not having enough fuel to burn properly) or too rich (too much fuel to burn air) net result being unburnt mixture gets passsed to your exhaust manifood where burns instead.... as steve said above a hole in manifold would cause idle to vary and make mixture weaker and cause a backfire.

 

I don't know the 2 litre engine at all, but seeings it only does it at idle i'd look at that side of thinks to see what it's doing to the mixture

[stevemac 0]

Grabbing at straws here, but is it possible that the exhaust or inlet cam timing is slightly out of sync ?

 

This would result in a small amount of unburned fuel passing straight from the inlet valve into the exhaust - as both sets of valves would be momentarily open at the same time (very common with some fast road cams).

[JBOB 0]

Thanks for all your help Steve, I think ive found the problem.

The car was back at the garage today and again they told me that they had fixed it. They cleaned the ISV and the mixture was to lean so the mechanic came out to check this time and it was still revving really bad and had the misfire.

He disconnected the ISV and the revs dropped to 800/900 and when reconnected it stayed up at 950ish and stopped misfiring.

Drove the car home without any problems, Mechanics says the ISV is sticking and needs to be replaced as its been cleaned out twice now.

 

Am i right in saying that IV's are really expensive and whereas the best place to get one??????

[martyjmcfly 0]

Had what seemed to be a problem related to the idle valve so bought a new one. They cost over £100!!!!!!! If you want it to last buy new and from VW dealers. I haggled with them and they gave me a 20% discount. I'm not saying all VW dealers are that generous.....

[JBOB 0]

Is it the same one on the 16v Golf or are there any other cars with the same one.

[stevemac 0]

So far as I know, we sell them. Not sure how much but should be a fair bit cheaper than VW..........

[JBOB 0]

GSF £89 + VAT its a bit cheaper than dealer LOL

[aide 0]

There's a guy on ebay selling them, forget his tag but the company name is lowtension ltd - can vouch for him as bought genuine VDO stuff off him before