Rough idle + Prowlers injector test

Hi Everyone,

I am new on here, just posted a message in the New members section  

I am hoping somone can help me with my problem, I have a 79 GTI with original 1.6 engine. When I bought the car I knew it wasn't right but it drove 2 hours home on the motorway ok.

Problem is a rough idle warm or cold. So far I have done the following..

1. Full service - all ignition components apart from the coil (it now starts nice and easy but still runs rough)
2. New intake gasket
3. Retorqued intake / exhaust manifolds.
4. Checked for other intake air leaks
5. Checked Aux air valve
6. New fuel filter
7. Mixture / timing
8. Car had a new cam belt fairly recently, so have checked correct alignment of pulleys etc.
9. checked resistance across pressure regulator
10. compression test (all cylinders approx 170 psi)

Next thing I would like to do is prowlers injector test, the test looks great and I am fairly confident my problem lies somewhere with the fuel system, the issue I have is that it details the fuel pump relay connections in a series 2 fusebox and mine is completely different. Has anyone done the test on a series 1 or have a good diagram / instruction manual for a series 1 showing the fuel pump relay location ?

Any help really appreciated

Many thanks
Kev

kevm said

….. it details the fuel pump relay connections in a series 2 fusebox and mine is completely different. Has anyone done the test on a series 1 or have a good diagram / instruction manual for a series 1 showing the fuel pump relay location ?

Any help really appreciated

…can't find a S1 diag of fuse box, and certainly have no pic, so if ANYONE can help out I can update the guide…..

Thanks Prowler,

I wondered if there is any reason I can't just disconnect the hotwire or HT lead from the coil and use the ignition switch instead of the shorting wire for the test. Any reason why this would not work / be safe ?

Cheers
Kev

..not sure about S1, but on my '87 GTI the relay takes a signal from the coil, and unless the engine is running it will NOT allow the pump to run….safety feature in case of a crash….

…you COULD IN THEORY just connect a switched supply direct to the pump…….but observe all safety precautions…….I just found it easier and quicker to go via the relay connections…

..still looking for S! fuse/relay box diag - sure I got one SOMEWHERE !!!!

Is your fusebox a bullet one? If so it may be the same as my 1.6 GTI: -



The fuel pump relay goes in position L - I looked up the relay pinout in the wiring diagram in the Haynes manual and bridged the relevant connections with a switch, and that worked fine.

Can't remember which ones they were though, it was so long ago.

HTH

Rich

Cheers guys for the pointers, its L13 and L14 just sorting out my bottles and will do the test shortly  

Thanks again, i'll come back with results tomorrow hopefully.

Kev

Ok I have managed to do the test tonight, I am a bit dissapointed that the fuel levels are all about the same but the test does state …

The fuel pump may prime, the injectors may chatter and a small amount of fuel may flow but should then stop. There should be no fuel flow to the injectors until the plate is lifted.

The spray pattern looks ok with the plate lifted but there is fuel flow out of all injectors with a small jet coming out at an angle on at least one of them when the plate is sitting,  I do also have the warm start problem I think, would this also cause the rough idle ? If so maybe I have found the fault ??

Cheers
Kev

That sounds like leaky injectors to me - it's probably running very rich when you start it due to excess fuel in the inlet manifold from the leakage.

Have you cleaned them with anything, or are you just investigating at this stage?

Rich

..you may find this interesting….I know the wksp manual is for Mk2, but it is still appropriate….

Bosch Fuel Injection (up to and including Lambda) - 6Mb

Kjet 8v Fuel Injection



…with fuel coming through and the plate down suggests either bad injectors or the plate adjustment is out….can't explain at mo - flu has affected my brain..!!!

Many thanks for the replies and info. I think the injectors are worn, they look like they could well be the original ones too so I think next step is to replace them. I will report back once I have changed them.

Cheers
Kev

Hi Everyone,

OK I have an update, I have fitted new injectors and it has fixed the warm start issue but the engine will still not idle properly. I have also renewed / ruled out the coil and HT leads.

So the rough idle persists, basically the engine shakes badly at idle and will only run a bit better with the timing advanced futher than it should be.

Therefore to recap I have done the following to try and cure the problem, many of these things needed doing anyway so its not all bad news:-

1. Full service - all ignition components apart from the coil
2. New intake gasket
3. Retorqued intake / exhaust manifolds.
4. Checked for other intake air leaks
5. Checked Aux air valve
6. New fuel filter
7. Mixture / timing
8. Car had a new cam belt fairly recently, so have checked correct alignment of pulleys etc.
9. checked resistance across pressure regulator
10. compression test (all cylinders approx 170 psi)
11. Coil
12. HT leads
13. New Injectors

Looking at the history the car had a new cam belt earlier this year and the receipt also lists 'Investigate rough running' clearly this has been a problem for a while !

I had already checked the cambelt had been fitted correctly but can you confirm I have done it right - I have checked the marks at TDC on the crank pulley and the cam gear ? here's some pics of the marks, do they look ok or should I check further ? I have read about a futher sprocket under the cam belt cover ?





Apologies for the long post but I just want to use the car now  

Any help appreciated.

Cheers
Kev

quick update - I have read up on the intermediate shaft and understand the importance now with the dissy timing. Anyway I have spent the last hour or so taking the lower cam belt cover off and checking that it lines up with the TDC mark on the crank pulley, all checks out ok so that something else ruled out.

So I am still looking for ideas on what to check next

Thanks
Kev

o.k. so are timed correctly at the dizzy with a gun? have you set the co and idle screw?

wooders said

o.k. so are timed correctly at the dizzy with a gun? have you set the co and idle screw?

I have timed it correctly with a timing gun but don't have anything to set the mixture with,  I have noticed however the engine runs alot better when I disconnect the advance pipes from the dizzy to set the timing specifically the pipe that connects to the main intake body (not the throttle body connection) therefore I am assuming the extra air its taking in when disconnected means its too rich in the first place.

Does that sound correct ? if so hopefully just need to get my mixture sorted  

Cheers
Kev

? I TAKE IT YOU MEAN YOU'VE GOT HER TIMED CORRECTLY, BUT SHE RUNS ROUGH STILL, THOUGH IF YOU DISONNECT THE DIZZY VACUUM PIPE, SHE RUNS ALOT BETTER? (sorry for caps)
 bearing in mind, the vac pipe retards the ignition under load, so it shouldn't run too well, then it is very possible that the co may just need setting. give it a full turn anticlockwise and see how she is.

Two things I'd check are the fuel mixture screw, as wooders suggests (3mm allen key next to metering head) and the idle screw (7mm nut on the back of the throttle body).

HTH

Rich

Ok so I went and found an allen key long enough to adjust my mixture, in both directions I can make it run worse and stall but in between it still runs rough like the mixture is still wrong, the engine shakes and it hunts badly. Introducing more air by removing the dizzy vacuum at the intake the other side of the throttle body improves the idle so is it still mixture related ? Air box / metering head problem ? haven't done anything with either of these yet.

Thanks
Kev

Check your idle screw - if it's too far in the engine won't get enough air at idle, which will cause rough running and hunting.

Once you've eliminated that you can move on to testing other things…

HTH

Rich

mcscrew said

Check your idle screw - if it's too far in the engine won't get enough air at idle, which will cause rough running and hunting.

Once you've eliminated that you can move on to testing other things…

HTH

Rich

Ok I have checked my idle screw, it does what it should do, all the way out fast idle but screwed in to put revs at about 900-1000 rpm the idle is still rough and it hunts badly. What should I check next, I don't think there's much left  :roll:

Thanks
Kev

I have been tinkering about with my car this morning again, I got a second hand Warm up reg and swapped them over, this seems to have make the problem worse and the car would barely start, I have now swapped them back and it still barely starts now, so I'm not sure how I have managed to make it worse ??

Anyway I have done the injector test again, hadn't done it since I replaced them. Looks like I may have wasted some money buying new injectors, they still spray / drip  without the plate in the metering head being raised, if I apply light downward pressure to the plate they do all stop dripping, does this mean the metering head needs adjustment or is the system pressure wrong ?

I have also removed the sender from the top of the tank and had a good look inside, looks very clean with no sign of rust or dirt.

So is the next step a fuel pressure test ? I can't really afford to take it to a garage at the moment (it won't start at the mo anyway   )

Thanks
Kev