Engine struggles to fire and has rough idle

[sonique 0]

My car (2.0l 16v 9a) has for a long time had the problem of stalling when coming up to juctions etc, but the other day it really struggled to fire and when it did, it ran really rough.

 

I've had it plugged into VAG-COM and had these fault codes:

 

00524 Knock Sensor 1 (G61)

03-10 - No Signal - Intermittent

00281 Vehicle Speed Sensor (G68)

03-10 - No Signal - Intermittent

 

I know that the speed sensor fault is due to the engine not running at the time, but should the knock sensor fault come up without the engine running?

 

Also if the knock sensor is faulty would it cause this kind of problem?

 

I couldn't get the car to fire so don't know if the knock sensor fault will come up again until the battery is charged up again.

 

I've had new these parts fitted recently to rule these out:

Distributer cap/Rotor arm

HT leads

Hall sender

Plugs

Lambda sensor

 

Thanks in advance

John

[Supercharged 2]

You checked the wiring on the KS - maybe chaffed on a hose clip...

[-Neil- 0]

any other ideas on this, ive got the same!

[dr_mat 0]

If the knock sensor is faulty it'll drop back to full (~11 degrees) ignition retard, which might cause some of the problems you're seeing, yes.

[Kevin Bacon 5]

Not at idle it won't....

 

I note you haven't changed the ISV Sonique. I remember from my 16V days that little pest causing those exact symptoms. Believe it or not, hitting it with a hammer freed it off on occasion and the car started instantly :-) Replacement is the only permanent cure tho.

 

If the 9A has a 5th injector (blue one on the inlet manifold), you might want to check the wiring for that as well as it's earthed at a shared junction, which often corrodes....

[dr_mat 0]

Not sure what control is required at idle, tbh, other than a fully functional ISV, obviously. But I'd expect to see "idle stabilisation not reached" or "idle speed too low" or something if the ISV was seized, no?

[Kevin Bacon 5]

Not on the valver, it's not half as nannying as Motronic 2.9! I don't know what management the 9A uses but obviously not K Jet if it can speak to VAG-COM, although not sure how he managed that as I've never been able to get VAG-COM to talk to digifant !

 

There's just a simple on/off microswitch switch on the throttle for the ISV and if it doesn't work, whack it :-)

[dr_mat 0]

Doh, I completely missed the fact this was a 16v! :)

The symptoms are sooo classic VR6 I didn't even think .. !

[-Neil- 0]

Not at idle it won't....

If the 9A has a 5th injector (blue one on the inlet manifold), you might want to check the wiring for that as well as it's earthed at a shared junction, which often corrodes....

 

 

the 5th injector, will it be pressent on a 1993 9A 2ltr 16v?

There is a BLUE thing on the right of the rail that runs along the FRONT of the inlet manifold as it curls into the head, what problems would that cause if it was faulty?

[bcstudent 0]

the 5th injector, will it be pressent on a 1993 9A 2ltr 16v?

There is a BLUE thing on the right of the rail that runs along the FRONT of the inlet manifold as it curls into the head, what problems would that cause if it was faulty?

 

 

Yes, that blue 'thing' is the cold start valve (also known as the fifth injector). It runs for a few seconds when cold to enrich the fuel/air mixture. The time it operates for is determined by the thermo time switch on the flywheel end of the cylinder head. As it only operates for a few seconds it can only be linked to cold-start problems....unless it's leaking when the engine is stopped, which can cause a loss of system fuel pressure and further dodgy starting.

 

I agree with Kev that the ISV (either the unit of the wiring) is the most obvious and likely cause of the fault at the start of this thread.

[Kevin Bacon 5]

Yeah I mentioned the 5th injector because one of my valvers used to take ages to start and when it did, it was lump city until warm. Reason being the earth for the 5th fella (attached to a junction on the battery side chassis leg on the Golf 2) was totally corroded and the 5th injector wasn't firing at all.

 

With the ISV, the same car could on occasion just plum refuse to start, regardless of temperature and whacking the ISV freed off the internal flap and it fired up instantly! That's VWs for you......a hammer should be standard in the tool kit!

[-Neil- 0]

Yeah I mentioned the 5th injector because one of my valvers used to take ages to start and when it did, it was lump city until warm. Reason being the earth for the 5th fella (attached to a junction on the battery side chassis leg on the Golf 2) was totally corroded and the 5th injector wasn't firing at all.

 

 

That sounds like EXACTLY the problem im having, will have a look tomorrow!

[bcstudent 0]

Ok, the 16v may not be all that quick but there's a lot to be said for a car with so few components in the fuel/ignition system. Especially when fault finding is required!

[-Neil- 0]

i measured te ohms in the 5th injector today at it came back at about 7.9 or something.

 

i did the coolant temp switch when the engine hadnt bee started and it said about 1.6 i think theni kept on trying and i wasnt getting ANY read out what so ever!

[-Neil- 0]

today i got someone to put the ignition on and I tested the voltage out of the 5th injector, it worked when the ignition was on so thats working ok.

 

so i think i should keep looking, maybe more into the coolant sensor.

[bcstudent 0]

i did the coolant temp switch when the engine hadnt bee started and it said about 1.6 i think theni kept on trying and i wasnt getting ANY read out what so ever!

That's what you should be getting - an infinite resistance reading means the switch is an open circuit.

[-Neil- 0]

so its working then?