2.0 16v A new candidate for the fault

[mrbeige 0]

I had a problem with my 2.0l 16v loosing power above 5500rpm, cos that pesky little lead wasn't sending it s little signal to the ECU. I would say you need to make sure that is in place to get it running ok. Stealth did the old VAG-com thing and mine gave a fualt code cos that little blighter wasn't plugged in!

[bcstudent 0]

Ah....well....damn.

 

On the 9A engine, is the cold start injector controlled by the ECU? Anybody got any idea what exactly determines the trigger-period? I've got the VW fuel and ignition system service manual for the KR engine but I'm assuming the 9A works slightly different.

[Lippy 0]

I thought you could only get fault codes from the ABS on the valvers???

 

Obviously not, i think a search is required.

 

But if anyone wants to post some more info in the mean time ;)

 

keep up the good work bcstudent!

[saysomestuff 0]

I thought you could only get fault codes from the ABS on the valvers???

Obviously not,

 

lol - yep my 2l 16v has some ECU fault finding ability.

[Supercharged 2]

Yep, all the late 16v's have the self diagnosis feature, traction control was also an option.

[bcstudent 0]

This morning I went out to the car and, not surprisingly since it was dry and warm, it ran perfectly. Without too many other ideas I picked up another cold start injector from a VW breaker.

 

On the way home I took Supercharged's advice and visited Halfords on a quest for an ignition coil. Sure enough they had one listed but it looks completely different to the one on the car currently. However, it was £4 so I bought it anyway! So, this question to all 2.0 16v owners...

 

Which coil looks that same as yours?

 

The terminal numbers are right so it's just occured to me that measuring the winding resistance may be a good idea. I'll do that after lunch.

[bcstudent 0]

Right, I measured the winding resistance of both coils and they're different.

 

Original coil:

 

Primary - 0.9 ohms

Secondary - 3.5k ohms

 

New coil:

 

Primary - 1.0 ohm

Secondary - 7.5k ohms

 

Clearly there's a large difference in the resistance of the secondary windings. Despite this I fitted the coil to see what would happen and the car started and drove fine from cold but in the dry. I'm not entirely happy about having the coil on the car if it's the wrong one, but it'll do for testing purposes next time it rains.

 

If anybody has pics/info. regarding 2.0 16v coils I'd love to hear about it.

 

Cheers :)

[sciroccotune 0]

not sure if the shape makes a differance but i have the round one. Ill check the part number later for you..

[bcstudent 0]

Ok cheers. I'm really interested in the winding resistances as well, but I can see that it's only simple to measure them if you happen to have a spare coil hanging around.

[bcstudent 0]

Well I'm out of ideas. It's just started raining so I hopped in the car for the ultimate test. Sure enough, when pulling out of the drive onto the main road, applying the throttle just caused the car to die and surge.

 

What I don't understand is the whole engine bay is dry. The outside temperature is no different to the temperature earlier in the day when the car ran fine. The only factor that guarantees the problem to occur is the rain.

 

What the hell is going on?!

[mrbeige 0]

The ignition coil that is on the car is a VW only part and IIRC costs around £175, as it needs to be bought with the ignition module as one piece. I replaced mine, to try and solve a problem where the engine kept dying and then wouldn't start again.

 

What about the engine earth? Might be worth checking that.

[bcstudent 0]

The ignition coil that is on the car is a VW only part and IIRC costs around £175, as it needs to be bought with the ignition module as one piece.

 

Really? That's interesting. The car had a new ignition module and distributor before it came to me but the garage didn't change the coil for some reason. I'm pretty sure the coil isn't at fault as the car does exactly the same thing with either coil and runs perfectly at all other times. I've been over and over this in my head and it makes no sense.

[bcstudent 0]

I took the car out again earlier - same conditions...same fault. No fault codes were stored so I'm assuming the one I mentioned in the earlier post was unrelated to this fault. After messing around in the garage for a while I found that I could cause the same fault by pressing the closed throttle switch (indicated in pic) with the throttle open.

 

This now appears to be a likely candidate, but I'd like to know more about the control philosophy of the closed and WOT switches if anyone knows how they work with respect to the 9A engine management.

 

* EDIT *

 

Ah yeah, with respect to the coil winding resistances, I checked the Autodata manual. For the 9A engine it listed the following...

 

Primary: 0.5 - 0.9 ohms

Secondary: 6.5k - 8.5k ohms

 

So, apparently, the odd looking coil from Halfords was right and the one that was on the car was wrong. However, like I said, it ran the same with either. Very odd.

[bcstudent 0]

Bump...because I really really wanna know what this switch does!

[Phil K 0]

Throttle position sensor? (I'm guessing)

[bcstudent 0]

I'm guessing that it has something to do with the ISV. By messing around with the closed throttle switch and the ISV I can recreate the symptoms of the problem regardless of the temperature of the air/engine. I've cleaned the ISV and I'm going to try and find a replacement switch at the breakers tomorrow.

 

The plot thickens...

[bcstudent 0]

I'll just keep talking to myself then :)

[mrbeige 0]

I'm wondering if the little microswitch on the throttle body contributes to the ISV, and therefore if it is knackered or has poor conductivity when damp, then the ISV isn't doing its job properly. Could you get hold of another 9a throttle body and try that?

 

I have a little blue book at work printed by Bosch, that details everything you need to know about engine management/engine development stuff. It does havea section of the KE-jetronic management that ios found on the 9a, so I'll have a look tomorrow to see if there is anything particular about that switch.

 

P.S you aren't talking to yourself :)

[bcstudent 0]

Thank God, I thought it was just me in here! :cheers:

 

Doesn't the 9A use KE-Motronic engine management?

 

When I took the ISV off last night to clean it I noticed that it was pretty filthy inside. I'm going to spend some time this morning trying to recreate the fault by pressing the microswitch, then seeing if clamping the ISV hoses sorts it out. Unfortunately my local VW breaker doesn't have any 9A throttle bodies and I'm not confident enough in my fault diagnosis to buy a new switch assembly and ISV just yet :scrambleup:

[mrbeige 0]

Right quick update, according to my lil' blue book (Bosch, Automotive Handbook), the throttle valve switch is used for idle and overrun and WOT. There is also an electrohydrylic pressure actuator that is controlled I think by that switch!

 

Any help?

[bcstudent 0]

Any help?

 

Everything people can tell me is a help, cheers. I ran the car this morning and, predictably, it was perfect since the weather was dry and warm-ish. It does at least seem to idle better since I gave the ISV a clean but I may be imagining that.

 

I'd love to think it was the ISV that was causing the problem, but after looking at the piping I can't see that even if was jammed open it'd make a difference with the throttle open. The air would just appear to have two paths into the inlet manifold - via the ISV and via the throttle butterfly.

 

I'm going to head to the Bosch specialist in Norwich this afternoon to ask him what he reckons. Hopefully he'll be in a friendly free-advice giving mood :)

[bcstudent 0]

Well, the Bosch specialist wasn't all that helpful really. It seems to me that either the ECU is being told by the closed throttle switch to put the car into its overrun cut-off mode, or one part of the overrun cut-off system is failing.

 

What I need to know now is what happens during the overrun cut-off phase, i.e. when the engine speed is above idle and the closed throttle switch is made.

[h100vw 0]

Above about 1500 revs with the throttle closed, the fuel will be cut off. This is done by a bypass valve near the fuel dissy. The valve opens and air flows through it, this causes the flap in the fuel dissy to drop. When the revs get below 1500ish with the throttle still closed the ECU closes the bypass valve and air is drawn through fuel dissy again and this then gets to the injectors.

 

If the switch were sticking shut, then the engine would not acellerate from tickover as the timing doesn't advance. It would bog down due to going rich I think.

 

With the throttle switch stuck in the open position the engine would not idle well as the ISV would not be used to control the tickover. Moving the tickover screw does nothing on the 9A and it should be screwed all the way in.

 

I think you can change the tickover speed with 1551/VAG COM but don't quote me.

 

I have a copy of the VW 9A manual but no time to read it now, sorry. I might be able to post some more info tomorrow. In the mean time, RW1 is the man to tell the world how it all works.

 

Gavin

[bcstudent 0]

Cheers Gavin, that's some useful info. I think my next step is to examine the components of the fuel distributor and maybe even swap the whole lot for one from a scrappy. There can't be much else to try!

[MickeyT 0]

BC, Halfords are currently selling Lucas coils at stupid prices, I picked up a G60 one for a fiver, may well be the same for yours...

 

Supercharged when I phoned up a couple of branches in my area they told me they didn't sell G60 coils. What did you ask for?

 

Cheers