VR6 has flat spots

[PBSTORM 0]

Everytime I drive my VR6 from cold it's always flat!

 

Only happens after a gear change...

 

It's then fine after about 5 minutes of driving...

 

Any ideas??

[Supercharged 2]

PBSTORM, welcome to the forum...

 

Could be alot of things, maybe best to put up a list of what has been changed recently - leads, plugs etc... and also get the car on VAG COM to see if there are any fault codes saved.

[PBSTORM 0]

I haven't long had the car, but I'm sure it was serviced about 5k miles ago..

 

Not sure what was replaced though....

[MoonlightVR 0]

Could also be the coilpack on it's way out (assuming it's a coilpack car). Commonly causes the symptoms you describe when engine is cold - no problem once warmed up though.

[PBSTORM 0]

Just found out that it's very flat whilst driven in heavy rain too!!! :(

[Rpmayne 0]

Maybe a moisture problem with the leads?

[saysomestuff 0]

whereabouts in S.Wales are you mate?

[PBSTORM 0]

Just outside Cardiff...

[Kevin Bacon 5]

When you say flat, you mean unresponsiveness and no appreciable acceleration?

 

Things like coilpacks and leads would definitely exhibit very noticable misfiring problems, like running on 5 or fewer cylinders.....especially in the wet.

 

You really need to get it on a diag machine as there are numerous reasons why it could feel flat.

[PBSTORM 0]

That's exactly what I mean! It can be very un-reponsive!

 

Got it hooked up to a machine this Wednesday, so I'll hopefully know more then.

 

One minute it's taking on and beating Cupra R's, the next thing, it's getting laughed at by passing sales reps in their A4's!!! :(

[Kevin Bacon 5]

Know what you mean, been there, done that.

 

The MAF sensor is an old favourite, as is the cam position sensor. If the latter decides to go to sleep, you lose 30hp.

 

I've also learned that the throttle position sensor is key. The ECU seems fussy with them, indeed it's the only plug in the entire engine loom to have gold plated contacts. I had a dead / dying throttle sensor recently which was amusing. I could hold the throttle wide open by hand and it just spluttered and died!

[PBSTORM 0]

You mentioned the MAF sensor, could the K&N induction kit be causing a problem.

 

It was fitted by the previous owner.

 

Should I put the old airbox on?

[PBSTORM 0]

Well, after plugging it in to the COM it came back with a crank sensor fault, which was causing the car to misfire..

 

My local VW dealer wants £125 for it. Any ideas where I may be able to get it cheaper??

[Kevin Bacon 5]

Was the engine running when crank sensor fault came up? it's just that some places wrongly blame the crank sensor as a fault when it's fine. If the engine was running and the message was something like "G28 - Crank position sensor - implausible signal - intermittant", then it's knackered.

 

If the message was "No signal" then the engine must have been off as you don't get that when it's running cause the engine wouldn't run at all with not CPS.

 

Cheaper....nope, dealer part I'm afraid.

[PBSTORM 0]

The actual fault was with the hall effeact sensor, but apparently my car hasn't got one, and was told it waould be the crank sensor?!?!?! :?:

[Kevin Bacon 5]

Hall sensor , yeah your cams use one, as does the crank. Hall sensor just means something that detects pulses, but VW call it XX position sensor instead, but it is essentially still a hall sender.

 

Put it this way, if your crank sensor was truly dead, the engine would'nt even start and run, but they can start losing resolution with age, causing the occasional stall.

[Dutch24V 0]

That could be the Crank position sensor but more than likely based on your description of the problem it's the Cam position Sensor.

 

Both sensors work on the hall effect.

 

Dutch

[Dutch24V 0]

...and as Kev said, if the Crank sensor was dieing your car would randomly stall and if it was dead the car wouldn't start at all.

 

When the Cam sensor is dead/deing, the ECU retards the timing to prevent damage, hence a flat feeling to the engine.

[RW1 0]

hall effeact sensor, but apparently my car hasn't got one

 

Yes it has. It's the alternative name in some diagnostic kits for the Camshaft Position Sensor. Reason is, that in a way it does control the ignition timing inside the ECU. The Goof diagnostics uses the terminology for it's CPS

 

If the fault was cleared when you went in, then the problem should have gone away until perhaps you put the engine up above 4,000 rpm. Depends on how old the fault is as the sensor deteriorates and the RPM comes down where it starts to fail.

 

If they didn't clear the fault, you can clear it by disconnecting the earth on the battery for a minute and then reconnecting. If from cold it drives normally until "revved", ie. keep the rpm down for while, while you test it, then the culprit is the Camshaft Position Sensor.

 

I have big doubts though that it is the CPS as you say it drives OK after 5 minutes from start up. If the CPS has gone, as written by Kev., "you lose 30hp", I would expect the problem to be there all the time. And only happening after a gearchange doesn't really fit in either with one of the normal fault reaction conditions which is retarded ignition, ie. "Limp Home Mode".

 

I am more inclined to think that this is a cold fuelling/mix problem and therefore would look at the temperature intake probe and what reading it's showing. It can be looked at in Measuring Blocks (08 ), Group 003, field 4. Suggest you look and see what the reading is as the engine starts, it should be somewhere near what the dash outside temp is reading but will rise to 60' or 70'C at running temps at idle.

 

I think the fault found was with engine not running, the good old 00513 April fool of OBD1 pre mid '90s cars like the Corrado.

 

.

[PBSTORM 0]

Here is the exact chain of events....

 

1.)Car seems to be losing power form cold starts and now again after driving for a while.

 

2.)Plugged ECU into computer, came back with the following faults

- 0513 Engine Speed Sensor (No Signal)

- 0515 Hall Effect Sensor (Short To Positive)

The technician told me to ignore the Speed Sensor fault.

Cleared down both faults, told me to drive it for a couple of days and bring it back for a retest. He also did warn me that once the Hall Effect Sensor packs in, the car will not run.

 

3.)Drive car home, still fells flat! :(

 

4.)Get in my my car yesterday, after not been driven for 2 days, and will not start!! It''ll turn over, but does not fire up.

 

5.)Was told by technician that I need Crank Sensor which retails at approx. 125 pounds.

 

Does this sound right?? As I don't want to spend over a ton on a part I don't require!!

[Supercharged 2]

Yep, sounds correct based on the diagnostics... dead Crank sensor will cause the engine to turn and not fire up, and the magnet inside it will have lost resolution over the 10 or so years... saying that, it maybe wise to check the wiring and plug connection before ordering!

[PBSTORM 0]

How can they justify charging £135 for this......

[Jim 2]

Is the crank sensor on the 2.8 VR6 different or is that one a 2.9 VR6 specific part? Just wondering if its one of those parts you could investigate getting cheaper from ford seeing as they used the VR6 engines in some cars..

[Kevin Bacon 5]

Still £135 ay?

 

It's one of those things..... VW know the car won't run *at all* without it, so they charge what they like.

 

Same with my Dad's Mondeo (current shape), he lost his plipper key and it cost £100 to replace. A plain key with no remote unlocking is about £20 but cause they know everyone wants the remote function, they sting ya.....

 

The world is full money grabbing organisations....

 

Jim, parts are the same across 2.8 and 2.9 and key parts like that are generally always dealer only....surprise surprise...

[PBSTORM 0]

Apparently it's a dealer only part. I did shop around but couldn't get one anywhere...