VR6 slight lack of power

[Fanjita 1]

Hi all,

 

I've had this problem a while and it's been bugging me, the VR6 just doesn't seem to pick up the way I'm led to believe it should. At low RPM the torque is noticeable, but at higher RPM it feels like there's almost a flat spot, certainly does't feel like a friend's standard VR6 that I've been in and driven!

 

After doing numerous searches, here's what I've done so far:

 

VAG-COM - now have my own copy, apart from the engine speed sensor fault which goes when the engine is running, no faults. I have also checked all the sensor readouts and importantly the o2 (lambda) is working fine as is the throttle position sensor.

 

Vac hoses - I have checked all of the vacuum hoses around the throttle body, and all are holding pressure. I did have a large hole in a hose joined between the inlet mani (just in front of TB), PCV valve and solenoid valve for the carbon canister. Fixed this yesterday and have felt no improvement. The sound supressor can by the ISV is also fine and holding pressure.

 

All temperatures are fine, and they all match up. I did notice a slight discrepancy on VAG-COM between instrument displayed water temp and the ECU's temp reading, they both rose as expected but were 10 degrees apart. This shouldn't be a problem should it?

 

As far as I understand, the MAF does not produce errors within the diagnostic system if faulty. This is one of my next checks, although after many searches it still doesn't seem fully clear how I go about testing the MAF. I should have enough electrical testing equipment for this so would someone be able to tell me exactly how to check it and what values I am looking for?

 

I will be doing a compression test today but I don't think I have anything wrong there as the engine is a stealth rebuilt one with around 35k on it since the work.

 

Failing that can anyone suggest any other port of call to check with this engine?

 

I have a few more symptoms that may help:

 

Very occasional cut out with dipped clutch.

Athough decat, may be running slightly rich - MPG does not appear too bad however.

I noticed that when disconnecting the MAF with a running engine, it spluttered and died, signs of anything?

 

Now it may be that I am being paranoid with this problem and the engine turns out fine. I do have a valid reason to feel that there's a lack of power, not just from what I feel when driving. I have had a couple of occasions where I give it beans to try and get ahead of someone clearly not content with letting me past (only rare occasions though!). It just doesn't have the edge and has lost out to a new type MR2 ( :gag: ) and a Mk3 VR6 to name a few!

[Fanjita 1]

Update:

 

Compression test results:-

1: 170 psi

2: 178 psi

3: 172 psi

4: 178 psi

5: 168 psi

6: 173 psi

 

Looks to be a healthy spread...

 

Cylinders 2 and 4 appear to be quite lean, the spark plugs not as bronzed as the rest. Could this be the injectors?

 

What's the cheapest way of getting a decent set to replace them with? These ones do look quite well used, probably the age of the engine, we were thinking of cleaning them in our ultrasound bath?

[tandino 0]

Have the chains been done?,

Trying to rule out the timing being out.

[Fanjita 1]

Have the chains been done?,

Trying to rule out the timing being out.

 

AFAIK Stealth did the whole engine about 5 years ago, and it's done roughly 35k since. It has quite an unhealthy tappety noise at 2000 rpm which I haven't yet addressed but I'm really confused as to what would cause it on such a supposedly good nick engine.

[tandino 0]

For the sake of about an hour or so's graft id pull the rocker cover/upper timing case off and check the cam timing.

[Fanjita 1]

For the sake of about an hour or so's graft id pull the rocker cover/upper timing case off and check the cam timing.

 

Ok I will give that a look, thanks!

 

Would you mind explaining to a novice just basic steps to checking the timing?

 

I've replaced a head in the past so I know what you mean about removing the aforementioned parts, and I also have a camshaft locking tool.

[Fanjita 1]

Also need help with how to test MAF, anyone got any advice? :shrug:

[Fanjita 1]

Just checked the timing, appears to be fine.

 

Piston 1 at TDC and the camshaft slots line up.

[tandino 0]

Just checked the timing, appears to be fine.

 

Piston 1 at TDC and the camshaft slots line up.

 

Well your timing and compression appear good.

 

I would say that your MAF appears to be working if the car dies when its unplugged.

Try plugs first if you say they are knackered, thats a cheap thing to replace.

[Critical_Mass 10]

Just checked the timing, appears to be fine.

 

Piston 1 at TDC and the camshaft slots line up.

 

Well your timing and compression appear good.

 

I would say that your MAF appears to be working if the car dies when its unplugged.

Try plugs first if you say they are knackered, thats a cheap thing to replace.

 

I think only early VRs stall when the MAF is unplugged, but it would still run like a bag of sh!te. Though i would expect a dodgy MAF to show up on vagcom.

 

 

It could be the leads or coil pack.

[Fanjita 1]

Cheers,

 

I'm pretty sure the engine and car is of the late variety, not sure on the condition of the coilpack but I'd assume that the engine would be rough at idle if there was a problem with that?

 

I feel like I've almost checked everything then, just haven't tested the MAF :scratch:

[Critical_Mass 10]

Cheers,

 

I'm pretty sure the engine and car is of the late variety, not sure on the condition of the coilpack but I'd assume that the engine would be rough at idle if there was a problem with that?

 

I feel like I've almost checked everything then, just haven't tested the MAF :scratch:

 

Not sure mate, bear in mind the coil pack will be under more load at higher revs. If the MAF was fooked it would run sh!t all the time.

[Rams 0]

what fuel are you using and have you recently replaced the fuel filter? Try some injector cleaner too. When using opitmax I notice a better pick up and a sharper throttle response over 95 ron.

[Mawrick 0]

Just checked the timing, appears to be fine.

 

Piston 1 at TDC and the camshaft slots line up.

 

Well your timing and compression appear good.

 

I would say that your MAF appears to be working if the car dies when its unplugged.

Try plugs first if you say they are knackered, thats a cheap thing to replace.

 

I think only early VRs stall when the MAF is unplugged, but it would still run like a bag of sh!te. Though i would expect a dodgy MAF to show up on vagcom.

 

 

It could be the leads or coil pack.

 

late one's will for sure run without it - actually forgot to put back on the maf with breather hose etc when I fired it up once - it had no trouble idling.....

[Kevin Bacon 5]

You can only really test the MAF with an Oscillscope, but you need to know what waveform to look for though!

 

If it's stalling and down on power and the timing and compressions are good, I would say it's the MAF. The fuelling is too lean pulling up to junctions and it's cutting out. Classic MAF symptom.

 

I would also check the idle valve as sometimes the blue foam inside the noise damper gets sucked into the valve, which can restrict it's movement.

[Fanjita 1]

Ok I will try that, cheers.

 

It's a 5 pin MAF, is that the late type?

 

I have a coilpack engine but I'm not sure how to tell, everything else (apart from the bumper strangely) is late on my 93 C.

[Kevin Bacon 5]

5 pin is the early wire type MAF, the expensive one!

[Fanjita 1]

Wonderful! Is there any way to run it on the cheaper one? :lol:

[Kevin Bacon 5]

Sadly not!

[Mawrick 0]

have you tried cleaning the MAF? (you can clean it up with spraying lots of start gas on ir) (take it out and hold it vertical so the dirt drains off - and do both sides - worked for me years ago on my Passat - never done any cleaning since then....;)

[Wompa 0]

My car also gives me low power... and the VAG-Com says its the G40 Hall Sender that is open or short to B+.. tested change that and the car felt alot better.

[Fanjita 1]

Unfortunately my VAG-COM is clear :( no easy fixes there

[Fanjita 1]

Looks like it may have just been psychological.

 

Been driving around in it lately and it seems to be ok, so I may have just imagined it was slow :(. Having said that it does seem to have more low down poke when the engine is cold and running on choke. I do look after my engine though and that is just from low RPM tests, could it be anything or is this normal?

[Kevin Bacon 5]

VR6s always feel best when they're warming up and not under Lambda control.

 

Then the Lambda cuts in (at 70 deg water temp) like an anvil and kills the fun :lol: