VR6 running Problem can't find answer in search update:22/06

[zak 0]

Okay I have 3 strange problems with my enginethat i cannot find the answers too through the search

 

As a background my car has been running perfectly without any issues, recently i fitted a flowed head and a set of schimmel 263 cams. The first day i had the engine back together it was running perfect, pulling nice and cleanly all the way through the revs with a solid idle. The following problems started a few days after, nothing was changed in between

 

1. When the engine is cold and I pull out at the junction at the top of my road my engine cuts out while I’m accelerating out. It has happened to me 5 times in the last week in exactly the same spot, today it clicked that the engine cuts out when reaching 3000rpm. After cutting out I coast to a stop then the engine will not restart straight away. When it does restart after a few tries it misfires for a bit and if i rev it past 3000rpm the engine cuts straight away. Once the engine warms up this problem goes away and the idle is rock solid

 

2. Generally the car seems down on power and is not accelerating like it did on the first day that i had the car running after fitting the head and cams. There is distinct lack of midrange and top end and it does not accelerate cleanly almost like when there is a misfire holding the engine back. This is quite frustrating as the first day the engine was pulling like a dream. I am booked in at stealth on the 30th of this month for a remap and want to get to the bottom of these problems before i go to get the most benefit.

 

I am unable to scan for fault codes as recently my vag com no longer reads the ecu. This is quite strange as I used to be able to read the ecu without a problem in the past and my vag com definitely works as i used it on several cars recently without any issues. Note this problem occurred prior to swapping the head and installing the cams and I have already checked that the pins are connected to the port under the gear lever.

 

Since I have a load of spare parts I have swapped the following without any success.

 

a. swapped the isv

b. changed the spark plugs

c. bypassed the isv damper

d. swapped the coilpack

 

I have a spare maf and blue temp sensor that i have to try and will do a compression test in the next few days but in the meantime can anyone suggest what could be the cause of the problems bearing in mind it was running fine for a day after the head and cams were fitted?

[buttles 0]

You really need to get Vag-Com up and running again. No. 1 could be the ECU power relay. Engine cuts out for no reason and won't start for a while. No. 2 sounds like the classic Cam Position Sensor. The relay is a cheap fix and worth cxing anyway. The Cam sensor is about £60 from dealer. Vag-com will show both if there is a fault. Then there is the one million other things it could be!! Neil

[Leonard 0]

Now I don't really know what Im talking about when it comes to engines :grin: But could it be cutting out due to not getting enough fuel?

[zak 0]

Thanks for the tips, yesterday i pulled out the ecu relay and all the contacts seemed clean but regardless i will change it as soon as i can get to a vw dealer on the weekend as the cutting out when cold still remains. I changed the cam position sensor and blue the blue temp sensor for spare ones i had and the drive is still the same, maybe i could have damaged the cam trigger wheel when i fitted it? As that would have the same problem as a faulty cam position sensor?

 

I also tried to scan the ecu with vag com but it still does not work, i plugged a spare ecu in to see if it would scan that but that also did not work, Where do the wires on the vag com port under the dash connect to? I already checked that pins are still in place in the port but now i need to trace them back so i can can check for damaged connection somewhere. Vag Com is still able to scan the abs so it must only be the wires relating to the ecu that i need to look in to. Any help much appreciated.

[dr_mat 0]

Yes, it's more likely to be the cam trigger wheel or the sensor itself. The thing with stuff that "suddenly goes wrong" is it's ALWAYS caused by the thing you took apart and put back together last.. I doubt the ECU relay would have anything to do with a rev-related failure.

[zak 0]

The strange thing is that the car ran perfectly the first day i had it running after i fitted the head and cams. the problems started from the second day.

 

Any ideas on which wires from the vag com port are connected to the ecu so i can trace them back??

[iceviolet 0]

Now I don't really know what Im talking about when it comes to engines :grin: But could it be cutting out due to not getting enough fuel?

 

Or maybe too much fuel?? Mine does this sometimes but only if i floor it when its cold, it will cut out and then take a minute or two to start again. I just let it warm up for 5 or 10 minutes. My mechanic friend said its just a bit of a choke issue, a bit too much fuel when its running the cold map and by putting the pedal down too quickly when cold will just flood it and put out the spark.

[Kevin Bacon 5]

Have you got a factory immobiliser? There's 2 wires from the K line distribution block (clipped to the metal centre console frame behind the dash), one for the ABS ECU and one for the Engine ECU. IIRC, the ABS wire is white and routes over to the passenger footwell and the engine one is grey routes off to the fusebox. Trace the grey wire and make sure it's not severed or unplugged, it uses brown single pin connectors. If you have the factory immobiliser, the grey wire will lead to the transponder box and then from there go to the ECU.

 

I'd start there if a spare ECU won't connect on the same loom either.

 

Did you notice what water temperature it's cutting out at? Around 70 deg? That's when the lambda takes over the fuelling, but it's unusual to cut out completely, even if running too lean. Sounds like total electric shutdown of a particular circuit. A dead cam sensor wouldn't cause that, but it would reduce power. It could be a crank sensor or fuel pump failure. They're the only 2 things I've experienced on a VR6 that will kill a running engine instantly.

 

As for the power being down, do you think you may have skipped a tooth on the cam timing? Did you pressurise the chain tensioner before starting the engine (crank it over several times with the crank sensor unplugged and spark plugs removed)? Drifted timing would almost certainly cause sluggishness, aswell as poor fuel economy as it throws the sequential injector timing out.

 

If you can't fix it, I'd be tempted to store it until the 30th to avoid any damage. Vince will find the problem!

[zak 0]

I have an AG ecu so don’t have a factory immobiliser, the information’s just what I need to trace the wiring I'll see if i can work on it in the next few days.

 

I didn’t notice the water temp, I’ll take it for a spin tonight and report back.

 

I'm pretty sure that i got the cam timing correct, when I installed the cams i turned the engine over about 5 or 6 times by hand and the timing was spot on each time. Vince also mentioned to me about the cam timing especially as my oil temps are about 8 - 10 degrees higher than before i fitted the head and cams. I’m planning to recheck teh timing on the weekend. After I installed the cams and engine i spun the engine on the starter with the fuel pump relay disconnected and the LT wiring disconnected on the coil pack. I didn't take out the plugs but i thought that should have been enough. Either way I’ll be rechecking all the above, I’m not driving the car apart from test runs at the moment but I want to resolve the issues before i get to stealth to avoid wasting time on the day.

 

Thanks for the help.

[Kevin Bacon 5]

OK, same drill as before then, but less the immobiliser box. I can't remember what pin on the ECU plug the k line wire goes to, but Vince'll be able to tell you.

 

Have you got a telescopic nurse / dentist's pocket mirror? I find it invaluable for timing checking. When the crank or flywheel notches are TDC aligned and the cams are in the correct position, I put the mirror down the head opposite intermediate shaft pulley, shine a light down and check I can see the arrow pointing north. If I can, then it's 100% c0ck on. It's just another way of being 100% sure, but sounds like you did the right things and got it correct.

 

Removing the plugs just gives the starter an easier life!

[fla 9]

deffo change the ecu relay. I lost months testing it incompletely, so just replace it annd rule that out.

[_leon_ 0]

zak you can try my new ecu and fuel pump relays if you want...

[zak 0]

I went to stealth today, the vag com problem and the cutting out problem are diagnosed. Vag com was not working because the terminals on the junction box behind the centre console were corroded. The cutting out is because the oil pressure relief valve is jamming shut when the oil is cold and jamming the tappets cusaing the valves to stay open and lose compression. Simple fix when i get round to it by changng the oil pump.

 

Finally got it on the rollers and the cars down on power making less than a standard vr, Vince suggested the intermediate pulley timing could be out from when i changed the chains + tensioners last year. So we agreed i would go away check the bottom end timing and the cam timing and bring the car back another day. SInce then ive been in the garage and stripped the inlet, cam cover and timing chain cover off. The cam timing was spot on. I removed the cams so i could swing the chain out the way to see if the intermediate pulley was alligned. Using kevs method i used a inspection mirror and torch and the intermediate pulley was pointing 12 o clock and lining up with the timing mark. So all looks in order.

 

Before i put the engine back together, i just want a second opinion on the timing, especially the part about the vr being a 4 stroke engine. If cylinder 1 is at top dead centre, the intermidiate pulley is at 12 o clock and the offset cam notches are alligned to the head correctly can the timing still be out? From what i understand that the cams spin one for every 2 revolutions of the crank? how many times does the intermediate pulley turn in relation to the crankshaft and cams? is there anything else i need to know as i want to be 110% sure that the engine is timed correctly before putting it back together.

 

thanks in advance

[iceviolet 0]

ive just rebuilt a vr engine and to set the timing, The ground down tooth on the crankshaft sprocket needs to be lined up horizontally,in line with the split in the bearing shells.(to left hand side if looking directly onto the crankshaft sprocket). Then the intermediate shaft sprocket needs to be lined up with one of the two marks on the plate and then the cams need to be lined with the timing tool plate.

[zak 0]

my engines in my bay with the gearbox fitted so i tdc'd cylinder one using the notch on the crankshaft pulley. and checked with with a wooden dowel through the plug hole.

 

After my post above i turned the engine over by hand a few times to monitor the position of the intermediate pulley. The intermediate pulley lines up with the notch at 12 o clock with every 4 revolutions of the crank. So whats the significance of lining it up at 12 o clock? since the cams line up with every 2 revolutions, this would mean that even if the intermediate pulley was timed using the 6 o clock position with two revolutions of the crank it would be at 12 o clock and the cams would still be in allignment.

 

Anyway ive got the engine back together with the intermediate pulley timed at 12 o clock, and the performance is the same. There are no fault codes so stumped what the issue could be. i want my missing bhp back :?

[_leon_ 0]

and the rest yet to enjoy!

[buttles 0]

Have you fitted a new Cam position sensor or just one you had lying around? I had a loss of power issue recently with no fault codes. After a week or two of scratching head the ECU eventually threw an intermittent fault with said sensor. Replaced with new and hey presto!

[Kevin Bacon 5]

Yep, if the cams align, the intermediate pulley aligns and 1 is on TDC, then that is spot on.

 

After my post above i turned the engine over by hand a few times to monitor the position of the intermediate pulley. The intermediate pulley lines up with the notch at 12 o clock with every 4 revolutions of the crank. So whats the significance of lining it up at 12 o clock? since the cams line up with every 2 revolutions, this would mean that even if the intermediate pulley was timed using the 6 o clock position with two revolutions of the crank it would be at 12 o clock and the cams would still be in allignment.

 

Correct, but aligning to 12 O'Clock means you can see it with the inspection mirror a lot easier than the 6 O clock position. If you ever get a backfire severe enough to cause a cam tooth jump (it can happen!), it's handy to be able to see the intermediate shaft timing easily.

 

The significance of the intermediate pulley and it's north or south timing is to ensure the correct timing for the sequential injection. If the intermediate pulley was misaligned, the rear sprocket's cam trigger wouldn't be at 90 degrees precisely when it should be and therefore screw up the injector timing. It's not a huge problem to be honest and not many people would actually notice, but it'll certainly show up on the MOT emissions test!

 

As far as I know, OBD1 Motronic turns off Sequential above 4000rpm and 75% throttle because Sequential works best at lower rpms (it's mainly for emissions purposes) and has no power advantage, so I don't know where your lost power has gone.

 

How old is the engine? Could just be old age and reduced compression or reduced valve sealing?

[zak 0]

okay thanks for the clarification. My car has high mileage but i sourced a 80k engine an swapped it over complete last year. After fitting i did a compression test and it made 150-160psi across all 6 cylinders. I'm going to do a compression test tonight and see if theres any issues with the new head i fitted.

 

Edit: in reply to Buttles, i replaced the cam trigger sensor with a new one when fitting the rear cam sprocket on to the new cams.

[zak 0]

i did a compression test and i got between 150-170psi across all 6 cylinders. Thats 11 - 12 bar in old money . So compression seems fine :?

[zak 0]

Vince suggested trying another cat incase mine is blocked up. Not sure if its worth taking a risk on a second hand cat, so may fit a decat pipe. Anyone know where i can get a 76cm one from?

[zak 0]

Ive sorted out the the problem with the engine cutting out when cold by fitting a new vag oil pump. But the car is still intermittantly down on power. The decat made no difference then i took the 263's out for a week and it was still down on standard power but the power seems to have come back in the last few days before i fitted the oil pump which is rather strange. Tommorow i plan to refit the 263's with a new cam trigger wheel and cam position sensor and hope that i dont lose the power so i can finally get the car remapped.

[zak 0]

As mentioned above the power was back with the standard cams fitted, and when i refited the 263's with a new trigger wheel and cam sensor and the engine still runs pefectly with a nice increase in power. Torque is back and it pulls cleanly to the redline. Ive had the cams in since Thursday and the power has been consistantly there. I also refitted a cat and now i have a lovely muted exhaust note again so can put my foot down with out drawing attention. So after this post i did not manage to pinpoint exactly what caused me to be down on power but its running fine now so i'm happy. Now to book myself in for a remap :D

[Leonard 0]

:clap: Nice one mate, glad is all good again.

 

Thank you for having the decency though to let me get my cams in and remapped first :wink:

 

Matt

[zak 0]

no problem Matt, i look forward to your results :D