Misfire and stalling

[Sallyanne 10]

Hi all, after a bit of advice if anyone else has come across this. My VR6 has always had a very occasional misfire/slight hesitation at low revs (no problem if you drive it hard!). I did wonder whether it was just because I'd had an 8v for years and years which would pull away in top gear and the VR6 just needed driving harder but I've just had a big service including plugs and leads and it seems much worse. Any ideas/advice about this?

My other issue (which may or may not be connected) is that it's sometimes a pain in the arse at stalling. This seems especially problematic if it's a bit hot, reversing on hard lock or sometimes just because it feels like it. It just won't rev and will take 3 or 4 restarts before it'll go. Again this seems to be getting worse.

I'm near Bristol if anyone knows of anyone good to sort it out? Thanks so much for any suggestions/advice!

[Cressa 44]

Changing my coilpack helped with a bad time I went through with my poor tickover. But could be a lot of other items...from cam sensor,crank sensor etc. 

When my car was warm, it became a pig to start. I put a one way valve at the pump, but did end up replacing my pump. I think they are tired at this age. 

That cured my starting issue, but pretty sure Matt on here did something else.

It's a money pit, but still a lovely one. Good luck

Cressa 

[Sallyanne 10]

Thank you! The fuel pump sounds like a good clue to the starting issue. It’s 30 years old and never had it touched as far as i can see from the history (thankfully i have everything from day 1 onwards!)

The occasional hesitation is more of a mystery i think though odd that its got much worse with new leads and plugs

[Cressa 44]

1 minute ago, Sallyanne said:

Thank you! The fuel pump sounds like a good clue to the starting issue. It’s 30 years old and never had it touched as far as i can see from the history (thankfully i have everything from day 1 onwards!)

The occasional hesitation is more of a mystery i think though odd that its got much worse with new leads and plugs

I had changed my leads  and that's when I got the poor tickover issue. Originally I thought they were faulty, but maybe they just wanted a new coil pack to be happy 😂 

It is nice to have it running and starting, thankfully. 

That's an impressive length of ownership  👍

 

[Sallyanne 10]

10 hours ago, Cressa said:

I had changed my leads  and that's when I got the poor tickover issue. Originally I thought they were faulty, but maybe they just wanted a new coil pack to be happy 😂 

It is nice to have it running and starting, thankfully. 

That's an impressive length of ownership  👍

 

 

Ah, well maybe you're right with that one too. I guess I just need to find someone local who's a specialist (recently moved from London to Bristol so lost my VW specialist sadly). And I haven't owned it for 30 years - just 6 or 7 (though I have had a Corrado of some description for that long!) but am lucky enough to have a low mileage, full history one.

 

 

Edited December 5 by Sallyanne

[oneohtwo 8]

Another quick and easy adjustment is to tighten the throttle cable. Possibly not quite the same issue as hesitation/misfiring but I remember on mine the peddle response often felt slow and hesitant, but there was just a lot of slack in the cable. Tightening it up made a lot of difference. 

Other things I did that seemed to help around low rev and idle issues were replacing the ISV (or you can clean it - it gets a bit gummed up with carbon deposits and stuff, so if you can free it up and then clean it with brake cleaner it helps) and the dashpot (I swapped mine for a Passat one I think), but as Cressa says there's an awful lot that it could be!

[Sallyanne 10]

5 minutes ago, oneohtwo said:

Another quick and easy adjustment is to tighten the throttle cable. Possibly not quite the same issue as hesitation/misfiring but I remember on mine the peddle response often felt slow and hesitant, but there was just a lot of slack in the cable. Tightening it up made a lot of difference. 

Other things I did that seemed to help around low rev and idle issues were replacing the ISV (or you can clean it - it gets a bit gummed up with carbon deposits and stuff, so if you can free it up and then clean it with brake cleaner it helps) and the dashpot (I swapped mine for a Passat one I think), but as Cressa says there's an awful lot that it could be!

Thank you! I just need to find someone in the Bristol area that I can trust with it (and not to rip me off!) Not sure it's this as it idles fine. It just hesitates and misses a bit when accelerating. I guess this could also be the fuel pump as Cressa mentioned re the stalling/not starting?

Edited December 5 by Sallyanne

[fendervg 33]

Could be any of the sensors - MAF, crankshaft, cam/hall sensor, distributor or coilpack, throttle damper, or most likely, a vacuum leak.  There's a small test nipple on the manifold at the front right, get a hose and pressure gauge on there and test the intake pressure at idle and under load.

Cutting out at low speeds/stopping or when returning to idle can be a fault with the ISV or the the trottle return damper (dashpot).

[Dox 23]

For the miss, pull one plug lead off at a time as the engine runs, find one that has the least effect and you've located the cylinder.

Plug

Lead

Coil

Injector

Compression

 

 

[Sallyanne 10]

Thanks everyone, that's given me lots of suggestions! The car doesn't "miss" most of the time though, it's more of a hesitation when accelerating if driven sensibly (fine if I rant it)!

I think the stalling when hot is probably the fuel pump as Cressa suggested

Edited December 6 by Sallyanne

[_Matt_ 32]

On 12/4/2024 at 10:56 PM, Cressa said:

Changing my coilpack helped with a bad time I went through with my poor tickover. But could be a lot of other items...from cam sensor,crank sensor etc. 

When my car was warm, it became a pig to start. I put a one way valve at the pump, but did end up replacing my pump. I think they are tired at this age. 

That cured my starting issue, but pretty sure Matt on here did something else.

It's a money pit, but still a lovely one. Good luck

Cressa 

Thanks Cressa, yes that is me, I have had all of these issues at some point. Though my hot starting issue only presented when the car was left for 15 mins, it would restart fine before that point when warm. 

I don't think this it is Sallyanne's issue, for me it was replacing the fuel pressure regulator (FPR) that solved it. 

Re the misfire and intermittent stalling, I wasn't able to get to the bottom of it with changing sensors and coil packs. The car went to Vince at Stealth for chains and a head refurb and came back fixed from that problem. It still had the warm start issue but I solved that later on with the FPR. 

 

[Sallyanne 10]

1 minute ago, _Matt_ said:

Thanks Cressa, yes that is me, I have had all of these issues at some point. Though my hot starting issue only presented when the car was left for 15 mins, it would restart fine before that point when warm. 

I don't think this it is Sallyanne's issue, for me it was replacing the fuel pressure regulator (FPR) that solved it. 

Re the misfire and intermittent stalling, I wasn't able to get to the bottom of it with changing sensors and coil packs. The car went to Vince at Stealth for chains and a head refurb and came back fixed from that problem. It still had the warm start issue but I solved that later on with the FPR. 

 

Thanks Matt, that's brilliant advice. As I've just posted above, it only stalls when hot if I'm restarting after say an hour AND weirdly on hard lock in reverse. The "miss" isn't really a misfire - more of a hesitation when accelerating (when driven sensibly only. Fine if I thrash it!)

[_Matt_ 32]

Just now, Sallyanne said:

Thanks Matt, that's brilliant advice. As I've just posted above, it only stalls when hot if I'm restarting after say an hour AND weirdly on hard lock in reverse. The "miss" isn't really a misfire - more of a hesitation when accelerating (when driven sensibly only. Fine if I thrash it!)

oh right the hot start issue is very much like mine then, this is a pretty easy fix. The fuel pressure regulator is controlling the fuel pressure so could also be your hesitation too. My FPR valve was allowing fuel to leak past it back to the tank so if i left the car for 15 mins when warm there was no fuel in the fuel rail and the pump had to deliver fuel back to restart, took many cranks. 

Since replacing my VR6 fires up with 1 crank/turn of the starter motor/fires immediately. 

It is located on the front right hand side of the engine with a small vac line attached. To replace you remove the clip holidng it in, give it a sharp pull, perhaps need mole grips as it is tight with age. Fuel will spill out so have a rag. Then slot the replacement in, install clip and reattach vac line. I did find that the vac input on the bosch sensor linked below was a smaller diameter than the one off the car so I put a small crimp clip on to secure it in place.

 

https://www.ebay.co.uk/itm/145607650219?chn=ps&_ul=GB&_trkparms=ispr%3D1&amdata=enc%3A1S-wO637KRceaKUYs1QIqBw40&norover=1&mkevt=1&mkrid=710-134428-41853-0&mkcid=2&mkscid=101&itemid=145607650219&targetid=2361267413036&device=c&mktype=pla&googleloc=1006493&poi=&campaignid=21690875685&mkgroupid=166734314545&rlsatarget=aud-1164958979220:pla-2361267413036&abcId=10027099&merchantid=118987990&gad_source=1&gclid=Cj0KCQiA3sq6BhD2ARIsAJ8MRwWp_HQTE-zWSb6-HEi2PKVV-K3OLNecTpqYRS8TAUOHPj2x46dF1OQaAoiKEALw_wcB

[Sallyanne 10]

2 minutes ago, _Matt_ said:

oh right the hot start issue is very much like mine then, this is a pretty easy fix. The fuel pressure regulator is controlling the fuel pressure so could also be your hesitation too. My FPR valve was allowing fuel to leak past it back to the tank so if i left the car for 15 mins when warm there was no fuel in the fuel rail and the pump had to deliver fuel back to restart, took many cranks. 

Since replacing my VR6 fires up with 1 crank/turn of the starter motor/fires immediately. 

It is located on the front right hand side of the engine with a small vac line attached. To replace you remove the clip holidng it in, give it a sharp pull, perhaps need mole grips as it is tight with age. Fuel will spill out so have a rag. Then slot the replacement in, install clip and reattach vac line. I did find that the vac input on the bosch sensor linked below was a smaller diameter than the one off the car so I put a small crimp clip on to secure it in place.

 

https://www.ebay.co.uk/itm/145607650219?chn=ps&_ul=GB&_trkparms=ispr%3D1&amdata=enc%3A1S-wO637KRceaKUYs1QIqBw40&norover=1&mkevt=1&mkrid=710-134428-41853-0&mkcid=2&mkscid=101&itemid=145607650219&targetid=2361267413036&device=c&mktype=pla&googleloc=1006493&poi=&campaignid=21690875685&mkgroupid=166734314545&rlsatarget=aud-1164958979220:pla-2361267413036&abcId=10027099&merchantid=118987990&gad_source=1&gclid=Cj0KCQiA3sq6BhD2ARIsAJ8MRwWp_HQTE-zWSb6-HEi2PKVV-K3OLNecTpqYRS8TAUOHPj2x46dF1OQaAoiKEALw_wcB

Aha! Thank you! That sounds like a really good start. I've been convinced that it's a fuel issue for ages. Thanks so much for your advice. I'll go with this first and take it to Vince if I get stuck.

[_Matt_ 32]

I tried loads of things with mine and the FPR was the last resort. It gets expensive throwing lots of parts at it, definitely good to go to someone like Vince if this does solve to save money in the long run. 

 

 

[Sallyanne 10]

Just now, _Matt_ said:

I tried loads of things with mine and the FPR was the last resort. It gets expensive throwing lots of parts at it, definitely good to go to someone like Vince if this does solve to save money in the long run. 

 

 

I'ved just ordered the FPR, my other half can manage that job. If that doesn't sort it, I'll take it to Vince rather than trying a million things on the off chance they're right!

[_Matt_ 32]

Good luck, it may work, but on my Corrado I had also refreshed the entire fuel system with pump, filter and refurbished injectors in an attempt to cure the hot start issue without success. The FPR solved so am unsure if it is was general weakness in the whole system or if it was just the FPR alone. For the cost of the part it is worth as the other parts i replaced were not cheap! I tested the fuel pressure before replacing stuff too. 

[fendervg 33]

Yep, faulty FPR or leak down on the pump outlet in the tank will cause the residual pressure to drop - a vacuum leak will also affect the FPR (there's a short air hose going to it)  as it uses that to regulate the pressure. The FPR is cheap and a simple replacement job as above and easy target when working through the list.

[Sallyanne 10]

On 12/6/2024 at 10:08 AM, _Matt_ said:

oh right the hot start issue is very much like mine then, this is a pretty easy fix. The fuel pressure regulator is controlling the fuel pressure so could also be your hesitation too. My FPR valve was allowing fuel to leak past it back to the tank so if i left the car for 15 mins when warm there was no fuel in the fuel rail and the pump had to deliver fuel back to restart, took many cranks. 

Since replacing my VR6 fires up with 1 crank/turn of the starter motor/fires immediately. 

It is located on the front right hand side of the engine with a small vac line attached. To replace you remove the clip holidng it in, give it a sharp pull, perhaps need mole grips as it is tight with age. Fuel will spill out so have a rag. Then slot the replacement in, install clip and reattach vac line. I did find that the vac input on the bosch sensor linked below was a smaller diameter than the one off the car so I put a small crimp clip on to secure it in place.

 

https://www.ebay.co.uk/itm/145607650219?chn=ps&_ul=GB&_trkparms=ispr%3D1&amdata=enc%3A1S-wO637KRceaKUYs1QIqBw40&norover=1&mkevt=1&mkrid=710-134428-41853-0&mkcid=2&mkscid=101&itemid=145607650219&targetid=2361267413036&device=c&mktype=pla&googleloc=1006493&poi=&campaignid=21690875685&mkgroupid=166734314545&rlsatarget=aud-1164958979220:pla-2361267413036&abcId=10027099&merchantid=118987990&gad_source=1&gclid=Cj0KCQiA3sq6BhD2ARIsAJ8MRwWp_HQTE-zWSb6-HEi2PKVV-K3OLNecTpqYRS8TAUOHPj2x46dF1OQaAoiKEALw_wcB

Any idea where to get an appropriate crimp clip from Matt? The other half has had a look and can do the job but doesn’t have anything to replace the clip with. Thanks!

[_Matt_ 32]

I just used what I had lying around - i have a box of these

https://www.ebay.co.uk/itm/374803688015?chn=ps&_ul=GB&var=643858318068&norover=1&mkevt=1&mkrid=710-134428-41853-0&mkcid=2&mkscid=101&itemid=643858318068_374803688015&targetid=2361039923645&device=c&mktype=pla&googleloc=9050372&poi=&campaignid=21697381820&mkgroupid=170109506289&rlsatarget=aud-1165757154899:pla-2361039923645&abcId=10027101&merchantid=424798499&gad_source=1&gclid=Cj0KCQiAsOq6BhDuARIsAGQ4-ziGG_oUq_HmswU1k1ZAP15wlS4ea_FkL25iNI0lEo0dFM0BeIlpAMkaAslzEALw_wcB

[Sallyanne 10]

1 hour ago, _Matt_ said:

I just used what I had lying around - i have a box of these

https://www.ebay.co.uk/itm/374803688015?chn=ps&_ul=GB&var=643858318068&norover=1&mkevt=1&mkrid=710-134428-41853-0&mkcid=2&mkscid=101&itemid=643858318068_374803688015&targetid=2361039923645&device=c&mktype=pla&googleloc=9050372&poi=&campaignid=21697381820&mkgroupid=170109506289&rlsatarget=aud-1165757154899:pla-2361039923645&abcId=10027101&merchantid=424798499&gad_source=1&gclid=Cj0KCQiAsOq6BhDuARIsAGQ4-ziGG_oUq_HmswU1k1ZAP15wlS4ea_FkL25iNI0lEo0dFM0BeIlpAMkaAslzEALw_wcB

Thanks! He’s always happy to have any excuse to buy tools that “that might come in handy” 😂