seat leon hesitation

[mk1cupradave]

right need some help as this is driving me mad.

I have a seat leon cupra with a bmc cda filter, splitter r and stage one remap. The car started to hesitate when driving with around half throttle. This happens in all gears. I can hold the throttle halfway right trough the rev range and the revs will increase then nothing then increase. Its like the car suddenly losses power and then goes again. If i floor it then the car will pull fine no problem.

I testing the maf on vac com and there where no faults. Fitted a new maf just to make sure and still the same. Unplugged the maf and ran the car, still the hesitation.

The old map was put back on and it was still there just not as obvious. Tried 2 more maps and it was doing the same.

Going to try the OE dv tomorrow and give the car a service. Then going to have it plugged into vac com and read the fuel and boost pressure.

Anyone else had the same problem if so what cured it?

 

[virdi]

Have you tried replacing spark plugs.?

 

[james_cupra]

i had this problem with my cupra, after endless changing sensors, checking the dv, new spark plugs etc it ended up being a small one way valve that was the problem. it was opening intermittently resulting in a pressure drop. can you hear your dv working when it is hesitating?

 

[mk1cupradave]

what one way valve was it? Not sure about the dump valve. When plugged into vag com its said something about an intermittent pressure drop between manifold and dump valve.

 

[Raks]

i had this problem with my cupra, after endless changing sensors, checking the dv, new spark plugs etc it ended up being a small one way valve that was the problem. it was opening intermittently resulting in a pressure drop. can you hear your dv working when it is hesitating?

Yes I have similar problem but in higher gears. Seems like dump valve is fluttering???

 

[nd-photo.nl]

Have you checked the vacuum hoses and (crankcase) breather hoses?

 

[mk1cupradave]

right well serviced the car today, replaced splitter r for standard and got the map removed and the original loaded back on. Also swapped the n75 for one off a friends car and still the same if not worse. I also had the engine running and sprayed brake and clutch cleaner on the vacuum hoses to check for leaks. None of this has solved the problem.

When i serviced the car i noticed while changing the spark plugs the two middle cylinders had been running lean, as there was a gray/brown layer.

Going to take the car to a bosch expert tomorrow, who also maps cars and has a rolling road, so will see if he can fit mine in.

 

[Russler]

I have a similar problem on mine (LCR) it has been sorted once by replacing a very old REVO map with the new Linear REVO map but now the hesitation is back..only when cold though? the original cause was bescause the car was running lean due to the old software...so who knows what it is now? I have new coil packs, new plugs, full service, new software etc... I am guessing here but could be lambda sensor shot giving a crap reading or N75 valve as I know mine is the original one, MAF? SEAT freely admit this is now a servicable item due to the number of faults with them or split hose somewhere? I have tried to check PCV and DV hoses etc but cant "see" any splits...it is so frustrating as my car is now feeling sluggish too so I know something is up!

Let us know how you get on at the garage today.

 

[james_cupra]

what one way valve was it? Not sure about the dump valve. When plugged into vag com its said something about an intermittent pressure drop between manifold and dump valve.

its a PCV valve that is under the intake manifold. the manifold had to be removed to change it. it might be visible if you remove your lower part of your engine cover and look down with a torch.

symptoms of my car before this was changed was hesitation on pulling away and working up the revs at a consistant level with a slight flutter from the dv. it was very annoying and sometimes sounded like the car wanted to cut out. after this was changed it was like driving a different car! the valve was only £6 from ingrams so its worth a try!

 

[mk1cupradave]

ok well today took it to a tuning company that specialize in bosch fuel systems they connected a smoke tester up to the boost system and there was smoke coming from under the manifold. Went to vw and spent £90 on all new hoses for under the manifold including the crank case breather pipe (is this where the valve was? (the green one) as i didnt replace this.) started the car and took it down the road and still the same.

Going to have it smoke tested again tomorrow to try it again.

 

[james_cupra]

ok well today took it to a tuning company that specialize in bosch fuel systems they connected a smoke tester up to the boost system and there was smoke coming from under the manifold. Went to vw and spent £90 on all new hoses for under the manifold including the crank case breather pipe (is this where the valve was? (the green one) as i didnt replace this.) started the car and took it down the road and still the same.

Going to have it smoke tested again tomorrow to try it again.

yes thats correct. PCV stands for positive crankcase ventilation. Hopefully this picture can help you.

 

[mk1cupradave]

lovely cheers mate will give this a go. When i replaced the pipes i looked at this valve and its just a small spring. It was very free and easy to push in. (Normal?).

 

[james_cupra]

not sure on that one i'm afraid mate, as it was just flung to the side when the new one was fitted. let me know how you get on, for the price of the valve itself there's no harm in changing it. good luck!

 

[ClearAction]

If your pcv valve is gone, you will likely need to replace the flat 'hockey puck' valve (you can find this under the dump valve. It is located on top of the turbo intake pipe.
If you don't replace it and it's broken it breaks any new pcv valves you replace. When it is faulty it can give the error - pressure drop between turbo and throttle valve (check DV). When I tested mine it still 'worked' (the diaphragm moved) but it was sluggish. Maybe clogged with breather vapours or a small hole in it somewhere.
Hope you find the problem

J

 

[mk1cupradave]

well good news!!!

Car went back in today and the n75 valve was playing up (the one off my mates car). I think the original fault was the PCV valve meaning my mates n75 valve was shot!!! Once fixed it went on the rollers and made 183 BHP. When i was called to say it was ready the guy said they had 20% off revo so i couldn't say no.

Needless to say when i picked the car up i was more than happy

Cheers for all the suggestions much appreciated

 

[adon30]

I think you've had a similar problem to what I have now. Any medium to hard acceleration, particularly noticeable in 3rd (but also in 4th, 5th and occasionally 6th) the car goes then stops every 500revs or so.
I've checked for engine fault codes and found none. Spark plugs all seemed ok as well. Found the upper breather had split so replaced with one from creations. In doing this I think I snagged the plastic lower one on the engine cover (razor sharp!!) and put a split in this one. So went to replace this one and whilst removing the entire pcv pipe assembly (easiest way I found to do it) I found the small pipe also had a split in it. Coincidentally this was where my small oil leak was coming from.
So replaced all them. Inspected the green pcv valve and cleaned the gunk up and all seemed fine. I was going to replace it but I think it was a silly price and no one local had stock so used the old one.
However problem still there and has become annoying and can even be worse at times. I think if the revs are kept high and then continue to accelerate again it's not noticeable. It's just from low revs and usually when your in the middle of overtaking a tractor with on coming cars!! Very unnerving.

I have been told that if main electrical connections become corroded at junctions it can give a similar outcome. However I have inspected them and they all seem good. I will give the pcv valve a try when I get around to dismantling it all again.

 

[mk1cupradave]

I would change the n75 valve as this was what caused mine. The pcv valve can look ok but be shot. I would personally try a new pcv valve first as this is the cheaper option. Let us know how you get on.

 

[adon30]

I would change the n75 valve as this was what caused mine. The pcv valve can look ok but be shot. I would personally try a new pcv valve first as this is the cheaper option. Let us know how you get on.

Well finally got round to replacing the £8 pcv valve. Unfortunately it's not made a difference but worth a go to rule out. Now either DV or n75 I guess. No idea what else it could be??

 

[virdi]

I think you've had a similar problem to what I have now. Any medium to hard acceleration, particularly noticeable in 3rd (but also in 4th, 5th and occasionally 6th) the car goes then stops every 500revs or so.
I've checked for engine fault codes and found none. Spark plugs all seemed ok as well. Found the upper breather had split so replaced with one from creations. In doing this I think I snagged the plastic lower one on the engine cover (razor sharp!!) and put a split in this one. So went to replace this one and whilst removing the entire pcv pipe assembly (easiest way I found to do it) I found the small pipe also had a split in it. Coincidentally this was where my small oil leak was coming from.
So replaced all them. Inspected the green pcv valve and cleaned the gunk up and all seemed fine. I was going to replace it but I think it was a silly price and no one local had stock so used the old one.
However problem still there and has become annoying and can even be worse at times. I think if the revs are kept high and then continue to accelerate again it's not noticeable. It's just from low revs and usually when your in the middle of overtaking a tractor with on coming cars!! Very unnerving.

I have been told that if main electrical connections become corroded at junctions it can give a similar outcome. However I have inspected them and they all seem good. I will give the pcv valve a try when I get around to dismantling it all again.

Sounds like MAF. Have you tested it..?

 

[adon30]

No I haven't done that, I don't think.

Ok stupid question time. Where is the maf and how do I go about testing it?