26 replies to this topic

[Danceman2020]

I have noticed a small Boost problem in different gears on med throttle and some times full throttle at different revs :-( Had the car in at Craig Moncrieff cars in Edinburgh for two days and they say that is seems like the dump valve is opening early but there is nothing showing on computers or fault codes ... Has anyone had this or similar experience and know what the problem is. Any Help would be great.

 

Danceman

[Ormes]

You haven't described the symptom that you are experiencing.  Joining the dots on what you've said, it feels as though it is down on power sometimes, what else can you give us to go on and we'll try and help... small split in a boost pipe/collapsing intake pipe, recirc, actuator, boost solenoid(s) would seem to be the obvious but if you can supply more information, we may be able to narrow it down... any noise when it loses boost?.... etc.

[turboluca]

Has this a upgraded dump valve ? If so scrape it . Recirculating valve 👍🏻

[Danceman2020]

Ok if you are driving and give it medium acceleration there seems to be a miss at about 3 to 5k just seems to die with a whooshing sound and then bang kicks back in and off it goes but it can be in any gear it does it :-( Does not seem to do it on full throttle well not that i have noticed...

 

I will ask Paul tomorrow CM if it has a different Dump valve and maybe that could be the cause and see what he says... 

 

Thanks Hopefully my description is a bit better.

 

Danceman

[Ormes]

Has your mechanic investigated spark or only boost?  Sure it's not an intermittent misfire?... Coilpack?

 

Doesn't feel like split boost pipe or collapsing intake given the symptom you've described.

 

Could still be boost solenoids. 

 

Not convinced it could be the actual recirc, as if it can sustain full WOT, then you'd expect it to sustain part throttle?

 

I've got throttle position sensor in my mind... if the throttle signal dropped at a specifc point in throw of the pedal, this would cause what you describe, but not heard of this occuring and unsure whether it could happen given the way it works.

 

Hope this helps

[Ormes]

Always worth checking all the vacuum hoses too!... but suspect your mechanic has already done this if he suspects a boost issue.

[Danceman2020]

I shall pass on your comments and see what his thoughts are I'm sure they tried all the usual stuff but thats why these forums are so good... Lots of people with same car lots of areas to look at :-)

 

Thanks again

[siztenboots]

if you disconnect the vacuum pipe at the recirc valve end and plug it , then you will eliminate a lot of potential problems , including the clutch pedal switch.

 

if the problem goes away then its that rats nest of pipes and joins, otherwise its the wastegate actuator / solenoid .

[Danceman2020]

Thanks everyone 

 

Seems to be slightly better since CM but they could not find the main problem they are talking about get rid of the Dump Valve and putting back to standard Recirculation Valve ... But will be a couple of weeks before that happens just going to live with the car as it is at the moment as its still great :-)  

[R30SS]

I don't know of CM - I'm sure they're good but in case you want a second opinion, there's a guy called Martin in East Kilbride (his garage is called MVR Scotland) and he is considered a bit of a wizard on the Z20 engine. 

[jonnyboy]

I'd check vacuum (I'm sure CMs would have) gapping plugs is a good one as well. We had a similar one in that was gapped way way out of tolerance to get it to stop misfiring. Could be DV sticking. Actuator sticking. Theres not a lot that will show on opcom that will work its just old fashioned trial and error. 

[Danceman2020]

Update almost ... Thanks R30SS for the recommend but when i called them up they said they were not interested in trying to find the problem lol so looks like i need to fine someone else to find the problem... Any more recommendations ?

[Danceman2020]

Boost problem now getting worse

[Danceman2020]

Boost problem now getting worse

[SteveA]

Have you tried unplugging the MAF?

[Johnturner]

Have you checked the actuator is not sticking

[Danceman2020]

Thanks for the answers :-) Not quite sure where the actuator is or the Maf Can some one point me in the correct direction ... I would have thought that those would throw on an engine management light ?

 

[SteveA]

The maf is between the air box and turbo inlet. It's the plastic thing with the electronic connecter in it. I've seen them be intermittently faulty and not throw an eml. It's an easy free test and can give symptoms like yours. Just pull the connecter out and go for a drive.

[Danceman2020]

Thanks Steve i will give that a go later today see if there is any difference :-)

[Danceman2020]

Ok Disconnected the MAF today and car was running a lot better altho it seem to be less punch top end but not dropping off after 3k rpm so ordered a new MAF (Bosch) one as dot trust the cheep ones on the net. Should be here middle of the week so will give un update once thats on :-)