1.8t overboost (problem diagnosed....i think)

[Sheraton]

Originally Posted by arodriguez

Let us know how you get on. I replaced my Pierburg unit but it didn't help. I've now replaced coil packs (one was faulty), leads, plugs (gapped to 0.6mm) and 3mm ID hoses but it still cuts out on overboost. It's a recon turbo too so I assume that's good.

Seems to be hit and miss when it cuts out (with flashing engine light) but I've no idea what's causing it. I was recommended to fit an upgraded MAC solenoid valve.. good luck.

i'll update any progress when the replacement arrives

Have you checked the wastegate actuator is functioning - i unclipped the silicone hose (at the solenoid) that feeds the wastegate actuator and it fit neatly into my bicycle track pump, pressurised and released a few times and i could see the actuator moving the arm to open the wastegate. also have you tried bypassing the solenoid - connect the compressor side straight into the wastegate actuator - if you still have overboost and ECU engine cut out, there must be an issue with the wastegate or actuator.

i am running with the compressor connected directly to the wastegate actuator and it is running perfect - no overboost or engine cut out no matter how hard i push hopefully the replacement solenoid will give back the wee bit extra boost the car is intended to have - not that it's needed


Paul........

[Sheraton]

How'do folks

I received my replacement Pierburg boost solenoid (ECBS electronic boost control solenoid) today

didn't take but a few minutes to get it on the car - i had bypassed the solenoid and "hardwired" the wastegate to avoid overboost and potential damage to the engine and gearbox etc...

i've had a wee run tonight and all seems well no overboost but i've got back that bit extra boost that was missing from the turbo - due to being purely mechanically controlled via the vac hose and the wastegate actuator spring.
the new part seems to be doing it's job...

here's a few pics....cos posts with pics are always better

wastegate "hardwired"

[IMG][/IMG]

New and old ECBS

[IMG][/IMG]

Wastegate actuator hose

[IMG][/IMG]

Pressure return hose (connected to air intake)

[IMG][/IMG]

Compressor hose

[IMG][/IMG]

All connected and in place

[IMG][/IMG]

[IMG][/IMG]


cheers for the help/feedback guys


Paul..............

[arodriguez]

Hi Paul,
Glad to hear you got it sorted. I tried disconnecting the solenoid so that the compressor is directly connected to the wastegate all the time as you suggested. It stopped the overboost straight away albeit with a minor loss of power. When I reconnected it the boost cut out returned intermittently as before. So I know the turbo / wastegate is good which points to a dodgy solenoid allowing too much boost but I changed that already without resolution. Not sure where else to turn??

Regards,

Tony.

[Sheraton]

Originally Posted by arodriguez

Hi Paul,
Glad to hear you got it sorted. I tried disconnecting the solenoid so that the compressor is directly connected to the wastegate all the time as you suggested. It stopped the overboost straight away albeit with a minor loss of power. When I reconnected it the boost cut out returned intermittently as before. So I know the turbo / wastegate is good which points to a dodgy solenoid allowing too much boost but I changed that already without resolution. Not sure where else to turn??

Regards,

Tony.

how'do Tony - do you have the hoses connected to the correct ports? have you checked/changed the vac hoses? was the replacement solenoid a brand new unit?

to my understanding - if you know the wastegate actuator is functioning then it can only be - either the solenoid is faulty, the hoses are leaking or connected to the wrong ports, or the electrical connection to the solenoid
is at fault.....

I know how frustrating this can be so i'd like to help you diagnose and fix the issue if I can

Paul..........

[Sheraton]

Originally Posted by arodriguez

Hi Paul,
Glad to hear you got it sorted. I tried disconnecting the solenoid so that the compressor is directly connected to the wastegate all the time as you suggested. It stopped the overboost straight away albeit with a minor loss of power. When I reconnected it the boost cut out returned intermittently as before. So I know the turbo / wastegate is good which points to a dodgy solenoid allowing too much boost but I changed that already without resolution. Not sure where else to turn??

Regards,

Tony.

just checked your first post on this thread

as you have changed the hoses - double check the condition and the connections - in the pics I posted of my new solenoid installed - the yellow hose connects to the wastegate actuator.


Paul.......

[arodriguez]

Hi Paul,
Yes everything was replaced with new. The hoses are firmly connected and connected correctly. I even downloaded the Pierburg tech sheet to make sure. The boost cut is intermittent and only tends to cut in when I'm about to overtake (4th to 3rd gear) which is very annoying. I'm thinking about a manual boost controller if I can't sort it.. The only thing that helped previously was regapping the plugs to 0.6mm but that shouldn't affect the boost so I'm stumped now??

Regards,

Tony.

[Sheraton]

Originally Posted by arodriguez

Hi Paul,
Yes everything was replaced with new. The hoses are firmly connected and connected correctly. I even downloaded the Pierburg tech sheet to make sure. The boost cut is intermittent and only tends to cut in when I'm about to overtake (4th to 3rd gear) which is very annoying. I'm thinking about a manual boost controller if I can't sort it.. The only thing that helped previously was regapping the plugs to 0.6mm but that shouldn't affect the boost so I'm stumped now??

Regards,

Tony.

are your symptoms - violent engine cut-out? or - loss of boost power/misfire?

the overboost i had gave massive power surges and excessive boost and if boost got high enough, the ECU cut power to the engine - it was a violent sudden loss of all power to the engine - i had misfire when i bought the car too - this was due to the ignition - oil in the plugs under the coil packs - a dose of Redex in a full tank of fuel cured this misfire initially (before i noticed the oil) i cleaned the oil found/fixed the slight leak and gapped the plugs to 0.80 this cured my misfire - i'm going to run another dose of Redex next full tank - clears carbon build up and should clear any residue of oil in my fuel system....i hope ......my car runs great at the minute tho

as you've gapped and i assume checked your plugs lol.....you'd have noticed if you had my problem..lol it may be worth trying some Redex - around £5 for 4 full tank doses and requires no mechanical work i know this has worked for some other folks who have had misfire issues - carbon build up can affect an engine in lots of ways and Redex really does make a difference - or any other brand of fuel system cleaner lol...


Paul.....

[bear-mg]

I had all the same problems on my first zt, again after much head scratching I tracked down the fault to the electronic turbo solenoid as mentioned, you can bridge the two terminals with 12volts and listen for the solenoid operating which is a simple test,try a squirt of penetrating fluid as it may be stuck .. I managed to source a new replacement for about 20 quid

[arodriguez]

Originally Posted by Sheraton

are your symptoms - violent engine cut-out? or - loss of boost power/misfire?

the overboost i had gave massive power surges and excessive boost and if boost got high enough, the ECU cut power to the engine - it was a violent sudden loss of all power to the engine - i had misfire when i bought the car too - this was due to the ignition - oil in the plugs under the coil packs - a dose of Redex in a full tank of fuel cured this misfire initially (before i noticed the oil) i cleaned the oil found/fixed the slight leak and gapped the plugs to 0.80 this cured my misfire - i'm going to run another dose of Redex next full tank - clears carbon build up and should clear any residue of oil in my fuel system....i hope ......my car runs great at the minute tho

as you've gapped and i assume checked your plugs lol.....you'd have noticed if you had my problem..lol it may be worth trying some Redex - around £5 for 4 full tank doses and requires no mechanical work i know this has worked for some other folks who have had misfire issues - carbon build up can affect an engine in lots of ways and Redex really does make a difference - or any other brand of fuel system cleaner lol...


Paul.....

Hi Paul,

I'm a fan of Redex too and the 75 has had a few bottles through the tank over the last two years. I also tried cataclean which is excellent and got my last Tomcat turbo through an MoT when the emissions were high. Didn't help with the boost cut though. When it cuts in it is quite violent and stops the engine revving any higher. It's like hitting a rev limiter. It is intermittent though which is odd - sometimes it revs cleanly all the way up..

Regards

Tony..

[Sheraton]

Originally Posted by arodriguez

Hi Paul,

I'm a fan of Redex too and the 75 has had a few bottles through the tank over the last two years. I also tried cataclean which is excellent and got my last Tomcat turbo through an MoT when the emissions were high. Didn't help with the boost cut though. When it cuts in it is quite violent and stops the engine revving any higher. It's like hitting a rev limiter. It is intermittent though which is odd - sometimes it revs cleanly all the way up..

Regards

Tony..

how'do Tony

Aye, Redex wouldn't help with overboosting issues - but with misfire/ignition problems - if you hadn't already tried it - I had misfire and overboost problems after purchasing the car initially - both had similar symptoms and as both only happened under hard acceleration it can be difficult to distinguish the difference between them .

the misfire was more of a stuttering loss of power (no ECU cut-out) which could be powered through - the overboost was a violent loss of power, like something has broken ......something will likely break (drivetrain) if ECU cut-out is triggered repeatedly due to overboost...

Also with a fault in boost control - the turbo will be overboosting even at half throttle - as there is no boost control to reduce pressure via the wastegate - the turbo will be spooling up and building pressure regardless of throttle position - it's possible for the symptoms to seem intermittent..

i.e - dropping from 4th to 3rd, boost pressure should be dumped upon releasing the throttle through the recirculating dump valve(?) and build again (in 3rd gear) as the throttle is opened - if it takes a few moments to get an overtaking opportunity, you may be on half throttle with high enough revs (2500-3000rpm even) to be spooling the turbo beyond intended boost pressure (this pressure has no way of releasing until you release the throttle - through the dump valve) then when you floor it you will quickly trigger the ECU cut-out - unless you (release the throttle) and change gear before this happens.

it's also possible to go foot to the floor and never hit ECU cut-out (even if you definitely have no boost control and an overboost situation)
i.e - (from my own diagnosis test run experience) coming on to a small roundabout, dropping to 3rd then 2nd - boost pressure is dumped(recirculated) upon throttle release, minimum throttle position used to negotiate roundabout, foot to the floor upon exiting (to a long straight) in 2nd gear, I was able to hit 95mph in 3rd gear, changing to 4th and easing off around 110mph (this was on my own private test track of course ...lol...sure) without triggering ECU cut-out - I assume as the gear changes were coming quick enough to dump the boost pressure (on throttle release) also as it was overboosting the power was increased and this would have reduced 0-60 times etc...

lol....sorry to rant on a bit

I'd recommend changing the solenoid again - for £23.98 delivered to your door from Germany - it's worth it (I think) if you still have issues then you can be (almost..lol) sure the problem is elsewhere
I'd say however - if you're satisfied that bypassing the solenoid cured the problem, it's got to be boost control that's the problem.
can only be one of 3 problems (to my understanding)
1 - Hoses, leaking or incorrect connections
2 - solenoid unit faulty
3 - electrical connection to solenoid at fault

http://s14.postimg.org/yv52nryj5/boost_Vac_hoses.jpg

http://www.bestpartstore.co.uk/ersat...word=PMK000030

https://www.google.co.uk/url?sa=t&rc...q-2k7rEtwoo5gA


Paul.........