Regular Limp Mode Only After A Warm Restart

[AMacdonald]

My old (250K!) Alhambra TDi90 has an annoying problem. If I start from cold it'll run all day without a hiccup but if I stop and restart before the engine has had a decently long rest it'll be determined to drop into limp mode which, since I live in quite a hilly area can be a real pain! I've checked and replaced all the vacuum pipes and swapped the MAF out but nothing has helped yet. Could cleaning the turbo help? I've only done it once and that was about 50K ago.

[chrispb123456]

If it's going into limp mode it wil register a fault code so scan your car with vagcom, may save you time and guess work.

[AMacdonald]

That's on the list for today, now I have a couple of hours free. Here's another thing though - I've noticed that the engine never really gets warm so could a faulty thermostat be upsetting the ECU somehow?

[AMacdonald]

After clearing out all the old codes, provoking the fault and rechecking the only fault code is 00575 which appears to finger the n75 solenoid or associated tubing. The pipes have been done so I guess it's time to shop for a new n75. I'm still confused about why it only happens after a warm restart though.

 

On another subject, I've seen a number of people singing the praises of blanking the EGR on this engine. Is it just a matter of making a suitably shaped bit of aluminium to go between the manifold and the EGR plus blocking off the vacuum pipe or is there more to it?

[seatkid]

Fault 00575 is an overboost fault - Intake Manifold Pressure: Control Limit Exceeded

 

More likely to be a sticky vane actuator on the turbo. Hot turbo - more sticky.

[zorgman]

cant be sticky vane as its a 90hp seatkid, i pulled my hair out on a sim problem found its the internal pipe in the ecu that goes to the map sensor all clagged up and sticky,while i was in there i put in a 4.7v zenner so turbo can be turned up and not limp car out

blank your egr off with that ali and car will thank you for it had mine done since day i got it after decoking the inlet manifold

[new nige]

If its a mk1, the map sensor is on the ecu circuit board, have you replaced the manifold tube that runs from the manifold nipple to the ecu nipple AND the tube inside the ecu between the sensor and the internal nipple on the box? if not serch on here and there are detailed descriptions of how to do this, fiddely but saved mine and others 00575 code on a mk 1

[seatkid]

cant be sticky vane as its a 90hp seatkid,

All PD engines on MK2 even 90 bhp are variable vane turbos. Mk1 90 bhp is fixed geometry/waste gate.

 

Sorry but dont know which OP has, as usual no enough info posted. :unsure:

 

If its a Mk 1, I'm inclined to go with zorgman/new nige's suggestion about pipe to map sensor.

Edited November 20, 2011 by seatkid

[walshe]

I cured a random limp mode on my mk1 90bhp by sealing all the cracks that had appeared on the hard plastic brake vacumn pipe that goes from the pump to the servo. Funnily even though there were leaks on this pipe i never lost braking power

[AMacdonald]

Thanks guys. It's a mk1 from 1997 (in my defence it does say that just to the right of the topic title ;-) ) so fixed turbo geometry. I haven't replaced the pipe through to the ECU yet - it's next on the list if the n75 doesn't work. If that still doesn't work the pipe inside the ECU is my last hope but, having tried to gain access over the weekend I'm not looking forward to it. I followed the excellent pictorial guide on this site to get in past the instrument cluster but where the poster has a comparatively clear run through to the ECU, I have a massive rigid wiring loom over the top of mine. Getting past it is going to be no fun at all.

 

My rationale for doing it this way is pipes shouldn't really suffer changes from heating and the ECU shouldn't see much difference either but the n75 is likely to heat up and is electromechanical to boot. It's also easy to change!

 

Thanks for the EGR confirmation. I'll get my hacksaw out over the weekend.

Edited November 22, 2011 by AMacdonald