2004 Discovery 2 TD5 overboosting at high RPM

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27th March 2020, 12:01 AM
discorevy

how easily does it start ?
27th March 2020, 12:51 AM
Young1

Quote:

Originally Posted by discorevy

how easily does it start ?

Yes the ERG was removed when I got the car.

Starting is usually fine...
When warm/hot it always starts first time.

When cold it will start first time, immediately followed by low rpms (600-700) and rough idling for 4-6 second before jumping into its smooth idling.

When it's been left for like 2+ days cold I will start first time, but the drop on Revs will sometimes drop so low it stalls. Usually starting fine the second time.

A bit strange.
It started showing these starting symptoms after the head gasket replacement 2 years ago.
Since then I have changed the glow plugs and the injector washers/O-rings were done when the gasket was.

This is on my list but always thought it would likely be un-related.
27th March 2020, 02:10 AM
discorevy

re check the cam timing
27th March 2020, 07:17 AM
Kaaaiju

Check the intercooler that it's not split
27th March 2020, 07:05 PM
Young1
Quote:

Originally Posted by sierrafery

Did you measure the boost with wastegate at 10 threads? cos if it doesnt got higher it can be a turbo fault too... provided you are 100% sure there's no boost leak, you should do somehow to pressure test it.... and btw, OEM MAF is just a branded aftermarket, usually those VDO units which failed the tests imposed by LR to become genuine but still ISO compliant within a wider accepted reading range... it's possible that in your case not the sensor is the problem but it can be ruled out only with genuine LR(i know it's expensive but it's the only 100% reliable) Drive it with MAF unplugged untill you find the culprit to be able to fix it for good.

Another relevant test would be to clamp the hose which goes to the wastegate valve and make a drive test that way with MAF unplugged ... if the boost side is OK it should go to overboost below 3000rpm, if it doesnt the problem is on the boost side or the MAP sensor is reading low. This is an ugly fault and needs lots of tests

I am officially confused.

Tested a few configurations today:
1. MAF plugged in,10 threads on wastegate actuator, wastegate modulator plumbed as per factory. max 16 PSI while driving.
2. MAF plugged in,10 threads on wastegate actuator, wastegate modulator plumbed as per factory but blanked at wastegate actuator (no hose to actuator). max 16 PSI while driving.
3. MAF plugged in,10 threads on wastegate actuator, wastegate modulator bypassed, wastegate actuator plumbed straight to inter cooler pipe. max 16 PSI while driving.
4. MAF plugged in,12 threads on wastegate actuator, wastegate modulator bypassed, wastegate actuator plumbed straight to inter cooler pipe. max 16 PSI while driving.
5. MAF plugged in, 9 threads on wastegate actuator, wastegate modulator bypassed, wastegate actuator plumbed straight to inter cooler pipe. max 16 PSI while driving.
6. MAF UN-plugged in,10 threads on wastegate actuator, wastegate modulator bypassed, wastegate actuator plumbed straight to inter cooler pipe. max 18 PSI while driving. (did not overboost)
Does this show that these is a boost leak in the system?

This boost leak must have appeared while i was at the shop fitting the MAF sensor (previously the car would not be limiting boost with the MAF unplugged)
The MAP sensor seems to be reading correct values on the last nanocom run.

Guess i will be taking out and checking the intercooler hoses tomorrow (for the third time now)
27th March 2020, 07:23 PM
sierrafery

I can't follow all those tests you made with different wastegate setups and MAF scenarios cos you should have made only one relevant test: with MAF unplugged and clamped hose to actuator, not bypassed or removed cos once removed it is a boost leak there if it's not clamped... never mind cos it's quite obvious with that 16psi reading all over the place that there is a boost leak somewhere or the turbo is not producing enough boost... btw did you read the boost with a gauge or it's based on nanocom ?
27th March 2020, 08:07 PM
PhilipA

geez with the modulator pipe disconnected on mine it sees 28PSI.
Regards PhilipA
27th March 2020, 08:18 PM
sierrafery

Because your's is producing enough boost unlike the OP's and as long as it doesnt go to overboost at 28psi it must be tuned as well
28th March 2020, 07:27 AM
PhilipA

Quote:

Because your's is producing enough boost unlike the OP's and as long as it doesnt go to overboost at 28psi it must be tuned as well

The 28Psi was only seen momentarily because the hose to the wastegate had broken. It then went into overboost. I just posted that in comparison to the posters test when with modulator bypassed he only got 16-18 PSI. Mind you , you have to have foot down with a trailer up a hill for that to happen. I doubt whether it would spike to 28 unless those conditions are met, not normal driving.

I have a Turbo technics wastegate controller that cuts at 22PSI for normal running and my map has been altered to allow that without overboost cutout. The turbo technics boost controller allows much faster boost rise above 15PSI whereas by shortening the rod there is always boost bleed above 15PSI as I am pretty sure that the shortened rod causes the flap to be partially open..
Regards PhilipA
28th March 2020, 07:50 AM
sierrafery

Quote:

I am pretty sure that the shortened rod causes the flap to be partially open..

How would that happen?

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