Turbo wastegate modulator pulse test

Recently had a couple of random occasions when the engine was really flat with no power after about 2000 rpm, but within 30 seconds or so the power returned. I had heard that it might be the modulator on its way out, so bought a new one. Genuine LR £35 dead easy to fit - process of elimination etc.

Whilst trying out my latest toy - Hawkeye I was going through all the circuit tests and there's one which pulses the modulator. Should I hear a ticking noise either inside the cab or with my head under the bonnet? I couldn't hear anything.

I get live data of around 7+ % for the wastegate when going for a drive and everyhting appears normal.

Just curious, thanks.

It depends on the boost you've got cos the higher the boost is the greater the modulator's percentage should be, haven't you got overboost fault code logged? cos usually it's there when the modulator fails but not necessarily

No - no overboost fault. Only ones I usually get are EGR related....because I deleted it I have had the odd high and low airflow logged, but the MAF sensor appears to be working fine according to live data at the moment.

EDIT - As I can feel the turbo boosting, the %age does increase, but not beyond 7 and a bit .

that 7 is low or you have some boost problem, hawkeye is a good tool but not very bright when it comes to live data as you can't record them... nanocom rules in this area, it's hard to figure out if the air flow is good or not with hawkeye cos you should watch the manifold and the ambient pressure at the same time to have the full image, see how much the ambient pressure drops when you floor it, measure the manifold pressure then too... air flow faults if the MAF is certainly good can be caused by worn depression controll valve cos the excess or lack of crankcase gasses can mix up the readings so if you know it's old just replace it cos even if it works it can be hurt if it was exposed long time to those hot gasses... IMO it should be treated as a let's say 30k miles service item

Just had to google depression control valve! I never realised that was a valve. It looks like it has been on there a while. For the price I'll replace it, thanks.

The thing is that the performance seems sprightly enough, she certainly goes well, especially from 2000 rpm. I've not been in another stock D2 TD5 to compare, only one which was remapped, and that one went like a sports car!

see how much the ambient pressure drops under load too cos it's important

Ambient press only drops about 5 kPa. Manifold pressure is almost 200 kPa during full boost. Hard to watch the Hawkeye & drive at the same time! I do have a stud missing on the exhaust manifold which won't be helping.

so the full boost is low, what's the ambient pressure at idle? ... anyway give a clean with MAF cleaner or something to that AAP sensor, also is the MAP clean enough?

Ambient is about 98/99 kPa IIRC.. Where is the AAP sensor please? Map I'll check and clean..

AAP is in the side of the airbox

Ah... that one! :doh:

Cleaned the AAP sensor. AAP only dropping about 2 kPa or so.

Incidentally, what kind of ball park figures should I be seeing for all of these?

Had another logged high inlet air temp fault. Could these be causing the random flat spot at 2000 rpm - backing off the power due to the hot inlet air?

Cheers!

Hi IAT fault code usually means that you need a new MAP, in most cases it's IAT side is failing... the AAP should be equal with the ambient pressure measured with barometer(around 100kPa) and drop 5 -10 under high boos but you have low boost that's why it doesnt drop to much... MAP should go to 230 at full load, btw do you still have EGR?

Didn't clean the MAP :doh: EGR is deleted.

I'vve not touched the intercooler at all since I got the D2 2 years ago, would cleaning that out make much of a difference?

if the MAP/IAT sensor is fubar'd cleaning the intercooler wont help, see the IAT on live data, it should be very close to the real outside temp on cold start then grow to between 10-30 degrees greater than the ambient temp with warm engine depending on engine and ambient temp too, the greater it is the more difference in IAT will be

I'l check and report back - I "think" the IAT is within those limits.

Went out for a drive yesterday lunchtime at work (about 12 miles). Once the engine was warmed up, I got the flat spot issue which then vanished (had to floor it in second gear a couple of times to get it over 3000, then it boosted ok. After work I hooked up the Hawkeye for the drive home - had the high IAT fault logged. Because the engine bay was still warm, the IAT was about 26/27 degrees C upon startup (higher than what I'd seen on a run), but she started and ran fine (IAT dropping as colder air was sucked in).

OUCH! Dealer prices for MAP and MAF sensors are over 100 quid!! Should I buy another fuel pump?? It's acting like it did when the old pump packed in.

I just replaced my MAF sensor, a VDO one was about £80 from Brookwells 4x4. Not that much cheaper though.

Actually nothing wrong with my original, 14 year old MAF - until it slipped out of my hand while cleaning it....:doh:

DIFFLOCK66 said:

Went out for a drive yesterday lunchtime at work (about 12 miles). Once the engine was warmed up, I got the flat spot issue which then vanished (had to floor it in second gear a couple of times to get it over 3000, then it boosted ok. After work I hooked up the Hawkeye for the drive home - had the high IAT fault logged. Because the engine bay was still warm, the IAT was about 26/27 degrees C upon startup (higher than what I'd seen on a run), but she started and ran fine (IAT dropping as colder air was sucked in).

OUCH! Dealer prices for MAP and MAF sensors are over 100 quid!! Should I buy another fuel pump?? It's acting like it did when the old pump packed in.

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have you tried running it with the maf unplugged to see if it goes past the 3000rpm

No John. I might try that when it happens again. The lack of power is random, most of the time she's performing OK (sierra says the numbers are a bit low, but she seems to go).

EDIT: The MAF readings always seem pretty good, around 70 at idle and over 600 on full bore.