It's driving me MAF - er mad! Please Help

[keppler]

Ok, maybe I'm missing something here but Ive read through your last two post's and I cant find any mention of a test run with a disconnected maf?
Your reading indicates that the turbo is barely spinning at all.
However this is a common symptom of a faulty maf, as the ecu will not allow the the vacuum solenoid to send a vacuum to the actuator.

[bytecode]

Ok, maybe I'm missing something here but Ive read through your last two post's and I cant find any mention of a test run with a disconnected maf?
Your reading indicates that the turbo is barely spinning at all.
However this is a common symptom of a faulty maf, as the ecu will not allow the the vacuum solenoid to send a vacuum to the actuator.

Hi Keppler,

thank you for your response. I guess that I neglected to mention that on the drive into Plymouth on Saturday, I tried disconnecting the MAF (Siemens, 2nd hand, assured good by seller - that I had assumed was also faulty on fitting) for approximately 17 miles - but saw no change whatsoever.

Installing the brand new MAF (£85 off the shelf) caused the Antipollution fault and IML (I don't know whether to refer to this as the IML, MIL or EML) to go away for approx 10-15 miles before they returned. But no improvement in performance/smoke symptoms.

As I'm sure you've gathered - progress was halted by mistakenly disconnecting the battery in an "earth cleaning" attempt to ensure good current flow and spurious resistance clouding the issue. Once I re-associated the key with the ECU such that the immobiliser let me start the car after a 1.5 - 2 day period, I took it for a short run - It felt better - I even made it up into 4th gear, 2nd and 3rd felt positively "surgey".

I returned home as I had to continue working (from home).

I walked down the steep hill into the village after work to look at someones computer - fixed that, and was picked up by a sour faced girlfriend who had just driven the car again with no power, black smoke.

Climbing out of the village of Polperro in 2nd gear at a steep gradient and 15-19 mph with clouds of smoke ain't fun.
The symptoms are currently:

• After clearing all fault codes via PP2000
• the concrete of the driveway beneath the downwards facing exhaust is blasted with black soot.
• You press the accelerator to the floor in neutral - the engine gradually builds up to approx 3.1k maybe 3.2k rpm with clouds of black smoke,
• Once it eventually hits 3.1k - 3.2k - the engine judders back and forth on its mountings, as if a limiter is kicking in
• the concrete of the driveway beneath the downwards facing exhaust is blasted with black soot.
• I did a 5 mile run this evening, I had the permanent pre/post heater relay stuck fault and the low coherence fault.
• Over the past few days, even dropping the car into a lower gear to push the engine into greater than 3.2k RPM on a steep hill downwards was a struggle, and deceleration was significant - I don't think that it's a valve issue ( I'm used to going down hills in say, first or second gear at low speed - speed matching the engine to the road to facilitate smooth speed/gear transitions)
• My comments re: turbo noise - when everything is working there are two noises that I'm familiar with - on pedal - spinning up there's a whine sound, off pedal, it's a "spinning down sound" that is slightly more clattery and I don't know how to describe.
• When the car malfunctions - I hear neither sound - I do not know whether this is because it is turning over, accelerating AND decelerating so slowly that it's not perceptible, or whether It's because the turbo's not working, or maybe I'm not listening hard enough.

Things that are confusing me:

• Antipollution fault messages - these have always occurred (twice in the past) after severe flooding issues. I've since cut the swanh-neck intake pipe between the air-filter box and the wheel arch segment so that they are no longer connected. There's a 10 CM gap between, I intend fitting a pipe through the panel of where the intercooler would sit were there one to this pipe for a little bit of ram air and less flood damage.
• The Antipollution messages continue to appear at the moment, but did not persist after changing the maf months ago. Hence my recent assumption that it was another maf failure. I now think that I'm entirely wrong.
• "Air flowmeter signal. Air flow too low coherence." - I just don't understand what that means - googling yields about 3 posts, one of which is this thread.
• Intermittency - this problem of poor power, lots of smoke seems to occasionally be fine - until I really push the engine (after gentle warming) - such that it makes me think that something is a little bit sticky, like liquorice - or dirty and gunky.
• The turbo flow readings - is it normal for turbo pressure to be 988 mbars at 3.1Krpm? - I have no frames of reference for this
• When in this state, the engine really struggles to climb into revs above about 3.1/3.2krpm - even in neutral. it's as if something is really blocking or wrong.
• I've changed the air filter and checked the pre-filter pipework (what's left of it).
• Oil filter were changed approx 4000 miles ago.

It's started raining outside which means that my plans for jacking the car up on the drive in the morning and getting started upon figuring out how to disconnect the turbo to see whether there's a blown seal, leak or just lots of gunk to clean out before work may be thwarted.
So far, my employer is being sympathetic to my plight.

I have 10-11 days to sort this out before I'm essentially rendering our holiday in France car-less, it looks like the pressure is on

Two further questions:

• Can anyone suggest a testing plan?
• What happens around the 3.1/3.2 K rpm range on an HDI that might be significant?

I'm off to bed - I appreciate any thoughts, thank you.

[bytecode]

PS: I don't know whether tying to somehow remove an clean the turbo is going to help - I'm just running our of options and running out of time, and whilst I've never taken a turbo off a car - I don't know what else is left.

[keppler]

• My comments re: turbo noise - when everything is working there are two noises that I'm familiar with - on pedal - spinning up there's a whine sound, off pedal, it's a "spinning down sound" that is slightly more clattery and I don't know how to describe.
• When the car malfunctions - I hear neither sound - I do not know whether this is because it is turning over, accelerating AND decelerating so slowly that it's not perceptible, or whether It's because the turbo's not working, or maybe I'm not listening hard enough.

[*] Can anyone suggest a testing plan?
[*] What happens around the 3.1/3.2 K rpm range on an HDI that might be significant?[/list]

I'm off to bed - I appreciate any thoughts, thank you.

It is definitely not normal to have such low pressure at such high revs, 3krpm should max out your turbo. nothing normally happens after 3krpm except all your torque seems to disappear. Anything interesting happens between 1500-3000rpm
The clattery sound is worrying............do the pipe squeeze check stated before but also would be worth putting your finger against the compressor blades and see if there is any play in the shaft of the turbo. if the the shaft has alot of play and definitely if they touch the housing of the turbo well then
Things I would also check,
Vacuum...... there should be enough negative pressure in the pipe feeding the solenoid so as you can feel it when you press your thumb up against the end of it. there should be at least a half bar there anyway
the solenoid itself.......try exchanging it with the egr one or a known good one from a donor car
the map sensor.... again try exchanging it with a known good one from a donor.

Turbo removal is no walk in the park on these cars unfortunately

[bytecode]

It is definitely not normal to have such low pressure at such high revs, 3krpm should max out your turbo. nothing normally happens after 3krpm except all your torque seems to disappear. Anything interesting happens between 1500-3000rpm
The clattery sound is worrying............do the pipe squeeze check stated before but also would be worth putting your finger against the compressor blades and see if there is any play in the shaft of the turbo. if the the shaft has alot of play and definitely if they touch the housing of the turbo well then
Things I would also check,
Vacuum...... there should be enough negative pressure in the pipe feeding the solenoid so as you can feel it when you press your thumb up against the end of it. there should be at least a half bar there anyway
the solenoid itself.......try exchanging it with the egr one or a known good one from a donor car
the map sensor.... again try exchanging it with a known good one from a donor.

Turbo removal is no walk in the park on these cars unfortunately

Hi Keppler,
I spent the night dreaming about vacuum, pipes and solenoids.
Reading your kind suggestions this morning inspired me to do a little "pre-work" investigation.

Removing the vacuum pipe from the vacuum pump showed that there is vacuum being generated,
my brakes work too, so I guessed that there was some vacuum at least.

The note of engine changed also - deepening/getting lower in pitch.

Reconnecting the pipe to the vacuum pump, I traced the vacuum pipe first to the brake booster I found the tee-piece where another pipe splits off and goes to the two solenoids mounted on the bulkhead behind the inlet manifold and egr system.

I noted that the second solenoid in the chain, had a vacuum pipe leading to the EGR valve, and that the prior solenoid had a pipe leading down into the depths of the engine bay.

Removing the vacuum pipe from the primary solenoind and sucking on it with the engine off, I could hear a clicking noise somewhat like I'd expect to hear if it were operating the turbo.
I reconnected it and with the engine running, disconnected it again. The engine note went deeper/lower again.
I sucked on the pipe - the engine note lifted to normal idle - I stopped sucking, it dropped again.

I then asked my GF to sit in the car, and hold the pedal at 2000rpm, and once there. not to move the pedal unless I signalled to shut the engine off in an emergency.

With the engine at 2000rpm, I disconnected the vacuum pipe from the primary solenoid again, and the engine immediately kicked up to approx 2600 rpm. sucking on the pipe I found that I could control this behaviour.

After shutting down the engine. I swapped the 2way wiring harnesses for the EGR control solenoid (secondary in the vacuum chain) and the Turbo actuator control solenoid (primary in the chain).
I couldn't stretch the EGR vacuum pipe to meet the turbo solenoid, so I temporarily blanked the connector on the solenoid with a latex glove and elastic band, so that the solenoid wouldn't be putting a drain on the available vacuum in the ciruit.

With the turbo now controled by the EGR solenoid, I tested the car - it WORKED, pulling away was smooth, not juddery, hitting 19000-2000rpm the turbo could be felt kicking in, I Couldn't see any smoke. The car accelerated and the revs climbed to 4000rpm easily.
At lunchtime, I shall physically swap the EGR and Turbo solenoids.

I'm contemplating simplifying the vacuum pipe circuit, dispensing with the additional tee-piece and terminating the vacuum at the turbo solenoid, as I'm not using the EGR system anyway .

I'll do some testing, and if there's enough time in my lunch break, I'll take some pictures to illustrate the components that I'm switiching.

I'm hoping that this *is* the solution, that the turbo solenoid was faulty.

I found it interesting that on the HDi 2.0 90bhp, the turbo does not provide boost WITH vacuum, but DOES provide boost without.
Not knowing how the Solenoids are designed, I'm wondering now whether the little filter on the turbo solenoid may be clogged, or whether the solenoid is just duff.

Thank you for your help so far.

[crackpotterpig]

sounds like you have sussed it out.............in time for the trip to france as well,basically the vacumn solenoid is operated by a voltage being switched on and off energising a coil and opening closing the solenoid valve allowing or not allowing the vacumn to flow.
As your egr is blanked off I would just leave it how it is now using that solenoid to control the turbo.

[keppler]

crackpotterpig is right if you ask me!
Just switch over the solenoids and leave it at that, you could maybe disconnect the vacuum pipe from the egr valve itself and plug that if you want but i wouldn't bother messing and cutting pipes.
Besides a new solenoid is only around 45 euro's here in Ireland from the stealer, so id imagine it would only be about £30 in the uk. They call them electrovalve's btw
Glad to hear you sorted it

[bytecode]

Hi crackpoetterpig, keppler and all you fab guys....

Yes - thank you all for taking the time to help - it's fixed!

I swapped the two solenoids around - I had too - the piping and wiring weren't happy with the "test" arrangement.

In the process of disconnecting and rearranging the solenoids, I've found the following:

The solenoids have three pipes; on top, a pipe for the source of the vacuum, a pipe for the device controlled by that solenoid, at the bottom, there's a pipe for the little air filter that presumably allows atmospheric pressure to balance the vacuum.

On the EGR solenoid, (with the filter removed) I discovered that (whilst disconnected) If I sucked through the "source vacuum" pipe, whilst covering up the "device control" pipe, I could cause air to be sucked in through the "air filter/atmospheric" pipe on the bottom of the unit.
Covering and uncovering the bottom (atmospheric input) pipe with my thumb, would allow/stop air throughput.
Whilst there was throughput, the solenoid would make a gentle buzzing/wheezing sound.

With the turbo solenoid, the story was different - there was NO throughput at all from the atmospheric input pipe - I sucked and blew with all my might but no luck here (little pig, little pig). The little filter on the atmospheric intake pipe was sufficiently clear, although in testing by sucking I got a mouthful of er... dirty dusty gunk

I cleaned the filters, refitted them and then refitted the solenoids, but reversed.

The EGR solenoid (which had airflow) is now my Turbo control solenoid, where as the Turbo solenoid is now on my EGR valve providing nothing more than "end of tubing" duties.

I took the car for a short run, it was perfect, quick to respond and pulled in 2nd, 3rd, 4th and 5th.
This evening, we went to the supermarket in Bodmin, about half an hour away - no smoke, no judder - the car actually pulled away at Tee-junctions, I didn't have to stare in the rear-view mirror hoping not to get rear-ended.

I could accelerate up hills - in 4th and even 5th on the gentler hills.

My fuel economy has gone from 35MPg (pre-fix) to 53.4MPG (post-fix) and that includes a few "ooh look - I can accelerate - moments"

After getting back from the supermarket, cooking and eating, I connected the laptop and ran PP2000. After about 30 minutes of it being temperamental (old laptop, USB1) it finally talked to the car and I read the codes - ALL CLEAR except the glow plug pre/post heat issue that I'm going to ignore unless the weather man says it's going arctic.

No, as suggested, I shall not fiddle with the tubing - not until we're back from France at least - but I might tidy it up a little, after the French trip.
I just have to avoid bragging to the outlaws, as they'll be nervous as anything!


Thank you - thank you all.

Thank you Kepler, Crackpotterpig, Rwb, CaptainJack, plus everyone that at least looked at my posts. Without you to chat to, I'd probably have the car in pieces and still not be the wiser.

Thank you for all of your time.

I've taken some pics, but need to process them to sort contrast, labelling etc. I'd like to make a post about these problems for the next person that comes along - but I need bed tonight.

Sleep well

[crackpotterpig]

Only to pleased to help as I am sure everyone here is........be good to see those pics and hopefully it will help anyone that comes on here with similar issues in the future.

[Editor]

I've taken some pics, but need to process them to sort contrast, labelling etc. I'd like to make a post about these problems for the next person that comes along -

Hi bytecode-did you ever get these pics etc up please?

it will help anyone that comes on here with similar issues in the future.

for sure-guess what my step-dad's has just done!!