Thread: TD5 Fluctuating boost under load

No harm will be done with the MAF unplugged believe me, it was conceived to work on default mode without damage, only the consumption is a bit greater than with a perfectly working one

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Originally Posted by sierrafery

No harm will be done with the MAF unplugged believe me, it was conceived to work on default mode without damage, only the consumption is a bit greater than with a perfectly working one
Good luck

Hey Sierrafery, heres looking at you mate,

SO my buddy has a similar D2 to mine, same year, HSE, few more kays, buy well under 200K.
He has recently fitted a De-Cat down pipe, and center muffler removal pipe to his Disco, soon after, he was comaplining of a "miss" and, as he had been having trouble with Oil Ingress, had a new in-head harness fitted, as he thought that was more than likley the cause.

Well, turns out, that his MAF may have **** also? The 'miss' he was complaining of, turned out to be more of a flat spot, just off boost, that made the car almost undriveble, and when he explained it to me, it sounded JUST like the problem I was having!!!

Anyway, He had a new Siemens MAF fitted by LR workshop, and whadaya know, still undrievable...

I then told him to unplug the MAF alltogether, and BOOM! perfectly driveable again...

WTF?!?

• Has the MAF failed??? It would appear not, as a replacement MAF didnt fix it?!?
• Has MY MAF failed??? Possibly not? Same Symptom, am I wasting money throwing a new MAF at mine???
• Same Mods? Does the reduction in Exhaust back pressure from removing the CAT do something to the system, and throw it into chaos??? Or, does removing the CAT hightlight un underlying problem that was always present????????

Really need some answers here, does unplugging the MAF just bandaid fix a bigger, nastier deeper problem?

Unsure...

Is your or/and your friend's ECM remapped?, also to not read the whole thread again, EGR is bypassed?

Egr is bypassed on both trucks.
I doubt either ECM has been remapped, both trucks stock-as-a-rock when purchased. I would be 99.999% sure that the ECM's are standard.

Ok, are the EGR modulators electrically unplugged too?, if not do that and isolate well the plug against earth , if this is covered as well i dont see any reason why the car runs well on default mode but not with a faultless MAF unless there's some wiring issue in the plug which alters the MAF signal when it's plugged in, quite unlikely, more possible i that the new MAF fitted to your friend's car was DOA or something cos as i understood you didnt fit a new one yet... i can't give other explanation right now, for more detailed answer i need a live data log like you posted cos if you remember i've suspected the MAF on yours based on some strange readings

so i dont know what to say about that but i can't find more logical explanations, if i was you i'd try with a known good MAF though

as an additional information, just found out and seems very interesting so i'll test it on my own car as i can afford though i can't recommend you to do that on your money but it seems that there's a same shape MAF used on other cars: VDO p/n 5WK9608Z which is listed as indirect cross interchange part for the genuine MHK100620 but has a wider curve at the middle air flow range which should overcome such issues also it is used on D2s by reliable remappers for some remaps to be smoother...

Can only speak for my own vehicle here, but the EGR modulator is still plugged in. I was under the impression that a code was logged if it were unplugged.

Strangely enough, I don't get any codes running with the MAF unplugged. Nothing that shows up on the Nanocom at least.

That's definitely not normal for standard ECM, you should have got" EGR stuck closed" fault code if it's blanked even if it's plugged just that then the solenoid can put unnecesary drain on the MAF and wastegate modulator's circuit also an "air flow circuit" fault code for unplugged MAF... the only logical deduction i can make is that the ECM is remapped with an unproper map or there's some glitch in the "software" .what's the ECM part number and the last 8 characters of your VIN?

I have a big miss just off idle with same mods. It's hard to find as you normally drive past it. Otherwise drives fine. So earthing the egr plug is the go? Thought that might short something when it tries to open.

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