Runs worse after disconnecting MAF?

Evening all,

The last couple of days I've occasionally had what feels like a misfire under light throttle when pulling away. Tonight I also had it whilst cruising at 60mph. The loss in power is only a split second - exactly like when you lift off the throttle and slap it back down again.

Suspecting the MAF maybe at fault I disconnected it and went for a drive. It was noticeably worse with a definite vibration and numerous misfires/pauses. It didn't throw any dash lights.

My mechanic kindly hooked up his diagnostic machine and saw that there was only 1 stored fault, something to do with the throttle position. We went for a drive whilst it was connected and sods law... the car was fine and no new codes were found and throttle voltage was consistent :frusty:

The MAF was reading 43 @ tickover. He's getting me a new one to try tomorrow.

What's also puzzling me is that whilst searching for this type of problem/solution, everyone appears to think that disconnecting the MAF should make the car run fine - so why was mine noticeable worse?

Any comments/suggestions of what else to check will be gratefully received as I appear to be on a bit of a bad luck streak with a new window regulator last week and new aircon piping the week before - oh, and we won't even mention the oil leak and sunroof showers

BTW it's a 2002 TD5 Auto on 109k. Full major service 4000 miles ago.

My MAF was showing a maximum of around 220 on nanocom. I tried running around with it unplugged for a while and noticed absolutely no change in the way the engine ran. Got a new one (shows up to 550 as it should) and still no difference at all.

I don't know what it does but whatever it is is not perceptible to me.

If you have a definite misfire then I would suspect the engine injector harness. There are crimped connections within it which appear to break down with oil ingress. I have soldered mine.
My MAF sensor is disconnected and the car runs great, as well as it did new. It's also a TD5 auto with 114k miles. The MAF appear to control the EGR system but if I re-connect it, despite the EGR being scrapped, it brings a hesitation to the engine especially around 2000 to 3000 revs. I have assumed that this is because the engine ECU is trying to initiate Exhaust re-circulation and is setting conditions for it despite the fact that I have removed the EGR. I have also assumed also that disconnecting the MAF stops the engine re-circulating the exhaust gas full stop.
I wish I really knew.

This is an something that I would like to know more about? I have recently installed EGR kit and have noticed a big difference, however the engine is less than expected. It stills feels a bit sluggish and has a judder when I push it hard at higher revs (I have put a new harness in & it still does it) so my next thought is the MAF, can someone please advise on the pros and cons of disconnecting the MAF? Will it affect power output / fuel economy? Your help would be greatly appreciated.

Gregor

Sorry it's an TD5 auto ES

Disconecting the air mass meter/ air flow sensor on any car will make the car run worse providing the sensor is working correctly in the first place and plus they are a common fault on alot of cars. try a new 1 and see how that goes.

Thanks for the input lads - really appreciate it.

Sods law continues to shine on me... the car ran like a dream today!

I'm not really moaning but is there anything more frustrating than intermitant faults?

Anyway, going to put the MAF on tomorrow and will monitor closely.

Tonight I checked the air filter - very clean. Didn't appear to be much oil around the connection block by the CPU. But I didn't check the wastegate behind the EGR. After researching for my current problem I've read up on the de-EGR debate. I'm going to give it a go and will order a blanking plate etc tonight.

One thing that occurred to me today was that I filled up with Esso diesel at the weekend. I've never used it before and wondered if the car didn't like it. My old M5 was very sensitive about certain fuels but I didn't expect the Landy to be that picky?

Probably barking completely wrong tree :doh:

I have had that problem before but with tesco fuel never thought someone else would of had the same problem.