75ZT Community

[Grossebaby]

I have returned from hols and the car is still on 40 a day but I notice the fluttering throttle effect is very apparent.

It goes like this, 1750rpm up a hill steady speed not accelerating or slowing intentionally and you can feel the car surge then return to no acceleration, I am not moving my foot on the throttle, me thinks the maf is probably duff but do suspect the SLIGHT airleak is not helping. What say you?

[raistlin]

Have you tried running the car with the MAF disconnected to see if it makes any difference?

[Duncan]

I reckon I have a MAF starting to show it's age. I get the fluttering but no signs of smoke.

I bought a supposedly new replacement, but the flutter became a shudder, and had no power pulling out at junctions.

An air leak might cause overfuelling, but if the MAF was undereading surely the leak would help compensate? Saying that, it depends where the leak is. Pre turbo, it would increase the underrrading by drawing in unmetered air. Post turbo the air would leak out depending on boost pressure, compensating for an underreading MAF.

[Grossebaby]

I'm just going to get a bosch maf instead of the pierburg one, which I now suspect is not a good replacement for oe.

[James.uk]

Due to the recent discoveries made by BigRuss I think you are right. There deff seems to be considerable doubt as to the older PB Maf being a suitable fitment for the m47r engines..

As you say, fitting a Bosch may solve the problem, but why not PM Russ for more information first? I'm sure he can advise you..
...

[Grossebaby]

Well it's a bit late as I have ordered a bosch maf but I might see what big russ has to say anyway.

[JohnDotCom]

If you are using the Pierburg I take it you either have a Mafam or Synergy as they won't work properly without,
when installing a new Bosch MAF don't turn on the Compensation on either a Synergy box or a Mafam,
will cause it to over-fuel and give poor performance as well as wasting fuel..

[Grossebaby]

After all this, it transpires that the intercooler was blocked at least partly so we were only getting vastly reduced air flow and would explain the whistling.

Car now goes like s**t off the proverbial shovel, it must have been gradually sickening for a long time, I have known it was getting worse for a few months but I reckon the first bit was gradual.

Interestingly the pierburg maf was dodgy.

[MrB]

Could I ask how you worked out the intercooler was partly blocked? Also how you unblocked it?

I have a very similar problem to yours at the moment. The car is hesitant at around the same revs as yours, especially on a constant throttle.

I am just wondering if I have the same problem as you.

Chris

[Grossebaby]

Mechanic took intercooler off and sent it to be tested for holes. It had no holes but the oil in the bottom was almost solid I understand so instead of burning off over time it was just stopping there.

[Duncan]

Interesting point. When I first read it I thought 'where does the stuff that blocked it come from?'

It would have to come through the air filter.

But oil and stuff kind of makes sense. Will have to have a good cehck of mine when doing the front end....

[MrB]

Mechanic took intercooler off and sent it to be tested for holes. It had no holes but the oil in the bottom was almost solid I understand so instead of burning off over time it was just stopping there.

So was it cleaned or did you have to replace it?

If it was cleaned, using what?

Thanks

Chris

[Grossebaby]

Cleaned, but what with I do not know. I presume we ended up with cooked oil sludge rather than liquid oil so that was the problem.

[MrB]

Was also wondering where you took it as I am just up the hill from 'Fax in Queensbury.

Mine didn't smoke today but was still hesitant on a constant throttle.

Should add mine only does it when cold, once the temp gauge is above say a 3rd it runs smooth as silk.

Chris

[Grossebaby]

Think it is likely to be maf related then, or dirty egr/ dirty pcv or leaking o-rings. Check for oil spray around the front left hand side of engine bay, on the black rubber pipes. I took mine to cw motors Steve Dennison at Rastrick but have used the people at Queensbury MOT and found them to be very fair.

[MrB]

Thanks for the info.

It has had a new PCV fitted and an EGR bypass fitted, so I guess that leaves the MAF.

Should be seeing Russ very soon, as I need to pick up some bits from another member near him and we need to finish a T4 session we started months ago now but never finished. Hasten to add, my fault, not Russ's.

Chris