CDT revs pulse at idle.

[Comfortably Numb]

Since I replaced my defective MAF sensor with a new cheapo one, the car is now generally a pleasure to drive. However, it now pulses slightly at idle, a sort of 'thrum, thrum' every second, a bit like a truck or bus engine, although it doesn't show on the tacho. In itself, this is not particularly worrying, except that I could imagine it might accelerate the tendency of the crankshaft pulley to de-laminate? Comments please.

[marinabrian]

Since I replaced my defective MAF sensor with a new cheapo one, the car is now generally a pleasure to drive. However, it now pulses slightly at idle, a sort of 'thrum, thrum' every second, a bit like a truck or bus engine, although it doesn't show on the tacho. In itself, this is not particularly worrying, except that I could imagine it might accelerate the tendency of the crankshaft pulley to de-laminate? Comments please.

Probably a duff cheap MAF Andrew ;)

I can say this, I've yet to find a satisfactory alternative to the proper item, and my advice is simple..........."buying a cheap MAF is akin to rolling up three ten pound notes, and setting fire to them"

Unplug it and see if the symptoms persist ;)

Brian :D

[Comfortably Numb]

It is almost definitely caused by the new MAF sensor, as is the improved performance. As my current 130mile round trip involves mostly motorway and A roads (A66 and A590), and very little stationary time, I'm going to persist with it for now. If you re-mapped it with the current MAF sensor, Brian, (a) could you eliminate the pulsing? and (b) would you need to re-map it again if I changed the cheap sensor for a Bosch later? (c)Is this pulsing likely to be weakening the bottom pulley? - As I say, it's not a strong enough pulse to move the tacho needle.

[marinabrian]

It is almost definitely caused by the new MAF sensor, as is the improved performance. As my current 130mile round trip involves mostly motorway and A roads (A66 and A590), and very little stationary time, I'm going to persist with it for now. If you re-mapped it with the current MAF sensor, Brian, (a) could you eliminate the pulsing? and (b) would you need to re-map it again if I changed the cheap sensor for a Bosch later? (c)Is this pulsing likely to be weakening the bottom pulley? - As I say, it's not a strong enough pulse to move the tacho needle.

I have a couple of used MAF sensors which are within spec Andrew, and we can see what your el cheapo is actually telling the ECM before and after.

If the information it provides is so out of kilter, no amount of tinkering will resolve that, however I could provide you with a report of it's lock of fitness for purpose so you can obtain a refund from the seller ;)

Just a thought :cool:

Brian :D

[grivas]

It is almost definitely caused by the new MAF sensor, as is the improved performance. As my current 130mile round trip involves mostly motorway and A roads (A66 and A590), and very little stationary time, I'm going to persist with it for now. If you re-mapped it with the current MAF sensor, Brian, (a) could you eliminate the pulsing? and (b) would you need to re-map it again if I changed the cheap sensor for a Bosch later? (c)Is this pulsing likely to be weakening the bottom pulley? - As I say, it's not a strong enough pulse to move the tacho needle.

Without meaning to be rude, it has been pointed out many times before on this forum, DO NOT BUY non OEM MAF sensors, they are a waste of your money buy the original Bosch OEM type.

[sworks]

I bought a new maf from the local factors which interestingly came with a calibration certificate. Fitted it and it was out of spec according to T4 as was the second. They refused to supply a third :D

[Comfortably Numb]

If I hadn't seen several reports on the lack of longevity of the OEM MAF sensor, I would have saved my pennies up for one. I'm still wondering whether the Tiger tuning box is responsible for the pulsing, but I can't afford to start messing around with it while the car is reliably earning my keep, and otherwise being a pleasure to drive.

[sworks]

I'm still wondering whether the Tiger tuning box is responsible for the pulsing, but I can't afford to start messing around with it while the car is reliably earning my keep, and otherwise being a pleasure to drive.

That’s the first thing I’d disconnect

[Comfortably Numb]

"That’s the first thing I’d disconnect" I'll leave that to Brian, when I see him!