CDT revs pulse at idle.

Comfortably Numb · 5th February 2018, 21:56

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 · 5th February 2018, 23:00

Quote:

Originally Posted by 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.

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

Comfortably Numb · 6th February 2018, 23:01

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 · 6th February 2018, 23:12

Quote:

Originally Posted by 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.

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

Brian

grivas · 7th February 2018, 16:45

Quote:

Originally Posted by 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.

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 · 7th February 2018, 19:36

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

Comfortably Numb · 7th February 2018, 20:16

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.

5th February 2018, 21:56	#1
Comfortably Numb Posted a thing or two Rover 75 Saloon Join Date: Dec 2017 Location: Penrith Posts: 1,336 Thanks: 165 Thanked 303 Times in 241 Posts	CDT revs pulse at idle. 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.

7th February 2018, 19:36	#6
sworks This is my second home Rover 75 Tourer, Classic mini Cooper S, Abarth 595 competizione, MG TF and a Hyundai Tucson PHEV Join Date: Feb 2007 Location: Cumbria Posts: 13,073 Thanks: 1,033 Thanked 1,686 Times in 1,040 Posts	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 __________________ ................................................. 'Marmite' Possibly one of the most famous 75 tourers produced! left the production line as the last of only Three Rover 75 tourers produced in Trophy Yellow. 48 hours later Longbridge closed. The last sold ordered 75 Tourer. Paid for by the Phoenix Four and handed over by John Towers to the Warwickshire Northampton Air ambulance service as a Rapid Response vehicle

6th February 2018, 23:01	#3
Comfortably Numb Posted a thing or two Rover 75 Saloon Join Date: Dec 2017 Location: Penrith Posts: 1,336 Thanks: 165 Thanked 303 Times in 241 Posts	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.

7th February 2018, 20:16	#7
Comfortably Numb Posted a thing or two Rover 75 Saloon Join Date: Dec 2017 Location: Penrith Posts: 1,336 Thanks: 165 Thanked 303 Times in 241 Posts	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.