max 30mph

wammers · May 1, 2020

Mark Piercy said:
Morning,
Did it develop the hot start after you removed the box?
If the cars performance drops when you plug the maf back in and raises when you unplug it, that would point to an issue with the maf.
On live data (via nanocom) you should be able to see the maf réspond when you rev and hold the engine.

Nope not on an M51 there is no MAF reading taken. Only thing you will see on Nanocom if you unplug it is air flow fault.

mrtayto · May 1, 2020

wammers said:
Possibly the tuning box is your problem or the EGR is stuck open, the MAF sensor has nothing to do with how the engine runs it is for EGR only. However if the MAF is completely shot in can send the ECM into a fit as it is not receiving expected signals and can go rouge.

I'll remove tuning box and check EGR next time im over at the car.
would it be best to block the vacuum pipe to the EGR when im at it?
will disconnecting the MAF improve things if the EGR was actually stuck open?

Mark Piercy said:
Morning,
Did it develop the hot start after you removed the box?
If the cars performance drops when you plug the maf back in and raises when you unplug it, that would point to an issue with the maf.
On live data (via nanocom) you should be able to see the maf réspond when you rev and hold the engine.

haven't remove the box yet.
the hot start issue might have always been there,yesterday was the first time since i bought it that i actually drove it long enough to come up to temp.

wammers · May 1, 2020

mrtayto said:
I'll remove tuning box and check EGR next time im over at the car.
would it be best to block the vacuum pipe to the EGR when im at it?
will disconnecting the MAF improve things if the EGR was actually stuck open?

Remove vac pipe to the EGR. See what you get. Should be ok to leave MAF connected providing it is sound as ECM then will be happy. If MAF is duff it could cause your problems because it could cause the ECM to go haywire opening EGR when it should not be open. Take the EGR valve off clean it and make sure it is closed and the spring is sound that holds it closed.

mrtayto · May 1, 2020

wammers said:
Block the pipe to the EGR. See what you get. Should be ok to leave MAF connected providing it is sound as ECM then will be happy. If MAF is duff it could cause your problems because it could cause the ECM to go haywire. Take the EGR valve off clean it and make sure it is closed and the spring is sound that holds it closed.

thanks wammers for walking me through the process.
will probably be close to a week before i get back to have another look at it but i will report any updates when i have them.

Datatek · May 1, 2020

A duff MAF can certainly cause loss of power, there have been more than one reports of that being the case. The car will run perfectly well with it disconnected as a temporary measure. Leave the vacuum pipe to the EGR disconnected, the EGR will then remain closed and you will not be filling your engine with shyte and it is then not necessary to block the EGR pipe which is more difficult.
I would certainly disconnect the power box, I removed the one from mine a long time ago and sold it, they can cause damage to the autobox.

wammers · May 1, 2020

Datatek said:
A duff MAF can certainly cause loss of power, there have been more than one reports of that being the case. The car will run perfectly well with it disconnected as a temporary measure. Leave the vacuum pipe to the EGR disconnected, the EGR will then remain closed and you will not be filling your engine with shyte and it is then not necessary to block the EGR pipe which is more difficult.
I would certainly disconnect the power box, I removed the one from mine a long time ago and sold it, they can cause damage to the autobox.

By block pipe to the EGR i meant Vac pipe not the main feed.

Datatek · May 1, 2020

wammers said:
By block pipe to the EGR i meant Vac pipe not the main feed.

Ah, OK

wammers · May 1, 2020

Datatek said:
Ah, OK

Have edited it can see it may have caused confusion.

mrtayto · May 1, 2020

wammers said:
Nope not on an M51 there is no MAF reading taken. Only thing you will see on Nanocom if you unplug it is air flow fault.

what kind of signal does MAF give,is it volts or mA or something else entirely?should i check output with meter to see if its linear through out its range?

Datatek · May 1, 2020

mrtayto said:
what kind of signal does MAF give,is it volts or mA or something else entirely?should i check output with meter to see if its linear through out its range?

Quite difficult to check with a meter, I wouldn't bother. Unplug the power box and check if that sorts the problem. If no different, unplug the MAF and check if that sorts the problem, if it does, replace the MAF, if it does not it will be necessary to look elsewhere.
Putting a meter across the output of the MAF will change the output.

wammers · May 1, 2020

mrtayto said:
what kind of signal does MAF give,is it volts or mA or something else entirely?should i check output with meter to see if its linear through out its range?

Check the EGR valve as said leave MAF unplugged. The MAF measures the exhaust gas ingestion into the manifold from EGR valve. As EGR valve opens the reduction in airflow through the MAF tells the ECM how much exhaust gas is being ingested and modulates the EGR valve to increase or decrease as needed. It works on a hot wire principal the cooler the wire the more the airflow. Keith can maybe explain it better.

mrtayto · May 1, 2020

Datatek said:
Quite difficult to check with a meter, I wouldn't bother. Unplug the power box and check if that sorts the problem. If no different, unplug the MAF and check if that sorts the problem, if it does, replace the MAF, if it does not it will be necessary to look elsewhere.
Putting a meter across the output of the MAF will change the output.

wammers said:
Check the EGR valve as said leave MAF unplugged. The MAF measures the exhaust gas ingestion into the manifold from EGR valve. As EGR valve opens the reduction in airflow through the MAF tells the ECM how much exhaust gas is being ingested and modulates the EGR valve to increase or decrease as needed. It works on a hot wire principal the cooler the wire the more the airflow. Keith can maybe explain it better.

thanks lads thats giving me lots to be getting on with,will reports back with results

RangeRoller dt · May 1, 2020

Have a check see if your glow plugs come on the dash when you click the ignition to on with a warm engine

mrtayto · May 1, 2020

RangeRoller dt said:
Have a check see if your glow plugs come on the dash when you click the ignition to on with a warm engine

they dont

wammers · May 1, 2020

mrtayto said:
they dont

They won't glows don't work on a warm engine only come on with engine cold.. Unless you have hot start mod fitted.

mrtayto · May 1, 2020

wammers said:
They won't glows don't work on a warm engine only come on with engine cold.. Unless you have hot start mod fitted.

once i get the lack of power sorted the hot start mod is next on the list.

Datatek · May 1, 2020

mrtayto said:
once i get the lack of power sorted the hot start mod is next on the list.

Better off to do the FIP timing, the hot start fix is a bodge IMO.

Datatek · May 1, 2020

wammers said:
Check the EGR valve as said leave MAF unplugged. The MAF measures the exhaust gas ingestion into the manifold from EGR valve. As EGR valve opens the reduction in airflow through the MAF tells the ECM how much exhaust gas is being ingested and modulates the EGR valve to increase or decrease as needed. It works on a hot wire principal the cooler the wire the more the airflow. Keith can maybe explain it better.

The diesel MAF is hot film rather than hot wire but the principle is exactly the same, mass airflow is measured by the reduction in temperature of the film caused by the air flowing over it thus producing a change in the resistance.

wammers · May 1, 2020

Datatek said:
The diesel MAF is hot film rather than hot wire but the principle is exactly the same, mass airflow is measured by the reduction in temperature of the film caused by the air flowing over it thus producing a change in the resistance.

Cheers electronics man.

Datatek · May 1, 2020

wammers said:
Cheers electronics man.

Still doing OK with the lock down I hope Tony? Apart from the return of winter, all is OK here, been having fun putting a wrecked Quad back together

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