Engine won't rev and hunts

[ANDTWENTY]

Originally Posted by Laird Scooby

My wiring might be slightly different but i know of a 1990 744 with LH2.4 that had the connector in a similar place. Have a look under the coolant tank and all round that general area.

If all else fails, if you can physically block the AICV off, whether by clamping or by taping over the end of it or whatever to set the base idle speed, that's a work-around.

Ive had a look all round and really can't find anything apart from that one with the pink wire. I can clamp the hose, would disconnecting the plug not do the same thing as that wire?

[Laird Scooby]

Originally Posted by ANDTWENTY

I can clamp the hose, would disconnecting the plug not do the same thing as that wire?

You'd think so really, wouldn't you? Sadly not though as earthing that white/red wire puts the ECU into test mode and makes it close the AICV completely. Simply unplugging it is literally a game of roulette as you don't know where the barrel of the valve will be when you pull the plug.

That's why i said clamp the hose, you could unplug it as a "belt'n'braces" measure so the valve doesn't try and open up while you're setting the idle.

Any sign of the new/secondhand MAF yet?

[ANDTWENTY]

Originally Posted by Laird Scooby

You'd think so really, wouldn't you? Sadly not though as earthing that white/red wire puts the ECU into test mode and makes it close the AICV completely. Simply unplugging it is literally a game of roulette as you don't know where the barrel of the valve will be when you pull the plug.

That's why i said clamp the hose, you could unplug it as a "belt'n'braces" measure so the valve doesn't try and open up while you're setting the idle.

Any sign of the new/secondhand MAF yet?

Ah okay I see what you mean, I'll give it a go with the hose clamped off. The MAF should have gone 1st class today so perhaps Monday or Tuesday.

Probably won't get a chance to do the idle valve till Tuesday cus of work but depending when the MAF comes I'll try that.

[ANDTWENTY]

Just got in from work and the MAF sensor has arrived, popped it on and tried it but the issue is still there. On the up side the idle is good now, was about 600rpm at first but was sitting at 900rpm soon after. Will try the fuel pump and change the filter under the car in the morning, not sure where to go next? The TPS is giving the correct readings and the car diagnostics comes back as okay, could this still be an issue?

Also not sure if its possible that this may sensor is also bad? the back best is damaged, potentially in the post as the box was knocked but was in a fair bit of bubble wrap!? few flies on the mesh and is dirty but the guy said it worked?

[Laird Scooby]

Originally Posted by ANDTWENTY

Just got in from work and the MAF sensor has arrived, popped it on and tried it but the issue is still there. On the up side the idle is good now, was about 600rpm at first but was sitting at 900rpm soon after. Will try the fuel pump and change the filter under the car in the morning, not sure where to go next? The TPS is giving the correct readings and the car diagnostics comes back as okay, could this still be an issue?

Also not sure if its possible that this may sensor is also bad? the back best is damaged, potentially in the post as the box was knocked but was in a fair bit of bubble wrap!? few flies on the mesh and is dirty but the guy said it worked?

Did you pull fuse #1 for 30+seconds before trying the new MAF?

You've tested the TPS several ways including with the cars own diagnostics which report it's ok.

You've got a tyop there i think and i don't know what a back best is? Where/who did you get the MAF from?

[ANDTWENTY]

Originally Posted by Laird Scooby

Did you pull fuse #1 for 30+seconds before trying the new MAF?

You've tested the TPS several ways including with the cars own diagnostics which report it's ok.

You've got a tyop there i think and i don't know what a back best is? Where/who did you get the MAF from?

Sorry been a long day! The 'back mesh' its meant to be.

I didn't at first but I did after trying it once and it didn't make a difference, was out for a couple of mins

[Laird Scooby]

Originally Posted by ANDTWENTY

Sorry been a long day! The 'back mesh' its meant to be.

I didn't at first but I did after trying it once and it didn't make a difference, was out for a couple of mins

As long as the mesh hasn't touched the hot wire inside and whatever bouncing around it suffered hasn't broken anything inside, you should be ok.

At the moment, i'd concetrate on the electrical connections to the main underbody pump and making sure it's running. Sometimes if they've stopped through lack of use, as long as they have a decent power supply, a gentle tap with a wooden mallet or lump of wood can jolt them back into life - not always though.

[ANDTWENTY]

Originally Posted by Laird Scooby

As long as the mesh hasn't touched the hot wire inside and whatever bouncing around it suffered hasn't broken anything inside, you should be ok.

At the moment, i'd concetrate on the electrical connections to the main underbody pump and making sure it's running. Sometimes if they've stopped through lack of use, as long as they have a decent power supply, a gentle tap with a wooden mallet or lump of wood can jolt them back into life - not always though.

No the mesh isn't touching anything inside, Maybe its worth a clean bit some brake cleaner as its a little grubby?

Yea will give it a test tomorrow when I change the filter, I can hear it prime but could the impeller be seized?

having another hunt around the world wide web, someone suggest the PCV valve blocked or not working. I had a blocked one on my other Volvo and didn't cause an issue, could this be something do you think? might whip it off and clean it out though.

[griston64]

Originally Posted by ANDTWENTY

No the mesh isn't touching anything inside, Maybe its worth a clean bit some brake cleaner as its a little grubby?

Yea will give it a test tomorrow when I change the filter, I can hear it prime but could the impeller be seized?

having another hunt around the world wide web, someone suggest the PCV valve blocked or not working. I had a blocked one on my other Volvo and didn't cause an issue, could this be something do you think? might whip it off and clean it out though.

Don't clean it with brake cleaner

[ANDTWENTY]

Originally Posted by griston64

Don't clean it with brake cleaner

Engine degreaser? panel wipe degreaser? don't have any maf cleaner but could order some