High Running Idle

[PurpleTurbo]

Hi again!
I had just left the local shops today after work and the 940 wouldnt start, I have been having issues with it not turning over on the first try when hot for a couple weeks now. However, this is the first time it wouldnt start at all.
Anyway after about an hour of sitting in the car park questioning my life choices it finally decided to start.
But, it decided to idle at 1.5krpm then when I started driving it increased further (see video) but if i came to a stop it would drop back to 1.5krpm.

Has anyone had an issue like this and could anyone shed some light on whats wrong?

Video: https://youtu.be/b9TFm93eY6o

[TonyS9]

There won't be a magic one symptom one fault answer. You need to diagnose it.

Start by checking any codes logged

Then when it doesn't start check if the rev counter is moving atall during cranking. If might not move for the first second or so. This will tell you if you have most of the conditions for sparks.

Then check if the pump is priming, listen for the whine when you turn the key (96 on need about 10s before it will prime again).

Lack of speed signal cause cause it to rev high if you use full power, but it would usually start.
You could also have an air leak.

And if you are looking for help, some details on the car and engine would be helpful.

[PurpleTurbo]

Originally Posted by TonyS9

There won't be a magic one symptom one fault answer. You need to diagnose it.

Start by checking any codes logged

Then when it doesn't start check if the rev counter is moving atall during cranking. If might not move for the first second or so. This will tell you if you have most of the conditions for sparks.

Then check if the pump is priming, listen for the whine when you turn the key (96 on need about 10s before it will prime again).

Lack of speed signal cause cause it to rev high if you use full power, but it would usually start.
You could also have an air leak.

And if you are looking for help, some details on the car and engine would be helpful.

Its a 2.3 LPT 5 speed manual, the car will fire for like half a second when starting before spluttering to a stop, I also need to have full throttle to turn the car over when it does start.
Ill listen for the fuel pump in the morning, I dont have a code reader either so will order one ASAP.

[Laird Scooby]

Originally Posted by PurpleTurbo

Its a 2.3 LPT 5 speed manual, the car will fire for like half a second when starting before spluttering to a stop, I also need to have full throttle to turn the car over when it does start.
Ill listen for the fuel pump in the morning, I dont have a code reader either so will order one ASAP.

First comment is you appear to be driving? Difficult to tell as it's filmed in portrait mode and not landscape so all i see is a narrow strip of image down the middle of the screen.

What year is the car, what fuel are you running on and are you having any cold start problems?

[PurpleTurbo]

Originally Posted by Laird Scooby

First comment is you appear to be driving? Difficult to tell as it's filmed in portrait mode and not landscape so all i see is a narrow strip of image down the middle of the screen.

What year is the car, what fuel are you running on and are you having any cold start problems?

Yes I'm driving, the idle only acts like that while I'm driving.
Its a 1998 celebration and I'm not 100% sure what fuel I'm running.
No issues on cold start

[Laird Scooby]

Originally Posted by PurpleTurbo

Yes I'm driving, the idle only acts like that while I'm driving.
Its a 1998 celebration and I'm not 100% sure what fuel I'm running.
No issues on cold start

When you stop, what does the idle speed do?

Where do you buy your petrol and what grade?

[TonyS9]

If its working atall the pump should be working, I was thinking more general diagnosis when I said that.

The rev counter is your best indicator to start with. The needle should flicker if its not starting, indicating a fuel problem. If not its an ignition problem, but not 100% certain eitherway. If its firing a bit, sounds like you are getting sparks, but needle movement during cranking would be easy to check and confirm (mostly) its a fuel issue.

For codes you don't need anything fancy, there is an OBD2 socket but an OBD 2 reader won't work unfortunately, you need to build you own, but you can basically do it by jamming in an LED on a wire (this is basically how the pre-96 OBD works, but you get the LED in the car without the pretend OBD socket).

Having to apply throttle could be a sign of low fuel pressure, the fuel pressure regulator is a common problem, but high idle is not normally a sign, it might be an unknown reaction buy the later managament systems. Ideally get the fuel pressure checked.

[PurpleTurbo]

Originally Posted by Laird Scooby

When you stop, what does the idle speed do?

Where do you buy your petrol and what grade?

When I stop the idle was settling to normal levels. After yesterday it settles to 1.5krpm but I havent driven since then.

[PurpleTurbo]

Originally Posted by TonyS9

If its working atall the pump should be working, I was thinking more general diagnosis when I said that.

The rev counter is your best indicator to start with. The needle should flicker if its not starting, indicating a fuel problem. If not its an ignition problem, but not 100% certain eitherway. If its firing a bit, sounds like you are getting sparks, but needle movement during cranking would be easy to check and confirm (mostly) its a fuel issue.

For codes you don't need anything fancy, there is an OBD2 socket but an OBD 2 reader won't work unfortunately, you need to build you own, but you can basically do it by jamming in an LED on a wire (this is basically how the pre-96 OBD works, but you get the LED in the car without the pretend OBD socket).

Having to apply throttle could be a sign of low fuel pressure, the fuel pressure regulator is a common problem, but high idle is not normally a sign, it might be an unknown reaction buy the later managament systems. Ideally get the fuel pressure checked.

Is there a guide somewhere on here on how to do the odb thing? I'll try to get the fuel pressure checked next week if not this weekend

[TonyS9]

https://www.matthewsvolvosite.com/fo...ic.php?t=31187

Not sure exactly which pins are for which ECU, each ECU has its own pin to trigger it to flash the LED. But more googling could find that out.

There are designs on here somewhere with a full parts list and switchable reader.