B230FD Problems :)

[Laird Scooby]

Originally Posted by Volvo940GL

Yes, I recently took a compression test to a dealer

Before or after this problem with #4 cylinder misfiring started?

[Volvo940GL]

Originally Posted by Laird Scooby

Before or after this problem with #4 cylinder misfiring started?

After my car died. And when it started again. Cyl4 misfires

[Laird Scooby]

Originally Posted by Laird Scooby

What is the Bosch number on those injectors? Should be 10 digits starting "0 280"

Looking them up in the 7/900 Data Pocket, it says 0 280 150 762 which are 185cc/min @ 3bar pressure.

However, they are listed as 200cc/min @ 3bar on this site :

http://www.injectorcleaning.co.uk/flow.htm

They have a resistance of 15.9 Ohms so you won't have an injector resistor pack which makes them the same spec injectors as mine. When i can access a particular site that i'm having trouble with at the moment, i will get you an upgrade/update injector part number which has 4-pintles instead of one so runs smoother and gives improved economy and power and less likely to block up.

Managed to find the info i needed another way, the upgrade injectors are 0 280 158 015. Used a lot by Vauxhall and others, you may have to buy a set of 6 secondhand but gives you a coupleof spares.

However the problem might still not be the injector.

[Laird Scooby]

Originally Posted by Volvo940GL

After my car died. And when it started again. Cyl4 misfires

Just to be clear, you've had a compression test since #4 started misfiring?

What were the readings for all the cylinders?

[Volvo940GL]

Originally Posted by Laird Scooby

Just to be clear, you've had a compression test since #4 started misfiring?

What were the readings for all the cylinders?

I have come to conclusion.
It’s either the IAC, MAF or ignition ECU

[Laird Scooby]

Originally Posted by Volvo940GL

I have come to conclusion.
It’s either the IAC, MAF or ignition ECU

None of those will cause a misfire on a single cylinder. If swapping the plugs, plug leads and injectors didn't move the misfire then it either has to be low compression on #4, too tight a plug gap, too wide a plug gap, HT lead shorting out, dizzy cap shorting out, dizzy cap contact for #4 dirty or broken or similar.

The AICV and MAF both feed air into the engine, nothing to do with the igntion, there's no reason to suppose that the ignition ECU is dropping a cylinder as it takes it's signal from the CPS and the other three are firing so there must be another problem somewhere.

[Volvo940GL]

Originally Posted by Laird Scooby

None of those will cause a misfire on a single cylinder. If swapping the plugs, plug leads and injectors didn't move the misfire then it either has to be low compression on #4, too tight a plug gap, too wide a plug gap, HT lead shorting out, dizzy cap shorting out, dizzy cap contact for #4 dirty or broken or similar.

The AICV and MAF both feed air into the engine, nothing to do with the igntion, there's no reason to suppose that the ignition ECU is dropping a cylinder as it takes it's signal from the CPS and the other three are firing so there must be another problem somewhere.

Then I don’t know?

There’s nothing wrong with my rotor, distributor. Or that distributor shaft.
Coil is working. Tested another coil and same result. Tried another rotor. Still same idling. Tomorrow I’ll try a new MAF. I don’t know what’s the problem. Threads on cyl4 is bad af

[Volvo940GL]

Originally Posted by Laird Scooby

None of those will cause a misfire on a single cylinder. If swapping the plugs, plug leads and injectors didn't move the misfire then it either has to be low compression on #4, too tight a plug gap, too wide a plug gap, HT lead shorting out, dizzy cap shorting out, dizzy cap contact for #4 dirty or broken or similar.

The AICV and MAF both feed air into the engine, nothing to do with the igntion, there's no reason to suppose that the ignition ECU is dropping a cylinder as it takes it's signal from the CPS and the other three are firing so there must be another problem somewhere.

I’ll try to thread that cyl4

[Laird Scooby]

Originally Posted by Volvo940GL

Then I don’t know?
Threads on cyl4 is bad af

Originally Posted by Volvo940GL

I’ll try to thread that cyl4

Seems you've found the problem!

If the spark plug is loose in the head, it won't be making a good earth, therefore there is nowhere for the spark to jump to.

That means it will not spark.

You will also be losing compression round the threads, resulting in an even harder to fire mixture.
No wonder the Engine Management Light is on!

The thread will need to be Helicoiled, if you don't know what that is or can't do it, either find a mobile service who will come to you and do it without getting swarf into the cylinder (likely to be expensive!) or remove the head, take it to a machine shop and get them to Helicoil #4 plug thread and check the others while they're at it.
Would also pay to get them to check the flatness of the head and skim it if needed.

[Volvo940GL]

Originally Posted by Laird Scooby

Seems you've found the problem!

If the spark plug is loose in the head, it won't be making a good earth, therefore there is nowhere for the spark to jump to.

That means it will not spark.

You will also be losing compression round the threads, resulting in an even harder to fire mixture.
No wonder the Engine Management Light is on!

The thread will need to be Helicoiled, if you don't know what that is or can't do it, either find a mobile service who will come to you and do it without getting swarf into the cylinder (likely to be expensive!) or remove the head, take it to a machine shop and get them to Helicoil #4 plug thread and check the others while they're at it.
Would also pay to get them to check the flatness of the head and skim it if needed.

Tried threading. That did not help at all. I’m out of ideas. And I need that car. I have no idea what to do now. New plugs aswell. I was angry and had it on redline for 10 seconds and it helped a little bit and is more smoother at idle. But still uneven. So I have no idea anymore