Need help diagnosing engine running rough

[Clan]

Originally Posted by SalvadorP

I know what you mean. But what's the fun in going to a garage and have it solved? I like the chase. While it's cheap things that I want to replace soon anyways, or issues I can test for, I'm alright. Learning is the end goal.

ahh good for you then you will learn a lot ,
Ok if you don't have to use the car 👍

[griston64]

Originally Posted by Laird Scooby

DON'T TOUCH THE AICV/IAC VALVE!!!!!

It's almost certainly not the problem and you may cause more harm than good.

First thing to do with any misfiring engine is to make sure the ignition is correct, all the way through. It is a RHYTHMIC misfire so will be a plug, HT lead, injector or poor compression on ONE CYLINDER only!

You've ruled out compression, injector, plug so that only leaves the HT leads. Sadly if one is failing, it's a fair bet the rest aren't going to be far behind. As such i'd strongly suggest buying those leads i linked to, if they end up being Bosch then so be it, Bougicord would be better but at the price probably Bosch and will do the job better than most other aftermarket parts.

After sorting everything on the ignition side, then start considering fuel related components but not the ones that unilaterally change the whole engines running like the AICV but i'm pretty certain if you renew the HT leads, the fault will disappear.

I got gen Bougicord from PFV online. If you contact him he will tell you what he has in stock and you can decide. I specified Bougicord and that's what he sent.

It more than likely won't be the idle control valve but cleaning it along with the hoses that lead to it won't do any harm. Just cover the elec connector and spray some brake cleaner in and let it swish about. Dry and refit

[SalvadorP]

So today i decided to do what little was left to do.
1 - I cleaned the distributor and rotor a bit better and now they are perfectly clean. No change.
2 - i disassembled the IAC and cleaned it (very carefully Dave ). It wasnt very dirty at all but still. No change.
3 - I inspected the ht leads thoroughly. First i sprayed water abundantly on them. No change.
Then i fiddled with them, touched, moved, pulled on them while the engine was running. No change.
Then i removed each one an inspected them visually and cleaned the contacts with contact cleaner. No change.

I was going through the Excell maintenance sheet i have from Volvo and I'm led to believe the HT leads were last changed in 2019 30k km ago. They are Bougicord, Volvo original. Not saying they can't have gone bad, but it sounds impluasible right now.

[griston64]

Originally Posted by SalvadorP

So today i decided to do what little was left to do.
1 - I cleaned the distributor and rotor a bit better and now they are perfectly clean. No change.
2 - i disassembled the IAC and cleaned it (very carefully Dave ). It wasnt very dirty at all but still. No change.
3 - I inspected the ht leads thoroughly. First i sprayed water abundantly on them. No change.
Then i fiddled with them, touched, moved, pulled on them while the engine was running. No change.
Then i removed each one an inspected them visually and cleaned the contacts with contact cleaner. No change.

I was going through the Excell maintenance sheet i have from Volvo and I'm led to believe the HT leads were last changed in 2019 30k km ago. They are Bougicord, Volvo original. Not saying they can't have gone bad, but it sounds impluasible right now.

It's not the leads then

[Laird Scooby]

Originally Posted by griston64

It's not the leads then

Maybe not but that last lead shows a date code of 1997 so could well be original! Perhaps the others have a later date code and only they were changed and the one with the 97-17 date code (week 17, 1997) wasn't changed and by coincidence is on #2 plug?

[SalvadorP]

Originally Posted by Laird Scooby

Maybe not but that last lead shows a date code of 1997 so could well be original! Perhaps the others have a later date code and only they were changed and the one with the 97-17 date code (week 17, 1997) wasn't changed and by coincidence is on #2 plug?

Honestly, I also saw that. But I was like, "what would the 17 be?". Are you positive this relates to week and year?

I assumed they were changed in 2019 30k ago because that's when the last set of spark plugs was changed and I couldn't find on the excell sheet that the leads were ever changed. So I just thought they can't be the original and were probably changed with the plugs.
But as I said, I did notice the 17-97 mark and that's why I took a picture of it.
This lead is the one on cyl#4.

If you confirm that the 17-97 corresponds to week and year, then it's safe to assume they were never changed, because that's actually backed by the maintenance sheet I have not ever mentioning them being changed. They look so good though, how the hell can they be 25yo!?
I didn't look if the other leads also had the 17-97 mark.

EDIT: That would be april of 1997. The car was bought and registered on 11 of June of 1997. Would make sense.

[griston64]

Originally Posted by SalvadorP

Honestly, I also saw that. But I was like, "what would the 17 be?". Are you positive this relates to week and year?

I assumed they were changed in 2019 30k ago because that's when the last set of spark plugs was changed and I couldn't find on the excell sheet that the leads were ever changed. So I just thought they can't be the original and were probably changed with the plugs.
But as I said, I did notice the 17-97 mark and that's why I took a picture of it.
This lead is the one on cyl#4.

If you confirm that the 17-97 corresponds to week and year, then it's safe to assume they were never changed, because that's actually backed by the maintenance sheet I have not ever mentioning them being changed. They look so good though, how the hell can they be 25yo!?
I didn't look if the other leads also had the 17-97 mark.

EDIT: That would be april of 1997. The car was bought and registered on 11 of June of 1997. Would make sense.

They look in remarkable condition for 25 year old leads !

[griston64]

Just checked my Bougicord leads and can't find a date stamp anywhere. Is the date stamp not normally month first and then year like on tyres ?

[griston64]

Answering my own question here as it looks like they are indeed date stamps

See comment below

Bougicord wires have a manufacture date stamped on each wire. They may look fine like my 15 year old ones did. But they were the only cause of a misfire problem I had. Find the date and you can get a better idea if they need replacing. If it tends to misfire more under brisk acceleration but does not when you accelerate lightly, I will guarantee it is your wires

[SalvadorP]

Originally Posted by griston64

Answering my own question here as it looks like they are indeed date stamps

See comment below

Bougicord wires have a manufacture date stamped on each wire. They may look fine like my 15 year old ones did. But they were the only cause of a misfire problem I had. Find the date and you can get a better idea if they need replacing. If it tends to misfire more under brisk acceleration but does not when you accelerate lightly, I will guarantee it is your wires

Thx for confirming. I looked online, couldn't find any i fo on this. But was assuming Dave was right.
I also think they look remarkably good for 25 years and 500k km. But yeah, if they are indeed 25 years they did their service.
They passed all the tests, but I'm changing them based on the age. Hoping it solves the problem. If not, I'll have to assume it's the MAF. Or keep chasing.