Rough Idle - need advice

sunnyrollins · Post by **sunnyrollins** » 02 Mar 2013, 19:39

Hi everyone,

I can't believe how helpful this site is, just joined while working on my XC90 (2005) 5 cylinder with over 132K on it. I'm experiencing the rough idle as many have complained about on here. I have tried a number of things, I'll list below. I took it in to the shop (general shop, not Volvo), it was a Misfire Cylinder 2 issue. They charged me $90 for a new plug and diagnoses.
Then I have been scouring this site ever since. It is a lot easier to start, revs clean, and is a lot less rough, but the lights flicker and engine is abnormally rough in the low idle. Here's what I've done so far.

1. Changed all new platnium plugs.
2. Cleaned and installed all new screens and grommets on fuel injectors.
3. Removed and scoured the throttle body.
4. Cleaned the MAF sensor, filter, air tubes.
5. Removed and cleaned the PTC valve, vacuum tube and the PCV tube running near oil cap is new.
6. Fuel filter is 1 year old.

Things it could be after reading threads:

1. 02 sensors
2. seal around oil cap (doubt it, but I've read some of you had that issue)
3. Vacuum tube leak
4. Turbo Control valve
5. Wire harness to Cylinder 2 (advice on how to check that)? ran ohm on voltometer but nothing read on any of them.

Anyhow, if I find out what it is, I'll post on here. I'm thinking of running it in to dealership, getting a diagnosis then fixing it myself if anyone's tried that. I have paid them plenty over the past 8 years, so no remorse.

Any other ideas? I have to get a computer reader to pull the codes if anyone has a good recommendation.

cbotd · Post by **cbotd** » 04 Mar 2013, 07:22

Definitely get the codes read if your check engine light is on. It sounds like you've done quite a bit of work already. Two things that come to mind for me after reading your post;

Spark Plug packs. These are the electrical packs that are on top of the plugs. If you didn't change them at the time of the plugs swap, you might try at least changing the 2nd cylinder pack based on your previous code.

Fuel Pressure sensor. I had a rough idle that would flicker the lights and nearly stall and it was traced to the fuel pressure sensor. The XC did not drive properly though with this problem. I had a rich fuel smell, poor acceleration, poor gas mileage and even a backfire due to too much fuel being provided.

I don't know that 02 sensors would cause a rough idle...? But then again I don't have that much experience with the XC 02 sensors yet. Keep us posted.

sunnyrollins · Post by **sunnyrollins** » 04 Mar 2013, 22:54

It may be the fuel sensor, I'm taking it to the dealership to run a few tests tomorrow. I'll post a response and I hope its the sensor, that would be a quick fix...

sunnyrollins · Post by **sunnyrollins** » 05 Mar 2013, 17:58

Turns out after compression test it may be a bad valve in Cylinder 2 - so worse news that I thought. Cylinder 1 165, Cylinder 2 20 psi, 3 = 60 psi, 4 = 170, 5 = 165. It was recommended the cylinder head should be removed and inspected for valve damage or cylinder bore damage.

The car has 136,000 on it, I will take it to a local shop pray I can get them to estimate a fair price and get a few more years out of it. This is beyond what I have the know-how, tools and space to handle myself. The dealership was thinking "just try and get $500 for the car"... which can't imagine I'm at that point yet. But, it will probably cost a few grand in labor.

Anyone have any experiences with cylinder/valve issues?

sunnyrollins · Post by **sunnyrollins** » 16 Mar 2013, 20:08

Not that anyone is reading this thread, but to help those searching for the rough idle, problem in cylinder two at least in my experience was finally resolved. I hired someone to check it out, the camshaft was sliding out from the block pulling the timing belt practically off. Problem #1, Problem #2 the exhaust valve had a piece broken off and luckily passed through the exhaust without scratching up the cylinder.

The mechanic just couldn't believe the wear this thing had for the miles. I used 87 octane a lot, but still, a crack with 132K?
Who knew.

While the head was pulled off I asked him to replace everything - belt, waterpump, tensioner. etc. At least I know now the core is fine and I'm going to hold onto it for a bit longer, then probably sell it while it has some worth.

Post by **98T5** » 20 Mar 2013, 08:06

WOW, that's a crazy rough idle story. G'luck with the repair. I currently have a rough idle on my 940 but only when I slow down to stop lights, etc. I figurre it's a bad rotor and cap, those usually are the first place to look if you experience a rough idle on any type of vehicle. I suspect yours may have been bad for a while to damage a valve like that.

Post by **boosted5cyl** » 20 Mar 2013, 09:23

Wow thats weird. Sounds like the bolt on the camshaft backed out? Perhaps the cam seals were done at some point and the bolt wasnt torqued correctly. Or it was just one of those things.

Damn interesting though.