'06 XC90 2.5 "Surging Idle" 92k miles

teamcrossworks · Post by **teamcrossworks** » 07 Jul 2011, 11:37

Please help!

2006 XC90 2.5 Turbo AWD

This past winter on one of the coldest NJ mornings, our XC90 started running rough at idle. Believe it or not it's now July and the problem is still present. My friend who owns a general repair shop has tried to diagnose the problem without success. It has not, but seems like it might stall at any given time. Off idle it runs fine.

We have:
Replaced the gas cap
Cleaned the MAF
Changed spark plugs
Tried to check for vacuum leaks (to me that's what it acts like) but without a "smoke machine" it's very hard to see

Anyone have any ideas as to the cause or even the vacuum lines that would have an effect that I could just replace?

Thank you in advance!

TexasCoder · Post by **TexasCoder** » 07 Jul 2011, 18:59

I had the same issue, I would get an idle surge when coming to a stop at a stop light. I ended up taking my throttle body off and cleaning it, and also replacing the PCV system. As for finding vacuum leaks, a smoke machine would be your best bet. I built my own smoke machine using a fog machine that I bought from Guitar Center, it helped to find some EVAP issues with my Dodge Dakota. Come to think of it, if you had any type of vacuum leak, your Volvo would probably store a DTC code and display the check engine light. I bet your issue is going to be dirty throttle body and/or clogged PCV system. To check the PCV system, when the car is idling, do you see any smoke coming out of the oil dipstick tube (remove the oil dipstick and watch from smoke coming out of the tube). If you can't see the smoke, you can put a balloon over the dipstick tube and watch to see if it inflates, if so, then time to repair the PCV system. You can get a kit at IPD: http://www.ipdusa.com/product.asp?P_ID=4991&V_ID=11327

How many miles are on your XC90?

teamcrossworks · Post by **teamcrossworks** » 08 Jul 2011, 07:10

Thanks for the response and input Texascoder. I appreciate it.

The vehicle has 92,000 miles on it. I should have stated there is a code indicating (I forget the #) indicating what we first thought was a leaking gas cap (replaced).

I'll try the oil dip stick trick (PVC kit is pricey though).

I cleaned the MAF already but my friend (mechanic) thinks I might have to replace it. I'm thinking since it began on a very cold morning it is more feasible something cracked and is leaking.

???

TexasCoder · Post by **TexasCoder** » 08 Jul 2011, 11:01

Awesome, I hope you get it fixed. I love my XC90!

Is there anyway you can post the DTC code, so that we can help a little more. By you saying, "replaced the gas cap", I am taking a leap and guessing the code was something for the EVAP system. Which might have been a P04XX range, but please get that code and post it, so we can help.

xallenx · Post by **xallenx** » 08 Jul 2011, 13:40

Check the PCV hose on top of the engine right beside the oil cap..it gets very brittle and can crack. Also, check turbo hoses, especially underneath where the oil pools. Post your findings. I too have an 06 2.5 with 92K + miles, but so far no problems with idle surge.

teamcrossworks · Post by **teamcrossworks** » 09 Jul 2011, 05:53

Thanks guys!

I'll try all of the above and let you know how I make out. Working this weekend so probably won't have a chance until Monday.

Enjoy the weekend!

teamcrossworks · Post by **teamcrossworks** » 12 Jul 2011, 07:43

Update:

I tried the oil dipstick "trick". Pulled the dipstick out and started the car. I saw just the faintest bit of smoke but not really any more then I would expect from an open port to the crank, put the balloon on and it did [b]not[/b] blow up.

Not really sure how much smoke is the tell tale sign. Also the surging was not present during this test. It seems to come and go making trouble shooting even more "fun".

Not able to get down to my friend's today and get codes. While the engine was running I tried moving as many vacuum lines/hoses I could lay my hands on and the motor remained steady.

???

BerniniCaCO3 · Post by **BerniniCaCO3** » 20 Jul 2011, 20:09

It's been a week, anything discovered?

Please do pull some codes. I just discovered the dealership will pull them for free, so do so!

The dipstick trick is pretty good. If the pcv/ vent box is clogged, pressure builds up inside the crankcase/oil pan (same volume).
I'd try for the throttle body next. Just saw one in class today in fact; and it wasn't even all that dirty.
It's controlled by an actuator, so when the shaft that the throttle plate rotates on gets gunked up, the actuator ends up jerky, as it exerts enough torque to overcome the gunk and then spasms open. The results were surging, uneven idle, and codes for the throttle position sensor, throttle actuator (it had some other name in the code), and actually the fuel trim was off too-- it wasn't getting as much air as it thought it should, and there was excess fuel. When the engine tried to dial it down as far as it could go, it came up with a "fuel trim lower limit" error.
If you think about it, a sticky throttle plate is a greater problem at idle, because 5 degrees is a much greater percentage difference in air when going from 0-5 degrees cracked open, than say moving from 85-90deg; though technically there are performance effects across the entire rpm range, it's by far most noticeable at idle.

But, before you spend $600 on a throttle body or even just 3 hours cursing at an R&R job to clean your present one, DO just pull some codes and tell us what you're seeing!

teamcrossworks · Post by **teamcrossworks** » 10 Aug 2011, 18:36

Sorry for the long delay. I appreciate everyone's help and support on this.

Update: I finally got some time to bring the car back down to my buddies garage to work on. I had gotten some new parts from FCP Groton (awesome company to deal with by the way): new front struts, gas cap hinge, rear hatch struts and spark plugs. After everything was installed we focused back to the surging idle. The codes indicated pointed us more in the direction of the "leak detection pump" which is in the rear of the car above the spare tire (this will have to wait as the part is not cheap and I've been spending too much money lately)...LOL We didn't feel this was the cause of the surging.

After 2 hours of checking all the hoses and vacuum lines both visually and by spraying fluids that would possibly get sucked in and cause an idle change we concluded it must be the MAF.

Well today it came via UPS, installed it in 5 min and behold the surging is [b]gone[/b].

I wish this was the end but my luck is never that good. The car idles fine but it now idles around 600 rpm and almost stalls because of how low it is. Any ideas?

teamcrossworks · Post by **teamcrossworks** » 15 Aug 2011, 14:59

[size=150]SUCCESS![/size]

What a pita.

I followed the helpful hints (thank you) on this forum and removed and cleaned the throttle body. It was extremely gummy and carbon dirty. The intercooler rubber hose to the bottom of the throttle body was also very dirty and gummy inside...cleaned both spotless.

New gasket and re-assembled (lots of swear words...couldn't get those damm bolts lined up).

Runs perfect!

Thank you everyone for your input.