Weird idle - no rpm change

[brownhenn]

'03 xc70 w/112k - for the past couple of weeks it has had a weird idle. I've searched for posts but can't find anything quite like this problem.

The rpm's do not change, so it's not like it's going to 1k or 2k then dropping lower. For a split second it will idle smooth, then in another split second it idles rough, (like it goes in and out) then sometimes, it will idle weird for 10 seconds, then go back to normal (smooth idle). It doesn't always do it, mostly in the morning, but it does occur at random times throughout the day/evening. There doesn't seem to be any rhyme or reason, it's just random. This only happens when stopped (at a light, etc.), it runs fine on the interstate and roads.

The car has always had a smooth idle since we bought it (Feb '09 - we had the 105k service done, timing belt/pulleys/everything our indy suggested) - I've read a lot of posts that say the 5 cyl always have a rough idle, ours seemed to idle smooth. I just replaced the air filter, I plan on changing the plugs soon and cleaning the maf at the same time but I don't think those are the problem.

Thanks for any help

[sjonnie]

I had a something similar before my boost pressure sensor failed. Would be sitting at a light and suddenly the engine would lurch for no reason, like it had a hiccup, then go back to normal. Eventually the sensor failed altogether (P0236) at which point it was hard to keep the car running. Replacement fixed the problems.

[brownhenn]

Thanks, I'll check it out. I hooked up the scanner the other night, no codes.

[ifnt420]

Have you done a vacuum leak test?

[brownhenn]

I have not - I will. There is one hose that is suspect. Thanks for the suggestion. sjonnie mentioned the boost pressure sensor, I was just waiting for it to fail, or for it to give a code or something. The idle is really annoying because it used to be perfect, so it's really bugging me.

Once I do get it taken care of I'll report back

[The Fixer]

PCV system clog. Look in the resources section. http://www.volvoxc.com/resources/how-to/index.php

[Jorge-789995]

I had something similar. I initially thought it was the transmission because the Tach would not move. It turned out to be a bad plug. I would look to the obvious first. I would in this order, check the plugs, coil packs, vacuum leak and then o2 sensor.

[brownhenn]

update -

I changed the plugs yesterday, everything looked good, or as it should. It still has the weird idle. I did notice that the top engine mount (bushing) is shot (or there is a lot of movement) so I will be replacing that asap. Could that be the issue? I watched the engine to see how much it shook, it wasn't really that bad, but there is definitely some movement.

Haven't tested for vacuum leak yet but I will.

I'll update when I fix/find the issue.

[Aviator]

I think if you've had a vacuum leak all this time it would have triggered a fault code and MIL by now. I find a bit of the same thing and it happens this time of year because of the winter formulation of gas. Dump a bottle of fuel conditioner or injector cleaner down the old boat race into the tank and observe. The results won't be immediate but they will be noticed.

Dave.

[kamiar]

In another thread one guy was claiming, he changed the tranny fluid and it solved a similar issue!

this one http://www.volvoxc.com/forums/showthread.php?t=15763 posted by Allen...

[Allen]

In another thread one guy was claiming, he changed the tranny fluid and it solved a similar issue!

this one http://www.volvoxc.com/forums/showthread.php?t=15763 posted by Allen...

Thing is, my idle rumble was constant.

[Ocean Racer]

I have a similar thing happening with my 02XC, only I have a manual.
Randomly at idle, it would feel like the car suddenly drops out with a little stutter then it comes back again - whilst the tach shows nothing in the rpm needle. It only takes a second. :confused:
It appears I have just thrown a CEL too

[Allen]

I have a similar thing happening with my 02XC, only I have a manual.
Randomly at idle, it would feel like the car suddenly drops out with a little stutter then it comes back again - whilst the tach shows nothing in the rpm needle. It only takes a second. :confused:
It appears I have just thrown a CEL too


I know exactly what you're talking about. Mine does this once in a while. I have no idea what it is, but it seems harmless. It almost feels like the ECU is resetting something, because I only notice it at stoplights.

[brownhenn]

Ours does the same, 1 second idles normal, next second rough, goes in and out - only when stopped - does it in drive, neutral and park. Last night, I did notice, the dash lights dim just for a split second, like the car wants to cut off. They don't dim that much, I pointed it out to my wife, she did not notice :| but I swear it dims slightly for a split second. This is really driving me crazy because it used to be perfect. I checked the battery fluid levels, everything was good, the battery looks brand new. I have no idea how old it is - if I knew it was 7 years old, I would change it, but it really looks Brand New, hardly a speck of dust on it. I couldn't find a date on the battery, so I don't know if there's any way of checking it's age.

@kamiar, thanks for the post/advice - I don't know about tranny flush/drain - we bought the car used, with 105k, I don't know if the tranny fluid has ever been changed. It was supposedly taken to the dealer for every service - but the dealer would not give me the records from the previous owner - but when I called them they told me it was serviced there, and she took in for every service. I hear so many horror stories about tranny's going bad after a drain/flush - I'm afraid to chance it, as it's been fine so far. I checked the tran fluid this past weekend, it wasn't low (was full), it appeared dark on the stick. It probably needs the drain/refill - it makes me nervous.

I'll also search for a pcv system clog this weekend.

I kind of just wish it would give a code so I would know what's wrong. It's frustrating

Thanks everyone for the help

[Aviator]

I've got the exact same thing too. Usually happens after any type of drive, long or short, hot or cold. As soon as you come to a stop give it about 20 seconds just sitting there in gear or in park and you get a shudder for like a split second.....no change in RPMs or tach, nothing just this odd shudder as long as the blink of an eye. It doesn't happen all the time and there's no consistency to it, but I did notice it actually stopped for a while last year after I put in new spark plugs :confused:. It was actually very noticeable before the plug change....now it's barely there but it is there. Definitely odd. I'd call the dealer and quiz the service manager, but they'd probably want the car....makes sense.

Dave.

[kamiar]

I have a 04 with 120,000 KM, the tranny fluid seemed never been changed, so i did a drain and fill myself, i will do one with the next oil change, i don't see any possible harm with this method unlike the power flush... don't do a power flush at this mileage. also i don't think dealers would do tranny fluid service unless one asks them to do so, and yours probably has never been done like mine.

Search for the PCV clog test, i think its been done from the dip stick, if there is a vacuum or something else! not sure...

What i think about this issue is either the CVVT or TCV... if everything else is fine.

[brownhenn]

update:

Cleaned the maf sensor, ran perfect for almost 5 minutes, then the idle problem returned - btw, the maf was a PAIN to remove, had to really muscle it. Because it ran good for 5 minutes after the cleaning, it makes me wonder if it's failing/about to fail soon, still no codes though.

I'm really getting over it, I think we'll take it in soon - I checked all the mounts, they are all fine, but while I was under the car I noticed oil dripping from the turbo - I'll be replacing the turbo return line gasket soon. Though I don't think that will affect the idle.

[brownhenn]

another update:

Last Friday, I plugged in the obd scanner and got an error code P0420. Funny because I plugged in about a month ago and got nothing. Check engine light has not come on at all. Anyway, I cleared the code (it was a 'pending' code) and the problem is gone. It has been running perfect since Friday. If it comes up again, guess I'll start at the o2 sensor.

I had already made an appt to take it to the independent volvo tech on Monday. I took it in, explained the situation, he said it would probably be a waste of $$ for them to plug in since it's running perfect now. Told me to bring it back if it comes up again.

Thanks again for everyone's help