Idle problem won't go away

[atbspinner]

'01 XC 101k
First I had a very rough idle only on a cold start and the local Volvo dealer checked all vacumn hoses and replaced the throttle after it threw a code.
Ran perfect for 3 weeks.
Now I have an idle that stays steady except it drops to 400-500rpm every
15 seconds like clockwork and almost cuts off before returning to normal.
I pulled and cleaned the MAF 2X with no improvement. I also have a can of
Seafoam in the gas trying to clean the injectors. No codes.
Could the MAF be bad but not giving a code?
Also, about 6 months ago I had a code for the cat but the dealer cleared that and it has been fine. Could the cat cause this type of idle problem?
:confused::mad::confused:

[howardc64]

Could the MAF be bad but not giving a code?


Just replaced my bad MAF, random sputtering and engine cutout with no codes. Actually I did get code a couple of times but it was rare. Each time I had 3 codes also didn't directly point to failing MAF.

If you know someone with a similar car, you might try what I did the find the MAF problem. I swapped MAF (2 security torx screws to remove) with a car that was good and found the problem.

[RockitShip]

On my Audi all I need to do is measure my trim at idle; anything -5% or + 5% is out of whack... say a reading of +15% would be way too high, thus pointing to a bad MAF.... it may not necessarily throw a code.

I suspect this can be done on using an OBD2 reader on Volvo? Does anyone know?

You should also make sure you don't have any vacuum leaks as they can also mess with your idle.

[JRL]

ETM is starting to fail

[MoeB]

Now I have an idle that stays steady except it drops to 400-500rpm every 15 seconds like clockwork and almost cuts off before returning to normal.

A dirty throttle body due to clogged PCV breather system will cause a similar effect. When the PCV system clogs, oil can get into the throttle body and gum it up. You then have to remove and clean the throttle body (Seafoam won't cut it) and PCV system. A crankcase pressure test will determine if the PCV breather is clogged.

If it isn't clogged, then it's the ETM going bad like JRL said.

[Aviator]

ETM is starting to fail

He's already replaced that. Sounds like your engine may be starting to choke on crankcase gases building up which would mean it's time to pull off the intake manifold and dig into your PCV system.

Dave.

[sjonnie]

He's already replaced that. Sounds like your engine may be starting to choke on crankcase gases building up which would mean it's time to pull off the intake manifold and dig into your PCV system.

You could be right but then he would also have smoke either from the tailpipe or dipstick, plus why would the engine sag exactly every 15s? It would really help if he could hook up a OBD reader to figure out what's going on with the fuel mix. Is this still only happening during the open loop phase on a cold start?

[Aviator]

You could be right but then he would also have smoke either from the tailpipe or dipstick

You wouldn't get smoke out the arse end just from crankcase vapour; if anything you'd see oil leaks starting from the excess pressure. I would be inclined to check the spark plugs first and read whatever story they tell, then check vacuum just to see if that changes every 15 seconds as well. Some visual data would be nice to see as well.

Dave.

[atbspinner]

Well, took it to the dealer and the mechanic started looking it over and found the problem. He said a sensor on the intake hose had worked loose and it created a hole on the hose. He snapped it back into place and did not charge me anything. Runs perfect now!! Cheapest visit to the dealer ever.[thumbup] Thanks for all the input.

[kamiar]

Well, took it to the dealer and the mechanic started looking it over and found the problem. He said a sensor on the intake hose had worked loose and it created a hole on the hose. He snapped it back into place and did not charge me anything. Runs perfect now!! Cheapest visit to the dealer ever.[thumbup] Thanks for all the input.

Good to hear that the fix was easy and cheap for you...

[billr99]

Well, took it to the dealer and the mechanic started looking it over and found the problem. He said a sensor on the intake hose had worked loose and it created a hole on the hose. He snapped it back into place and did not charge me anything. Runs perfect now!! Cheapest visit to the dealer ever.[thumbup] Thanks for all the input.
Guys, here is another case where it proves you should check the easy stuff first before you start suggesting the gloom-and-doom answers. A quick calculation would have had the OP spending hundreds of dollars on fixes that would not have fixed a simple problem. You know if he would have waltzed into a dealer and mentioned all these suggestions, they would have been more than happy to relieve him of said hundreds all the while making the simple fix as well. Either way, car runs normal and customer is happy (just unnecessarily poorer).

Cheers,

Bill

[kamiar]

And also this is a proof that there still are professional technicians an honest dealerships, wish we had only one in Montreal...