P0505 and engine stumbling - 1999 S70 base

[Mccjim12]

My ‘99 S70 base model intermittently stumbles upon deceleration. This is usually followed by a poor throttle response upon trying to accelerate again. I keep getting a P0505 code - Idle air control - when driving at highway speed and then braking to slow down.

A couple of times I have cleaned the MAF sensor and it seems to make the problem go away for a while.

My car has the dreaded “white label” ETM which I believe is original. Hard to believe since it has 166k. I’m also thinking O2 sensors have probably never been changed. (I am second owner and it has the original spark plugs at 140k).

The freeze frame data on my code reader also says Open Loop fuel status. I have heard that this will cause the vehicle to run rich, which the spark plugs condition would have be believe.

Sorry if my post is a bit all over the place but just looking for some advice on these fronts.

Is it an ETM issue, O2 sensor? Also have heard maybe coolant temp sensor?

Any help appreciated! Thanks!

[scot850]

Spark plugs are way past their sell by date.

Your car does not have an IAC. It is part of the ETM.

This thread may help:

viewtopic.php?t=31247&start=10

The ETM at this age an mileage is likely to be heading toward a re-build with contactless position sensors from the likes of Xemodex.

My buddy who bought my 00 V70 SE base about 4 years ago has swapped the ETM twice in the lat year with used ones. Last one was a yellow label 05 rebuilt unit but it started throwing the odd code. I gave him a white label ETM I had pulled and he carefully cleaned it with CRC throttle body cleaner on a cloth and cotton buds as required (don't soak the throttle flap). Currently car is now running ok but who know for how long. I have suggested he gets the other one re-built as he plans to keep the car long term wit now over 200k miles on it.

Initially I would look at swapping the plugs for good quality ones, Volvo OE/Bosch/NGK gapped correctly.

O2 sensors have their own codes as does the MAF.

Unfortunately I think the ETM may be the issue here, but maybe try simple stuff like the plugs as it could just be a bad and not firing strongly enough.

Neil.

[Mccjim12]

Thanks much. I realized I made a typo in my first post. I did change the plugs at 140k. When I pulled them off they were heavily fouled and oily. There was also oil in a couple of the spark plug wells and the coils were soaked in oil. Figured maybe a clogged PCV but I brought it to an independent shop and they seemed to be leery of doing the job but did say they tested crank case pressure and it was no cause for concern.

I have heard of the XemodeX rebuilt ETM units. Maybe might be worth it.

Do you make anything of the car being in Open Loop?

Thanks again!

[scot850]

That part I don't know as I am not that data savvy.

However, first thing, was there oil in the #2 and #3 spark plug wells and also oil in the general top area when you took the cover off?

If so, immediately replace the oil filler cap seal. If you have done it recently with an aftermarket one chances are it is too thin so allows oil to leak past it. If it is unknown when you last changed it, or when it was changed, it will be like stone and does not seal leaking oil into the area you are finding it. Replacing it with a OE part or recommended aftermarket part should fix it.

There is another possibility, and that is the hose from the oil catch tank to the top of the head has gone hard and is no longer sealing at the head end between #2 and #3 cylinders is leaking. Check it and if it is brick hard then it may leak. If it is not brick hard and has a pipe clamp on it (not the Oetiker type) try seeing if you can tighten it slightly. Don't go crazy as you don't want to split it. It is one of the pipes that gets replaced as part of a CV swap. I recently had helped a son of a buddy to swap that pipe on his S60. Fortunately he has small hands and the bendy part of youth so he was able to reach it to tighten the clamp on the oil catch tank end. He had this issue with a URO pipe that had been used by a previous owner.

You can test the PCV system by using a latex or rubber glove tightly placed over the oil filler hole with the cap removed. The start the engine and see if it inflates. If it does not then the PCV is ok. If it stays flat, then rev the engine and see if it inflates. If it does then it will need done in the near future.

I don't know why repair chops pee their pants at this job. It is not particularly hard, but is time consuming.

I still want to try doing one again on a P80 but try pulling the cooling fan assembly to see if it can be done without removing the intake.

Neil.

[Mccjim12]

Thanks again Neil. Yes I believe there was oil in cylinders 2/3. I did replace oil cap but did not check the hose going down to catch tank. Will do that.

Also I did do the glove test some time ago and no inflation. Although I did not rev the engine. Will revisit that. Thanks!

[abscate]

150-200k on the ETM isn’t that uncommon. We get sparse data here and usually just upset failures from recent purchases.

VIDA will sweep the throttle positioners and tell you if the ETM is working and how well.

Guessing will cost you $150 on eBay for a late model contactless unit. See ETM room forum below for details on part numbers