Very Rough Idle Problem

[nelly2000]

Hi Everyone,

I really need some advice on a mot fail issue with my 2002 V70 2.4 petrol (non turbo).

Thanks in advance.

Car has been great and well looked after. It's had an oil leak for 3-4 years, not enough to fail mot and no-one ever wanted to try and fix it so I've been living with it, topping up whenever needed. A few weeks ago it started suddenly to rough idle, I drove home and checked oil level, almost dry, I couldn't believe I must have left it longer than I thought I had. I topped up the oil and have had the following symptoms ever since...now the low oil may or may not be significant here, I really don't know.

Car starts and runs great for about 5 minutes, then starts to rough idle, it's fine when throttle is up a wee bit. Engine light comes on and it goes into limp mode. If I restart car it's out of limp mode but same thing happens again.

If I stop car and let it cool down, then it will run fine again for 5 mins and so on.

I was told that I need a new throttle body, so have investigated what I need to do there, sourced a used throttle body off of same year and model car and found someone to fit it, who can re-program if required. But, I have some doubts that it is the throttle body, how can I be sure?

Any thoughts or advice very welcome before I go and replace something that is not required.

I saw an old post on here about dirty pcv valve, which sounded similar to my issue, which got me thinking.

Oh, I gave the current throttle body a thorough clean yesterday, both sides, but the issue is the same.

Thanks very much in advance.

[Maccmike]

I take it there was some oil on the dipstick? if so this might just be a coincidence.

Get a fault code reader on it.

Initial guesses would incl throttle body.
Vacuum pipe leak.
Bad plug or coil.

[stegreg]

As a cheap check, id pull the plugs out and look at the plug tips, see if the colours match all cylinders, or if any oily deposits on a plug tip maybe.

[vtwinpilot]

Just to chime in, my 2.4L petrol engine, and I think the design of the engine in general not just mine, is very sensitive to spark plugs.

I ran some platinum plugs during the last interval and they deteriorated fast, to the point that I had rough idling. I forget what the service interval is for spark plugs (I think it's every 30k miles?), but whatever it is, be sure to follow it. It matters.

Also, I went from the platinum, eye-watering expensive plugs to the cheaper OEM Volvo plugs ($30 for a set of 5 on ebay), slapped them in, and the car was transformed. Smooth as silk afterwards.

[nelly2000]

Hi everyone, thanks for your responses and sorry for delay in coming back, busy day. I'll try and address all your points below...

There was a tiny bit of oil at end of dipstick so not good I suppose.

I have checked for all splits, tears etc. Where air is traveling, fixed a couple of minor things.

I will have a look at the spark plugs, but they were replaced in March 2019 at last service, maybe 15k miles ago.

The car has thrown me completely after today, I had actually decided to sell it on and cut my losses, so cleaned and hoovered it. I had to turn on engine to clean round gear knob base, so put it in neutral. I went back in house and forgot I left it running, came back 20 minutes later, and decided to test it on road. My jaw was literally dropped after it ran smooth for over 10 minutes.

I'm confused now. I'm going to get some engine cleaner into the oil, per old post on here with similar symptoms, and see how it goes.

I'll do that, check the spark plugs and think about the code reader, but it's something I don't have myself.

If it keeps running smoothly, I'll get mot done again and sort the smaller things to get it road legal, front suspension arms basically.

Fingers crossed, and I'll come back with an update in a few days or a bit more.

Thanks again, and any more ideas, please let me know.

[nelly2000]

Here is the link to the old post on here I referred to above...

https://www.volvoforums.org.uk/showthread.php?t=223708

Cheers

[skill]

Hi, sounds exactly the same trouble I had on my V70 T5. Did the same things as you and even was going to sell it for spares as I had given up.
Then as luck appeared someone mentioned about a breather pipe for the engine which was absolutely chocka causing the engine to loose power after 10mins and push out oil.
The pipe was taken off cleaned and put back, nothing new and at no cost but difficult to get at. The car runs fine now.

Hope this helps.


I didn't do the work myself this time, so sorry I don't know the name or position of pipe.

[nelly2000]

Hi,

That's reassuring thanks for responding. I think that must be the pcv system breather pipe, not sure if the engine flush will solve that, I'll look it up. I'm doing engine flush next Thursday because it needs an immediate oil and filter change after running the engine flush, so I've booked it in and got it all timed. I'll check out the breather pipe now. Thanks again.