Rough idle, lumpy revs and stalling after heavy acceleration - 1999 Volvo C70 2.3 T5

Lily · Post by **Lily** » 02 Jul 2021, 15:44

Hello everyone, completely new to the forum so bear with me

I have a 1999 Volvo C70 2.3 T5 with 240K km and I absolutely love it. Today I was driving more spiritedly than I perhaps should have and did a 0-100 acceleration with full throttle. Shortly after this, I lost throttle response and the engine began to run extremely poorly - the revs started to become lumpy and "jump" erratically and soon after it ended up stalling. I also noticed a rotten egg smell and significantly more pronounced whistling sounds from the turbo when revving it - I am really fearing the worst here.

I was basically stranded at this point as the car was virtually undrivable, but to my surprise it started to run much smoother after I disconnected the MAF - not perfect as the idle was still rough, but decent enough to allow me to drive it home. Have any of you experienced something similar or have any ideas what might have caused this? I tried to disconnect the battery for an extended period of time to eliminate the possibility of electrical issues, but it made no difference. I also disconnected the MAF and tried cleaning it - no difference either. I also tried to inspect and see if any hoses to the turbo had come loose or cracked, but some of the ones far down are really difficult to see/reach.

Have I ruined my car by pushing it too hard or am I facing a massive repair bill? The rough idle and loss of power just won't go away no matter what I try. I have also used a basic OBD scanning tool but no codes are shown even if the car is running really poorly.

Any help would be much appreciated, I am really worried about this.

Post by **misha** » 02 Jul 2021, 15:52

I would check turbo hoses first.
There is a big chance that some hoses are blown.

Lily · Post by **Lily** » 02 Jul 2021, 15:59

misha wrote: 02 Jul 2021, 15:52 I would check turbo hoses first.
There is a big chance that some hoses are blown.

Thank you, what is the best way to do this? Some of them are a pain to reach from above. Is it worth lifting the car up for better access?

Post by **misha** » 02 Jul 2021, 16:34

Garage with a built-in channel or a lift.
You need a carefull inspection of those turbo hoses.
I bet that you will find a blown turbo hose.
While you are there ...inspect ALL vacuum lines too.

If you are not working on your car yourself...maybe it's a better idea to take the car to a trusted mechanic....a Volvo specialist.

Post by **Sveedy** » 02 Jul 2021, 17:05

I had a similar thing happen. Turned out that I had cracked that plastic tank on the intercooler. It took a smoke test to find it.

Lily · Post by **Lily** » 04 Jul 2021, 07:14

misha wrote: 02 Jul 2021, 16:34 Garage with a built-in channel or a lift.
You need a carefull inspection of those turbo hoses.
I bet that you will find a blown turbo hose.
While you are there ...inspect ALL vacuum lines too.

If you are not working on your car yourself...maybe it's a better idea to take the car to a trusted mechanic....a Volvo specialist.

Thank you for the valuable insight, I really appreciate it. I will try to inspect all of the turbo hoses more closely as best as I can, but I unfortunately don't have access to a lift - I'll have to figure something out. If I am lucky there is an accessible turbo hose that came loose and only has to be tightened, worst case scenario I'm going to have to replace blown hoses. Do you know if there is a diagram/schematic out there of all of the turbo hoses and vacuum lines? For somebody not so very mechanically inclined, this is a bit of a daunting task for me haha.

Lily · Post by **Lily** » 04 Jul 2021, 07:15

Sveedy wrote: 02 Jul 2021, 17:05 I had a similar thing happen. Turned out that I had cracked that plastic tank on the intercooler. It took a smoke test to find it.

That is very interesting, I appreciate the insight. So there was no visible physical damage on the plastic tank in other words? How much did it cost to replace?

Post by **Sveedy** » 04 Jul 2021, 08:46

In my case there was a 8" long crack along the bottom of the tank. Kind of hard to see. That is where the smoke test came in. It would open up more under pressure, say wide open throttle, but still caused other running and idle issues.
The replacement intercooler ( do88 ), all metal, cost less than the OEM one. About $ 500 USD. Not a hard job, but the radiator has to be removed to replace the intercooler.

Post by **Clemens** » 04 Jul 2021, 13:24

If you wanted to save on the intercooler - if it teally is cracked - you could get one from the junkyard for pretty cheap. Before you atart throwing parts at it, be sure to carefully troubleshoot and find the cause.