I recently posted about my catalytic converter being bad. There are new developments now, but I will give the whole story in hopes of someone having an idea of what is wrong with my car.

About 2 months ago the brackets on my exhaust system rusted and broke, and the whole exhaust system dropped and dragged on the ground for about 1.5 miles until I got it back to my apartment. I used some tie wire and secured it up and took it to a shop that welded it back up. At that time they said I had a hole in my flex pipe, and I declined to have it fixed as it seemed to be causing no problems and was not too loud.

Not too long after that happened (within a week), I noticed that my car was chugging under heavy acceleration, appox. 4500 rpm's, like when I was getting on the freeway and needed to get up to speed quickly. It would chug, and chug, and then eventually get up to speed and then drive fine. It drove fine under all other circumstances as well.

About a month ago, the check engine light came on while I was driving on the freeway and I took it to an independent Volvo mechanic. They said that the catalytic converter was bad - that the honeycomb had collapsed and that I should not drive it because I might burn up the valves and seals in my engine. they quoted $2100 for the catalytic converter and the O2 sensors. I found that to be outrageously priced and drove my car home and parked it and haven't driven it since.

In the meantime, I borrowed a code reader from a friend and got the P0420 code - Cat Below Efficiency Threshold code. I took it to another independent shop, one that knows cars but not necessarily Volvos, and that is where it sits today.

They took a scope and looked at the cat and thought it looked fine, so they welded a new flex pipe on and said it was good. As soon as I drove it off, it started chugging under normal acceleration and I could not get it up to speed on a 45 mph road. I immediately took it back.

At this point in time, they have cleaned the mass airflow sensor, checked the fuel pressure, cleaned the VVT per a TSB and none of those things fixed the acceleration. They tell me they are getting great pressure out of the tail pipe and do not believe there is a clog in my exhaust system.

Any ideas?? They are good mechanics but are not familiar with Volvos and not great at troubleshooting. Could it be the air filter?? Is it possible to have good flow out of the tail pipe and still have a clog in the exhaust system that would bog down acceleration? Do I need to replace the Mass Airflow Sensor?

Thanks for your help!!

 

I want to mention that I took it to one other shop in between the $2100 shop and the shop it is currently at, and they cleared the P0420 code and it has not thrown a code since. So, no codes, but chugging and not accelerating at around 2K rpms.

 

I'm afraid I can't help because I think I have the same problem. Mine, if you ask it for medium/hard or hard power, it fluctuates, pulsating revs and hardly accerates at all. However driving it sedately is fine. My Volvo Main Dealer/Service Centre is baffled. They say it's gearbox (auto) but their recommended autobox centre says it's engine!!
Volvo changed a VVT solinoid due to an error code, but it hasn't helped. Have they made these cars so complicated that even they can't fix them? It's getting worse (tho sometimes gets better!) so do I really have to wait until something goes bang to identify it?? I have noticed no smoke out back when power is asked for, tho engine sounds louder than usual under acceleration. Volvo says autobox fluid is too brown and smells burnt, so I'll see what the autobox man says when I go back to him on Monday. If I eventually sort this out I'll let you know!

 

I should say that my car is a V70 SE (170bhp) auto 2.4 (late 2002) petrol model. It's done 112,000 miles - I've had it from May '08 at 77,000 miles and it's been great up until these/this problem(s). First noticed it about six months ago when accelerating hard up a slip road in the wet, thought it was traction control doing it's job. Didn't have any problems for a while, then it starts doing it at less and less acceleration pressures. ie therefore (because I don't often boot it) I noticed it more and more. Worst at 4k rpms with kickdown and struggles with hills.

 

News: my Volvo garage has tried taking the cat off and driving it. They said all the problems went! Thus it does seem that the cat is to blame.

 

so the original mechanic was right huh. i'm looking to buy my first V70 in the early 2001 and up models and am getting the idea that they are full of problems. i was even looking at the XC models. i almost feel i should steer clear of these Volvos. i test drove a 2005 V70 2.5T today and actually really liked it but now i don't know. i know Volvo's aren't cheap to fix either.

 

I have to say that I've had hardly any problems with mine since I bought it 5 years ago. You'll be hard pressed to find any vehicle that doesn't have problems occasionally! Although Volvo quoted me £800 for a new cat, I found National Tyres and Exhausts did one that met Volvos spec for £336. It is possible to run these cars for a reasonable cost, but I can't claim they are very cheap to run! I've now learnt that cats can be 'damaged' or blocked up, by driving efficiently all the time! They need a good blast from time to time to blow away all the crud. I knew they didn't like flood water and short journeys, but this was news to me!! Modern cars are full of stuff that didn't exist 20-25 yrs ago and 'the more there is to go wrong', the more there is to go wrong! Short of buying a classic (if you have somewhere to garage it) and working on it yourself, there's not much we can do about it. :-(