$6500 for repairs?

[matthew1]

Andy, I have two things to add. Some codes point to exact parts that are the problem. P0420 isn't one of these. Good news is we have a deep collective knowledge of P0420, lots of experiences here with that. The O2 sensors are the downstream culprit with this code and the code's description mentions them, but it's almost never these sensors. It's always a spark/air problem upstream.

Second, find out what parts brand they used for spark plugs and coils. If it's not on the service papers, call. This will help us quite a bit.

[SuperHerman]

Andy: To sum up your shop's latest advice - "the parts are so powerful the system cannot handle it."

First - why did they put them in and if this is the case they should take them out and replace with Volvo OEM. Continuing on this lunacy, the coils are designed for the car and should be exact replacements. This leaves the plugs, which could be the problem.

Second - the car has a computer system that is extremely sophisticated. It is monitoring everything and adjusting everything each second. In the end the O2 sensors are sniffing the exhaust and reporting back the output doesn't pass their smell test. Even though the system is trying to adjust so that the sniff test is passed, the system cannot adjust the air fuel ratio to get the proper burn.

At your miles, assuming your engine is not an oil burner, which the plugs, tail pipe and oil consumption would tell you - your cat should be fine. That CataClean is junk. Tried it on my Audi 3.0 which is a known cat eater, and it did nothing. I think your cat is fine. But, looking at the oil consumption would confirm if you may have a cat problem. Pulling out the O2 sensors and looking at the Cat would also confirm.

My thought - the shop needs to look at the O2 sensors and fuel trim live data to tell what is going on. It is most likely an air leak - as a result of unmetered air entering the system - the computer cannot compensate for this. As you didn't have the issue before, and they worked on the car, it is most likely a broken hose, clamp that is not tightened or some plastic piping that was damaged or not seated correctly. I had this same issue on my old Subaru and the problem was a cheap Autozone air filter. After doing some digging on the internet I found others having the same code and the same problem after an air filter change. I bought a new quality filter, replaced it and the code was gone. The live data on the 02 sensor will also show how the sensors are working - the data will be moving in a predictable manner any competent mechanic can identify. The shop has to do its homework.

[AndyG]

This is all so helpful. Thank you, everyone. I’ll keep you posted on my epic saga. Keep the suggestions coming. I’ll try everything.

[pgill]

Andy,

For my 2010 S80 3.2 the Thermostat failed but I had no symptoms.

I replaced it only because it was known to fail for others.

The post that convinced me that being proactive with the change can be found here
(This is the post with the ignition coil failures)

http://www.volvoxc.com/forums/showthrea ... -2009-XC70


if you want to know how the Thermostat works then take a look at this post
(it is significantly more complicated as compared to the simple circular style thermostat)

viewtopic.php?f=31&t=86205

Take care

Paul

[xHeart]

Personally I would buy my own set of plugs/coilpacks and a thermostat and start over.

CONCUR!
OP is better off with a trade-in for newer vehicle if not a DIYer.

[mrbrian200]

Stay away from that shop, they ripped you off BIG time.

For the 6-cyl engine, even 6 spark plugs and 6 coils do NOT cost more than $300!
For example (rmeuropean.com):
- Volvo Ignition Coil $70/each.
- Bremi Ignition Coil $36/each.

You need to find an independent and honest shop that knows something about Volvo.

I concur. Coils and Plugs should have been around 2 hours labor + parts or around $600 total including diagnostic. Looks like they 'padded'' the bill by about $1000. You'll get a better 'deal' at a dealer. This level of dishonesty usually goes in hand with cheapo parts marked up to dealer price +. RUN

[AndyG]

Is it possible that the faulty coil and incomplete spark would have sent fuel back into the catalyst?

[precopster]

The first thing that happens when a coilpack fails is you get a rotten egg smell from the exhaust. I always have an ELM327 plugged into the OBDII port coupled with the Torque App so if a coilpack fails I pull the corresponding injector plug to prevent un-burned fuel going through.

At $5 each for a cheap ELM327 from China I have one permanently fitted on all our vehicles. They can read and reset transmission codes too.

How long did you drive for with the vibrating/jerking engine?

[AndyG]

I drove it about 2 miles after engine vibration (just enough to get to the office), then had it towed. There was no rotten egg smell, or any other smell. Since the cheapest option is trying CataClean, i’m going to try that today. If that doesn’t work, I’ll move on to pulling the thermostat, trying different plugs, etc.

[abscate]

You cat is fine, Andy. You need to really drive it hard with lots of fuel to damage a cat.

Just work on getting the misfire fixed and it will be fine. Pull plugs on weekend and lets see what they put in.