-01 C70 2.0t misfire, possible ECM failure?

MarcusV · Post by **MarcusV** » 01 Jun 2014, 01:59

Hi everyone, my new convertible is pestering me with misfires in cylinders 1&2. (They are both completely dead) The car was standing still for six months before I purchased it and it worked fine before I tested it so the previous owner was able to drive it out from the garage. So far I`ve replaced the following:

-All 5 new coils (Bosch)
-All spark plugs twice (First with Bosch, second with original Volvo)
-New large Bosch battery to replace the 10 year old one.

Still gives me the usual codes:
P1113 Outside temperature sensor
P1350 Ignition Coil 1 primary
P1352 Ignition coil 2 primary
P0300 Random misfire

I took the car to a competent Volvo specialist last week and first he was confident that there should`nt be many options left. The next few days were radio silence until I visited the shop just to hear that the most evident option is a failed ECM and the original costs 1500 dollars.. First of all its very rare in Volvos that this happens. I did manage to get a second hand ECM for 150 bucks and found a specialist who is going to clone the immobilizer from my old ECM to the new, he told me that sometimes the processor fails in Bosch ECU:s resulting in misfires. Any thoughts on this issue? I should be having the job done next week. Thanks for your advice!

Post by **abscate** » 01 Jun 2014, 03:40

Compression test on cylinder number 1and2 to rule out major problems

Have a good look at wiring to the coils for 1,2. Trace back as far as you can looking for shorts especially still cover pinch points.

ECM failures are very rare.

MarcusV · Post by **MarcusV** » 01 Jun 2014, 05:13

I did check the wiring and found one slightly pinched wire which I soldered and insulated properly. Just to make sure, I also did a new connector to the negative wire of the first coils. The shop tells me its 90% sure that its an ecu-related problem, they have already measured the wiring and tell me its ok. The resistance of coils 1-2 was different than the others when measured from the connector of the coil.
The original ECM is chipped somehow and was definitely opened so it could be possible that this procedure has had some effect on the case. I havent checked the compressions but got to mention that the cylinders are completely dark with zero spark..

Post by **abscate** » 01 Jun 2014, 05:35

When these cars sit they can develop lawn mower syndrome which is a compression failure that is easily fixed with some oil into the cylinders.

It is now common enough to be googleable

MarcusV · Post by **MarcusV** » 01 Jun 2014, 05:57

Cheers very much, sounds logical. Though I wonder would it make the spark disappear too when lacking compression?

The best explanation for the "lawnmower syndrome" is that the rush of petrol washes the oil away from the rings and the tolerances on these cars is so close that it relies on a film of oil around the rings to achieve compression.

Post by **precopster** » 02 Jun 2014, 14:30

When you say the ECU is chipped you don't mean there's a small chunk missing out of it do you?

When my '99 Denso V70 was purchased it would drop spark after a certain number of crank attempts. According to Jimmy this is normal for the 99 Densos. Could it be that you're not checking spark prior to cranking but after repeated attempts?

MarcusV · Post by **MarcusV** » 02 Jun 2014, 22:05

Yeah, fortunately nothing so evident as a missing piece

Actually that was the diagnosis of the shop that it completely dark so I`m not sure about that. Tomorrow is the day, the ECM:s were delivered yesterday and the "ECM-guru" told me he`s sending them back soon so I`m getting them installed, I sincerely hope that it resolves the issue as my daily driver(Alfa GT) keeps blowing the fuel pump fuse filling this summer with electronic problems

MarcusV · Post by **MarcusV** » 05 Jun 2014, 10:49

ECM replaced to an used unit with immobilizer cloning. Car runs like a dream, cheers everyone

And remember this everyone, it can fail but it can be replaced if you find someone with skill and equipment!

Post by **abscate** » 05 Jun 2014, 12:44

The original ECM is chipped somehow and was definitely opened so it could be possible that this procedure has had some effect on the case.

I missed this earlier. If you or PO hasn't opened the ECU (or ECM) it probably isn't the cause of bad running.

MarcusV · Post by **MarcusV** » 06 Jun 2014, 09:18

Yeah, have`nt examined the malfunctional ECM yet, would be nice to know why it went bad.. Though the most important thing now is that the car is a joy to drive, finally