2000, S70, GLT - Intermittent Stumble/Possible Misfire

Rbaratt · Post by **Rbaratt** » 10 Aug 2014, 11:53

I am hoping others on this forum may be able to shed some light with a recent issue with my 2000 S70. This vehicle just turned over 62,000 miles and other than replacing the MAF sensor this vehicle has been running well since I purchased it with 46,000 miles.

A couple of days ago I started the vehicle and drove a bout a half a mile and at a light I noticed and felt a bit of a stumble at idle. It did this every few seconds and aside from feeling this symptom I noticed the tach would also dip at the same time.

I was thinking engine misfire and that possibly I my have ignition wires that are breaking down. I take a look under the hood and to my surprise this vehicle is equipped with coil packs. I have never done a tune up on this vehicle so I was surprised to see that there were no wires. I checked for codes and found no codes had been set.

I proceeded to pull the coil packs and plugs to do a quick visual inspection. I did not see any obvious cracking or insulation breakdown with each coil pack. All spark plugs looked as though they had been firing normally.

I took another drive this morning and again after half mile at my first stop the stumbling/possible misfire was very prevalent at idle. I continued to drive and noted that I do not feel any misfiring under load. I noticed that the problem seems to get better after driving a while but its still there at idle, just less frequent than when I first start out.

Tomorrow I will get some new spark plugs. I have never changed them so I thought it might be a good idea to eliminate the plugs as a possible cause. Other than that I am not sure how to proceed. Any thoughts would be appreciated.

Rbaratt · Post by **Rbaratt** » 11 Aug 2014, 14:02

Decided not to change plugs, as they were done at 46,000 miles. They are OEM Volvo plugs and the gaps were all fine.

Post by **shaker_chi** » 11 Aug 2014, 14:21

I don't have a Volvo with coil packs, but that would be the next place I check. Also, if you were getting a true misfire your CEL would go on and if you had multiple misfires it would be flashing.

Rbaratt · Post by **Rbaratt** » 11 Aug 2014, 18:42

I took a look at the coil packs, and found some hairline cracks in the hard plastic but no signs of insulation breakdown in the rubber portion of the pack. As you mentioned I would think that I would get a code for misfires but as of yet no codes have been set.

I am beginning to think I am experiencing a throttle body issue, the ETM on these years are known for issues at around this mileage. I have the white label ETM on this car, and it looks like a PITA to remove and clean the ETM, however I may have no choice but to try this.

I have seen some videos on cleaning the ETM and a service (circuit solutions on Ebay or xeModex) either of these is an expensive repair for several hundred dollars. I now need to research more in depth the safest and best way to clean the ETM and I'm thinking of heading to the junk yard to extract a donor part to send to xeModex.

Not sure how to proceed but as usual any advice would be greatly appreciated.

Post by **abscate** » 12 Aug 2014, 08:30

Coils fail on both miles and time, jim replaced two of mine on my 2005 with only. 80k. The beauty of the ME7 system is that you get rid of a lot of things to troubleshoot. The downside is the components are expensive.

I don't think you can rely on a CEL to flag a misfiring cylinder, based on my reading experience here.

Did all the plugs look the same?

Rbaratt · Post by **Rbaratt** » 12 Aug 2014, 12:11

All plugs looked the same. No CEL or ETS lights. I may have to bring this to an Indy that has diagnostic equipment to isolate which cylinder. Do you think it could be the electronic throttle body?

Rbaratt · Post by **Rbaratt** » 13 Aug 2014, 17:10

Finally got a code, PO301, cylinder 1 misfire detected.

Post by **abscate** » 14 Aug 2014, 06:16

Aha!! Move coils 1 and 5 , keep driving and see if the misfire code moves.

But check the ground bolt (10mm) on coil 1 first, snug and tight

Rbaratt · Post by **Rbaratt** » 14 Aug 2014, 17:32

Swapped coil1 with 4, cleared code and took a drive, about 15 minutes later the CEL came on with code po304. Ordered a new Bosch coil from eeuro parts since I had a $25 coupon. With shipping it came to $41. So glad it's not the $500 ETM...hopefully I have a few more miles left in my white label ETM.

Reinie · Post by **Reinie** » 18 Aug 2014, 08:52

Sounds like you have a good diagnosis on the coil pack. FYI, the ETM went bad on my 1999 S70 which sent it into limp mode and the cruise control wouldn't work. I took it off and sent it to Xemodex for rebuilding. Shipping to Canada was a little weird. Re-installed without any software updates and works great. Cost $482.05 USD