2006 S60 - Chasing a Gremlin: Coils, Throttle, Transmission, Battery or Something Else?

[shilocase]

I've been chasing a gremlin for some time. There are not many Volvo mechanics around here and the dealer knows that and charges an arm and a leg for service.

This hesitation can be described as ... during acceleration, the power cuts out or is muted. When going slower, it'll feels like, even though it's an automatic, the clutch is being rolled out and sometimes followed up by a hard punch. This has already resulted in a broken, front-right engine mount. The crazy thing is, in the morning after sitting overnight (cooler - longer not sure), it runs great but towards the end of the day it runs like crap. Next starts all over.

It started with minor intermittent hesitation during acceleration so I changed the spark plugs. Seemed to fix the issue for a couple months but it started up again and it felt like something was up with the transmission so I had a specialist look at it and he said the transmission was perfectly fine. Symptoms lead me to believe it was either the coils or the throttle body so I changed the easier of them, the coils as well as wrapping all the wiring to prevent any shorts against the engine block. That seemed to help for a few weeks but then it started again, same hesitation like a clutch rolling out followed by a knock or punch, so I replaced the throttle with a used one claiming I didn't need to have the dealer re-program it with my serial, that it was only necessary for new ones (true or not?). That seemed to work for a few more weeks. It started back up and so I found a mechanic who ran a variety of diagnostics saying four of the five coils were bad, low voltage on a number of items and that I needed to replace the battery with at least 750 amps so I got one with 900. Immediately, it was the best it had been before it all began ... three days later it started acting back up. I took it back to the mechanic and he scanned it again saying no errors or codes. I can pay $50-100 for a diagnostic not guaranteeing he'll find what it is.

Any suggestions? An exorcism? Holy Water?

[oragex]

The mechanic found 4 bad coils?? Sounds like a corner of the street garage

Do you get any lights on the dash board when this happens? How many miles on the car and is it the 5 speed transmission or the 6 speed with manual shifting?

[shilocase]

Hi Oragex and thank you for your response,

The mechanic ran a report that showed a variety of low-voltage errors and had a diagram with five circles with the center circle being the only one showing with a "good" reading. I have since replaced all four coils and the battery and the issues are slowly coming back. I'm beginning to think it's the computer going bad.

There are no lights on the dashboards. I've been hoping for a "check engine" light so I can get some code to work with. I took the car back to the mechanic two weeks ago and they did the same kind of scan an AutoZone can do and found nothing. I asked about the report they had ran and printed out for me before and he said that cost $50. He ran it for free before. It's a five speed automatic with 178,000 miles on it.

How can I trouble shoot the computer?

[oragex]

I remember 2 or 3 people having weird electric issues with 2005-2007, can't remember the solution though.

I'd make sure the alternator is charging properly, all cables to the alternator and battery have no crack or corrosion, all ground cables around the engine are in place and in good condition. Perhaps also check the condition of the alternator and a/c compressor pulleys. All these should take no more than 20 min and no money to inspect.

If the problem is the engine computer (ECM) located in the box just in front of the power steering reservoir, maybe have the two modules removed (absolutely disconnect the car battery). A special key is usually needed or like this
Look at each contact pin for corrosion. While there also make sure the little cooling fan turns easily - just blow on it it should keep turning a few seconds. Hopefully the modules are in good condition because replacing these is too expensive.

Other things that come to mind are the injectors, and also the cables that run to them along with the cables to the ignition coils. These become brittle and are exposed to high temperatures and sometimes become crushed under the top engine cover.

[shilocase]

Wow! Oragex - thank you! I'll run through these and report back.

[mrbrian200]

The throttle body on the '06 is the Bosch type, it's design is relatively simple. Replacing does not require programming, but merely a ECU reset so that it adapts to the new throttle body to properly control idle speed. I believe without a reset the ECU still adapts, but just takes a little longer.

You probably want to start out by checking the battery feeds to the CEM (Two larger red wires on a single plug), trace for voltage drops through these wires, across connector 54/40D in the trunk below the REM on the left side, the fusable links (small fuse box next to the battery) through to the battery (red wire that bolts to the + battery terminal. I would also check the CEM ground terminals that bolt to the chassis underneath the LH plastic trim at the footwell. On mine one of the terminal crimps on one of these wires at the CEM had developed resistance and was fixed by unseating the terminals from the connector and soldering over the wire crimp.

My symptoms weren't as severe but as the electrical connection gets worse I would imagine similar behavior to a overheated/failing CEM which includes herky jerky drivetrain behavior. I was afraid for awhile I was going to have to send my CEM in for rebuild but decided to apply some due diligence regarding the power/grounds to it first. Which would seem prudent in you case as well.

[shilocase]

Thank you MrBrian200, I will check those out.

To follow up with Oragex. Here's what I've done so far ... I cleaned all the ground cables with a wire brush. Checked the connections to the Alternator and they look fine. The serpentine belt needs to be changed with cracks - that's on the to do list in the next few days. I'll have a better look at the alternator as well. I will also check the A/C compressor pulleys at that time. All ignitions coils are sparking good.

After checking the ECM and cleaning the area out. There was no fan. Just a unit that spiraled the air flow around the outer circle with a couple contacts in the center. The airflow was weak and came through the firewall as if from the air conditioner (confirm please).

Here's a link to an image: http://i.ebayimg.com/thumbs/images/g/tD ... s-l225.jpg

I did a little research on both modules. If I understand correctly, one of them is for the transmission. One article I read said that disconnecting the battery alone does not fully reset the transmission module saying that I needed to remove both +/- cables from the battery and touching them away from the battery posts for 10 minutes to fully discharge the transmission module. I did that on Sunday. Surprisingly, it fixed the issue for three days. What changed? Hot day, I used the A/C yesterday and it starting acting up again. I discharged again over night and it worked great today but starting acting up again. I wonder if it's related to the A/C or if the transmission module is going bad. This time I have a better idea of what's going on. It feels like the clutch plate timing is off. It shifts down from 3-2 and 2-1 hard and when I accelerate while in any of those gears, it feels like it rolls out and then grabs hard.

I'll do the other checks this weekend and report back.

Thanks!

[abscate]

What's the history on the transmission? Last time ATF and filter was changed?

The electronic modules seldom go bad, it's much more likely the trans has a valve body problem.

[shilocase]

ATF and Filter or changed out about 3 to 4 years ago.

[shilocase]

The mileage was around 120,000, and it is now 186,000.