So, my 2000 C70 convertible has been running fine for the most part. My wife put a tank of 87 octane fuel in it, and I could have sworn it was a little sluggish. I put 93 in it, and it felt OK, as far as I could tell.

On our way out to dinner last night, I hit a pretty deep pothole, and the odometer/trip odometer went to dashes instead of digits. When we came out of the restaurant, the car ran rough, the ABS and Brake lights were on, and a triangular yellow light popped on as well...traction control? Any way, it ran like crap, stumbled off idle then seemed OK at higher RPMS, and the tach and speedometer were not moving.

My thought is that something got popped loose, but what? ANy thoughts on where to begin my diagnosis?

 

Its quite possible hitting the pothole put the ABS control module out - its a circuit board that is prone to having its solder joints crack. There are services that will test/repair the board. Also to note there's a speed sensor that feeds into the ABS module which could also account for unexpected behavior. Google Volvo ABS control module repair and see if the articles show symptoms consistent with what your car is showing.

 

I would also re-seat the ECM module/modules. My 98 has 2 side by side.

 

Stupid car drove fine most of the last two days, only light on was the SRS, which is always on. Then it stumbled for just a second or two, under light acceleration, and went back to running fine.

The ABS and Brake lights came back on, but it still ran OK, for the most part. Then, the odometer went back to -------- and it stumbled once. Then the tach and speedo flatlined and it started acting up again.

I am painting bathrooms this weekend, but I will look at the modules and see if there is anything jostled loose under the hood.

The ignition switch is in the process of dying too...sometimes it thinks the key is still in the ignition when it isn't, and sometimes it doesn't want to release the key without jiggling it.

Thankfully this is a 4th car beater/summer toy for us, so I can let it sit for a day or two...I don't need it to get to work Monday morning.

 

Well, bought an ABS module from abs midwest, had my mechanic install the dumb thing because I couldn't get my fat fingers down there to change it out...just picked up the car, and it's doing the same darn thing...drives fine for maybe 10-15 minutes, does one little, almost imperceptible stumble occasionally, then ABS and BRAKE lights come on, then a few minutes later the odometer does to ------- and the tach and speedo needles drop. Today the drive-ability didn't get any worse, it never really wanted to die off-idle, and the RPM's were not audibly fluctuating like they were prior to the ABS module replacement. What am I missing here? What's my next step?

If I turn the key off and restart, the lights disappear and all is well for some period of time...

 

Popped the battery out, had it tested...good, but showing a low charge. Bought a multimeter, and all is well, with one noteworthy exception...13.88 volts at idle, 13.7 volts at 2000 RPMS...

I am starting to think I have a charging issue, most likely an alternator.

Anyone care to chime in?

 

I haven't touched the car in a couple of months...parked safely in the garage. I will dig back into it over the weekend and see what the heck is going on. Meanwhile my '97 V90 wagon has been trucking along, working perfectly, thank heaven!

 

...And the weirdness continues...bought a jump box, didn't have time to properly charge it, so I left the jump box plugged into the wall, jumped the car to get it out of the garage to get to the Christmas tree...as long as the jumpbox is attached it runs just fine. Within a couple of minutes of disconnecting it, as it gets up to operating temp, the lights come on and the car runs like crap. Should I surmise that the alternator is not working properly? I let it run with the jump box attached, for 40 minutes, not a stumble or anything else.
And before anyone tells me to get codes pulled at the dealer, they are 40 miles away and try to crack my skull every time I go there...the parts counter guy is cool but the rest of them are thieves...and the same company owns both local stealerships.

 

Here's a few tests to try to determine if you have an alternator or battery problem using a simple volt meter (even a cheap Radio Shack unit will work):

1) engine off, measure voltage across the battery terminals - should be 12.6V or so. If its below this your battery may need replacing.

2) start car, measure voltage across battery terminals - should be 14-14.5V across the terminals. If you still see 12V you probably have a bad voltage regulator or alternator. If you see a high number (say 15V+, you have a bad voltage regulator which can overcharge a battery and mess with your electronics).

3) add electric loads - blower, rear defrost, headlights etc. measure voltage - should remain mid high 13s. If the car can't maintain 13V, it suggests the battery isn't charging.

4) let car run and when it starts to run lousy, measure voltage across battery... Also feel the battery cables - if they are getting hot it means you have a bad connection (resistance will throw off heat) and may need to clean the terminals. Also feel around for the various relays (ie fuel pump, ignition/injector - could be up by the radiator)

 

Most auto parts stores will check your complete charging system, no load and under load for free, including Batteries and Bulbs, used to be Batteries Plus. In USA.

 

I recommend making voltage tests accurately yourself.


If the system is putting out 14.5 volts, that's enough. If you want to measure the difference between jump box "on" and jump box "off" then you can measure that. I always say half of life's problems require a volt meter to solve.

 

I did my own testing, and even at 2000 RPMs with no load (a/c off, etc) it never gets above 13.8 volts. I haven't taken the time to really delve into this but surely that can't be good...wich the damn alternator was easier to get to...

On the same subject, is there any reason to get a battery from the dealer instead of an aftermarket equivalent? I have a wholesale parts account so dealer parts aren't quite as horrible as they would be otherwise...