Voltage to Mass Air Flow sensor on 99 V70XC

[warcraftjunkie]

Took the battery out and took it to both Autozone and O'Reilly Auto parts. Said the battery is toast. In fact the battery is 8 years old. I'm surprised it has lasted this long... volvo branded battery. I'll be replacing that tomorrow... but will continue to make sure all electrical delivery is healthy, otherwise I know my car will be eating that battery as well.

With that said, is it possible that a battery that is bad could be causing all those codes, and the rough running engine and poor idle? I get that an alternator can do that, but once the car is running, doesn't the juice come from the alternator... not the battery?

[warcraftjunkie]

Ok, put a new battery in and no surprise that there's no improvement. I was able to get a few more pieces that may just make a tougher puzzle.. or provide those missing bits you guys might need.

When I turned off the engine, I could hear a whine and a high pitched buzzing noise coming from under the hood. After about 5 seconds the whine ceased. This noise was coming from the throttle body from best I could tell. The high pitched buzzing noise continued and I honestly couldn't pin point where it was coming from. Some I almost think that it was coming from the rear of the engine bay near the firewall... but honestly I'm not 100% certain. I tried for about 3 minutes to find the source of the noise with no luck.... at this point I disconnected the negative terminal from the battery and that instantly killed the noise (of course). Next I started the engine up again and after about 1 minute I turned it off again... same combo of noises. This time instead of disconnecting the power, I simply turned the key back from the first position to on and then back to off. This caused the high pitched buzzing to stop.

As you may have read earlier in this LONG thread, I've suspected there's a wiring/electrical issue that's aggravated when I go over bumps. To test this I started up the engine and let it idle for a few minutes. While it was running rough I pushed down on the front driver side of the car and this caused absolutely no change in the performance. I moved over to the passenger side and mashed the car downward and sure enough, it caused the RPM's to stumble. I was able to get this to repeat several times by pushing down hard on that side.

I read in a different thread that someone had kinda the same issues I'm having and they were corrected by adjusting the ground that's beneath the ECU box.

The mystery continues....

[warcraftjunkie]

Ok, another test with new battery in.

Connected voltmeter to Pos and Neg terminals, fired up the engine and was getting about 13.45 v. Reved engine up to 2000 RPMs and the Volts stayed the same. Turned on seat heaters, defrost, cabin fan and headlights and the volts dropped down to 12.2. I could play with the accessories and see that they had a direct impact on the voltage passing between Pos and Neg.

[warcraftjunkie]

limped the car back to autozone and did the alternator test with it in the vehicle. Reported in as producing 39.75 amps. Looks like next weekend I'll be taking it out and doing the more accurate test.

[warcraftjunkie]

Ok, new rebuilt Bosch alternator in my car. Rebuilt locally at a trusted shop. Anyway, once it was put back in the idle was more steady,however when trying to accelerate it still shuddered and had issues. I disconnected the MAF and it all went away. So it seems that I had a bad battery, bad alternator, and most likely those two caused the MAF to go bad. I'll run it for a day or two with the MAF disconnected while I source a new one. Only error codes I'm getting now are P0236, P0237, and of course the one for having the MAF disconnected. I'm assuming the turbo boost error codes are related to not having the MAF plugged in. Is that a safe assumption?

[warcraftjunkie]

Put in a new MAP sensor to try to address the P0236 and P0237 codes. Still waiting on the MAF sensor to arrive. Car is still idling a bit rough at first start but then settles into a groove. It still feels like it's missing the turbo because when I throttle it real hard I don't feel that boost, but the transmission just stays in lower gear longer to facilitate the oomph I'm requesting.

Once I get the MAF installed I'll update with results.

[warcraftjunkie]

Ok, put new MAF in the car and it's as though I just choked it! The car runs rough and will not get above 2000RPM. The fuel indicator says I'm getting 2 miles to the gallon. Needless to say I immediately pulled that plug and the engine returned to idle and normal acceleration.

I suppose its possible that I got a bad sensor. Any thoughts? when I get home from work, I'm going to put the old sensor back on and test the difference. The old one didn't choke the car quite like this, but I could definitely tell that the car ran better when it was unplugged as well.