Experts Please Help: 99 V70 Wiring/emissions/ecu

[GTGLT]

First things first: 1999 V70 GLT (LPT) with ~110K miles; recent timing belt, water pump, O2 sensors.

SORRY FOR THE LONG POST BUT WANTED TO BE THOROUGH.

I purchased the V70 April 2007 and this problem first began in late May.

It first showed up as CEL with code P0134 (front O2 sensor) but the car was running completely normal.

The previous owner had both O2 sensors replaced at Volvo dealer (OEM parts) (I assume in order to sell without CEL).

The car slowly developed a rough idle and then came the black smoke. By now a P1171 code (fuel trim) was tripped. The cars behavior seemed completely random (hot, cold, relaxed driving, spirited driving, A/C, all made no difference). Sometimes it would run completely normal, other times it would smoke (like a freight train), lurch forward, almost die, etc.

After weeks of searching these forums I replaced all vacuum hoses (silicone), fittings, clamps, and check valves. I also cleaned the MAF with MAF cleaner, and cleaned the MAF wiring harness and the O2 sensor harnesses (confirming secure connection). I would clear the codes with a scanner after each attempt and they would come back.

So I gave up and took it to my local Volvo experts (Atlanta Volvo Service in Suwannee, GA). They found that the O2 sensor was showing NO modulation at all. After a day or so of poking around they said they cleaned the MAF and the "preheat circuit" for the front O2 sensor. (Can't remember exactly but he said it is known to actually wick oil into the wiring). They didn't think it was fixed but couldn't get the car to misbehave again so I came to get it. The next day the light was back (along with rough idle, smoke, etc.)

On their second go around they had it for 3-4 days and tested in all different conditions (hot, cold, etc.). They ran it over and over with VADIS hooked up and after 4 days they called and said they thought it to either be the main wiring harness or the ECU . Both of which will be very expensive to replace. He said they were getting crazy readings from all over the place. I can't remember the units but he said the AMM would read somewhere around 35-40 when 13-18 is normal (which is clearly not possible). And as this was happening the O2 sensor would be reading normal, while black smoke was pouring out the back and the car is surging like crazy. They swapped the front O2 sensor just to check, and the results were the same.

So I took it back and have not had time or money to fix it, so I have been cruising around for the summer with this random problem. When I say random I mean probably close to 20/40/40: running good/running decent/running terrible. And more recently it has become more like 10/20/70, and there have been 3 occasions when it has died at stops. Another note: once up to highway speeds it always seems to run fine, all of the problems are at city street speeds (0-30 mph) and idle at stops is the absolute worst.

Yet another note: I have very rarely noticed the brakes act up when the engine does. The pedal becomes soft and pulsates; sometimes braking power drops to almost 20-30% and is very dangerous.

Thank you so much for reading all of this and helping in any way. I am a college student (tight budget) and bought this car mainly for summer use, but have to get it running again.

[Dmsee]

You from Atlanta

Where exactly at?

We might work something out

[GTGLT]

You from Atlanta

Where exactly at?

We might work something out

Midtown: Peachtree St.

[GTGLT]

Over 20,000 members and nobody has any advise?

[GTGLT]

Can I move this to the 1998 and prior? Maybe somebody there can help?

[terrytcl]

check the grounds.

i've seen something like this in the past. check all of your grounds, make sure that they are free of corrosion.

i'd also check for a pinched wire on the harness somewhere. it could be shorting or intermitent shorting.

make sure all of your grounds are tight, clean, and secure.

[MrWinkey]

Over 20,000 members and nobody has any advise?

Have plenty of advise here? Just not giving my cherry up to 6 newbie posts?

Search a bit harder and perhaps you will find what your looking for?

These P codes have been covered in detail many times before?

[GTGLT]

Have plenty of advise here? Just not giving my cherry up to 6 newbie posts?

Search a bit harder and perhaps you will find what your looking for?

These P codes have been covered in detail many times before?

I have searched for 3 months. Everybody either has 1. vacuum leak, 2. bad O2 sensor, 3. bad MAF and/or harness problems. I have tried to PM the people that have had similar problems with no help. This is not the usual problem. The vehicle will no longer run. I have 6 posts because I bought the car in April and have been searching, not posting (Which is no indication of automotive knowledge/experience and should have no bearing on your offering of help).

Also another thing about searching: why is it limited to more than 3 characters when everyone in this forum uses acronym after acronym?

[GTGLT]

check the grounds.

i've seen something like this in the past. check all of your grounds, make sure that they are free of corrosion.

i'd also check for a pinched wire on the harness somewhere. it could be shorting or intermitent shorting.

make sure all of your grounds are tight, clean, and secure.

Thanks, I will take a look this weekend. So you would lean more towards grounds/harness than ECU? My gut says a pinched wire somewhere in that wonderful wiring job Volvo did. This is my first Volvo and after looking at the design, I have been very disappointed. SO many things look like an afterthought, or were never thought out in the first place. Anybody else here feel this?

[MrWinkey]

OK if your 100% sure you have no vacuum leaks. Then I would say you need and AMM(MAF) . Especially considering your rough idle and smoke. Cleaning doesn't always work and actually I have never cleaned one for a code related incident.