I am working on my wife's 1998 Volvo V70 XC station wagon, Cannondale Edition, and it's giving me fits..
I was a mechanic for about a decade, and I did a lot of driveability repair-but almost exclusively american cars. We had an excellent Volvo place near our shop, and we sent the Volvo stuff to them. That was in Salt lake, in the late 1990s. Now we live just outside Seattle, Washington. Sadly, Herm's Volvo in SLC, UT is no longer an option
Now, I have her car here, and it has about 113K miles on it. Before this, it has never given a day's trouble. We are the third owners, this car has lived in Seattle all its life, and was bought new at Ravenna Volvo. The emissions label is missing, so I don't know if it is fed or CA emissions, but it has the turbo option, AWD, automatic, and has a distributor ignition versus coil on plug.
It started out as running severely rich, just spewing black smoke out the tailpipe. It would somewhat run if you mashed the gas, but it barely made it home. I have an Innova OBD II scan tool, which seems to correctly negotiate the ISO 9141 protocol and get codes and live data from the computer. At that time I plugged in the scanner, and no codes were given except for an O2 sensor code, the front sensor. That kinda made sense, because I know the turbo's oil seal leaks too much oil out the exhaust side, and could have been plugging up the sender. Still, a slow O2 sensor shouldn't make this much trouble..
I checked the fuel pressure and even while it was cutting out, it had about 37psi, which seemed about right. It also held pressure for over an hour (before I disconnected the gauge). I thought that meant the regulator and injectors were OK for leakage, but just to be sure, I took the injectors out and had them flow tested and ultrasonically cleaned. They said one of them was kind of sticky but otherwise fine.
While there I replaced the plugs and wires, the wires were factory and the plugs were pretty gas fouled and needed it anyway. The oil cap had been leaking slightly and the area underneath the plastic cover was full of oil, so I cleaned that out. There was also an odd little rubber plug n the center of the valve cover, which seemed to plug an exhaust passage. I re-siliconed that back in too. The cap and rotor didn't look too bad so I cleaned them up, but now I will replace them anyway just to make sure.
Meanwhile, I got all this done and started it back up. Well, I tried, but was getting almost no spark at all. The injectors clicked, the primary circuit was triggering, so I unbolted the coil from the car-it started right up! I could touch the coil bracket to the body and make the car die every time. The coil was leaking secondary current through its metal core and out to the bracket/ground. Problem solved!
A used coil from Northern European auto wrecking was installed, and the car ran great
I gave it back to my wife, who drove it to work the next day. On the way home, it did the exact same thing it originally did, cutting out severely (it feels like ECM fuel cut, just nothing happening at all till the engine dies or comes close to it) alternating with running very rich. I tried unbolting the coil and running the car with it sitting on the plastic air cleaner housing, as before. No change this time.So this time, it throws a MAF sensor code, and the live data indicates the sensor isn't putting anything out, or else it held steady at 30 lbs/hr airflow-with the engine idling. This makes sense, and from what I hear it's a fairly common failure so I replace it. I start the car, clear the codes, it runs OK, so I test drive it. For about a mile, then it dies, then sort of restarts, then strands me and I have to walk home, but only half a mile. At that time, the check engine light comes right on.
I'm getting a code for the turbocharger solenoid A reading too low. That code is also intermittent. Then the MAF code returns, also intermittent. I'm starting to think wiring or ECU itself, but the Haynes manual is incomplete in its ECU wiring schematic. Volvos seem to be wired a lot different from the domestic cars I used to work on. So other than getting continuity from the ECU's harness ground pins to the engine block or to battery negative, and getting good voltage to the ECU harness terminals, I'm running out of stuff to check. Tonight, it was running bad (when it would run at all!) with no trouble codes at all, and no check engine light on either. It's getting more and more neurotic all the time!
The new wires I put in were NGK and not Bosch, but they were resistance wires like the originals. Hopefully that rules out electrical interference.
I also notice that when it is running bad, the temp sensor usually indicates the correct engine temp but once it read 201 degrees when I could put my hand on the block under the intake manifold and it was just warm to the touch. The IAT always has read correctly (between 37 and 50 degrees, it is winter here) and the O2 sensors always fluctuate quickly between .1 and .8 volts. The problem can happen cold or warm, by the way.
From the limited schematics I do have, it seems like the turbo wastegate solenoid (the wastegate itself functions correctly, btw) and the MAF sensor are on the same circuit, they seem to ground in a common way to the ECU.
Finally, I also notice that often when it dies completely, the computer scan tool loses communication with the car, like the ECU just shuts off completely.
Could this be in any way related to the coil issue? Could the whole ECU somehow be grounding through the power stage connector's ground circuit? As in, it shouldn't be exclusively doing so?
I joined this forum because I didn't know where else to ask. Sorry for the long post, I tried to include everything I could think of. Thanks for reading, hope someone here can help!
