History:

This is the mother-in-law's car, an 89 B230 with Bosch Fuel and ignition system. It's got about 135-140,000 and starting to display some aging. Yesterday she was driving it and, as she says, "it started to chug" (under throttle). She pulled to the side of the road and parked, not wanting to go further or try to return home and risk having it die at an inoportune time. It would idle just fine though.

I went out after work and drove it home. It ran fine, but the "Check Engine" light was illuminated. I pulled the codes and got the following (3):

2-3-1 Fuel trim (lambda control) too lean or too rich at part load

1-2-1 Faulty signal to/from Air Mass Meter

1-1-3 Fuel trim (lambda control) too lean or rich

I cleared the codes which extinguished the "Check Engine" light, drove the car again for about ten minutes which included all throttle settings, etc. No codes reappeared and it ran fine. Through all this though, I made some observations:

The engine temp guage doesn't work.

The clock doesn't work. (She says the clock quit working the last time it was at the local Volvo indy for oil change.)

Questions:

Without crawling clear under the car, I couldn't see the O2 sensor like I can on our 1990 Regina car. Where is it on the Bosch car?

Where are the engine temp sensors? (Both for the guage and for the CPU) They don't share the same sensor do they???

Is there any common components that can cause the clock and the temp guage to die? The fuel guage and all other guages/instruments seem to work OK.

Thanks for any comments/idea/help/offers to come fix it.

Temp guage and clock are unrelated to the problem. There is a separate coolant temp sensor for the ECU located on side of block under #3 input manifold runner, hard to see and get at, not part of the problem. A bad or flakey signal from the AMM is quite possible and that could cause the other codes relating to O2 sensor. I would check or better yet swap out the AMM as test. Intermittent problems can be tough to diagnose.
--
David Hunter

Chris,

Not sure what MIL means by "chugging." When the air mass meter died on my 240, the car would loose power, and then surge back to normal, loose power, surge again, etc. until I shut it off. It would restart and idle, but was not driveable.

The connection on the wire harness that goes to the air mass meter could be oxidized, loose or dirty. Or the air mass meter itself could be on its last legs. If the o2 sensor is not the culprit, the next time that this happens, pull to the side of the road, turn off the ignition and pull the lead to the AMM. Restart the car and see what happens. If the AMM is faulty, the car will be driveable, but only at low speeds, and will idle roughly, when it is disconnected. The computer, receiving no input from the AMM, defaults to a "limp home" mode and the engine is basically getting unmetered fuel.

I was prepared to do that when I went out to get the car last night, but it fired up and drove fine. I examined the AMM plug - It was well connected. I pulled it loose and reconnected it thinking the same thing you are. The contacts looked very clean as the boot is still in excellent shape. You never know though, it doesn't take much crud on a contact to cause problems. I may have helped it by just unplugging and replugging. I guess she'll just have to drive it and see if the chugging reappears. (I'm wondering as much as you are what "chugging" is exactly.)

Now if I could just figure out why there is no clock or temp guage action.

the o2 sensor is right before the catty on the 89 model its at an upward angel, when chris very bottom he didnt mean it actually stuck out he meant it was actually on the bottom of the exhust, but it actually is in a safe position.

As far as the gauges go, remove the cluster and make sure the plugs are snug on the back of the gauges.
The mechanic may have loosen them when he removed the cluster to reset the sevice light.

I thought about something like that, but the light is reset through the rubber plug in the face.

02 sensor on Bosch FI car should be directly underneath (hangs straight down)so you will need to crawl under to see it.

Thanks. I'll check it out. (Sounds rather vulnerable to damage in that position.)