Where Do I Start Looking?

If there is no check engine light, the likelihood of a code being stored is pretty low.

If you have 2 catalytic converters, then you probably have 4 O2 sensors - B1 S1, B2 S1, B1 S2, and B2 S2. In other words, a sensor before and after each catalytic hconverter.

If the catalytic converter is doing its job, the signal from the post-cat sensors should much flatter than the signals from the pre-cat sensors. If you look at the factory service manual under DTC P0430, it should show what the o2 sensor patterns should look like.

The cylinder misfire codes could be caused by ignition system misfires or from an over-lean fuel mixture. If you have aftermarket ignition parts, consider using OEM next time you change them because I have seen some aftermarket ignition parts cause problems. Some aftermarket ignition parts are fine and some cause problems. I have not been able to detect a pattern so I recommend OEM ignition parts. A lean-misfire usually brings up other DTC's unless the pre-cat sensors are beginning to fail, but your scan seems to indicate that they are OK.

As far as what caused the car to stall, I would check fuel pressure with a fuel pressure gauge. A fuel pump or fuel pressure regulator that is not up to stuff or a clogged fuel filter might not deliver sufficient fuel pressure to keep the engine running and they would not necessarily set a check engine light. I would check the fuel pump, fuel pressure regulator, and fuel filter in that order. A failing fuel pressure regulator often causes long cranking during cold starts, which you did not mention, and a fuel filter that is clogged enough to starve the engine for fuel would probably not allow a re-start, leaving the fuel pump as a more likely culprit.

Ray,

The "funny" sensor is the one after the catalytic converter. Only one converter on the car. The manual does say that the patterns should look calmer.

I'll start looking at the fuel delivery system (but I have to buy the tools first). I got this car from my brother-in-law about 6 months ago so I really don't know the service history as he also bought it used. Only things I've done on it is timing belt, waterpump, crank seal, four shocks and a lot of touch up paint (Colorado car, lots of gravel there in the winter.)

There is no problem with power of the engine and it easily runs 80 MPH. Car starts just fine, no long cranking. But I'll check fuel system performance (any excuse to buy more tools!!)

I'll probably dive into the MAF meter, IAC valve and throttle body and see how dirty it is and change the fuel filter this weekend. Thanks for the ideas Ray, at least I have a starting point now.

Paul.

"Ray O" wrote

If the after-cat sensor is active with a pattern like the pre-cat sensor, I would imagine that you get have DTC P0420 because the cat is failing. The cat may be on its way out but not bad enough to set a code yet.

No long cranking tends to rule out the fuel pressure regulator and fuel filter but the fuel pump can be bad.

If the car idles OK, the IAC valve is probably OK.

If the throttle pedal sticks in the closed position, then the throttle plate (butterfly plate) in the throttle body may be gummed up and need cleaning with carb cleaner. A gummed up throttle body will not cause the engine to stall.

If you do not have a volt-ohm meter, it would be a good investment.

Good luck!

I don't know for sure on yours, but I do come across a similar fault on Vauxhalls in the uk. 9 times out of ten it is the crank position sensor.

mrcheerful

I'll have to check the wiring on that sensor. It was in the way a lot when I changed the water pump and timing belt. I may have pulled on it too much.

Thanks, Paul.

The after-cat sensor is the same pattern but much less amplitude. I'll watch it though. Maybe I'll run the car around with the OBD laptop attached and record the patterns with different RPM's and load.

Good to know!! Once I get the fuel pressure gauge I can check the whole system out.

Electrical gear I have. Digital and analog VOM, ampmeters, etc. I'm better at electrical problems than mechnical but I like working on both.

Thanks for the help Ray!!

Paul.

Similar pattern but much less amplitute is good because that means that the cat is cleaning up the nasties. If the patterns match frequency and amplitude - in other words, the same signal, then the cat is not working.

You can probably diagnose 95% of the electrical components in a car with a good digital meter, and if you know how to use it, even better!

The crank position sensor that someone mentioned is worth checking out, although I would imagine that a problem in that circuit would set a MIL and DTC.

In terms of thinking about problems that would not set a MIL, the fuel pump is a possibility.

Good luck!

BTW, what kind of OBD laptop are you using and where did you get it?

I use an old laptop and plug in an adapter into the OBDII connection. It allows me to see plots of O2 and several other systems. It also will log data and save it for review. Viewing and resetting trouble codes is easy. I think it only reads the power train codes (Pxxxx).

The connecting cable came from OBDII Automotive Diagnostics

and the software and upgrades are free with the converter purchase (OBDII interface $83; CAN interface $77). He also sells the parts if you want to make it yourself and the electrical drawings/schematics are on his site for free. One work of caution though, the OBDII connection needs a serial port to plug into. The newer laptops do not come with a serial port anymore. That's why I use an old laptop. The older ones are readily available and are more bullet proof that the newer laptops (2 to 3 year life expectancy before hardware starts to fail on the high end units). Biggest problem with the old laptops is the batteries are old and don't hold a charge and I'm too cheap to buy new batteries.

The unit got a nice write up on

. There are some reviews of connecting cables at . Paul.

"Ray O" wrote

Thanks for the info! I have a couple of old laptops sitting around, maybe I can put them to better use than as a doorstop.

I'm not sure that I can justify another scanner, even though it is better than the one I have, especially since you can check just about everything out with a DVM, but maybe for the next go-around...