sacman

I'm due for another Smog check in California and i have some intermittent misfires across several cylinders. Could I clear them without clearing the readiness status? I do have an Actron CP9185 scanner but I'm hesitant on erasing them. Two years ago I had to spend $300 to get the readiness code reset after 6 tries of the drive cycles without any success because of battery replacement. Has anyone done this before? Thanks.

QN

wallra

your not going to be able to clear misfire codes without having to reset readiness. If your check engine light is off you will pass smog. the emission machine does not see trouble codes. It's only checking readiness

sacman

Thanks for the prompt response and that is what I'm afraid. My CEL is on because of this.

QN

pp000830

Yes if you eliminate the cause of the misfire codes I believe the misfire codes will clear themselves over a certain number of restarts and no reset of the readiness codes will be needed.

pp000830

+1

pp000830

If you get random misfire codes across several cylinders it in many cases is a good size vacuum leak that should be easily identified. Beyond this, a fouled rotor or distributor cap or a loose distributor cap can cause this issue. Both items easily checked by removing a cap and looking for carbon tracks inside of it. A cap with two or three years of use can throw a misfire code. Also, I would check your distributor belt and ignition modules as well by pulling the center wire from the cap of one of your distributors and see if your car starts, then replace the center wire and unplug the center wire on the other cap and see if the engine runs. If it starts at all in both cases the belt is in place and both of your ignition modules are working.

Her is some info on the 993 misfire codes:
All misfire codes are "Signal implausible / Implausible Component Section / Malfunction"

Check engine light legend for below faults
2 MIL is on and a previous Freeze Frame is overridden
3 MIL is blinking and a previous Freeze Frame is overridden (a serious problem immediately shut off the engine and resolve the issue)

Misfire fault code list:
Read code, Description, PCodes, MIL LIght Status
62, Misfire emission related, P0300, 2
75 Misfire, damaging to TWC P0300 3
50 Misfire, cylinder 1, emission related P0301 2
63 Misfire, cylinder 1, damaging to TWC P0301 3
51 Misfire, cylinder 2, emission related P0302 2
64 Misfire, cylinder 2, damaging to TWC P0302 3
52 Misfire, cylinder 3, emission related P0303 2
65 Misfire, cylinder 3, damaging to TWC P0303 3
53 Misfire, cylinder 4, emission related P0304 2
66 Misfire, cylinder 4, damaging to TWC P0304 3
54 Misfire, cylinder 5, emission related P0305 2
67 Misfire, cylinder 5, damaging to TWC P0305 3
55 Misfire, cylinder 6, emission related P0306 2
68 Misfire, cylinder 6, damaging to TWC P0306 3

sacman

All rotors, distributors belts, plugs and wires have been replaced. What are the possible area of vacuum leak?

QN

pp000830

A common leak is from one of the vacuum actuators. If you purchase a short length of hose that slips over the hose nipple on each actuator and you can draw air with your mouth. If the actuator has a leak you will be able to draw air and the actuator needs to be replaced. The Variorum cars have 4 in the engine compartment and one behind the Climate Control unit in the dash. The non-varioram 1995 has fewer. The one in the dash is easiest to test as it makes a clunk when you press the recirculation button on the CCU. The others can also be tested as they go through an actuation cycle when the ignition is first turned on. There are several threads on the subject here. Also, a good test as to if your car is building and retaining vacuum is to run the engine for a little while, turn the ignition off then back on w/o starting the engine and press the recirculation button on the CCU. If vacuum is available you will hear the actuator inside the dash cycle.
Beyond this, a technician can smoke test the entire system.
Also consider adding an injector cleaner such as Techron to two consecutive tanks of fuel. My experience is that it can clean minor injector related issues that may be contributing to an errant misfire..

pp000830

There is only one distributor belt internal to the dual distributor. Is this what you speak of? Even so it should be tested as it can fail with no external evidence.

nine9six

I respectfully disagree...

Maybe not external evidence visually, but the car will not be running right in a very noticeable manner and will be significantly down on power.

Pulling the primary coil wire is a simple method to test if the distributor belt which drives the secondary distributor, is intact or broken. If broken, the car will not start.

samurai_k

Do bad spark plug wires also cause misfire codes?

sacman

So I started checking for air leak today by checking all the rubber hoses. I also replaced all 3 belts with Porsche branded and actually used a belt tension gauge. The old belts also porsche branded but they were on the car since I bought them. I've been carrying a brand new set of belts for emergency but I thought, heck, why not replace them all. As soon as I restarted the car and to my surprise, the CEL went away. I have no explanation for it and I'll take the car to the smog station tomorrow to see if it makes it without CEL. I'll keep everyone posted on the outcome. Wish me luck, guys.

QN

pp000830

The system counts the number of misfires over a period of time/engine cycles. If the number falls below a preset limit the light goes out and the OBD Code clears. However, it may return if it goes over the limit again.
Andy

wallra

If the cell went out go get it inspected now you will pass

sacman

You are right. The CEL comes back on my way to the smog check station and now i'm tempted to clear the code using the GoPoint BT ODBII reader now. I'm at lost now. All belts (distributor and engine) were replaced, new plugs, new wires, new air filter, obvious air hoses checked. I have until 7/16 to get the car smogged.

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