Running on 5 cylinders, running rich

[acolella76]

Took my car to an autocross the other day for a shakedown, and after two runs my car sounded like a Subaru. I let the engine idle and started pulling off plug wires. When I pulled plug wires 4&6, the engine died. I pulled the plugs out and 4&6 were fouled while the rest were fine, so I guess that's the reason for the misfire. I replaced the plugs with new ones and the misfire in 4 went away... so I'm assuming 4 is either fixed or just less rich than 6. What I want to know is what could cause just those two cylinders to run rich? I have confirmed that they are getting spark. All of my injectors were rebuilt last month, so I really hope they aren't malfunctioning for some reason! No intake leaks that I know of. I am trying to search, but so far I haven't really found anything useful.

[jlevie]

Paradoxically a lean condition in a cylinder can look like a rich condition. The partial misfire from the lean condition will leave a fuel smell and sooty black deposits.

In this case the first things I'd do if the parts are 10 or more year old would be to replace the ignition wires, distributor rotor, and cap with new OE parts and check the valve adjustments. I don't know what plugs you have, but the best will be NGK ZGR5A's.

If that fails to fix the problem, swap injectors around.

[acolella76]

The spark plugs are very wet. I did install sort of new plug wires and cap (rotor had normal wear) that I had lying around since I didn't have time to wait for parts. I guess I will go try a valve adjustment!

[FLG]

Could possibly be a stuck injector. At this age it's a good idea to have them cleaned at the very least or replaced completely.

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[LJ851]

At this age it's a good idea to have them cleaned at the very least or replaced completely.

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All of my injectors were rebuilt last month, so I really hope they aren't malfunctioning for some reason!

If you suspect an injector (a good possibility), swap the offending ones with 2 others and see if the problem moves with the injectors.

[FLG]

Sorry I wrote that on the fly.

As stated try moving em. I've had new injectors be bad.

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[acolella76]

Got around to swapping the injectors and the misfire followed the injector, so I am assuming the injector is stuck open. Beans.