running rough and rich only when warm.

[weedshoes]

It happens immediately after switching to closed loop mode. All through the rev range. I think I can hear the fuel injectors louder than normal. Car smells like fuel when I get out. Any guesses?

[bluptgm3]

O2 sensors, pre-catalytic converter are over 100K miles old but not throwing codes…yet?


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[weedshoes]

I did my o2 probably 6k miles ago. Could a bad camshaft sensor cause this?

I'm also getting a check engine light for 1222 rich mixture, but no code for faulty o2.

[bluptgm3]

I did my o2 probably 6k miles ago. Could a bad camshaft sensor cause this?

I'm also getting a check engine light for 1222 rich mixture, but no code for faulty o2.

What brand of sensor did you install?
Sounds like O2 sensor.


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[weedshoes]

The new sensor was a bosch less than a year ago. I guess i'll pick another one up though. Thanks for the input!

[bluptgm3]

Plugs and extenders - how old?


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[weedshoes]

Plugs have been in for fewer than 1500 miles. If by extenders you mean coil packs, they looked good. no idea how old.

[notMpowered]

Did you do all 4 O2 sensors when replaced?

[bluptgm3]

If by extenders you mean coil packs, they looked good. no idea how old.

Between the coil pack and the spark plug is a rubber boot that extends from the coil to the spark plug - coil extenders or spark plug extenders. These degrade and begin to ‘leak’ voltage as cracks develop. These need to be replaced periodically, they can cause rough running.

Did you do all 4 O2 sensors when replaced?

Only the fwd O2 sensors control mixture.
The post-cat O2 are ‘watch-dog’ sensors monitoring catalytic converter efficiency.

And an OBDI M50/S50 only has one each fwd and rear.




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[notMpowered]

I didn’t realize it was a 95 but I was aware about the pre/post cat. Just was trying to get all the info.
The issue mimics my cars pre cat o2 issues for sure.

[bluptgm3]

I didn’t realize it was a 95 but I was aware about the pre/post cat. Just was trying to get all the info.
The issue mimics my cars pre cat o2 issues for sure.

Actually I assumed OBDI with the statement that sounded like one was replaced.
My fault, not yours. It isn’t clear what car it is.....


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[AJLM34A]

What year really helps when asking for help.

If you are able to monitor when it immediately goes into close loop, what are the other inputs showing?

Are you 100% sure the engine is reaching the proper temp? A stuck open thermostat or a bad temp sensor would be a guess. Change the oil after fixed.

[weedshoes]

The car is a 1995. Only one o2 sensor. I'm not able to monitor it actually going into closed loop, but the temp gauge reads the same every time when the problem starts. Cold the car runs great, as soon as the temp gauge gets past the blue section it's like a switch gets flipped and it runs like crap. Making me think a sensor only monitored in closed loop to be the issue. Thanks for all the replies.

[AJLM34A]

ODB1 engines have 2 temp sensors; 1 for the DME and 1 for the cluster. When the engine starts to run bad, check the upper and lower radiator hoses, if they are close in temperature, the thermostat could be staying open. If they are 2 different temps, the temp sensor for the DME could be faulty.

[tjm3]

The injectors tend to become louder when the cam sensor fails, MIL or not. The default failure mode is to cycle them on and off all at the same time, which is why it's louder.
It'll run rich, idle rough and produce the gas smell. Check for frayed wiring at the sensor under the connector boot.

[ScotcH]

Water temp sensor (for DME) and air temp sensor (in intake manifold). Check the siring as well inside the boots.

[weedshoes]

The injectors tend to become louder when the cam sensor fails, MIL or not. The default failure mode is to cycle them on and off all at the same time, which is why it's louder.
It'll run rich, idle rough and produce the gas smell. Check for frayed wiring at the sensor under the connector boot.

What do you mean by MIL? In only understand that to mean mother in law.

[jayjaya29]

What do you mean by MIL? In only understand that to mean mother in law.

MIL = Malfunction indication light...just another way of saying a CEL (check engine light)

[weedshoes]

MIL = Malfunction indication light...just another way of saying a CEL (check engine light)

Was hoping you'd chime in. Thanks.

[weedshoes]

Finally got around to replacing the cam sensor. No improvement.

[weedshoes]

Just back to update. I had an injector that started to stick closed when warm. Swapped in a spare (I had 2 extras because they're from a mustang) and it goes like hell.

[Gene V]

Thanks for the timely update! lol