Rough Idle Only When Cold (P0301)

[Camry97LE]

My 97 Camry 4 cylinder has been running rough the first time in the morning. After the engine has heated up, it runs fine. Today for the first time it threw a P0301 code at me. I erased the code and the CEL (Scan Gauge II - thanks) has so far stayed off. For the rest of the day it should run fine, but in the morning it feels as if is going to stall. Any ideas, I do know that it's a misfire on cylinder one, so is it time for a tune-up, now?

Thanks folks,
Darren.

[hill8570]

Have you checked the ECT? Any time I see a temperature-sensitive idle, I like to check the ECT before anything else. If it were reading too warm you're going to be getting too lean of a mixture at first, which will cause difficult starting and a low rough idle. It'd take a pretty lean mix to cause a P0301, but I'd check ECT before checking plugs or wires. See www.camrystuff.com , Generation 4, SFI (Sequential Fuel Injection) section, starting at page 48 for the ECT specs.

FWIW, the Scangauge may be able to give you the direct engine temp reading that the ECU is seeing, which would make checking the ECT dead easy...if engine temp is reading quite a bit higher than air temperature after an overnight cold soak, you've found your problem child.

[Camry97LE]

Hey thanks for the quick reply. I don't know what the engine temperature was at the time but Scan Gauge was indicating a CWT (Celsius Water Temperature) of about 4. However, I will check that site you listed.

Thanks,
Darren.

[hill8570]

Originally Posted by Camry97LE

Hey thanks for the quick reply. I don't know what the engine temperature was at the time but Scan Gauge was indicating a CWT (Cold Water Temperature) of about 35. However, I will check that site you listed.

Thanks,
Darren.

CWT actually stands for Celcius Water Temperature (it also has a FWT for use by your neighbors to the south). That reading is coming off of your ECT.

35 degrees C (95 degrees F) is way high for an engine that has been cold soaking overnight in Ontario, even if garaged (that's assuming the engine isn't running at the time of the reading).

[Camry97LE]

Actually I amended that to say Celsius - so when I started up the CWT was 4 degrees Celsius. Which by my reckoning seems fine. Since this a common problem in the morning I will look at the CIA and CWT at start up tomorrow. If they seem relatively consistent with each other then I imagine it has something to do with the wires...

Methinks that is...

Thanks,
Darren.

[hill8570]

Originally Posted by Camry97LE

Actually I amended that to say Celsius - so when I started up the CWT was 4 degrees Celsius. Which by my reckoning seems fine. Since this a common problem in the morning I will look at the CIA and CWT at start up tomorrow. If they seem relatively consistent with each other then I imagine it has something to do with the wires...

Methinks that is...

Thanks,
Darren.

4 degrees C doesn't seem out of line if the car was garaged. Otherwise, seems a mite high (seems like y'all have lows in the -7 C range this time of year).