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my 2005 Civic has been staring up fine even on below zero days. after clearing snow off car, shut it off, and then went to start again, cranks but won't start. Several hours later, same cold weather, starts ok. Took it to local shop who found no problems. Drove for 2 weeks fine, same problem happened. 3 hours later starts again. Did some web searches, added "heet" additive today at suggestion of local auto parts store. Thoughts?

 
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I think this is your problem.

DO NOT SHUT IT OFF COLD!

If you are going to start the car, you damn well better drive that car -- all the way through warmup.




When you don't get the engine hot, the spark plugs get carbon fouled and then it "floods" upon the next start attempt. You GOTTA run it til there is enough heat to clean the plugs so they don't foul.

 
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Oh yeah, welcome to the forums!

 
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so, one time ran it for 7 minutes but did not drive it since needed to save parking space that I cleared all the snow, then it did not start. how long should I run it and do I need to drive it around the block at least to minimize the problem you described with spark plugs etc. thanks for your help! your humor is fine with me

 
Rep Power: 517

Ideally, it should be run up to operating temperature, and hopefully maintain that for some length of time.

Driving is far better than idling, idling is not making the engine do work and create a bunch of heat in the combustion chambers. Heat is what gets the carbon burned off of the spark plugs.

7 minutes of just idling when it's single digits (F) here sure doesn't get mine warmed up, but 7 minutes of actual driving will get me some heater output.
(NOTE: SOME heater output is still not reaching operating temperature)


I can't actually see/hear/experience the problem for myself to see what's actually going on.
I'm just guessing that it got flooded when you did this, but your scenario fits the issue. This is extremely common when people only move the car a few feet and shut it off, it can even happen in warm weather.
I deal with it all the time at the car lot, and there is no way to fix the salespeople that cause it.


Next guess...... might be to monitor PCM data and see what it thinks the coolant temp is when it won't start.


HTH

 
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I would say if you are not driving it..... then don't start it at all until you actually do drive it and get it to temp.

 
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sometimes problems like this are caused by a poor ground or grounds

i would check all of your main ground connections including the battery terminals and make sure they are all clean and tight, replace them if nessessary, and dont forget about the ground strap/straps between the frame and the engine, those are very important