Slightly rough idle at startup - 03 Cobra

[nytebyte]

When I start my car when it's completely cold, it sounds like it's running slightly rough for about 60 seconds or so.

Also, when it's still cold, if I do something like start off at 3 mph in 2nd gear, it will hesitate just a bit. It never used to do this before. All of these symptoms go away after it warms up and then it runs perfectly.

My guess is that I might need to re-gap or replace the plugs. The car has about 30K miles on it and I've never touched the plugs. Mods include just an intake and catback. I still have the stock pulley.

At this mileage, should I just re-gap or replace the plugs? I think the gap for a stock 03 Cobra is .042, correct?

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[CobraSusie]

we are gapped at .036

did you do the blower idle by-pass?
(we tried it, and it messed with our idle) - so we switched it back :biggthump

 

[nytebyte]

Did not do the blower idle bypass.

A gap of .036 sounds kind of short for a stock blown 03 Cobra.

 

[cyac5l8trfcar]

sounds like injectors. plugs and wires tend to act up when warm and under load. throw a full bottle of injector cleaner in with a half tank of good gas (shell V power) and run it dry.

 

[Flyn]

Do the usual maintenance. Filters, [air and fuel], plugs, maybe clean the MAF wire.

 

[nytebyte]

OK, I pulled all the plugs, then cleaned and re-gapped them.

Two were out of spec and all had a huge amount of carbon deposits on them, but other than that, they looked good.

I carefully cleaned all the carbon off with a dremel tool and a small wire brush attachment. Now they look as good as new.

After re-gapping them and reinstalling, the car started very quickly and just turned over less than once before firing up. It idled nice and smooth.

While I had the lower intake out, I decided to clean the air filter. The filter is still drying, so I'll clean the MAF before reinstalling it.

 

[nytebyte]

OK, I finally took the car for a spin. The low RPM hesitation is gone, however now I've got a stumble that occurs between 1500 and 2000 RPM's. No problems at WOT though.

I've done some research and it seems that a plug gap that's too narrow can cause this. I gapped all the plugs between .042 and .046.

Should I just get new plugs (maybe Brisk - no gapping needed), or should I pull all the plugs again and check the gap?

What are your thoughts?

 

[Flyn]

OK, I finally took the car for a spin. The low RPM hesitation is gone, however now I've got a stumble that occurs between 1500 and 2000 RPM's. No problems at WOT though.

I've done some research and it seems that a plug gap that's too narrow can cause this. I gapped all the plugs between .042 and .046.

Should I just get new plugs (maybe Brisk - no gapping needed), or should I pull all the plugs again and check the gap?

What are your thoughts?

Buy the new plugs. It's a $35,000 car. Don't skimp.