I start my truck, in the morning, strictly cold starts, she seems to start fine as of late (about 90% of the time). But lately after I've let it sit 4 to 8 hours in the day while at school or work, if I start it up I get what I think is a misfire. It runs really tough like a cylinder isn't working (or what I suspect) i.e Misfire, and only idles at about 1100-1200 RPM's compared to the normal 1500, yet if I give the engine a little bit of gas and rev it say to 2500 RPM's for just a 2 or 3 seconds it smoothes right out and idles at normal cold start idle. The truck runs ok...the idle when she's warmed up is just ever so slightly rougher than before, I'd say it's about 97-98% of normal say, the engine pulls fine...doesn't feel any different. What do you think the problem is? I reason it could be a dirty injector, perhaps revving the engine might clear some crap out. Or maybe a bad O2 sensor? Maybe a good exhaust push cleans the surface of the O2 sensor from revving it? Any ideas?

 

cold start injector ?

 

Actually sounds like a leaking injector to me... Usually what happens is, when you have a weak injector and it leaks, it'll releive the pressure from the lines into the intake.. this gas kind of pools up and makes starting a lil difficult not to much but makes idling until it gets burnt up a lil difficult.

 

Maybe time for new plugs?

 

Isnt 1500 rpm a little high for your normal idle speed? Mine idles at 1000, and the Chilton book says 750 is what it should be. (For a 22re)

 

plugs? and run a bottle of injector cleaner? see how it goes? those are both cheap fixes, and it works, then great, if not, you didnt waste much money, and neither of those things can hurt...

 

My plugs are pretty new - stock Denso's, replaced about 8000 miles ago. This problem started a few thousand miles after I had new plugs so I'm pretty sure it's not the plugs fault. Oil is synthetic, only 3000 miles on oil, good air filter, etc.

1500 isn't my normal idle speed. 1500 is my warm up (cold start) idle speed i.e. when the engine starts at 1500 RPM's and progresses down operating temperature idle (800-900 RPM's-ish) as it warms up. I think you guys know the 1500 Warm up idle speed as far as I know is for emissions purposes i.e. so the truck warms up faster because you puke out the most emissions when the engine is running cold because the cat isn't yet hot enough to burn any excess fuel.

So like I said she starts sometimes and runs rough and idles below normal cold start idle, and if I give 'er a little gas the rough run goes away.

 

Either one of these sounds good to me.