this is driveing me nuts the car miss fires when it idels but it doesn't seem to affect it when accelerateing i've hcanged the plugs and wires bout a year ago and it still doesn't seem to have fixed ithad it scannedawhile back and it said number 7 miss fire so i change the what i thought was the number 7 coil last one on the left. any help would be great.

 

A bad injector will cause a misfire also. Try swapping the #7 injector with one of the others and see if the misfire follows it.

 

would that still cause it to missfire on exellaration?

 

Not always. I had a couple of bad 28# injectors recently that caused hard start problems and idle misfires, but would clear up and run smooth off-idle. Swapping them out with some new 36# injectors fixed all of the issues.

 

i'll have to look into that. then. how hard would that be for me to change that?

 

Double check your plugs and wires. The ceramic cracked on one of my plugs and caused a similar misfire.

 

Pulling the injectors is easy...4 10mm bolts and pop the injectors out of the intake. You can leave the fuel line connected and just wriggle the rail out a little and then flip it over. Use the schrader valve on the rail to relieve as much pressure as you can. If the injectors have never been removed before, they may still have the metal clips holding them onto the rail. The clips just pry off with a small screwdriver. Make sure you lay something under the rail to absorb the fuel that will drip out and then pull the #7 injector and another of your choice and switch. Make sure you get the orings out with the injectors.
I agree with what Torqued said above about rechecking plugs and wires. If you haven't changed plugs in a year, now might be a good time to pick up a new set.

 

injectors, coilpacks, wires or plugs are usually the only causes of misfires. Ive noticed a few people with blown heads gaskets, including myself, have had this issue only I was misfiring on both 5 and 7. Good luck!
Nino

 

would a bad injector (sticking) throw a SES light? My car hesitates at around 2600-2800 rpms at light throttle but seems fine at WOT, its not throwing any codes. My previous tuner did have my injectors nearly maxed out so I am wondering if one of them is starting to fail?

 

I would lean more towards an ignition problem if it is occurring over a brief rev range off-idle. You might want to see if you can borrow some logging software (if you don't have any) and record some light throttle driving to try and pinpoint the problem.

 

Check your plugs and wires. I had a similar problem when a couple of my wires were riding too close to my headers. Only misfired at certain times until the heat finally melted the insulation completely. Haven't thrown any O2 codes have you?

 

Well my car FINALLY thru a Code, its my ECT (Engine Coolant Temp Sensor) I asked one of the techs at work and he said that could very likely cause the problems I have been having, might have been working on and off and then finally gave out, the code it thru was P0118 (http://gearchatter.com/viewtopic8760...b39cfd000b3982) So im gonna replace it and see if thats it.

 

let me know how much the sensor is. i may replace mine too just to be safe.
Nino

 

its around $30 at a GM dealership. I looked at mine during lunch and its broke where it joines the brass fitting going into the head. I can wiggle it with my finger back and fourth so its pretty broke. I hope thats the problem, I will find out tonight. You might wanna check with a Autozone or PepBoys to see if they can get it cheaper.

 

Autozone, Pepboys, Checkers, etc do have a cheaper version ($20 I think), but it's also hit or miss on quality. I went with the Checkers part and just crossed my fingers. Its been working just fine for the past 3 months. My original one was broken in the same spot, most likely from a spark plug change before I bought the car.

 

did it cause the same problems as I mentioned?

 

No it didn't. Doesn't mean it couldn't be the cause on your car though. On mine I didn't even notice it until I changed my plugs and the electrical connector just fell off of the sensor! I know there are timing tables that reference ECT which could cause problems if the ECT signal was erratic.

 

Wonder if I should just unplug it until i get the new one which wont be until tomorrow?

 

I wouldn't. If anything it could make the car run worse. If it were me, I'd just leave it alone until I got the new one. Remember to use some silicon tape on the threads to prevent coolant leaks.