I had a multiple misfire code and knew that the coilpacks are notorious for going bad. So I bought some used ones and replaced them. The code was still there. I just reset the ECU and the code left. When I accelerate hard the SES light now flashes and then turns off. I tested my old coils (according to the Haynes manual) and they are within spec and test okay. The main problems is rough idle, horrible gas mileage, and heavy hesitation under hard acceleration. I replaced the knock sensor not that long along because of the hesitation. The hesitation has been going on for awhile but just threw the multiple misfire code two months ago. I thought for sure it was the coils but the problem is still here! What could this be? Could this be a bad EGR or EGRC?

I am stumped!

 

Buying used coils might be the problem...


Unplug each coil one by one, the ones that don't change the engine tone are the bad ones. Replace all the spark plugs too.

 

theres a transistor for the ignition system on the right side of the engine square harness with black tape red wire and white or black ground, lot of people dont know about that transitor look it up in the factory manual if you have one sounds like under load its misfiring did you replace the correct coils? could be coils also did you check the plugs????

 

more important have you checked your coil grounds are you positive your fuel injectors are grouned to theres 2 screws on the front side of intake mani that ground out there you might have disconnected or broke them clean the connections and reset your pcm and go from there

 

Don't count out the fuel injectors...

 

I checked the coils out with a multimeter and they are within spec. I will check out about that transistor and the grounds for the injectors. I replaced the plugs when I switched out the coils. They were replaced with NGK's.

 

check the fuel injectors -- listen for the click-click-click (use a screwdriver to probe them, and put your ear to the handle).

pull the plugs and check for carbon fouling. if carbon fouled, probably leaky injectors.

maybe even a plugged fuel filter if it acts like it's starved for fuel (hesitation under heavy throttle).

just to be clear -- you are not getting cylinder specific misfire codes??

 

Even though the coils check out with the ohm meter test, it doesn't mean they are good.

 

I am experiancing a similar problem... spits and sputters under not heaevy load, but under load... only happened to me in second geer around 3500 rpms last nigh the CEL started blinking, and went out. it did it again this morning right when I pulled out of the driveway (still cold). I just replaced my plugs, fuel filter, cleaned my IAC Valve, Injector pulse tested within range, cleaned throttle budy, PCV valve... Gonna check the codes today at lunch, but ideas will help...

thanks guys
dave

 

All those symtoms are signs of an air leak also. When my knock sensor went bad, it missed and back fired enough to suck the rubber upper intake gasket inwards. After replacing the knock sensor, the only problem was a rough idle. After living with the EGR flow code for the past 100,000 miles i decided to finnaly fix it, as it never gave any other problems. It's when i pulled the uppter intake off i noticed the gasket was sucked in.

An easy way to find an air leak is with the engine running, sparingly spray some starting fluid around; when the engine revs up you know theres a leak.

 

dude i think they couldve seriously made a manual just for the emissions and ignition systems for these max's...lol

 

I still haven't figured this out. It is very annoying! When I add Seafoam, it helps but does not cure the problem. Could this be a MAF problem?

 

two people already told you to check the injectors. have you done that? if you're sure your coils and plugs are good, the next step is to check all fuel injectors with a multimeter. bad injectors can cause a misfire, rough idle and hesitation. a user on this board named eta_vu just had a similar problem. after we eliminated coils and plugs, he checked his injectors, and one was completely dead. he replaced it and his car is 100%.