still misfiring!! suggestions?
still misfiring!! suggestions? Ok, quick run thorugh. I did a cam swap a few weeks back pulling out my fm-10 and putting the stock one in. I started her up and she was misfiring on #5 and #7 cylinders, so i changed out plugs and wires and still the same thing. I check the pushrods (FMS chromemoly) and they were fine, the rockerarms seemed fine as did the springs. I get home yesterday and get to work on it and swap 1 & 3 coil packs with 5 & 7 and its still missin on 5 and 7 so its not any of the things i mentions. Any other ideas what the problem could be?? Im suspecting the lifters, but not sure...
If the plugs and wires are good and you swapped coils to verify that they are good, then the only thing left that could cause a misfire is an injector. How are you verifying the misfiring cylinder? When is the misfire (under load, at idle, higher rpms)? How many miles on the car? Did you change anything else when you originally installed the FM10? Did you retune the car back to stock? Need some more info.
Dave
Dave
im scanning it with EFILive and HPtuners, its at idle and underload. about 47k on the car. I changed out the springs with a dual kit and the PR's. I flashed it with a stock tune also.
id start by doing a CASE relearn... after that, if it comes back,id carefully inspect the coil connectors (they can break/corrode and cause trouble)
also, check the cam sensor and make sure its not broken or loose..
also, check the cam sensor and make sure its not broken or loose..
Can you check injector PW with those scanners? If so check that and see if there is anything wrong there. Also may try to swap an injector and see if it moves. I feel if a lifter was that bad to cause a miss you would have valvetrain noise, also.
Was the stock tune your original bin or a donor? With you saying it is underload I still feel the injector might be at fault. What is your fuel pressure? Did you ever check the duty cycle of the injectors when you had the FM10 in? Maybe the extra duty on the injectors weakened a few of them. Just some ideas to kick around.
Dave
Was the stock tune your original bin or a donor? With you saying it is underload I still feel the injector might be at fault. What is your fuel pressure? Did you ever check the duty cycle of the injectors when you had the FM10 in? Maybe the extra duty on the injectors weakened a few of them. Just some ideas to kick around.
Dave
there is a loud noise when i start the car and it shakes hard!!! Thats whats caused me to think its the lifters. I can check out the PW on the injectors with either one. Ill try swapping out the injectors tomorrow and see how that goes. The bin i used was a doner bin since my old tuner has my original. If it were the injectors, would i still be hearing the loud valvtrain noise?
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Well if you have the loud valvetrain noise you may have a lifter not pumping up. I would check the fueling first because that is alot easier than anything that has to do with lifters. LOL. How long was the FM10 in? Was ther alot of hard driving & track time? The higher seat pressures of the dual springs and the ramp rates of the camshaft may have cause a lifter to start to fail. You may take the valvecovers off and see if you have any up and down movement in any pushrods. That would show a lifter bleeding off. Should be very apparent.
Alot of variables involved but I would check all the fueling first and go from there.
Dave
Alot of variables involved but I would check all the fueling first and go from there.
Dave
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Verdad Gallardo If you remove the valvecovers and wiggle the rocker arms you normally will get some side to side play. If you have a lifter bleeding off you should also get some up and down play either in the rocker arm or if severe enough in the pushrod. I would think if the lifter is the culprit and you are getting misfires then there should be abnormal play on those cylinders.
swapped injectors, nothing new, did a compression check on the driver side and here's the results.
cylinder 1-175
cylinder 3 -175
cylinder 5-127
cylinder 7-0
any other ideas??
cylinder 1-175
cylinder 3 -175
cylinder 5-127
cylinder 7-0
any other ideas??
if you have 0 compression on the number 7 cylinder you need to do a wet compression test, that is add a squirt of oil to that cylinder to see if the numbers go up. if numbers go up your ring seal is the reason why you don't have compression. believe it or not its common to have 0 compression if the motor is cold with the low tension rings gm is running and need to get warmed up some to build compression. if you didn't run the car for a period of 12 hours or more that could explain a low reading. run the car for a minute or so not enough to make it burn you when you work on it but it will give you enough heat for the rings to expand and seal the cylinder. If a wet compression test of number 7 still shows less than 70% of other cylinders like 1&3 (number 5 is a little low but we'll deal with that later as at this point lets focus on 7) then a cylinder leakage test will need to be performed to determine if you have a head gasket, burned valve, rings, and etc.
well it all started after i did a cam swap. i also dont have the resources to do any of the other tests 
if it is a ring, what would need to be done? should i plan on getting a new motor? and or heads?
if it is a ring, what would need to be done? should i plan on getting a new motor? and or heads? Do you have an adapter to pressurize the cylinders? I would remove the valvecover & rocker arms on #7,fill #7 with air, and see if you can hear or feel a leak. Maybe a low tech idea but would give you a better idea if it is head or rings related.
Originally Posted by DWillTA
Do you have an adapter to pressurize the cylinders? I would remove the valvecover & rocker arms on #7,fill #7 with air, and see if you can hear or feel a leak. Maybe a low tech idea but would give you a better idea if it is head or rings related.
I would think since the problem came all at once after your cam change it would be more like a valvetrain issue. Maybe a valve hanging open. This could either be caused by a valve guide sticking or broken spring not releasing the valve completely.
Do you have the stock springs? May try swapping them. I presume you drive it daily or often anyway. So if it ran fine with the other cam and then you change back to stock and get a misfire I would think it was something you fooled with while swapping the cam.
I am no spring expert but what is the likelihood of an inner spring breaking? What would be the symptoms of this? Would the spring still have good pressure? I know most people feel the inner is to save you if the outer breaks but I am sure the opposite has occurred. Just some things to think about.
Why are you putting back to stock? Going a different direction?
Do you have the stock springs? May try swapping them. I presume you drive it daily or often anyway. So if it ran fine with the other cam and then you change back to stock and get a misfire I would think it was something you fooled with while swapping the cam.
I am no spring expert but what is the likelihood of an inner spring breaking? What would be the symptoms of this? Would the spring still have good pressure? I know most people feel the inner is to save you if the outer breaks but I am sure the opposite has occurred. Just some things to think about.
Why are you putting back to stock? Going a different direction?
Do you have an automotive stethoscope? You could just use a long screw driver or wooden dowel be careful and place it against your ear to listen for the noise. See if you can pinpoint the valvetrain noise. If it sounds like it is under the intake then it would be lifter noise. If it is under the valvecover then it most likely is in the rocker arm and spring area. Is the noise on #5 & #7 only or all over?