misfire in intake ???

[dally_de]

hi,
strange thing for me..i notice this days that i have misfire in my intake...can anyone tell me why?? could it be because of a distributor cap or rotor??something from ignition ?help please and i also have poor performance from the engine and big fuel consumption

[Razorback1980]

Only two things I can think of that would do that....timing off or ignition coming at the wrong time. Check your distributor cap for lines that look like a pencil drew them in there. Also look under the hood at night with the hood light removed and see if you see any sparks. That should cover the ignition. If it's a timing issue, then the timing belt has moved and you are lucky and haven't bent a valve or the DME is grounding the coil at the wrong time meaning there is something going wrong with the timing to the DME. Not sure which car you have so it could be many things causing this. If you put your year and model in your signature line, that will help us to help you. Most likely ignition and a new cap, rotor and possibly wires will fix the problem.

[dally_de]

it is a 944 n/a 85.5 ... i am also thinking that only something with timing can cause this..also noticed in the distributor cap i have a tick line ..something like rotor cut into the cap...could it be possible that rotor axle could be bent and not having a circular rotation??

[Razorback1980]

Timing is controlled by DME so for it to be off, the electronics associated with the DME are not working properly.

[Ctan]

You could also have an intake valve sticking occationally. a weak spring and a sticky channel can cause a valve to remain open from time to time... not to bad to diagnose if it's not in the rotor...look for the intake manifold section with carbon in it.

[1985porsche944]

Now I wouldn't go jumping to conclussions but you may want to check your O2 sensor. Mine had broken off and contiued to get worse until you had to be flooring the pedal for the car to run correctly. After I replaced the 02 sensor it worked perfectly. Now does your backfire happen all the time or is it intermittent?

[Ctan]

lol, I was under the car thismorning looking for an oil leak (Pretty sure it's the rear main...damn) and found my O2 sensor wire just kinda hanging there. hooked it back up and she runs better now :P

[dally_de]

i do not have a O2 sensor...i will change distributor cap and rotor and sparks(NGK iridium) and see from there...but i'm still not sure what can be the problem

[944 Ecology]

So, it has a supercharger, too? What else are you not telling us?

That said, check for a broken valve spring on an intake valve.

[dally_de]

for the moment supercharger isn't mounted ..everything is stock. it was few times when the engine was running incredibly good, but after stopping the engine same problem again