94gt e303 cam and misfiring

50GTMach1 · Nov 24, 2010

My car feels like it is constantly misfiring when driving. I have changed some hardware (coil, plugs, plug wires, rotor and distributor cap) so I am looking for an actual problem but a buddy suggested that the characteristics of the e303 cam may give this feeling during normal driving. Can an aftermarket cam give a misfiring type of feeling as a normal affect during driving.

Thanks.

95-stang · Nov 24, 2010

Above idle my E cam was absolutely fine, all the way to the redline, just the idle was poor but since i have put in a B31, same great acceleration but with a much better idle.

modo · Nov 24, 2010

50GTMach1 said:
Can an aftermarket cam give a misfiring type of feeling as a normal affect during driving.

no

you need to look for a miss. start pulling spark plug wires while the motor is running. if you don't notice a change you have found the misfire.

TheNatster513 · Nov 24, 2010

mine does this. i just figured it was the computer. does it still "miss fire" as you get higher in the rpms?

remow2112 · Nov 25, 2010

Let me offer a little help. I have this cam in a 95 Stang I just bought. Wow it has been an adventure!

First make sure you have no chips. I did it caused a silly rich condition.

From what I can tell the E303 does not like idling in a 94-95 at less then 850ish rpms. I have mine set for just about 900. This requires a base idle reset. If you need me to find a link I can.

Make sure the PVC is not leaking and you are not running breathers on the valve covers. A vacuum leak almost guarantees what sounds like a miss.

Exhaust leaks also wreak havoc on the idle.

I have not found a way to smooth out the lope that this cam generates. So the idle will always sound bouncy?

If you have gears the hanging idle issue (which from my research is built into the computer) will drive you nuts. But that is the subject of a different post.

HTH,
Dan...

50GTMach1 · Nov 25, 2010

Thanks folks. I will be spending a little time on thanksgiving morning in the driveway. I'll keep you posted with the results. Thank you for your suggestions.

95-stang · Nov 25, 2010

remow2112 said:
Let me offer a little help. I have this cam in a 95 Stang I just bought. Wow it has been an adventure!

First make sure you have no chips. I did it caused a silly rich condition.

From what I can tell the E303 does not like idling in a 94-95 at less then 850ish rpms. I have mine set for just about 900. This requires a base idle reset. If you need me to find a link I can.

Make sure the PVC is not leaking and you are not running breathers on the valve covers. A vacuum leak almost guarantees what sounds like a miss.

Exhaust leaks also wreak havoc on the idle.

I have not found a way to smooth out the lope that this cam generates. So the idle will always sound bouncy?

If you have gears the hanging idle issue (which from my research is built into the computer) will drive you nuts. But that is the subject of a different post.

HTH,
Dan...

Well put, virtually everything i experienced.

50GTMach1 · Nov 26, 2010

I removed one wire from the spark plugs at a time and would start the engine but didnt notice a idle change on any occurence. The car would continue idling as if all 8 cylinders were firing. Also since my last post the car developed a tick noise from the drivers side valve train and the vacuum is between 14-15 with a very very fast oscillating needle. I pulled the valve cover and did a quick check and could not find any loose roller rockers or pushrods. I will work on the car this weekend and post up what I find. Hopefully this is a simple valve train problem like a sticking lifter.

Oh and the misfire sympton happens throughout the rpm range. My idle is pretty smooth after a 3-4 minute warm up. i do have a chip on the car and it was dyno tuned after I installed the cam.

modo · Nov 26, 2010

50GTMach1 said:
I removed one wire from the spark plugs at a time and would start the engine but didnt notice a idle change on any occurence. The car would continue idling as if all 8 cylinders were firing. Also since my last post the car developed a tick noise from the drivers side valve train and the vacuum is between 14-15 with a very very fast oscillating needle. I pulled the valve cover and did a quick check and could not find any loose roller rockers or pushrods. I will work on the car this weekend and post up what I find. Hopefully this is a simple valve train problem like a sticking lifter.

Oh and the misfire sympton happens throughout the rpm range. My idle is pretty smooth after a 3-4 minute warm up. i do have a chip on the car and it was dyno tuned after I installed the cam.

pull the plug wires while it is running, if that plug is firing you will notice a difference when you remove it... if you pull one and nothing changes i would start there

2002BLGT · Nov 26, 2010

How many miles on the car ? Has the distributor ever been replaced , ive seen bad bushings in the distributors cause some wacky missfires

50GTMach1 · Nov 26, 2010

2002BLGT,
Car has approximately 275000 miles on it, original engine. The distributor is a MSD Billet. Bought new 1 1/2 years ago. since the onset of the misfiring I have replaced plugs, wires, coil, distributor cap, rotor, and fuel filter.

TheNatster513 · Nov 28, 2010

^same here. the thing with mine is it will stop "misfiring" on random occasions... like if i get above 1700 rpms. or will just shut off almost like the computer notices what its doing and fixes it. i am running with out a tune.

2002BLGT · Nov 28, 2010

Have you tried replacing the TFI module ?

50GTMach1 · Nov 30, 2010

replaced tfi module two weeks ago with no change. ran car with and without msd box connected, also swapped distributors from msd billet to stock and back to msd billet again. car still has a miss. not on a consistent interval. but every few seconds it will miss once, then a few seconds later 2-3 times in a row. you can feel it at idle or while driving. its as if the engine skips a beat. i opened up the drivers side valve cover and tightened roller rockers but the ticking noise is still there. will have to wait for a weekend with decent weather to do a thorough check on the valve train. im not driving the car until this is fixed. thanks for the help I will post up results.

rz5.0 · Dec 1, 2010

have you checked for codes. you could be lean

50GTMach1 · Dec 3, 2010

two items, the timing was down at 2 degrees btdc ! and the valve tick noise turned out to be a cracked spark plug that had electricity arcing from plug and to the block. I could see the spark when I opened the hood at night.

so i fixed those two issues, set the timing to 14 degrees and bought a new spark plug, drove the car for 15 minutes....

and blew a head gasket!

and the hits just keep on coming.....

but those were a great 15 minutes!

ugh..

95-stang · Dec 3, 2010

They say it never rains but it pours.

50GTMach1 · Dec 5, 2010

the symptons were, temperature sensor sweeping from normal to hot and back to normal in 20 seconds, heat going ice cold, air bubbling in coolant resevoir and coolant overflowing from resevoir. did a coolant pressure test and the system held the pressure for close to two minutes. thought maybe the radiator cap was the weak link since the system held pressure with the coolant pressure tester acting as a radiator cap. replaced the radiator cap and all is good!

Im driving the 5.0 again!
Thanks for all the help!

LONG LIVE THE 5.0!