Diagnosing possible misfire
07-12-2011, 04:03 AM
#1
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Diagnosing possible misfire
I think I may have a misfire at one of my plugs. I suspect this because at idle, if I remove one of the coil wires (I do this with engine off) the engine runs a little rougher. Curiously, the engine runs smoother when when running from the secondary distributor (the one being driven by the belt). Am I right?
If I am right, can I use my timing light (a very basic one) to isolate the bad wire/plug/etc?
Thanks
If I am right, can I use my timing light (a very basic one) to isolate the bad wire/plug/etc?
Thanks
07-12-2011, 11:12 AM
#2
Nordschleife Master
if you have a misfire, you should get a CEL with code P0300, as well as P030X, where X is the cylinder number. It can be a single cylinder, or multiple.
i.e. P0300 Random Misfire, P0301, cylinder 1 misfire
i.e. P0300 Random Misfire, P0301, cylinder 1 misfire
07-13-2011, 11:33 AM
#4
button queen
Found a picture in the Streather book to help me make it right.Good luck.
07-15-2011, 07:49 AM
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My car has a new LWF setup and is a 95. I am not sure if my version of the DME can send these misfire codes. Do I need a OBD I reader to read these codes?
I still can't understand why my engine runs rougher with secondary distributor than with the primary?
I still can't understand why my engine runs rougher with secondary distributor than with the primary?
07-15-2011, 11:00 AM
#7
Burning Brakes
One of the plug wires is in bad shape or the cap/rotor has issues?
In theory, I think you should be able to check wiith the timing light. Have you pulled the cap and rotor on the questionable distributor to check it?
Age of wires and cap?
In theory, I think you should be able to check wiith the timing light. Have you pulled the cap and rotor on the questionable distributor to check it?
Age of wires and cap?
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07-16-2011, 02:30 AM
#8
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Caps, rotors and plugs are new. Wires are original. I may have a bad one, I know.
Just wondering if someone could disable one coil and then the other to see if there is a difference in sound and or running smoothness.
I will try the timing light trick to see if it get me anywhere.
Just wondering if someone could disable one coil and then the other to see if there is a difference in sound and or running smoothness.
I will try the timing light trick to see if it get me anywhere.
07-16-2011, 09:34 AM
#9
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I'm getting random misfires occasionally. The CEL will come on, then a few starts later will be off again.
I'd think a vacuum leak would keep it on all the time.
Glad you mentioned the DMF, I've been looking for an excuse to go the LWF route. I'll wait until the light comes on and stays on more often. And hopefully the diagnoses leads in that direction.
I'd think a vacuum leak would keep it on all the time.
Glad you mentioned the DMF, I've been looking for an excuse to go the LWF route. I'll wait until the light comes on and stays on more often. And hopefully the diagnoses leads in that direction.
07-16-2011, 12:36 PM
#10
Three Wheelin'
I'm getting random misfires occasionally. The CEL will come on, then a few starts later will be off again.
I'd think a vacuum leak would keep it on all the time.
Glad you mentioned the DMF, I've been looking for an excuse to go the LWF route. I'll wait until the light comes on and stays on more often. And hopefully the diagnoses leads in that direction.
I'd think a vacuum leak would keep it on all the time.
Glad you mentioned the DMF, I've been looking for an excuse to go the LWF route. I'll wait until the light comes on and stays on more often. And hopefully the diagnoses leads in that direction.
LOVE THE LWF!
07-16-2011, 01:43 PM
#11
RL Technical Advisor
I'm getting random misfires occasionally. The CEL will come on, then a few starts later will be off again.
I'd think a vacuum leak would keep it on all the time.
Glad you mentioned the DMF, I've been looking for an excuse to go the LWF route. I'll wait until the light comes on and stays on more often. And hopefully the diagnoses leads in that direction.
I'd think a vacuum leak would keep it on all the time.
Glad you mentioned the DMF, I've been looking for an excuse to go the LWF route. I'll wait until the light comes on and stays on more often. And hopefully the diagnoses leads in that direction.
FWIW,....misfires that trigger the CEL play havoc with cat temperatures and will really shorten their lives. Given the $2900-3K cost of a new one, I advise my clients NOT to postpone the resolution of such issues as its far more expensive to fix these problems after the fact.
Naturally, JMHO.
07-16-2011, 10:16 PM
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"Just wondering if someone could disable one coil and then the other to see if there is a difference in sound and or running smoothness."
Anyone willing to help me on this?
Anyone willing to help me on this?
Last edited by michel j; 07-20-2011 at 04:35 PM.
