a little over a week ago my car threw a cel at me. random misfire in cylinder 4. I reset the ecu and the car was fine for quite a few miles. then the other day i got the dreaded cel again. this time it was random misfire in cylinders 2,3, and 4. So today I went and bought some new plugs. Decided I'd go with bosch platinum over the ngk v powers as the v power plugs' electrodes tend to wear out pretty fast in my experience (there is barely a V left in the electrode). Anyways, i changed the plugs, reset the ecu, and idled for over 10 minutes. no cel, until i back out of the garage to take it for a test drive. I got out to close the garage and when i came back... another cel. So i check the code again. Now its a random misfire in cylinders 2 and 4.

What gives?? I will be changing the wires next. the Dizzy cap and Rotor were replaced not more than a couple months ago. The car still feels as peppy as it always has. Once in a while my car will sputter at a traffic signal when i come to a stop. But it will go away once i drive away and reach the next traffic light. The car idles pretty decently. Lots of vibration only due to my race mount inserts. Idle fluxuates only slightly (needle is always hovering over the rpm mark, but moves up and down still).

I mis-shifted once a long time ago (quite a few months), but that never yeilded a cel and my valves do not sound abnormal. Any thoughts?

My setup:
4/2/1 2 piece header, high flow cat, 60mm to 2.5" cat back exhaust. DIY cold air box with KN filter and 3" mandrel bent intake arm.

Oh yeah, and i THINK that the cel came on right after I removed the upper radiator hose to put in a temp sensor adapter (which never went in because it was the wrong size, so the hose was put back on and the lost coolant replaced).

 

When is this misfire occuring: high or low RPM? When is the last time you changes your fuel filter?

 

First off, take those shitty bosch plugs and flush them down the toilet. The NGK plugs are cheaper and a million times better. Change the plugs every two oil changes, its still cheaper than buying one set of bosch plugs. Secondly, you have the same problem that I do. I blame the wires simply because I know that one of them arcs. Get a set of NGK wires.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Dogginator &raquo;</TD></TR><TR><TD CLASS="quote">When is this misfire occuring: high or low RPM? When is the last time you changes your fuel filter?</TD></TR></TABLE>

low rpm's last time it went on. I had changed the plugs, reset the ecu to erase the CEL, idled the car for 10 min to refresh the ecu, then backed it outta the garage to take it for a test drive. i got out to close the garage door and when i went back to the car, the CEL was on... rpm's didn't go above 3k while backing out.

i plan on changing the fuel filter next. it sounds like a good possibility considering the fact that lower rpm's would yeild lower fuel pressure thus being more suseptible to starvation with a clogged filter element.

the wires are due for a change anyway. the rubber boots are now brown so they just look ugly. whether they are bad or not, they'll be swapped for new ngk's soon.

 

I would suggest a compression test at this point. A clogged fuel filter is typically problematic at high loads or high RPM.

 

is it possible that a fouled primary O2 sensor could cause a misfire? Somebody mentioned in another web board that he got a misfire code and when he changed the primary O2, it fixed the problem. Any thoughts?

 

It could, but it is unlikely. Check the following.

1) Valve clearance
2) Compression
3) Wires
4) Distributor