Contour Enthusiasts Group Archives Forums General Troubleshooting Random Misfire

Well, I'm not usually one to post here, but I've got a problem that I've been unsuccessful in tracking down thus far.

The car I'm working on 3L swap 2000 SVT Contour has a random misfire that I can't isolate or even find any particular way to reproduce. Currently it seems more affected by damp weather as it's most likely to misfire within the first 5 minutes of run time leading me to beleive that it's an issue related to condensation. Typical misfire happens at low RPM (under 4K) and will usually resolve itself within 30 seconds or less and/or with a rev of the engine above 4K without any load on it (press in clutch, rev it up and it clears out). No hard CEL lights. Only the flashing CEL to acknowledge the misfire and even then that's only on a prolonged instance of more than 5-10 seconds which is rare.

Fixes I've tried thus far:
New spark plugs- (currently on 2nd set since 1st set was lightly fouled during the initial startup) Motorcraft platinums.
New plug wires- 8mm magnecores.
Swapped coil packs- transferred over the coil pack from my car that had no known ignition issues.
Revised chip program- had ADC review and revise the chip slightly to see if they could figure out any reason in the chip end of it.
Triple checked all plug, wire and coil connections.

Misc other info (just to avoid any questions about it):
IAC is in good working condition (had to replace it all ready due to idle issues)
MAF is in good working condition
EGR is operating and both it and the TB are cleaned.
Engine is 3L with 3L PnP heads, 19lb injectors, stock SVT MAF, ADC chip, MSDS headers, and SVT intakes. No issues with engine operation other than random misfire.

My next planned step is to use a spray bottle in attempt to isolate the area of the misfire if it is moisture induced. Beyond that, what additional issues would you look for or can I try to document without taking the car in for a diagnostic. Does anyone with an Xcal know if I can datalog and/or anaylize anything in particular that would help me? I've got the Xcal2, but have yet to use it yet since my car was out of service when I got it and I've only used it to reset some codes at this point.

Thanks,
Rick

It sounds like you have covered a lot of posibilities. There isn't much left in the ignition system that could explain it.

Some other things that can cause a mis include:

lean mixture (fuel pump, plugged filter, vacuum leak, dirty injectors)(some vacuum leaks can be tricky and even intermittant)(fuel quality has even come into play here, too much alcohol can play havoc if the system doesn't have enough mixture range to accomodate the leaner running fuel)

valve problems (weak springs, valve starting to burn, carbon shrouded valve, worn cam lobe)

cam timing issues

carbon build up in combustion chambers

ring flutter (usually only at high revs on a "loose" engine)

I have seen all of these things cause wierd engine misfires, and they were often hard to track down.

Have you tried driving it with a fuel pressure gauge installed while it is acting up?

Good luck with finding it.

I have been as thorough as I could be before coming here.

I'm doubtful of the lean mixture as I've been through the fuel system pretty thoroughly unless it's at the injector itself. It has a new fuel filter in place.

Valve springs have 8K miles on them and the heads were freshened up and cleaned when they were PnP'd by Kinger.

Cams are properly timed.

Combustion chambers are clean (see PnP)

Ring flutter- doubtful as pistons and rings were throughly cleaned and checked and have under 20K on them.

I have not tried a fuel pressure guage on it, but considering it is an intermittent problem, I don't think that would be an issue as that would cause something more than a random misfire in my thought process. I'm beginning to wonder if it might be a bad connection with an injector or possibly a partially clogged injector causing the issue. It almost acts more like it's getting too much fuel than not enough.

Rick

I had the same problem, im know this info wont help you at all. But if it was really low humidity I would never have a problem. But once it got really sticky out again, misfires like crazy. I could never figure it out, I had a new ignition coil, new wires, new spark plugs. So I decided what the hell, I bought an accel ignition coil for $20 used. Installed it, havent had a single misfire since.. Im sure this isnt the case with yours, but I thought I might shed some personal experience.

If I hadn't taken the coil off my personal car which I know hasn't had any issues whether wet, dry, or monsoon, I'd be tempted to look at it again. Heck, at this point I'm considering looking at the plug wires again even though they're brand new and Magnecores on top of that.

As an update, I did try to go out and liberally squirt down the electrical connections and plug wires to see if I could cause a misfire with the squirt bottle and no such luck. I might try again when the car is stone cold since it had only set a few hours when I tried tonight.

Rick

I'd almost bet it's the tune since you've covered your mechanical bases for the most part.

I had a misfire that was totally random, but it happend after the car warmed up and while driving around. I got a brand new ford coil (accel has a replacment now, which I found after ordering from Bill J) and magnecore wires AND running an extra ground to the coil, and it solved it (250 miles without one CEL ::knock on wood::)

Is the misfire in any specific cylinder? My raptor would tell me which cylinder misfired, I'm not sure if the xcal does.

Well, hopefully you also tried running without a chip first since you are running the stock MAF and injectors right? If it has the same problem with stock code and it is misfiring then I'd look again at the ignition wires,coil, plugs, connections.

I would look at the connection to the coil pack where the four conductor plug is at. Make sure there is no corrosion, it fits tight and has the rubber seal. PCM plug can have a problem.
Corrosion problems are almost always affected by temperature too in my experience.
Last would be to test with good stock style plugs and wires.

I'm sure you'd get a crank or cam shaft sensor code, but there could be potential issues there.

I had a similar issue with my car before it died. I swapped the coils over and nothing...but that coil would work fine in the other car...(HONEST)
I ended up swapping the coil and at the same time doing the spark plugs. That did it...but not for very long...well the misfire didnt come back but I only put on like 1k miles til I destroyed the motor.

I am going to answer with a question then...is it possible to foul the plugs with a bad coil??

Anything new Rick!?

Rick - did you have to solder in new injector clips in or did you reuse the 19's and left the injector harness alone?

The reason I ask is because in the last 3L I did, I soldered in the 3L's clips onto the CSVT's harness and had random misfires in one cylinder. I later deduced it was a bad wire in one of the injector clips and swapped out the culprit and vio la, no more misfire. For me it was easy as it would misfire consistantly, and long enough for me to pull the spark plugs and find the one that was carbonless (due to lack of fuel).

At first I thought it was an ignition issue as well and after trying my new Magnecores out of the box on the car it still did the same thing.

Now...in your case you say it clears up...but dsoes it clear up for good during the time following the misfire or does it return while driving at all?