Distributor cap ???

KcMstang · Jan 31, 2007

I've been having a random miss with my car. Been through the whole check list of stuff except the fuel which this weekend I'm hoping to get to drop the tank and make sure the strainer isn't clogged or something. When I looked at my distributor I noticed the BOTTOM cap had a piece of the top part tore off. I'm planning on replacing it this weekend but wanted to see if that could cause a miss?

BigHairyMonkey · Jan 31, 2007

Most definetly. Cap, rotor, wires, plugs can all make for a nasty miss. Replace your plugs if you haven't done so already, i had 2 fouled plugs and i had a bad miss, changed them out and runs like a dream.

KcMstang · Jan 31, 2007

Plugs are good checked them the other day. The upper cap is brand new MSD w/ MSD plug wires + coil! Just saw the other day the top lip of the lower cap is torn and didn't know if it was a big deal or not. Looks like I'm heading to Advance right after work then.

HISSIN50 · Jan 31, 2007

I'd agree. I've had my share of caps cracking. It can lead to internal cracks and crossfiring. In the old days, that meant flames comin out the carb throats.

I have to say that I'm not sure I'd look at the fuel pump for a random miss.

Good luck.

KcMstang · Feb 15, 2007

Replaced the lower cap on the distributor and it didn't help with the miss. Starting to look into the fuel pump or clogged strainer. It doesn't miss all the time runs good then when I give it a little more gas it starts missing.

JChalfan · Feb 15, 2007

KcMstang said:
Replaced the lower cap on the distributor and it didn't help with the miss. Starting to look into the fuel pump or clogged strainer. It doesn't miss all the time runs good then when I give it a little more gas it starts missing.

It does sound like ignition to me. I bought a brand new cap once which looked perfect, but caused a high-rpm miss. I replaced it with a Ford cap, and the miss was gone. I wouldn't expect that problem with a MSD cap, but you never know for sure. If you have a spare cap around, I'd throw it on and see what happens. Sometimes parts are defective new.

When did the miss start? Did it start right after you did some work on the car?

On a car (not mustang) I once owned, it ran perfect, until I really got into the gas (more than 3/4 throttle or so), and then I had a nasty miss. After a lot of checking, it turned out one of my spark plugs had a VERY small crack right at the base of the porcelin. Usually the plug worked like normal, but when I would punch it (spark energy increased?), the spark would start jumping through the porcelin and grounding out into the head through the plug base.

It's pretty easy to crack a plug if you are using a plug socket without the rubber donut in it, and you would never even notice. It might be worth checking your plugs VERY carefully if you haven't already.

I agree with Hissin that a fuel pump problem is unlikely to cause a random miss, but I suppose anything's possible...

I'd rule out every ignition componenet first though.

EDIT: I just read your other post and saw you replaced the plugs already.

KcMstang · Feb 15, 2007

I recently checked the new plugs and they looked perfect so I ruled that out already. Car has me stumped though, I try two different caps with the last one being a MSD cap w/ plug wires.

HISSIN50 · Feb 15, 2007

I'd pull codes if it hasn't been done. If the miss occurs at or near idle, I'd run a cylinder balance test after KOER codes, and see if the test can help you narrow down the issue (random miss or relegated to just one cylinder).

It really does sound like an ignition issue (ignition issues are generally much more likely than fuel). A bad plug wire can really cause issues. Lookin for a light show at night is a decent dynamic test of the wires (I've had them Ohm out ok but still leak once there is high voltage running through them).

Good luck.

KcMstang · Feb 15, 2007

I have platium spark plugs in the car now and when I checked them they looking fine. Should I go ahead and replace them with copper plugs???

JChalfan · Feb 15, 2007

KcMstang said:
I have platium spark plugs in the car now and when I checked them they looking fine. Should I go ahead and replace them with copper plugs???

It wouldn't hurt. Regular ol' Autolites seem to work the best for me. I put some fancy plugs in one of my 5.0's a few years ago, and it didn't run nearly as well as the Autolites.

HISSIN50 · Feb 15, 2007

Plats can definitely be the cause. They can cause a miss at idle, and a cut-out at ~4K RPM.

Good luck.

superhuaman · Feb 15, 2007

HISSIN50 said:
Plats can definitely be the cause. They can cause a miss at idle, and a cut-out at ~4K RPM.

Good luck.

Really? Well if that is the case, then I will have 8 Bosch Platinum+4 plugs up for sale or give-away (more likely) with less than 2k miles on them.

HISSIN50 · Feb 15, 2007

superhuaman said:
Really? Well if that is the case, then I will have 8 Bosch Platinum+4 plugs up for sale or give-away (more likely) with less than 2k miles on them.

It's hit or miss. Some guys in here run plats and report no issues. Others have had issues. If you don't have issues, you really could just leave the plugs in there.........

In my case, I had a slightly low idle but didn't see a cut-out (I seldom tach up over 3K RPM as it is).
I figured I'd spend 10 bucks and get 25's to avoid possible issues in the future (let alone getting a hotter ignition spark in the process).

superhuaman · Feb 15, 2007

It has rough idle but that could just be the E-cam

KcMstang · Feb 16, 2007

It will miss at idle occasionally but not usually. Weird thing is I ran seafoam through the gas tank and vac. line once and the next day it drove fine all day long. Then the following day I got on the interstate and once I got up to about 70mph it started missing again. I can't get why the car runs good then all of a sudden go back to missing.

JChalfan · Feb 16, 2007

Have you pulled the codes yet? It's possible for a code to be stored without turning on the check engine light.

KcMstang · Feb 16, 2007

I'll try pulling the codes this weekend!

KcMstang · Feb 20, 2007

I tried to pull the codes from the car yesterday and I didn't get anything. So no help from the computer I guess. I've knocked out everything I can think of except just throwing a carb on it but I really rather stay fuel injected! Any other ideas?

KcMstang · Feb 20, 2007

My car sounds like I have the firing order completely out of whack but I have checked it a hundred times and it is right and NO it is not 180* out. Back to maybe think the MAF might be the culprit but when I through 19# injectors and stock MAF in the car that didn't help either. I have a friend that will let me try his Cobra Computer + PRO M MAF (calibrated for 24s + Cobra) should I try that???

KcMstang · Feb 20, 2007

Just remembered when I unplugged my MAF while the motor was running nothing changed! Any ideas what that is about???

Distributor cap ???

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