Random misses under load

[jaybertx]

Howdy fellas... Long story, short question...

Let me start out by saying that I'm not much of a "car guy". I can do simple maint. stuff -- oil, plugs, brake pads, etc. but that's about the extent of it.

I have an 01 GT auto. right at 60k miles that misses randomly. At it's worst it happens every three or four seconds. At it's best, it's only barely noticeable. Outside temperature or amount of time that the car has been sitting doesn't seem to make any difference. I've tried unsuccessfully to find a pattern. Money is really tight at the moment so I'm trying to resolve this myself. I finally broke down a week ago and took it to my mechanic and the car wouldn't miss while I was there (of course). His advice was "driveability problems are tough to diagnose. I could throw $1000 in parts at it and still not find it. You're almost better off letting it break". I'm not sure that is great advice.

I've been working with a couple of friends who are "car guys". They told me to check the "EGR" and "MAF". I first cleaned and then replaced the "MAF" but that didn't solve the problem. I can't seem to find the "EGR". I have a Haynes manual somewhere but can't seem to locate it.

Since the problem started I've had the fuel filter changed, had a complete fuel system cleaning, replaced the plugs, air filter, etc. With each change things seemed a little better at first (possibly because of computer reset when unplugging battery?) but it's always come back to this problem.

I can tell you the day and time that the problem started. I have a Hypertech Power Programmer III that I bought mainly to adjust the speedometer after my 4.10 gear install but I did have the "power" tune active. One morning I started the car and it started bogging down and missing badly. It was fine the night before. I noticed the needles sweep though when I turned the car on. The needles started sweeping every time the car started. I checked everything out, it turned out that my battery was going bad, so I replaced it. Needle sweep problem went away, missing continued...

Could the car's programming have gotten screwed up when the battery started to die? I'm not familiar with how this works exactly but know that is when this problem started and it has never stopped. I despise the local Ford dealer and REALLY don't want to go there if I can avoid it...

Thanks for any suggestions you might give... if nothing else if anyone in the Sarasota/Bradenton FL area could recommend a great Mustang shop that isn't Sarasota Ford, that would be helpful.

 

[Mike97gt]

do you have underdrive pulleys? if so check the crank pulley I have seen a couple of mustangs come in with random misfires and I found a few loose underdrive pulleys causing this problem. If you don't have underdrive pulleys then

1. when was the last time your plugs were changed, often plugs cause misfires liek you have.

2. have you cleaned and oiled a K+N latley.

please post back with as much info as possible, including codes. I will check back on this one later tonight.

BTW it sounds like your mechanic is awfull at EEC diag.

 

[jaybertx]

do you have underdrive pulleys? if so check the crank pulley I have seen a couple of mustangs come in with random misfires and I found a few loose underdrive pulleys causing this problem. If you don't have underdrive pulleys then

1. when was the last time your plugs were changed, often plugs cause misfires liek you have.

2. have you cleaned and oiled a K+N latley.

please post back with as much info as possible, including codes. I will check back on this one later tonight.

BTW it sounds like your mechanic is awfull at EEC diag.

I do not have any mods other than catback and gears. I do have a K&N. It has been on for about 30k and I have never cleaned or oiled it.

I changed the plugs within the last month. That was the last thing that I tried. When I first changed them, the car was running ROUGH so I pulled all of the coil packs, re-seated them all and it cleared up the roughness but not the missing.

I haven't had any codes read because I don't have any lights on -- is that incorrect of me?

Thanks!

 

[01Steeda]

I had a similar issue with my car. The stealership kept claiming it was a timing adjuster causing the coil packs to go bad ( I dont have a timing adjuster).. they would change the number 1 coil pack and it would clear up for a few days. well after the third time of the same thing I brought it to my current mechanic.. he tuned the car and changed the coil pack... problem solved. I dont know why.. but it worked.

 

[jaybertx]

I had a similar issue with my car. The stealership kept claiming it was a timing adjuster causing the coil packs to go bad ( I dont have a timing adjuster).. they would change the number 1 coil pack and it would clear up for a few days. well after the third time of the same thing I brought it to my current mechanic.. he tuned the car and changed the coil pack... problem solved. I dont know why.. but it worked.

Is a bad coil pack something that I can diagnose myself? If it's "bad" does it quit altogether or just start screwing things up? If I find out that it's missing on a particular cylinder can I move a coil pack to see if the missing follows it?

 

[Mike97gt]

Is a bad coil pack something that I can diagnose myself? If it's "bad" does it quit altogether or just start screwing things up? If I find out that it's missing on a particular cylinder can I move a coil pack to see if the missing follows it?

It might be tough for you to diag this on your own. if it misses often you cen get one coil and try each cylinder untill the miss goes away.

do you have any misfire codes?

 

[jaybertx]

It might be tough for you to diag this on your own. if it misses often you cen get one coil and try each cylinder untill the miss goes away.

do you have any misfire codes?

Just to finish up the thread, it finally got so bad that it threw a CEL so I took it back to the mechanic and it was a bad coil pack on cyl 8. Swapped it out and VIOLA, the fun pedal was fun again.

 

[Mike97gt]

typical coil gone bad.

well glad it's fixed. thanks for checking back in.

 

[Jackie Chan]

definitely typical, i never had one go bad on me, but my old bosses 02 auto did @ 50k.