weird problem...please take a look

rock4451

rock4451

20+ Year Stangneter :roc</strong><span class=
Nov 30, 2004
12
2
29
New Baden, IL
#1
Okay, I just got my 95 cobra last week, upon getting it home I noticed an exhaust leak at a gas station, no big deal, the x pipe is in the mail now. but i dont think thats related to my problem (help me out?) my car starts and idles fine, but when driving it feels like there's a slight miss in it. when i step on it, it doesn't exactly feel like a miss but just not as strong as it should. i replaced the wires, checked plugs (all look new), changed the oil, replaced the fuel filter, and changed the battery (it was bad anyway). it still feels like a slight miss, and my tach jumps up or down in intervals of about 2 or 300 when i'm cruising at say 60? from what i've read looks like distributor, but any other input is more than welcome.
 
#2
Check the MAF sensor for dirt and grime, clean it for sure. Spray some carb cleaner on a qtip, and lightly rub the dirt off until the qtips come out clean. Sounds just like a problem I used to have. Car ran great but just didn't pull hard past 3k rpms, and the tach would jump like crazy.
 
#3
302GTS said:
Check the MAF sensor for dirt and grime, clean it for sure. Spray some carb cleaner on a qtip, and lightly rub the dirt off until the qtips come out clean. Sounds just like a problem I used to have. Car ran great but just didn't pull hard past 3k rpms, and the tach would jump like crazy.
Click to expand...

DO NOT TOUCH the filaments in the MAF.. Just buy some mass air sensor cleaner and spray the hell out of it..
 
#5
okay, great idea, i didnt even think of that, slipped my mind. i'll give it a whirl tomorrow and let ya know how it works. until then, anybody else have other experiences that were similar they could attest a possibility to? any ideas at all would be fantastic
 
#6
so far i've ruled out the battery, wires, plugs, could be the coil (mine rattles a bit, its a MSD TFI Blaster coil, it can be wiggled up and down a bit) I am sure it is a spark or ignition prolem, because when it misses a bit, my rpms take a dip of about 2 or 300 for a split second...then come back up...and this can happen nonstop until i step on it. somebody has to have had some similar experience? i havent had a chance to clean the maf yet but thats a possibility, i just dont think it would affect a miss and my tach moving the same time as a miss
 
#8
Though the wires are new, check them for spark leak. They might be getting hot and limp and grounding out intermittantly.

Be sure the EGR is functioning properly.

If it misses at idle, run a cylinder balance test (you do that after pulling KOER codes).

Good luck.
 
#9
KOER codes? i am not familiar, I had the guy at autozone run his diagnostic OBD II on it, and it came up with no codes, i only did this because i didnt wanna spend the money on it if they did it for free. im not sure how to pull the koer codes...i replaced the coil and it appeared to be running alright, but then about 5 hours later i took it for a drive and there the miss was again...while i was out, my dad gapped the plugs at 52, the guy before me had then gapped at 34. stock calls for 52 but maybe that is too big for my setup for some reason for it to keep constant spark? i am just thinking out loud, please give your input if you're electrical/ignition knowledgeable...
 
#10
The 5.0 Mustangs are OBDI cars, not OBDII. The connector under the dash does NOT work on our cars. (it does work on the V6, Ford's way of saving money on parts) The scanner hookups for the 5.0 are behind the passenger shock tower.

KOEO - Key On Engine OFF tests. KOER - Key On Engine Running tests. The Autozone scanner can run these tests, then the codes are read. You have to run the KOEO test before running the KOER test. While each test is running, you'll hear things in the car click and turn on & off.
 
#16
My car was doing the same thing but it turned out my battery was shorting internally. It could be a bad ground. Bad gnds do weird things. You changed your battery though so I don't know what to tell you except that both my mustangs did this due to bad grounds. Good luck.
 
#19
problem didn't go away...at full throttle, there's no miss, when my foot's off the gas, no miss, but if i am going say 60 and hold it steady at 60 the rpms jump down about 2-300 in intermittent spurts and jump back up to what they should be. i can also hear the car miss at the same time and it feels to vibrate slightly when it misses but as soon as i step on it, or take my foot off completely it doesnt do it anymore. i am completely stumped. changed the coil, got rid of my msd box, cleaned the maf, new IAC (which is unrelated), changed my wires, gapped my plugs at 52. should i check the voltage at the coil? new stock distributor is in the mail to be here today. i am just scratching my head b/c if it was with my valves or compression wouldn't it be constant no matter what? just frustrating as hell
 
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