95 MK misfire

W

wkokaneeman

Active LVC Member
Joined
Jun 20, 2013
Messages
188
Reaction score
7
Location
Modesto
Pretty sure I know the problem, but i'm having an intermittent misfire on my 95 MK. When I first got it, was driving home one night, and it started misfiring on the freeway. got a couple of miles further down the road, and it cleared up, and has run fine ever since, but I haven't driven it much except around town. It's been parked quite a bit. I don't like commuting much, because it's 84 miles to work one way, and it gives me the creeps driving it in California commute traffic!
My 98 LSC is down right now, due to an air ride system pump, on order from American Air Suspension. So i'm on my way to work this morning, and i'm in od, and climbing a mountain, and it starts misfiring again. Stayed that way until I hit the next mountain range to climb, and then after dropping down the back of the mountain, it cleared up again, and has been running fine all the rest of the day.
So my 98 has done the same exact thing a couple of times, and it was always 1 of the coils. Being a gen 1 car (the 95), compared to my gen 2 car (98), the 98 uses a coil over every cylinder, and the 95 uses a coil pack, 1 for each bank of cylinders that fires 4 cylinders. A difference between the 2, but acting the same way.
So, you think it's a coil pack? Because if it was a plug or wire, it probably wouldn't be intermittent. It would probably always be misfiring. Any thought or ideas is appreciated!
 
The Gen1 coil is known as a Share Spark Coil. Each pack only contains 2 firing coils, each coil fires 2 cylinders. 1 of the coils fires is a wasted spark. Its not uncommon for a coil to go bad. Just unplug a wire from the spark tower on the coil and hold the wire just inside the tower..is it sparking??

After this check, check the plugs.. are the wires still the original wires? If so replace them , same with the plugs

An electrical misfire will generally trip the CEL, a fuel loss misfire will not. Check fuel pressure.
It almost sounds as thou you're dealing with a failing fuel pump or a clogged fuel filter
 
I've had similar problems with my 95 before while highway driving, it usually does it after hard acceleration getting on the highway, it gives a rotten egg smell and starts bucking slightly like there's a misfire and the CEL comes on..but then corrects itself after driving for another few miles and the CEL will turn off..and if it doesn't correct itself, it will if I shut it off and restart it. I always thought it may be one of the cats that is clogged..but never knew why it would cause it to misfire. We will find out when I put the new exhaust on and gut the front two cats.
 
I'm not getting any kind of warning lite on the dashboard. The car only has 38,000 miles on it.
 
I chased this issue for a while on my 95. Turned out to be a bad TPS alignment. I tried every brand I could get my hands on and they all sucked. Got a motorcraft off amazon for $46 and it was better. Checked the position with a volt meter and it was off. I drilled out the holes to adjust it to spec and I haven't had a misfire since. I don't remember what the voltage was supposed to be at 0% throttle, but I know mine was way off. I'm not saying this is your problem, But its worth checking. Try checking the voltage before ordering a new one.
 
SleeperMark said:
I chased this issue for a while on my 95. Turned out to be a bad TPS alignment. I tried every brand I could get my hands on and they all sucked. Got a motorcraft off amazon for $46 and it was better. Checked the position with a volt meter and it was off. I drilled out the holes to adjust it to spec and I haven't had a misfire since. I don't remember what the voltage was supposed to be at 0% throttle, but I know mine was way off. I'm not saying this is your problem, But its worth checking. Try checking the voltage before ordering a new one.
Click to expand...
At idle(closed throttle) the TPS is suppose to read under 1.0 volt. You want to be like around .95V at closed throttle. The reason is the car starts the enrichment right at 1 volt and above.
 
.97v kept coming to mind while I was typing that post, but I didn't want to give false info. Thanks for answering that for me.
 
If they're original they're motorcraft. I feel like those have a lot more life than 38k miles. But if you do, I just picked up a bunch off rockauto.com last week for $0.87 each!!
 
I had same problem on my 95 way back in 1999. Dealer checked it and said # 2 cyl has a problem. $500. for a tune up (holy cow) I changed wires and plugs and problem gone. Back then the wires cost me $130. Much cheaper now 10 years pass and the wires swelled to the size of a hot dog. Changed wires ($65.) Car has 112k miles and still runs great.
 
SleeperMark;

What's the TPS? not familiar with all of the terms on these cars. and you got a bunch of what for $0.87 from Rock autu? Spark plugs. and I'm not sure that the plugs are original, but I'm thinking its defiantly a possibility.
It just seems to me that the way it acts, just like my gen 2 car when a coil goes bad in it, is an electrical problem, because its intermittent. and it's not the gas. I've been using this gas for years in my gen 2 car, and never had a problem. I thought that it might have been gas too the first time it did this a month ago, so I put some injector cleaner in each car a couple of weeks ago, TPS? what is that? Thanks for the input.
 
Motorcraft spark plugs from rockauto. And yes, TPS is the throttle position sensor. In a Gen 1, it is really fun to get to as it is located on the back of the throttle body facing the firewall. The easiest way to get to it is by removing the throttle body. To do that, remove the 4 bolts (8mm I think) and disconnect the throttle and cruise control cables. The cruise cable is removed by pulling up, not out (I broke mine that way). Then lift the throttle body and you will see a wire harness running to the throttle position sensor on the back. I would recommend replacing the throttle body gasket also. Make sure your auto parts store gets you the correct one before you tear into it, mine ordered the wrong one 3 times. I you're patient and crafty, it is possible to get the sensor off without removing the throttle body. It's just a little tough. If you're not far militant with what a throttle position sensor does, it is a potentiometer that measures throttle input through change in voltage. It works with the mass airflow sensor and between the two, the computer uses a mathematical formula to correct the air/fuel mix. If the voltage at the idle position is off, it throws all the other positions off also and causes the car to run improper mixtures.
 
I'm really feeling it is a coil. Talked to a mechanic friend this morning, and he said if it was the TPS, it would be misfiring all the time. and we know the coils fail all the time in these cars!
 
I have almost 200k on my factory coils. I bought a new motorcraft set for an insane amount of money and they didn't make a difference, so I returned them. I would check the voltage on your TPS. It's a free check. If it's out, adjust it within spec and see what happens. Mine was intermittent also. If that is good, try plugs since they're the next cheapest option. Where do you get your gas? As odd as it sounds, every time I get gas at shell I get a misfire. I have to get gas at BP or Ayerco now.
 
wkokaneeman said:
Yeah, I get it. I still think its a coil. The intermittent thing is why.
Click to expand...
my brown Mark used to 'buck' intermittently, usually at low rpms (700-1200 roughly)....my double plats had about 35k on em and looked perfect, swapped em for new 764s and bingo, running like a german watch again...
-----
it may be the coil, or the TPS, but if your plugs have 38k on em, changing them is in order...imo...an easy inexpensive start at TS-ing
 
You must log in or register to reply here.

Members online

No members online now.
Total: 52 (members: 0, guests: 52)
Back
Top