Okay I need some help here. 2 problems with my 95 Mark. First of all it has a sick rough idle and has had it for a while. When I am sitting at a stop the rpms will jump around in the 5-600 range rough as hell. Sometimes it does it, sometimes it doesn't. I have had new plugs, new plug wires, check engine light was on for an 02 sensor so I got a new one. I have also just recently had a new radiator installed and an alternator. I try to treat the Mark like a king but it's not returning the favor! Also just had a new air filter installed and an oil change. A while back I was told the rough idle was due to low compression in one of the cylinders due to burned valves, so I payed a ton to have that fixed. It helped for a while, but the roughness came back shortly. Could it have something to do with injectors or the fuel pump? Please give me suggestions because I am out of ideas. Second of all, when the heater is on and I am stopped I get exhaust fumes in the cabin. AC works great and everything but the heat seems to carry exhaust fumes with it. Another thing that makes me think it may have something to do with the injectors is when I am driving along sometimes it will kind of "jump" especially when I accelerate lightly, I don't know if you can tell what I mean by that but it's the best way I can explain it. Help me out plz!

I had a similar problem on my '93. For me, it was a clogged EGR passage, and a broken EGR tube. I'll assume that your EGR tube is not broken.

I had to remove my hood and wiper motor assembly to be able to reach everything easily.

Clean out the EGR passage in your upper intake; just under the throttle body. It might be full of carbon which you'll need to chisle out with a screwdriver.

You'll have to unbolt the EGR tube from the upper intake to do it. Be careful not to hyperextend/damage the tube; it's 80 bucks.

Be sure to stuff the upper intake with a few rags before you start breaking the carbon loose; you don't want that carbon falling down into the engine.

Vaccum out the carbon you scraped out before you remove the rags.

So is this something I can do myself with little know-how? It sounds like I could do it of you drew me a diagram or something lol. I don't know much about engines, so should I take it to a mechanic instead or do you think I can do it myself?

Whats the mileage? Also your at the Fort, as in Fort Dix? If so theres a ton of cutomers of mine there with some bada$$ Marks. Look up Don Newlin.

About 85k miles. Nah I'm in Fort Wayne, Indiana. AKA Fort Fun! <---Sarcasm

i too have a 95 and had that had the same problem when i bought it. make sure you have good compression in all the cylinders. you could have dropped a valve like mine. that or have someone run a check with the computer. ive heard that iac may cause rough idle. but mine was the fact that a valve spring let loose. good luck man

Thanks man. I had it on a computer and all it said was the 02 sensor was the prob... Maybe it is a valve again, I'll be pissed if it is :(

So is this something I can do myself with very little knowledge? I'd really rather not fork more money over to somebody :(

You can order a compression tester kit form Harbor Freight pretty cheap. There are many sites out there for the proper procedure.
Do a site search on O2 sensors and you will find many helpful posts. The driver side upstream sucks bad, I still have a cut healing on my hand from doing mine almost over a month ago.

Nah I don't mean the 02 sensor. I got that replaced. I know a guy that owns a Hires and will let me use his testers, I'm just wondering if I could clean the EGR tube myself.

id say just check the compression for giggles thats what i did nothing came up when my buddy used the computer so i figured it was fine but it really wasnt. good thing i got the car cheap enough to go and be able to just pick up the motor from junk yard and still pay less for both then most people have on this sight for a good running car.

Just my 2 cents. I would try a new fuel filter first, keep it simple to start. I didn't see that you had changed yours yet.