About to sell this pos

M

metallicademon1

LVC Member
Joined
Jun 4, 2012
Messages
13
Reaction score
0
Location
somewhere
I have a 97 Mark VIII that runs fine if it's cold, but when it reaches operating temperature it either misses at higher rpm or seems to not be getting enough fuel. The fuel level sensor was replaced by a used one and I bought a new Bosch sending unit and it hardly ever reads right, but seems that when it does, it runs better. I figured it might have been catalytic converters, so I gutted them, and it does the same thing. I finally had enough and took it to a mechanic that put it on his lift and asked if I had done anything to the converters and I told him yes, and he automatically said well that's your problem. I knew he was full of **** and got charged anyways. He put it on a snap on scanner and no codes except for something about the security system malfunctioning came up. I've replaced the spark plugs, and checked for vacuum leaks, and there were none. Another weird thing is if I unplug any sensor except the maf or the iac, they don't do anything at all! No hiccups or anything. Any help would be appreciated. Thanks.
 
Sending units have NOTHING to do with fuel delivery. However, if you have having an issue where it seems to read more accurately AND the car runs better, it may be the harness going to them being defective.

Did any of the COP boots have oil on them? That is often the cause. The oil comes from leaking valve covers around the COP towers.

When were the upstream heated O2 sensors replaced?

When was the fuel filter replaced?

When was the fuel pump replaced along with the soft fuel line that can rupture? (I assume during sending unit R&R this would have been resolved, less the pump)

No sensors will affect the car much. It will just run open loop and burn more fuel. IAC of course will affect idle. And MAF will throw the system out of balance. The good new is, if these affect the car when unplugged they are likely good to begin with.
 
Well the funny thing is when I fill my tank up it reads full and reads correctly until it gets to about 3/4 a tank, then stays there no matter what, BUT if you are checking out your economy it will still read by saying you have 305 miles left until empty, and go lower and lower, but when I get back in and start it up, or check it again it will read a different number again.

As for the cop boots, I don't think so, but the old spark plugs definitely did have some oil on the side of them, but looked like they were burning clean.

Just replace the passenger side upstream 02 sensor, and replaced the fuel filter a few months ago. Even went as far as to take an air hose and blow out the fuel lines to the tank and the engine out the shrader valve on the fuel rail. Fuel pump was replaced about 9 months ago. By the way, this car had been sitting inside for about 7 years before I got my hands on it.

Well a good question would be how to get it out of open loop? Thanks for the quick reply. These cars can be pretty frustrating, as this is the 3rd I've owned, but first 2nd gen.
 
My COP boots looked good but were bad. Had a terrible misfire from the mid-range on up, replacement solved it.
 
Out of open loop? Dont know what you mean.

You blew compressed air into the lines? Probably the worst idea ever. If the pump was hooked up and you blew into the supply line, you probably blew the fuel pump check valve. If you only blew into the return lines, then probably okay. But if you blew into the schraeder valve with injectors still installed, you could have wedged any bad gunk into the screen filters of the injectors. They would need a rebuild now.

Where exactly was the oil on the plugs? If above the threads, then it will never burn off. New valve cover gaskets, plugs and COP boot probably required. Not a hard task, just takes time since stuff has to be moved out of the way.

Fuel level reading is the least of your issues right now and only an annoyance. It could even be a fault in the cluster causing a bad read (though not likely).
 
As for the operating-temp stumble, I would agree with the group here as to it being either a fouled COP or one that is failing internally. As electrical components heat up (from working), they change resistance and output. The coils are noted for failing at higher mileages and at operating temp (just had to replace two of mine for the same reason).
 
Twice since owning my 97 I have had rough idle and tip in when warmed up, but nothing when cold. I had hoped to be able to use the Torque app and my Bluetooth OBD-II adapter to get misfire counts for each cylinder, but it never has worked for my Mark VIII (I think I got it to work with my 2000 Grand Marquis). I had to wait for it to fail so bad that it set the CEL, and usually didn't do that with one marginal COP but with 2. I just keep a few (down to 4) COP/Boots from the junk yard in the car to swap them out as I can get them to fail.

I had hoped this would show counts, I do need to try it with one of the bad COPs in place, or leave one unplugged to see if it really is zero, but I think there are always misfires, just takes a certain number to trigger the CEL or blinking CEL.

23680435755_bb33df1ac9_b.jpg
 
Bangster said:
Twice since owning my 97 I have had rough idle and tip in when warmed up, but nothing when cold. I had hoped to be able to use the Torque app and my Bluetooth OBD-II adapter to get misfire counts for each cylinder, but it never has worked for my Mark VIII (I think I got it to work with my 2000 Grand Marquis). I had to wait for it to fail so bad that it set the CEL, and usually didn't do that with one marginal COP but with 2. I just keep a few (down to 4) COP/Boots from the junk yard in the car to swap them out as I can get them to fail.

I had hoped this would show counts, I do need to try it with one of the bad COPs in place, or leave one unplugged to see if it really is zero, but I think there are always misfires, just takes a certain number to trigger the CEL or blinking CEL.

23680435755_bb33df1ac9_b.jpg
Click to expand...

I've never been able to get the reading off the cops using torque either.

For a known bad cop (I've had enough of them) I use a good spare and try it on each one until the stumble goes away. Some do the lift test while running and listen to the spark. These cars don't like to throw a cel for a dying cop.


You might want to consider looking for a low mile set of Motorcraft cops.
 
I've had 2 vehicles that misbehaved and/or quit altogether when they reached operating temp (1 GM & 1 Ford). In both cases it turned out to be the ignition pick-up coil. The Mark doesn't have a distibutor, but, a coil pack with issues might do the same thing. If you've localized the miss to a cylinder or bank, you could try swapping the packs and see if it "moves".

...just a thought. (It is also the next thing upstream from the plugs & wires)

Jim

Old school check for bad plug wires - a spray bottle of tap water and darkness. With the engine running mist the water over the engine (don't spray a stream or you might learn exciting things about electricity). This is VERY low tech, but it can help find that one bad spot on one wire.
 
^ No coil packs on this car, its a 97. No wires either. Coil packs ended with 1996 year.
 
So what I'm getting is replace the coils. Any of you had any good luck with the ones off eBay for $40 a set that are copper windings? Also, is the car most likely in open loop mode from the description, and how do you resolve that?

And I would assume that it could very well be a coil and the more gas you throw at the engine the more it will miss? That's it in a nutshell. Gets much worse the more you drive it to the point you cant. I have had good luck shutting down the motor briefly while driving via neutral and turning it back on without it dying completely and it actually runs almost like it didn't happen for a few seconds, then goes back to crap again. Coils? ...
 
Start with boots and one new coil, then change positions until the stumbling goes away. Don't buy cheap coils because you will get what you pay for.
 
Closed loop versus open loop...

When cold, and first starting up, you are in Open loop. It doesn't use inputs from all sensors, it uses a known set. I don't know what triggers it going to closed loop, I always thought it was temperature. Once in Closed loop, it starts using inputs like MAF.

I used the misting technic to find bad COPs on my Grand Marquis, but obviously they are not hidden under a cover in the middle of the valve cover. I had tried running without the cover but obviously the coils are no longer held in place, and it didn't go well.

PERSONALLY I picked up used coils off the lowest mileage and best looking Navigators and Continentals for 5 bucks a piece at the you pull it place. These things should last awhile, I am at 280,000 miles on 6 of 8 original COPs on my 00 Grand Marquis, 2 were lost in intake manifold leaks making coils swim in coolant.
 
Quit guessing and run a datalog while driving.

If it's a ignition miss, it should detect it. if it's a fuel/air problem you will see it in your fuel trims. Any sensor having problems with temperature may be found logging the right parameters.
 
By the way this car just went past 100,000 miles the other day. Bought it with 98,800 in February. That is how little I got to drive it because of issues. What other vehicles have cops and which years work with the Mark?
 
I just did a post a few weeks ago for what I look for in junk yards.

Marauders, **Navigators, ***Continentals, Aviators are the most likely candidates for COPs. Lots more DOHC Continentals that all the others, but I find a DOHC Navigators also.
 
metallicademon1 said:
And how is this data log done?
Click to expand...

I use a SCT programmer and Live Link on a laptop. I also have an Innova scan tool to troubleshoot the other vehicles in the family fleet. Both will read any codes and read live monitors to diagnose drivability problems. Either will surely tell you what you need to know and in the long run is cheaper than blindly throwing parts at the problem.
 
Well I had the idea of running the car without the coil cover on the passenger side after it warmed up good with it on and started to miss like usual at higher rpms. After taking it off and letting it run WITH the hood closed for at least 20 minutes I have yet to have a miss at all. Another design flaw from Ford with the coil cover heating the coils to extreme temperatures. I'm contemplating an idea of rigging a filtered cooling fan into the coil cover area so this problem doesn't happen as often, as I can see the extreme temperature ruining a new set of coils. Any ideas?
 
Is it a good idea to go back to Motorcraft, or are there some aftermarket coils that are just as good? Also what is the oil on the boots a cause for a misfire? I pulled off a few of the boots and noticed dried oil on the coil leads on a few. I might try cleaning them and see what happens, and also check for cracks on the coil cases but didn't see any. Money is tight at the moment, so if they have a chance at being repaired they will.
 
It's always a good idea to get Motorcraft. It's just a question of spending the money.
 
You must log in or register to reply here.

Members online

Total: 163 (members: 1, guests: 162)
Back
Top