My '85 MGM, "Maisa"

[gadget73]

first just make sure its connected and not just hanging loose. If the wire busted off the terminal you can re-connect it to the intake or something that is more accessible. It just needs to connect to the engine and be in good shape.

[Arquemann]

I got around to the ground at the back of the head, tiny orange wire, seems fine and solid.
There's also a thick black wire going to I believe here:

A bracket just to side of the blower motor casing.

As I was putting back the cruise control servo, I somehow caught a vacuum line between something and that damn thin plastic line shattered like it's been next to a hot engine for the last 35 years.
The line attaches to this puck-thing on the fender:

What is the purpose of it?
Looking at the vacuum routing sticker, the plumbing would indicate it's the "VRESER", but isn't that the soup can further forward?

Trying to plug the broken off plastic line with duct take, yanked it a bit and another line shattered. This time the line that goes from the "T" to the TAD solenoid.

Went for a drive today with the o2 sensor unplugged, no change really. That rules out fuel delivery, right?
Now that I've driven it a bit more, I can say that the misfiring / jerkiness is worst at around 25 mph, it gets better going faster, still annoying at 40, finally at around 50-55 I can't notice anything really.
It idle, I can see the engine shaking irregularly and in my little experience, it doesn't seem right at all. These completely stock LoPos are supposed to idle and run buttery smooth?

[87GrandMarq]

Hmm mine used to run great with the o2 sensor unplugged lol, otherwise it had the typical cfi rolling idle. My guess would be a fuel delivery issue or perhaps a vacuum leak somewhere but thats just a guess. Have you tried capping off one system at a time to try to narrow down where a possible vacuum leak could be? How does your vacuum tree look? Also have you put a vacuum gauge on a vacuum line and ran a vacuum test? Its easy and tells you a lot about how the motor is running.

https://dannysengineportal.com/vacuu...han-you-think/

I had some of those tiny black vacuum lines go bad so I picked up a roll from autozone and some rubber connectors to slide the lines into for my ac and all has been well. I bet you could get some off ebay for cheap to replace the pieces of broken vacuum lines.


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[Arquemann]

Hmm mine used to run great with the o2 sensor unplugged lol, otherwise it had the typical cfi rolling idle. My guess would be a fuel delivery issue or perhaps a vacuum leak somewhere but thats just a guess. Have you tried capping off one system at a time to try to narrow down where a possible vacuum leak could be? How does your vacuum tree look? Also have you put a vacuum gauge on a vacuum line and ran a vacuum test? Its easy and tells you a lot about how the motor is running.

https://dannysengineportal.com/vacuu...han-you-think/

I had some of those tiny black vacuum lines go bad so I picked up a roll from autozone and some rubber connectors to slide the lines into for my ac and all has been well. I bet you could get some off ebay for cheap to replace the pieces of broken vacuum lines.

What do you mean by "rolling idle"?
My idle is very steady, but the engine shakes irregularly and listening to the exhaust, there's a similarly irregular "plop" sound

I hunted down quite a few vacuum leaks last year, last time there was a very minor leak in the heater controls (from vac tree to inside) also the throttle kicker is supposed to leak a bit yes?
I should go through all the stuff again for sure, first I've got to replace at least the lines that broke today.
Ought to be able to get cheap vacuum hose and fittings from a local parts store.

I'd like to know what all can I plug off temporarily to run the car while doing such vacuum tests.

[gadget73]

The puck thing is the vacuum reservoir for the thermactor solenoids. Soup can is for the climate control and won't be on the label under the hood. Thats purely for emissions stuff.

I usually use rubber hose to replace the petrified plastic line. If its colored hose, get some heat shrink or zip ties in the proper color to ID it if you like.

When CFI cars are right, they will typically idle smooth to the point you hardly know its running. Rough running is not something they are meant to do, but they do it when stuff is wrong.

[87GrandMarq]

What do you mean by "rolling idle"?
My idle is very steady, but the engine shakes irregularly and listening to the exhaust, there's a similarly irregular "plop" sound

I hunted down quite a few vacuum leaks last year, last time there was a very minor leak in the heater controls (from vac tree to inside) also the throttle kicker is supposed to leak a bit yes?
I should go through all the stuff again for sure, first I've got to replace at least the lines that broke today.
Ought to be able to get cheap vacuum hose and fittings from a local parts store.

I'd like to know what all can I plug off temporarily to run the car while doing such vacuum tests.

Surging really, its a common issue with cfi cars. Now the irregularities you describe are present on my 87 mgm as well but I figured it was the engine mounts. I would like to solve that too but its running pretty well and I don’t want my bad luck to rub onto this car some more lol. The ignition switch just went out too, its a great time too since I just started using it as my daily lol.

The throttle kicker is pretty much a small vacuum leak yes.

You could cap off one port on the vacuum tree at a time and the ports on the cfi itself. Just be careful if you are going to drive it like that because you will disable things like power brakes for instance.


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[Arquemann]

I hobbled together the broken plastic vacuum lines with new rubber hose and duct tape.
I should just replace them but I couldn't find the correct F-shape joiners and all the joiners are 2€ a piece FFS. For that price I am not going to just "grab a few of each" as I intended to.

The vacuum line from the fuel tank is split too, I'll get to that tomorrow.
The distributor cap still doesn't sit even on the distributor, it rocks a bit. Only 1 of the 8 contacts is worn a bit less than the others.
I put a timing light on each plug wire and cyls 7 & 8 seem to get intermittent spark loss. Would the coil cause interference that would appear as the timing light not flashing every time? Or do I really have spark issues that bad?

I'll retest anyways later, when I'm not freezing my fingers off.
Tomorrow I'll also check the plugs for any differences between them, dom't know id I'll see anything since I drove it with the o2 unplugged and it smelled quite rich.

[gadget73]

some of the caps don't fit quite right. The one on my Mark VII rocks, not sure why. I tweaked the clips to hold it down a little more securely but when I get bored sometime I would like to figure out what the high spot is so I can file it off and make it sit right.

[87GrandMarq]

How close are the 7 and 8 plug wires? They’re known to cross spark if too close.


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[Arquemann]

Would a dirty O2 connector cause the ECM to get a fouled signal, even if the sensor itself reads correctly?
Packing up stuff yesterday I noticed that the connector is super dirty with black crap.

7 and 8 plug wires go next to eachother on the (I assume) original plastic wire holders.
Should some wires cross and others not? I remember reading something like that somewhere about 302s.
But atleast 7 & 8 should stay far from each other?

[gadget73]

Won't help it any if the sensor connectors are crusty.


If you can seperate 7 and 8 in the wire looms as much as possible it might help. The big key it having space between them, so if you've got clips that will help. Do not zip tie them tight together though.


What does it actually do when you try a KOER test, just nothing? and how are you going about it?

[jaywish]

yes certain wires must be crossed. It is usually shown on the diagram if you look close.

[Kodachrome Wolf]

Here's a diagram with the wire routing from Ford.



While it looks funky how the wires bridge under each other, you can see it does it to get certain wires as far away from crossfire-possible ones. You'll need some wire separators, but it's real simple to get them routed properly.

[Arquemann]

Got some work done today,

Checked the plugs, managed to break only one plugwire, rearranged the plug wires as instructed above. Recut a split end of a vacuum line going to the gas tank.
Also cleaned the O2 sensor connector as best as I could with WD-40, brakleen and Q-tips. I might go back and put some dielectric grease if I find some lol.


4,5 and 8 are obviously quite lean and 7 seems to have been richer than all the others. (some electrodes have scratches from removal)

Here's how the wires look after rearranging them, I had to replace one with an old prestolite spare I found (not in image).

I moved the wires a bit back so they weren't on the coil wire.

The wires are Standard plug wires, Standard 6897, I think.



Drive test as usual, still jerks alot.
This seems to be somehow related to engine RPM.
35mph jerks bad in 3rd, not as bad in OD,
50mph is still quite bad in 3rd, but very slight in OD.
1 & 2 jerks also.
Accelerating with some thought is still buttery smooth. In 1, 2 and 3, I think it drops from OD almost every time I accelerate enough to make the jerkiness disappear.

As I got back home, the idle was a bit smoother in P, in gear its really nice, for about 10 seconds, then it starts misfiring again. Though this time it did not misfire at idle nearly as much, it misfires a few times 1-5, and then runs actually smooth for some time and misfires again. Best the idle has been so far.
It could have just been that the car wasn't feeling as moody today.

[Arquemann]

What does it actually do when you try a KOER test, just nothing? and how are you going about it?

Tried to do the KOER like the KOEO.
I have a test light that's like a flatblade screwdriver. I carefully put the tip in the STO, then the wire and from the test light to the battery plus.
For the ground I have a wire with a small male spade connector that fits snugly in the STI, other end has a spring clamp that I usually ground to the alternator bracket.

Just like you instructed in an earlier thread, I start the car, then connect the ground to the alt bracket.
And nothing happens, the test light wont blink no matter how long I wait.

I turn off the car and put the key back to run without starting, the KOEO test starts as it should.