Mgzt260 slight missfire

[Malcolmr]

After you try the injector move that Steve sensibly suggested, if that doesn't work, check the connection to the COP on #5. MSD's can be a tighter fit than the OEM COP's and not properly pushed home. Examine the COP for dampness (on and in the tube part), and ensure that the contact spring is properly seating on the spark plug terminal. Finally swap #5 COP and another in the same way as you did the injector. Peer down the plug hole and see if the plug insulator ceramic looks discolored or "different" to the others.

David

After I replaced all my plugs recently after a persistent low revs misfire, old 206 was initially worse. The misfire was more frequent, especially under a light load at low revs. Then one day I was driving in normal traffic when the car gave a little surge as if someone had turned on a "go faster" switch and the misfire went away. Now the car goes like a rocket! I'm still looking for that switch, but I presume what happened was one of the COPs wasn't seating properly, as David mentions, until more driving and vibration moved it into position. I had great difficulty with cylinder 4 (I think that's no 4 - the rear one in the bank on the right hand side of the car). Very tricky getting the plug in and out and then pushing the COP back into place.

Malcolm

[ColinE]

Very tricky getting the plug in and out and then pushing the COP back into place.

Easy with the engine out

[David]

... I had great difficulty with cylinder 4 (I think that's no 4 - the rear one in the bank on the right hand side of the car). Very tricky getting the plug in and out and then pushing the COP back into place.

Malcolm

The Ford V8 convention, Malcolm, is that that one (over by the EGR system) is number 8, not 4. When looking at the engine from the front of the car, the cylinders on your left are, front to back, 1,2,3,4 (Bank-1), and on your right, front to back, 5,6,7,8 (Bank-2). There is no universal numbering system, though. GM swap the banks over I believe. That is important to know, because the car's diagnostic system will refer to cylinders in the way specified by the manufacturer.

From Ford:

"Ford Motor Company numbers its cylinders along each side from front to back. When looking at the engine, start on your actual left-hand side with the cylinder closest to you as number one, followed by two, three and four. Then look to your actual right-hand side; the cylinder closest to you is number five, moving along the line away from you to number eight."

Been trying to avoid suggesting this, but the fact that the misfire is indicated on Rick's car at #5, points to the possibility of a problem with the intake install. #5 is the plug next to the thermostat and top hose connection. IF the plug hole is wet, then it could be a coolant a leak. If it's not wet, ignore the rest of this post!

Easiest to fix would be a top rad-hose to thermostat join leakage (common; new silicone top radiator hose from club shop).
Coolant seepage could also be from the thermostat-housing to intake alloy crossover joint (O-ring, silicone grease).
(The other common problem of a leak between the alloy crossover piece and the plastic intake there, is caused by "plastic rot", so highly unlikely with a new Ford intake).
Most likely, unfortunately is that the intake was not properly fitted. Wrong torque, wrong sequence, or not torqued cold and then again finally when warm. Another very common problem when fitting a new intake, is that, although the gaskets should be fitted dry, the head alloy becomes corroded at the joints with the water galleries. A good gasket sealant should be used sparingly, on the head-side and only around those 4 points, to avoid leakage. I had that happen and I know of one more from another member a few months back. My leak was from the gasket near plug #8, so a rear gallery, caused I suspect by no sealant being used on a corroded surface and, also not re-torquing hot. Not done by me, but by my (ex-)garage.

David