Lopo miss/autolite plugs and whatnot.

[1990Merc]

Spent some quality time with my first marquis, put about 200 miles on it this week driving to work and stuff. As I posted before it had a horrible miss, put new cap, rotor, wires, plugs, air filter, fuel filter and probably something else. I have a spare ignition module now a coil coming. Like an idiot when I did the plugs before I researched anything I thought "its a Ford, I'll get some autolite platinums" and I got the exact plug that everyone says not to use and also happens to be the exact plug that was in the car. Still getting a bit of miss, pretty rarely but still annoying. Can go 30 miles with out any and then it will noticeably miss a bit and go back to running great. Usually happens under light acceleration between 30 and 50 I'd say.

Is it worth pulling and replacing all those autolite plugs and putting in motorcraft coppers, or should I be looking elsewhere?


As a side note I've been slowly replacing my tranny fluid. Dropped the pan and changed the filter, and have been pumping out the fluid though the dipstick tube and refilling it a few times after running it for a while, get about 4 quarts out at a time. So far everything has gone well with that. Fluid looks good now, transmission is shifting well. Thought I'd gamble a bit and it may have paid off.

[Lincolnmania]

give it a shot.......me i prefer the motorcraft coppers in a smallblock ford.......i used to be a big big fan of autolite spark plugs till they started making them in china

[P72Crazy]

+1, change out the autolite platinum plugs. I tried these in my P72 w/5.8 and was never happy! Went back to Motorcraft copper all the way. You say it "had a horrible miss", definitive word "had".....the TFI can cause weird stuff at all RPMs. Eventually, you'll have to call for the hook when it goes. Look at all plugs when you remove them. I have actually measured the resistors in some of the Walmart stocked Autolite plugs (size 25 comes to mind) and found them with open circuits (resistor blown or non-existent). In other words low quality!

[1990Merc]

Definitely had a horrible miss. When I first got it, it ran like a 4 cylinder running on 3. It was truly terrible. Got a good deal on though on the hunch it would be an easy fix and luckily it was, well except for this minor miss. I think the main thing was arcing plug wires. Might swap out the TFI. The reason I got the spare was because my Grandfather was a big Buick guy, always had a spare HEI module with him...

I have 2 sets of motorcraft plugs now, probably swap them out this weekend since it sounds like the autolites are crap. Probably also do the tuneup on my other new '90 Grand Marquis while I'm at it. Then I have to get an exhaust done on that one. Debating doing it myself while converting it to dual exhaust or bringing it to somebody to have it done. I hate doing exhaust stuff. The muffler is half gone, the Y pipe badly broken and very rusty. Arg.

[miamibob]

Autolites MUST go - you'll respect yourself more in the morning!!

[91waggin]

Definitely trade out those plugs for Motorcraft coppers. Also pull codes.

http://oldfuelinjection.com/?p=13

I have had problems in the past with the EGR position sensor (hockey puck shaped thing sitting vertically on the front of the throttle body) sending incorrect signals to the computer and the computer inappropriately adjusting the mixture in response, causing the occasional miss. These items are notorious for failing, and the egr activates itself usually under cruise and light acceleration.

Ensure timing is at 10deg BTDC.

http://oldfuelinjection.com/?p=71

A cheap harbor freight timing light will enable you to do this.

Make sure your TFI module came with thermal paste (opaque paste) rather than dielectric grease (translucent jizz-looking stuff that you put on spark plugs). If there is improper heat transfer between the module and the distributor base, the new unit will fail in record time.

Bring back codes and other questions! These folks have lots of answers.