1987 Lincoln Town Car Misfire

RAINHOPPERROO

MEMBER
1987 LINCOLN TOWN CAR

I have a low idle misfire issue. Either at low idle or low load I feel a slight miss every once in a while. Its not enough to cause a major loss in HP but I want to get it resolved before I replace the cats and 02 sensors (cats arent working at full efficiency I registered 127 ppm HC during my last smog) though this might be part of the issue.

here is a list of things I have done so far to resolve the misfire.

tuneup
plugs
cap
wires
rotor
timing set properly and tested
fuel injectors cleaned (professionally)
seafoam in the crank case (helps free up lifters that might be stuck)
checked EGR
checked for codes, none present
new temp sensors (3)
coolant air and engine
fuel injector cleaner aditive for extra measure
inspected for maniforld leaks (carb cleaner around gaskets)
block sniffer, checking for exhaust in the radiator, none found (blue liquid)
inspected radiator at operating temp for signs of head gasket seepage (fizzing or bubbling)
inspected oil for signs of coolant leakage

now once under a good load the problem disappears, I've not reinspected the plugs but the last time I ha this issue the plugs looked fine (another 87 but in a non emissions state) and the right bank is a pain to get to so I've been putting it off.

This car is low mileage, 93,000 original has the 302 efi v8 engine and the only TSB that shows was for the sensor on the manifold which I checked and replaced. (Made a little diffrence in overall driveability but nothing for the misfire)

I was a mechanic (apprentice with 2 certs) so working my way around an engine is easy to do, I am willing to try some of the more unorthadox techniques as I am familiar with the safety and risk. But I need to track this down before I replace those cats, I dont want to frag them again and still not have a solution. Those arent fun to replace ^_^

6 Replies

SERVICE WRITER

MECHANIC
9,123 POSTS

Clean your maf sensor.
It seems that a "missing" engine culprit is actually the computer's sensor inside the Mass Air Flow Sensor (MAF). It eventually just gets a little dirty or builds up its own patina in the filament wires. A dirty or slightly patinated filament will send the wrong air reading to the computer, saying it is getting more air than it really is and the computer will tell the EFI to send in the wrong mix of fuel, thus, the bogging. The patina seems to form faster if you live in a damp climate. If you have had bogging or missing or idle spots, about every 25K miles plan on this quick cleaning job:
When your engine is cool, remove the wiring clip from the side of the black plastic sensor part of the MAF aluminum body. To remove the MAF interior sensor wire, you will need a Security Star (Size T15 or T20) screwdriver or screwdriver bit for a power screwdriver. Remove the two security star-head screws and carefully remove the sensor. You will see the two sensor filaments... They look almost like the filaments on a light bulb. Carefully spray the filaments with an O2 safe carburetor cleaner, such as Gumout. Let it dry thoroughly. I help mine along with a careful blast or two of canned dry air. While it is drying carefully wipe the aluminum mount surface of the MAF body if there is any dust there, but be careful not to get dust in the mount hole. When the sensor is dry, replace the sensor back in the MAF body and secure with the security star-head screws. These don't need to be torqued down, just simply hand tight. Replace the wiring clip. Then start up your engine.