Crown vic misfire

[marauderboi]

Hey guys I need help with my 1999 CVHPP I have a very bad misfire I also get these codes P0171,P0174,P0401,P0420,and P1000
I just replaced the spark plugs and the coil boots and I installed them with the dielectric grease I dont know whats going on any help is appreciated.
Thanks,Alex

[Black_Noise]

did the miss and codes happen before or after you did the new plugs and coils?

[scruff]

buy a new set of coil on plugs problem solved erase the trouble codes

[offroadkarter]

its probably the COP's that are bad.

[Blackened300a]

P0171 Sys too Lean (bank1)
P0174 Sys too Lean (bank2)
P0401 Exhaust Gas Recirculation Flow Insuff Detected
P0420 Catalyst Sys Efficiency below Threshold (bank)
P1000 Monitor Checks Not Complete-More Driving Required

Bad EGR or clogged cat? :confused:

[RF Overlord]

Alex, having both banks too lean sounds like you have a vacuum leak...IOW, you're getting unmetered air in the system. Look at all your intake connections from the airbox to the throttle body. Also check the PCV valve and hoses, and all the other fiddly little rubber vacuum lines.

A vacuum leak will cause the motor to run funny, miss, idle erratically or too high, etc...

You can ignore the P1000 code for now...

[cougar9150]

After Tuesday I'm off until the 5th of January. Have your dad give me a call. I can come over and give you guys a hand if you need it 1 day after Christmas.

[marauderboi]

After Tuesday I'm off until the 5th of January. Have your dad give me a call. I can come over and give you guys a hand if you need it 1 day after Christmas.
Ok thanks we are checking all the COPs today hopefully that is the problem

[offroadkarter]

Ok thanks we are checking all the COPs today hopefully that is the problem


Did you ever get a tune for your MM airbox and 80MM Maf? If you havent by now, there's your problem...

[omarauder]

Does the '99 Crn Vic have coil on plug (COPs) or does it have individual plug wires with 2 coil packs? If you have individual wires I would check that the wires are going to the correct locations on the coil packs.....

[offroadkarter]

Does the '99 Crn Vic have coil on plug (COPs) or does it have individual plug wires with 2 coil packs? If you have individual wires I would check that the wires are going to the correct locations on the coil packs.....


98+ was the conversion for COP's 92-97 (and 91 for towncar) was DIS ignition with plug wires.

[Blackened300a]

Does the '99 Crn Vic have coil on plug (COPs) or does it have individual plug wires with 2 coil packs? If you have individual wires I would check that the wires are going to the correct locations on the coil packs.....

COP's I already burnt out a few with nothing more then a little water.

[Drock96Marquis]

Ryan asked me to look at your thread


If you are indeed using an 80mm MAF with the stock tune switch back IMMEDIATELY. Otherwise that alone is making you run lean. Often when people try this the car runs so bad it's like a diesel lol.
Do that and then get back to us.



First off, did this happen right after the plug swap or later on?

How much dielectric grease did you use?

COP issues would throw misfire codes, but not (normally) lean. A COP not firing would leave the unburned fuel in the cylinder causing a rich condition for that bank's o2 sensor - not lean.

First thing I'd check is vacuum leaks. Since you have an EGR code as well, the vacuum lines for EGR system would be a good place to start ;)
Listen for hissing noises with engine running (indicating a leak). Check FPR vac line
A vacuum leak large enough will make the engine stumble and cause a lean code as the air is unmetered by the MAF.

Check all your fuel injector connectors to make sure you didn't bump any loose as well. Otherwise it would cause the lean and misfire condition.