Had problems with my car missing out. My son has an analyzer and found problem with the plugs. We replace all the plugs and coils with Blue Streak coils and Motorcraft plugs, on my 2004 Grand Marquis automatic that had 147,000 miles on it. Still had some missing problems. My son has an analyzer and found problem with the plugs.
Took it to Ford. 3 times. First time they said the connector on #5 was bad and they replaced it. They also cleaned the throttle body. Got it back and still had problems.
Back to Ford. They said coils on 1, 2, 4 were bad. So went to Oreilly's and exchanged them. Still had slight problem. Back to Ford. They said the coils on 1, 2 and 4 were not right, they they were hitting on the fuel rail. So back to Oreilly's. Ended up replacing the mas air flow sensor and the idle sensor myself. Still was not running great. So I remembered Scotty talking about a bad battery not having enough power to run everything, but would start the car okay.
So went to Oreilly's and had the battery checked, it was a 4 year old Interstate and it checked bad. Replaced it. After 2 or 3 days the car was running great for the past 3 weeks. When I took the car to Ford the first them, they pointed out that the intake manifold was leaking and I should get it replaced and keep an eye on the leaking for now. So I took it to Ford, Blue Springs Ford in blue Springs Missouri to get the manifold replace. Total including labor and parts around $1286.00. Picked it up yesterday and after warming up it started running lousy like before. So I turned around and took it back to Ford and left it. Today April 7th 2021, they called this after noon and told me all the coils needed to be replaced. They replace one on #7 and said it was running better. they wanted $800 to replace them all. In spite of the fact I told them mall had been replaced and the car was running great the past 3 weeks, until they replace the manifold.
{black}:pray: Considering the age of the car, could removing all the wiring and everything else to replace the manifold, could the wiring or connectors have been damaged due to the age of the car?
Unfortunately, the causes can be many. Stay away from dealerships. The vast majority of dealership mechanics anymore are trained to be parts swappers at your expense and they don't know how to use a logical approach to diagnostics beyond what their "test equipment" tells them. The very few that do know, usually don't have the time or are told Not to spend the time because it's too costly. If it makes you feel better, Yes a leaky manifold "could" cause a vacuum leak which can cause misfires, however, there are cheap ways to check this without using a "shotgun approach" of replacing an intake manifold / gasket at your expense on a guess.
This said, again, the list of causes is vast and I would recommend to sell / trade the car in and look for something less troublesome (Toyota, Lexus, Honda, etc. but if you are attached to the car and want to debug the issue yourself then I would start (again) with the basics.
- Get a Factory Service Manual Service and Wiring set (not Haynes, Chilton, etc.)
- Determine if you are actually encountering a misfire or if it just seems like a misfire
- Collect all the Check Engine Light codes using an ODBII diagnostic unit
- Clear all the Check Engine Light codes (CEL) by connecting an OBDII diagnostic unit and clearing the CEL codes or by Disconnecting the battery for about a few min (say 3 - 5 min).
- Run and/or drive the car to collect CEL codes again
- Run / Drive the car for a couple days to collect any additional CEL codes to see if more codes occur aside from just one or two)
- Test each component associated with the area one at a time (keeping in mind that a component elsewhere that affects the failing system area can cause the primary failure)
- Be patient and don't jump to conclusions as intermittent problems are the worst to diagnose
- Don't spend $$$ needlessly
A common list of potential engine misfires is as follows:
- Incorrect Fuel Octane (use correct octane fuel)
- Bad (or cracked) Spark Plugs, Ignition Wires, Coil(s), Distributor Cap and Rotor (when applicable)
- Bad ground wires and/or battery ground. (Grounding is critical especially for modern computer controlled cars)
- Incorrect Ignition Timing (worn timing chain / belt)
- Vacuum Leak(s) (vacuum lines, intake manifold, etc.)
- Poor / incorrect Fuel Pressure
- Improperly functioning EGR (Exhaust Gas Recirculation / Reburn) System
- Bad MAS / MAF Sensor (Mass Air Flow Sensor)
- Bad CPS (Crankshaft Position Sensor and/or Camshaft Position Sensor)
- Bad TPS (Throttle Position Sensor)
- Bad or cracked wiring / connections
- Bad ECU (Engine Control Unit / Engine computer)
- Other mechanical / engine Problems such as Low Compression, Leaking Head Gasket(s) or Valve Problems
- Etc.
Factor Service Manual (2004 Grand Marquis):
https://www.ebay.com/b/Repair-Manuals-Literature-for-2004-Mercury-Grand-Marquis/36085/bn_7088664640
Take it to an experienced independent Diagnostician and get an overall general inspection of the vehicle. And stay away from the dealer's service department.
