Missfiring on ford Modular v8 after long period of non-use - gummed up injectors?

I have a 1999 Mercury Grand Marquis that has like 86K miles but has not been used for probably almost 3 years. The car ceased to be used because it had the widely reported problem with the cracked plastic intake manifold. When the driver saw signs of steam from underhood, it was driven only a few miles and then shut off - and sat there ever since (oil pan has been checked to verify no coolant has been added to oil/crankcase). First off, the car is 100 miles away from me currently - and all the work so far has been done by a mobile mechanic.

I asked him to first verify that the motor was salvageable - he said he ran a compression check to make sure there had been no headgasket blown and also checked the oil in the crank case for water. The individual saw no problems with either of those areas. The individual thought that the motor would be reliable. Because the car previously had a problem with the fuel pump, it was suspect. The mechanic also said that soon after turning on the key, the fuel pump would energize for a few seconds and then stop. So the fuel pump has been replaced (and several gallons of fresh fuel added). They then tried to start the car but it would not run very well. The mech thought it might be trash in the fuel line/rail and tried to let that flush out some. But it really didn’t make much difference. The mech has since said that if he puts a rag into the throttle body (old school choke), that it was running better. And for that reason, he thought it might be gummed up fuel injectors. His next suggestion was fuel filter and then possibly a set of fuel injectors (and then finally replacing the intake if it was then running better). I guess Im getting a little tired of throwing money at it with little confidence of a good outcome.

Won’t these injectors eventually free up after they have had some fresh fuel? Otherwise, any suggestions for getting this thing operational without much more $$?


There’s not enough info known about the car to hazard a guess about the cause of any problems without knowing the exact symptoms, any codes that may be present, condition of plugs/wires, and so on.

Did this guy give you the compression readings and did he check for codes? If a compression test is performed those numbers should always be written down. I would add that sometimes those claimed to be good numbers are not good at all.
If he ran a compression test and reinstalled old plugs then shame on him.

There are some other things that make me question the person doing the work. The fuel pump shutting off after a couple of seconds is entirely normal for one. If he replaced the pump and not the filter then he has also erred there. Stuffing a rag into the throttle body (which removes the MAF sensor from the equation) is also some pretty shaky methodogy and if the intake is suspected to be bad then why do anything until that is resolved.

At this point I’m inclined to think the problem is not the car so much as the person working on it. These are good cars and 86k miles is nothing for them.

So did this mechanic replace the intake manifold?? This is a tricky job, the injectors and fuel rail and lots of other stuff must be pulled off the old manifold and installed in the new one…A job for experts…If it has individual coils for each plug, those too must be exchanged and they don’t like getting wet…

To clean stubborn injectors, BG 44K will do it, especially if it’s pumped right into the fuel rail. But it works pretty good when added to 1/8 tank of gas… Good Luck…

Usually a misfire will quickly cause the CEL to illuminate. Then you can check the trouble codes for the reason…

Do you know how the motor was running when it was parked? Most folks don’t park a smooth running car for 3 years, so it likely wasn’t running smoothly when it was parked. 3 year old gas isn’t going to help especially if there was no stabilizer in the gas.

Get it operational without much more money? Not likely.

The car has been unable to stay running for more than ‘10seconds’ according to the repair. No codes have been stored nor could any be pulled. The intake has NOT been replaced because the mechanic suggested getting it running ‘better’ first. The mechanic is one of three (at this specific business) and all of which are ASE certified. Again, the reason it was parked was bc of the intake manifold crack that was loosing coolant. At the time, it was running fine near as I can determine. As I understand it, the tank was mostly dry and several gallons of fresh fuel has since been added both before and after the fuel pump was replaced.

In addition to the fuel filter - a can of fuelinj cleaner will be added to about 5 gallons of fresh gas.

Ask them to pull 2 or 3 of the coils, back ones, and check that the plug wells are bone dry…If the leaking manifold sprayed coolant all over the engine and it got into the plug wells and sat there for 3 years, that could be a coil killer for sure…But the fact that it will start and then die sounds more like a fuel problem…

Another place to get answers to Ford 4.6L problems is Crownvicnet.net Scroll down to the 4.6 power-train forum…

I think the intake leak was at the front. But I asked him to check the rear cyl plug wells. thanks

I will check on the crownvic site.

You might as well pull them all and change the plugs while you are at it…They probably have never been changed…