Automotive Forums

I have an 89 Mercury Grand Marquis, 5.0L.  It started stalling from stop signs, and some rough idling.  I began to check all the ignition and tune up parts.  I found white corrosion on the ignition module, pulled the distributor, and replaced the module.  When I put the distributor back in the car wouldn't start at all, then I realized I had put the distributor back in the wrong place, even though I had the rotor marked on the #1 firing order. After trial and error, I did get the car to run about 90% to where it was.  Now it was running very rough, and sounds like it is dieseling, especially at acceleration while in overdrive gear, but sometimes from a stop sign as well.  The plugs, wires, distributor cap, and coil all had less than 10,000 miles on them.  I checked, and found some wires that were black and fouled, and they actually fell apart, so I replaced them with an expensive set.  Baffled, I took the car to the mechanic.  The timing was only off 6 degrees, so I did get it back correct.  They found that not all cylinders were getting enough fuel, due to the new plugs not being blackened any.  After a fuel pressure test that turned out fine, they didn't know what to do, except change the fuel filter, then the fuel pump.  I did just that, and the problem went away for about 25 miles, and now it's back, but a lot less frequent.  I changed the pcv valve and cleaned the filter.  I cleaned the egr valve inlets with a wire brush, and vacuumed it out, and replaced the gasket.  My other options that I've researched seem to be: EGR Valve replace, Map sensor, Oxygen sensor, the pcm computer, and the catalytic converters.  Sorry this is so long, but I wanted you to know the whole story.  The car is running very rough, almost sound like dieseling, even though it does not diesel when it is shut off.  Your thoughts please?
Chris  

Any of the above could be the problem,  my next move would be the map or 02 sensor.  Any exhasut shop should be able to perform a test to tell you if your cats are clogged.  so maybe get that checked out first.  

Thanks for your reply.  The other replies I'm getting on other forums, all say the distributor is not at TDC.  The mechanic told me the timing was only off 6 degrees, and was marked properly just as I had done.  Also, if the distributor was still not correct, wouldn't this problem be occuring all the time, and not intermittent?
Chris  

No,no, he changed it, but it didn't solve the rough running.  He really thought it was the fuel pump or filter.  He wanted the car to just quit running so it would for sure be the pump.  He also knows how stickler I am on money, and letting mechanics do to much trial and error fixing.
chris  

so the mecaninc told you it was off 6 degrees but didnt change it?  

All,

I acted on the following suggestion, and checked over everything that had originally been done in my email, except the distributor, because if the mechanic was wrong, and it wasn't off by 6 degrees, and is still off by whatever degrees, the car would be running rough at all times.  I separated the wires in the following TSB, drove 18 miles with the ac on max, in 93 degree heat, absolutely no problems!  Went out to drive it today, got less than 100 ft, and back to the running rough, especially on acceleration.  I'm going to get the Actron CP9087 scan tool that was suggested, as I can use it also on my 98 Intrepid with 153,000 probably in the very near future.  This way I can test everything except the catalytic converters, which I can get done for free, but I don't thinkg that's the problem, and the EGR valve, but I can test the sensors.  I'm ordering it over the internet, so I won't have an update for a week or so.  Here was the TSB, thank you to the person on this board that suggested it.

Also, there is one other thing that you might check. I believe that Ford issued a TSB for 5.0's in your year range. They warned about routing the #2 and #4 plug wires too close to each other. Also the same for the #7 and  #8 wires. If the wires are too close they can induce a voltage in the adjacent wire. Thus, #2 can fire the 4 plug, and #7 can fire the 8 plug out of sequence.

Chris  

Update:

Well, I received my Actron CP9087 scanner.  I did three tests on the ignition module, egr valve sensor, map sensor, and oxygen sensors.  The ignition module test is only for a dead, "no start".  It tested good, but I took it back off anyway, took it to the auto parts store, where they can heat it up, and test it, still good.  All the tests came back just fine except the map sensor failed all three times.  I replaced it and re-tested, it now passes, so I re-tested everything a fourth time, all passed. I replaced the egr valve.  I pulled the battery cable to reset the computer.  Nothing has worked.  A better description of the rough running would be, it sounds and acts like you have a manual choke, and while you are accelerating you are fine, but in overdrive,  you are choking the heck out of it!  My only other option is to replace the computer.  Your thoughts please, and recommendations.

Chris  

hmmm..  Hopefully someone else has some ideas and can help.  So the condition is the same.


Everything checked out fine except for the map sensor.  You replaced the map sensor and it didnt help.  

This is where you are at now correct?  

Updated:
I took the car to the mechanic, in case it might be fuel injectors, compression tests, etc.  He thought egr as well, but not after he knew I replaced it.  He said he would cover all the bases.  I'll let you know what he comes up with.  When I drove it up there, I had driven 21 miles with no symptoms.  I'll let you know.
Chris  

Thanks because I would sure like to know.  

I was gonna mention your injectors.  check your ckp and cmp sensor connections, make sure they are not super dirty and still have a good connection.


Good luck  

How is your timming Chain free play. You may have a chain that is real loose. To check it: take a rachet and socket and go on the bolt in front of the crankshaft pulley and while turning it back and forth watch the rotor in the distrubuter. It should start moving as soon as you move the crankshaft. Now rock the crank back the other way. If it doesn't start moving right off. You have a loose chain. Which could cause your problem. Because it is some times in time and other times not  

Final update:

I took the car to the mechanic.  79 miles later still no problems.  Before I took it up there, I did take the ignition module off, and had it tested, which was fine.  The only thing myself and the mechanic can think, is that there wasn't enough heatsink on the module, or the heatsink didn't do it's job.  I put plenty on this last time I put the module back on, just like I always do.  I don't know, it's not having any problems now.  Thanks for all your help.

Chris