89 Merc CP Stumbles or stutters 5.0

thats what i thougth Krash, so the coil and distributor are both new as well.
Ive replaced or tried the following, and probably some im forgetting.
Maf sensor
distributor, coil, wires, plugs, cap, rotor
O2 sensors
fuel pump, filter, pressure regulator
fresh vaccum lines
voltage regulator
engine temp sensor
egr valve and solenoid, pcv valve and screen.
throttle position sensor
ignition module

Since there was no change in the voltage issues with a new regulator im thinking i may be having a problem with the Alternator itself. With the way the stumble can be provoked by adding AC or headlights.

 

If you decide to change the alternator, I would try to find the heay duty one that came with the Insta-Clear indshield. It is, I believe 120 amps, instead of the standard 65/70 amp unit. It may have a different wiring harness, and likely a heavier power cable. It works well, though, and extra power never goes astray. The Thunderbird has a 200 amp PowerMaster in it.

Just had another thought. How are the battery cables? I have switched to 1 gauge cables for all 3. The positive to the relay, the negative to the block and for the relay to starter. I have added a 4 gauge to ground the body separately. It seems to work well, and was an easy install.

 

How good are the gurus on the Ford Panther forums?
Which one do you go to? I drop in on grandmarq.net on occasion, but things seem pretty slow over there. They do have at least a couple of 5.0 experts though.

 

Has to be a sensor or something. The 5.0 is not the problem...the same problem has happened with 2 different engines.

 

a friend suggested it could be an injector with trash in it, or an injector sticking open or closed since it goes and comes. i liked that idea until i realized its not a random condition. its intermittent but not random. i can induce it by turning on headlights or AC.


now that brings the question.. am i inducing by adding electrical drain on the electrical system, OR by adding pull on the engine from the alternator making the problem present.

if i knew the proper way to test for power use or output on the alternator.. i could watch that for changes when the misfire goes away?

 

There is a very easy way to monitor the voltage output as you drive. Get yourself a cigar lighter inverter than has a voltage display on it. Plug it in, and keep an eye on the voltage as you go.

When you replaced the coil, did you use a factory type that uses the horseshoe connection, or did you go after market? If you went aftermarket, make sure that you didn't accidentally reverse polarity. It will run but not get as much spark. If you are using the horseshoe, make sure the contacts are good. They could well be worn. The horseshoe pigtail is available from the local Ford dealer.

By the way, I've been driving nothing but Panther platform Fords since January 28, 1989. I sort of work on the just a little bit!

 

Had a suggestion somewhere else to check the o2 sensor feed lines to see if they were backwards, they were.


OK. Swapped the wires yesterday. drove it around, and then to work this morning. Misfire isnt as severe but still present. Still low power climbing hills. Still appears when system goes into closed loop.

what other sensors activate in closed that arent active in Open loop?

 

The O2 sensors may need a bit of time to 'cook' themselves clean. On top of that, the computer needs time to bring everything back into calibration. I would be tempted to give it a day or two and see if it gradually improves. If things were that far out, you will actually feel it changing as the settings adapt to the new conditions. Don't forget, too, that the owner's manual has a prescribed procedure for 'teaching' the computer how to run the car after the battery is disconnected. It takes 20 minutes of idling, and don't be surprised if the car stall a time or two during all of that. It is actually freaky to sit there and HEAR the changes happening.

 

Thanks Mike, Ill look for that teaching lesson and follow it thru. That is when i get the car home. Noticed after the wire changes that it took a few more turns of the starter to fire. Then Friday afternoon, leaving work in a balls out hurry, she wouldnt start. No fuel pump. Heading over in a little bit to see if we can bang on the tank and at least get it home. If not then something came unplugged somewhere.

PS its a new fuel pump, but was very loud, so always suspected.

 

just pulled the car home, and it fired right up. great. i cant find anything in the owners manual that states how to reteach the computer, but ill look better. in the meantime if anyone knows which section that is in, or knows the procedure please post it.

yesterday the fuel pump never came on, and im wondering if that was some computer problem. will keep my eye on it.

 

According to the owner's manual for my 89 Grand Marquis, for fuel injected Ford cars, start it up, a/c OFF, let it idle for 5 minutes in park, then 5 minutes in drive. Turn ON the a/c, and 5 minutes in park, 5 minutes in drive. You will actually hear it adjusting things. Don't be surprised if it stalls a few times, especially in drive, a/c on. The manual says that you CAN drive the car without, but because of the changing conditions, it will take quite a long time for everything to calibrate properly. The car can also stall out under certain conditions, often at inopportune moments.

 

Wow, I had no idea that an 89 Ford product had that much of a "learning" computer.

 

It is a fully sequential system back when Chrysler was still using the lean burn 2 bbl carb on the 318 and G.M. was using the 'cross fire' multiport system that sent fuel out all 4 injectors on each back simultaneously. My 89 was a 351/Trailer Tow III car so it had the electronic feedback 2bbl VV carb on it. Before I read the owner's manual the second night I had the car, getting it to start cold was an interesting experience, since the dealership had warned me it was fuel injected so not to touch the gas when starting it. I almost had to tow it in on the first morning, until I did break down and touch the gas. Oh, well. Still drove like a dream

 

OK... played with the car this weekend. no more trouble out of the fuel pump, so no telling what that was about.

the misfire came back at idle. it lasted long enough for me to pull each plug wire to see if i could find the wire that didnt make a change in the rythm. well all 8 changed the rythm. so it has to be something else.

the miss that im chasing sounds like "bomp" the sound pulling the wire makes is "Plaagh" so pulling each wire goes from " bomp bomp bomp bomp" to "Plaagh bomp.. plaagh bomp plaagh bomp, or bomp plaah bomp plaagh"

what can make the exhuast sound like a miss, but all 8 are firing when they are supposed to? im starting to suspect cats, but i have more pressure coming thru the wagon exhaust than the towncar has, and i know the cats are good on the TC. Why isnt anyone close enough to help me with this haha

 

Read this then let us know what you think.

http://www.aa1car.com/library/2003/us80312.htm