98 Mercury Mountaineer Major Problems Need Advice

Bought from dealer with the front timeing chains already replaced drove for 34 days and the back chain broke. Car was under warranty so dealer took it back and had it fixed. Shop that worked on it was very inexperienced to handle such a complicated job. When the shop got done with it I had to have the trans rebuilt, replace the complete motor and trans wire harness, and to much more to talk about. Needless to say lets get down to the problem. When you are driveing it it will kick in and out of overdrive constantly when you get it in higher gear, I call this bug jumping. It will also bug jump when its ideling. You will hear it slightly idle up and down. I have replaced tall O2 sensors and heaters, throdle sensor. anti knock sensor, plugs and wires, wire hareness. This car only has 80000 actual miles and is loaded, but I am stumped any suggestions will be wonderful. Thank you in advance!

Are you sure it's going in and out of overdrive, or could it be a misfire there just like at idle?

Were the plugs and wires replaced to try to fix this, or just before the miisfire started?

Have you inspected the vacuum lines and intake air tubes to make sure they are not cracked and installed correctly?

Also check the PCM for pending codes.

-Rod

I have had the trans totaly rebuilt twice, because it would keep takeing it out around 150 miles. The only codes showing are antitheft. The shop that worked on it probed the pcm with a test light and I wonder if the pcm could be bad. I replaced the wires and plugs in hopes that it would take care of the missing and it didn't help at all. I can't even lock the overdrive out on the end of the shifter. The shop that rebuilt the trans looked at it for me and said that it was fine, that they think it is an electrical issue. The shop that worked on the timeing chain done a number on this car, but I hope that I can get it figured out. There were some vacume lines that I had to change around, I wonder if a major vacume problem would keep it from running down the road. I think I am going to get a vacume schematics from our local ford dealer and see if I can find any problems. Thanks for your input. Are you sure it's going in and out of overdrive, or could it be a misfire there just like at idle?

Were the plugs and wires replaced to try to fix this, or just before the miisfire started?

Have you inspected the vacuum lines and intake air tubes to make sure they are not cracked and installed correctly?

Also check the PCM for pending codes.

-Rod

It doesn't really sound to me like you have an overdrive issue. It sounds more like a misfire, either due to a vacuum leak or due to an ignition or fuel injector issue. You said that the engine wiring harness was replaced. Maybe an injector connector got swapped with its neighbor.

If you can find someone or a shop that has a scan tool and can access the CIDS/PIDS for the Mountaineer, go through them and check the misfire counts on the individual cylinders. Even if the counts are not high enough to trigger the Check Engine Light, they will still register. If you find one cylinder with more than zero, concentrate in that area. If there are a couple of cylinders with misfire counts, then see if those two cylinders share a coil pack.

Which engine does your Mountaineer have? Since you say it's loaded, you probably have the V8. However, if you have the 4.0L V-6, you may have the fairly common intake manifold gasket leak.

-Rod

Mountaineer has 4.0 V6 with overhead cam in it. When i got it back from the shop the first time there was all kind of vacume lines messed up they even had some of the lines plugged into bolts! They had even broke the output shaft sensor part in the trans other part on the wire harness, this is why the trans had to be rebuilt the first time. Would a vacume leak make it kick in and our of overdrive when you get it in high gear though? it will misfire at an idle and kick in out of OD when you drive it. I can't lock out OD on the end of shifter either, but i think that may be a linkage problem, hopefully. I have replace enter engine and trans wire harness, all o2 sensors and heaters, TPS sensor, antinkock sensor, wires, and plugs. What confuses me is that it will misfire at an idle occasionally and will always kick in and out of OD in high gear. Any info that you can give me will be appreciated thank you.It doesn't really sound to me like you have an overdrive issue. It sounds more like a misfire, either due to a vacuum leak or due to an ignition or fuel injector issue. You said that the engine wiring harness was replaced. Maybe an injector connector got swapped with its neighbor.

If you can find someone or a shop that has a scan tool and can access the CIDS/PIDS for the Mountaineer, go through them and check the misfire counts on the individual cylinders. Even if the counts are not high enough to trigger the Check Engine Light, they will still register. If you find one cylinder with more than zero, concentrate in that area. If there are a couple of cylinders with misfire counts, then see if those two cylinders share a coil pack.

Which engine does your Mountaineer have? Since you say it's loaded, you probably have the V8. However, if you have the 4.0L V-6, you may have the fairly common intake manifold gasket leak.

-Rod

When you try to lock out OD, does the OD Off indicator illuminate in the instrument cluster?

-Rod

OD light flashes. This, according t my local ford shop, means that there is internal trans problems, but I know this isn't the issue. I am leaning on the problem being a vacume leak, pcm fried, or maybe when they put the chain in they got it a little off. We all know that if the timeing isn't exact it won't run right. The shop that worked on it didn't even have a mechanic that knew how to change the chain not to mention they had to go borrow the tools to do the work. One of the mechanics that worked on it admitted to me that they had to hire someone to come and complete it. Oh well I'll get it fixed sooner or later, I am just hopeing that I don't have too pull the motor. I had a Ford mechanic call this motor the ford exploder. If I can't figure this problem out by summer I may just put a new motor in. I priced one and it is only $2500. Thanks for your input.

When you try to lock out OD, does the OD Off indicator illuminate in the instrument cluster?

-Rod