91 Merc Grand Marquis won't start or run in park. Will start in neutral but stalls

[limecat]

91 Grand Marquis (5.0L with AOD trans) will only start in neutral and stalls if I put in park reverse or 1. It moves in drive but not taking off in lower gear like it should. i have to drive real slow till it gets up to 35 mph then shifts and goes great, almost like there is no 1st gear, it imeediately stalls when shifted into R or P like the engine comes to an immediate break.In 20 years of working on cars I never seen anything like it. Can anyone help please.

[1990LTD]

That's friggin' bizarre.


I would suspect the neutral safety switch for at least part of your problem.


In what condition is the transmission fluid? Is it a high mileage transmission that has recently been serviced/flushed, by any chance?


What is the condition of the TV cable and its bushing at the throttle body? It's the one that isn't the throttle cable or cruise cable. Check at the transmission end, too.



Can you check it for vacuum leaks?

[sly]

+1 bizarre.

sounds like the torque converter may be too tight (I thought they would just let go when going bad, not tighten up though) or the engine has severe vacuum leaks or is running f'n rich (re: no low end power).

[johnunit]

I think you have multiple problems. Start with basics. Check codes and vacuum gauge.

[86VickyLX]

Won't start in park? sounds like misadjusted linkage at the trans. as for stalling, dead iac or major vacuum leaks.

[1990murc]

Anyone ever figure this out? I am have the exact same issues with my 90 gran marquis

[VicCrownVic]

I agree with replies to the OP, multiple issues and possibly miss-aligned linkage at the trans.

If you can't start in park, what exactly do you mean:
Cranks but will not start
OR
No crank no start?

Also, did the issue start after having some work done to the car or was it fine one day and not fine the next time you tried to drive it?

[Tiggie]

I lost first gear for a few weeks after continued short trips in very cold weather. A normal person wouldn't notice the 2nd gear starts - there was very little difference in acceleration. I actually liked it in town. First came back after an extended highway run and has been back ever since (15 years ago). The OP may have been stuck in 3rd starting out, but not 2nd.

We definitely need more details.

About the only way a trans could stall a properly functioning engine would be a torque converter lock up problem, or if the pump is locking up. These have an inner and outer input shaft, and if the inner got stuck engaged (lock locked position), I think you would have some very unique problems with stalling or not starting.

[1990murc]

How it happened for me was I had just picked up the car yesterday out of town, I drove about 600kms and all was great! Then when I pulled in to get gas the car seemed a little rough coming to a stop seemed to lock up when I put it in park. I tried to turn it over and it would crank but felt.like the engine was almost locked or something. Then I put it in neutral and pushed it out of the way of the gas pumps and noticed that while in neutral it would start up perfectly fine. But if put in first, reverse or park would stall or lock up again. I am able to move forward in d and od and the car seems to shift pretty normally at speeds over 35 to 40kms per hour. I'm gonna go check out the linkage now and report back. Wanted to have a better look when I got home last noght but it was around a 23 hour day of driving so I just went to sleep instead haha. Really hoping I don't have to pull the tranny on the car as I just picked it up yesterday and it only has 45000kms on it all oem. Any tips would be great guys! I'm no mechanic but a driller with pretty good mechanical understanding! Thanks for any help!