1991 D150 shudder at light throttle

[gtrotter]

Hey al, I've got a 1991 D150 with 318 and auto. 49k miles.

I'm having a shudder pop up at light idle that is especially pronounce when the torque converter goes into lockup. Its worse from 50 to 65 mph, but seems to go away at higher speeds. If I kick overdrive off it goes away when cruising at say 60. Trans shifts good, and truck pulls hard(for a raging 170 hp). It needs a muffler from sitting, so hard to tell but it almost seems like a slight miss at idle.

I pulled codes and got 12, 17, and 55. 17 is the only one I'm concerned with, so I replaced the temp sender. I've checked for vacuum leaks and found nothing. Truck sat alot of course, so could it be fuel pump related or would you guys lean towards torque converter? Could a bad thermostat being stuck open cause this?

Also, pictures of the truck for those interested.

 

[PaPitt]

Well been to long since I was at Chrysler. i've forgot what those code mean .
BUT i'LL TAKE IT TO some local shop like maybe AMMCO . I DON'T KNOW WHERE you live so I don't know WHAT AVAIBaLE in your area .
But I'd ask them for an estimate & ASK if the estimate is a part of the price of the repair.
I believe you have some kind of trans issues .

 

[Joe w.]

Nice looking truck hope you find out what your problem is.

 

[reek]

Hey al, I've got a 1991 D150 with 318 and auto. 49k miles.

I'm having a shudder pop up at light idle that is especially pronounce when the torque converter goes into lockup. Its worse from 50 to 65 mph, but seems to go away at higher speeds. If I kick overdrive off it goes away when cruising at say 60. Trans shifts good, and truck pulls hard(for a raging 170 hp). It needs a muffler from sitting, so hard to tell but it almost seems like a slight miss at idle.

I pulled codes and got 12, 17, and 55. 17 is the only one I'm concerned with, so I replaced the temp sender. I've checked for vacuum leaks and found nothing. Truck sat alot of course, so could it be fuel pump related or would you guys lean towards torque converter? Could a bad thermostat being stuck open cause this?

Also, pictures of the truck for those interested. View attachment 232734

View attachment 232735

you did the temp sensor so you must know what the codes mean. but just in case, I believe 12 means the battery was disconnected/dead within the last 50 key cycles.
17, temp sensor
55 end of error codes/no errors.

if the truck is taking for ever to warm up, you might check the T stat.

doubt fuel pump if kicking off OD, it runs fine. that would increase fuel demand as RPMs rise and the pump seems to be keeping up.

if there was no vac leak, I'd consider a tune up (plugs and distributor). I don't remember if the later years even had mechanical/vac advance or if ECU controlled everything. if it's not ECU, make sure timing is 10 BTDC, or if you do total timing, I believe 32 total timing on the motors.