Engine shudders, late downshift?

ohiomustang · 02-24-2006

My wife has a '93 with 2.3L engine with 88,000 miles and automatic tranny. Whenever the car has reached 40-45 mph and then has the brakes applied to slow down, the engine will briefly shudder at about 15 mph as it is slowing down. The shudder reminds me of stall that happens when a manual transmission is shifted into a high gear at low speed. It seems to me that the transmission is not downshifting soon enough which causes the engine to shudder for a second or two until the downshift is made (too late). Can anyone explain what is happening? I am a do-it-yourself guy, but i'm not too good at diagnosing problems. Could it be the vacuum modulator or another vacuum related problem?

stepman · 02-25-2006

Sounds like a "lock-up convertor" not letting go. Not real familiar with the fords but have experienced it. There may be an electrical plug that can be temporarily unplugged to diagnose it. If you unplug it and it drives normal, except for not having the extra gear...you know. Might be worth a little research.

Tominator · 02-25-2006

Does it have an 'overdrive' button? Will the car do the same thing with the OD off?

I'm thinking the lockup convertor as well.

ohiomustang · 02-26-2006

Thanks for the tips. I did a little research and found I have a A4LD tranny and the LD means Lockup Device. The lockout occurs in 4th gear. Couldnt figure out which wires to disconnect to diagnose, so I put the selector on 2 and drove to 45mph which I think is where 4th kicks in. The slowdown shudder didn't happen, so I'm thinkin' that since it didn't lockup, it didn't need to unlock, thus no problem. I also noticed that there is tranny fluid in the engine compartment that seems to be originating from the vacuum line to the modulator. I've read that when the modulator is broken, that tranny fluid will come through to the vacuum line. So, I'm going to replace the modulator first (it's cheap) and see if that fixes it. Other things that I read that can cause the "no unlock" condition is a faulty lockup converter valve which is internal and may lead to a rebuild.

hondahunter93 · 02-26-2006

have fun with that modulator. its cheap all right, but its a pain in the a** to get off and on. i did it last year and had to end up going to the mechanic because it was harder than i thought.

ohiomustang · 03-10-2006

Finally got the time to put in a new vacuum modulator. When I took the old one off, i got a lot of tranny fluid out of the hose. Unfortunately the converter is still not unlocking.