Mazda99Nikon

My 91 N/A coupe (automatic transmission) was running pretty well this summer but since the weather has dropped down below freezing, it's acting a bit sluggish until it warms up.

Typically I'll warm the car up about 4 minutes before I drive it whenver the temperature is below 32 degrees. The car starts and revs perfectly all the way to the 3000 RPM cold starting sequence and settles down with a great idle at around 1500 rpm. After a couple of minutes through my little town it settles down to a perfect 700 RPM idle when fully warmed up. During the first four miles on the way to work, the car accelerates to 65 mph but the transmission just keeps downshifting at around 5000 RPM. I find myself driving down the highway at 3800 RPM in 3rd gear. The car seems to lack power, like maybe it's only operating on one rotor. It never wants to go into 4th (2400 RPM) until I come to my first stop sign, six miles down the highway, when it's really good and warm. Power returns then, shifting points return to their proper RPM and the car drives perfectly the remainder of the 16 mile trip to work.

I've checked all the vacuum lines, the car is throwing no codes, I've got new spark plugsand a new O2 sensor.

Any idea what the problem could be?

Icemark

when was the tranny fluid last changed... sounds like it is burnt or gunked up

Mazda99Nikon

Had the transmission fluid changed last spring. The transmission seemed to slip all over the place for the first couple hundred miles then settled down perfectly during the warmest part of the summer.

I'm wondering, could a clogged transmission filter cause this? I bought a new one but haven't been able to get at it. It really looks more like a wire strainer.

There's also a vacuum hose that comes off the transmission. If that wasn't sealing right, could that cause this problem?

BTW, the car has 162,000 miles but the compression on the second engine (78,000 miles) seems perfect. 5th and 6th ports are probably frozen but it doesn't keep the car from reaching 90 mph when it is fully warm. 0-60 times in the summer have been right around 8 seconds so I don't thinks it's an engine problem.

misterstyx69

iTrader: (142)

the symptoms sound so familiar..I had the same thing go on in my "other" car,didn't think it was the transmission fluid level..but that's what it was..I'll side with Icemark on this one..

spot_skater

I'm also going to side with Icemark on this one, check the tranny fluid. Also, when it is below freezing out it will take a bit longer for all the fluids in the car to come up to operating temp. This includes the oil, tranny fluid, gear oil, etc. I don't know about the AT's on these cars, but on my buddy's GMC Jimmy, he had a big vac line (3/8") off his tranny disconnected, and it completely disabled his 4WD...

Good luck,
James

Speculum

damm autos ... if all else fails try throwing some lucas in it.

RotaryEvolution

iTrader: (30)

sounds like a misadjusted throttle input to the transmission or the valves in the valve body are sticking, try some Trans-X transmission treatment and it may unstick the valves. not sure about the throttle input side of these transmissions though as i have never dealt with autos in a rotary before, they should never have come with an auto but i don't want to start in on that again...