I have a 1991 Honda with an automatic transmission and 125,000 miles and it has the following problems:

Very poor acceleration.
Revs very high when shifting from 2 to 3.
Doesn't want to go any faster than about 50 MPH.

Could this be the MAP sensor, or is it a transmission problem?

 

Any CEL codes?

When did you last replace the spark plugs, wires, cap, and rotor?

Is the transmission fluid low? Have you tried draining and refilling the transmission with Honda recommended ATF?

 

Thanks RONJ for the reply.
NO CEL's.
Plugs, rotor and cap were replace about 18 months ago.
Yesterday I found that the seals around the spark plugs were leaking oil onto the plugs and boots - so I changed the seals, pulled the plugs, regapped them and wiped down the wires and boots. Minor improvement.
Yesterday, while the engine was idling, I pulled the vacuum hose going to the MAP sensor and plugged both the manifold tube and the hose going to the sensor - the engine went from idly smoothly to rough.

The transmission fluid looks red and is full, but never has been changed. I did add about 1/2 litre of oil last week because I thought it was down a bit, but it made no difference.

When doing a slow acceleration from stop, the car appears to run fine - I notice the lack of power when doing a harder acceleration - such as a merge on a highway. I really notice the lack of speed at around 50 MPH (80KPH) - if I push down the accelerator at this speed, the transmission down shifts and the engine revs upto 4,500, but there is no gain in speed.

 

Consider replacing the plug wires and pull the distributor cap off and inspect the contact points inside and on the rotor.


Drain the transmission fluid and refill with a Honda recommended ATF. Drive around the block and then repeat the drain and refill. Then go from there.