97 S320 extreme hesitation and lack power on hard acceleration
 

My 97 S320 with 118K miles has two problems which I believe may be one in the same. First when the engine is cold and you attempt to drive at a normal acceleration it would not accelerate and loss power. If you very gradually apply gas it would accelerate but would not change into second gear unless I would ease off the gas pedal then reapply. After about 1 tenth of a mile it would accelerate normally from then on.

Second problem, driving at highway speed, if I perform a hard acceleration (gas pedal to the floor) it would down shift as expected, rpm would increase, but power would drop off and decelerate. I can gradually accelerate to any speed I desire with no problem.

The car receives all regular maintenance (including injector cleaner with oil change) and is use to commute 160 miles per day at 75 plus mph, other than those two issues it run perfectly.

Any advice?

There are many things that can go wrong in these cars unfortunately. I would strongly suggest you have a good technician scan each system in the car for any stored fault codes. The results will help you narrow in on the problem.

I did pulled the error codes, P0170, P0450, P0130, P0301, P0305 and P0302 was everything on the stack....

I'll try and look those up soon...will let you know.

P0170 = Fuel Trim Malfunction (Bank 1)
P0450 = Evaporative Emission Control System Pressure Sensor Malfunction
P0130 = O2 Sensor Circuit Malfunction (Bank 1 Sensor 1)
P0301 = Cylinder 1 Misfire Detected
P0305 = Cylinder 5 Misfire Detected
P0302 = Cylinder 2 Misfire Detected

Certianly looks like it could be a fuel delivery problem. I don't know much about the Fuel Trim system. Maybe someone with more info can help out?

No harm to change/clean the MAF sensor.

based on those codes the maf sensor is the problem,but the you will need to reset the adaptions.

I agree in this point of view.

The symptoms indicate a mixture problem, and basically there are two things involved, the air mass sensor and the oxygen sensor.

I had a problem with air mass sensor, which gave same symptoms (too lean mixture).

Don't continue driving until problem is fixed, or you may blow the catalyst into the exhaust system, requiring the lot to be replaced, as happened in my case (some 4.500 bucks).

thanks for all of the replies, but a couple of questions, does anyoone DIY procedure for checking and replacing these sensors and also would running some injector cleaner help the situation?

Some people have had success cleaning the element inside the MAF using electronic equipment spray (make sure it doesn't leave ANY residue), or gently brushing the wire element with isopropyl alcohol. Try using the search feature. You should also check the condition of the wiring to the MAF...

http://v12uberalles.com/AMM_rewire.htm

Shorted wires will cause all sorts of problems.

I will try cleaning this weekend. Is there any way of testing its operation with a scope and meter?

thanks again for the responses...

I haven't found a test procedure, but I did find a description of operation...

PURPOSE
Depending on air flow, the air mass sensors (B2/3 and B2/4) send a signal (current) to the LH control modules. Each control module can now calculate the air mass entering the engine and adjust fuel injection duration as needed. The air mass sensors are of the hot-wire sensor type. Factors such as ambient temperature, humidity and pressure (altitude) are taken into consideration with this type of air sensor.

OPERATION
The measurement sensor (inside the meter housing) consists of a wire (hot-wire) which is maintained at a temperature 180°C (356°F) higher than the air entering the engine. As the air mass passes over the hot-wire, wire resistance decreases and more current is required to maintain the correct temperature. The amount of current required is used to calculate the air mass entering the engine. When the engine is turned off, any dirt on the wire is burned off electrically by a one second burn off cycle that heats the wire to 1000°C (1800°F). Any dirt remaining on the hot-wire can cause it to sent a faulty signal to the LH control module.