85.5 944 runs rough/flat when warmed-up

[djnolan]

I have a problem with my 85.5 944 automatic. The performance seems to tail off or get flat as it gets warmed up. It doesn't miss or anything, but the acceleration just seems to be flat or reduced. The mechanic said try high-test gas but it has not helped.

Based on experience with other makes of cars, I would suspect something in the emission systems is not correct. Does anyone know of a good reference to use when diagnosing running problems with these cars?

One other point, I replace the oxygen sensor with the universal bosch o2 sensor and I soldered the pigtail to the connector from the old sensor. This seemed neater than using the extra plug/connector that came with the new sensor. I read somewhere (can't find it now) that solder could increase the resistance of the wire and might cause a problem. Does anyone have experience with this repair? (I am about to order the OEM sensor to see if it makes any difference. )

Thanks!

[ERAU944]

i'm not sure that the O2 sensor is the problem. i have soldered an O2 sensor into my '84 with no adverse effects, and am about to do the same in my 951...

it sounds like you may possibly have a clogged catalytic converter, that gets hot and impedes performance by blocking exhaust gases... that's just my guess...

[IXLOR8]

When was the fuel filter replaced?

A plug fuel filter will cause a lean condition. Lack of power. Cause backfires? They are about $18. Well worth a try.

While a car is warming up the car gets extra fuel, that is why it may run better while cold.

[djnolan]

I have a new fuel filter and intended to replace soon. Will make sure i do this soonest. Thanks for the advice.

[djnolan]

The catalytic idea is interesting. Is there any way to further pin down the converter as the problem?

Have you tried the bosch connector kit instead of soldering?

[Razorback1980]

All that wire does is transfer voltage to the computer. Whatever method you use, just make sure you get 0 ohms reading through your connection and it will be fine. It is important that solder doesn't run down on the O2 sensor.

[Zero10]

Originally posted by Razorback1980
All that wire does is transfer voltage to the computer. Whatever method you use, just make sure you get 0 ohms reading through your connection and it will be fine. It is important that solder doesn't run down on the O2 sensor.

Not true, that wire is also an O2 feed for the sensor to do it's comparison.
That is why you have to either crimp it, or strip a section between your soldering and the sensor.

[djnolan]

I tried the bosch connector (it is a screw compression type, not a crimp) and the performance improved somewhat. Maybe I did something else that affected it, though!