My 940 wagon ('93, automatic transmission) recently started to have quirks. When car is cold and I am driving on a slight hill/trying to merge into hwy, the car won't accelerate beyond 20mph-25mph. The tach freezes around 2000 RPM and does not climb any higher.

When I floor the gas pedal, the car even slows down instead of switching into lower gear and accelerating (sometimes the engine seems to eventually overcome this weird behavior, then the RPM would surge to 3-4k and car would start accelerate). This is ok in a city, but is really scary when trying to merge into hwy. When car warms up, things get back to normal, so the issue seems to be intermittent.. Any ideas/suggestions would be appreciated.

 

Check the fuel pressure. My '92 940 (Regina system) had similar symptoms... bogging down on inclines...sudden acceleration. Testing the fuel pressure showed an erratic amount of pressure (putting the adapter on the test valve ain't easy). Putting in a new in tank fuel pump cured the problem.

 

i'd verify the coolant temp sensor is reading sane values for cold vs hot. but usually that fails the other way, telling the ECU the engine is cold when its warmed up, causin git to run way too rich and waste fuel.

 

The car was recently out of gas and then it indeed behaved very erratically. The issue that I have is not like this, moreover it does not depend on the incline (I checked just today): the car just cannot bypass the 2000 RPM even when I am going down the hill and flooring the gas.

 

The temp sensor was tested when the radiator was replaced, but I will verify it again.

Could this behavior be potentially caused by the holes/leaks in the exhaust pipe between engine and Oxygen sensor? The car was recently in an "accident" when it slowly ran over the road sign pole, bending it so it was stuck under the car. I didn't see any damages but I guess it could have potentially damaged the exhaust system. What is the best way to check for leaks? (smog test is due only in 1 year, so it's not an option)

 

a visual inspection of the exhaust downpipe from under the car should show if it was bent in any way.

 

a clogged air filter would also cause this, however that would normally be at any time excessive load is applied.

 

the coolant temp sensor normally isn't something a shop would check when replacing a radiator. they'd check and/or replace the thermostat. maybe the sensor in the radiator that controls the aux cooling fan. but not the coolant temp sensor, thats in the block, and is wired to the fuel injection ECU and ignition ICU.

 

The pipe seems ok at the bottom, however there is a slight slit where it is attached to engine, see the attached image. Could this be a problem?

 

no visible image. a cracked exhaust manifold will suck in extra air at lower throttle settings, causing the O2 sensor to think the mixture is too lean, and cause run problems.

 

Sorry, I had a hard time attaching image here. May be this time it works better. Do you see the image below?

 

hmm, hard to say from the sharpness of the pic, but that looks like the heat shield, not the actual cast iron manifold, so no harm.