OK, I've avoided this problem for two years because of the diagnosis 
difficulties, but now it's occurring more regularly. 

During acceleration and/or during cruising speeds, I sometimes get a 
momentary cough, where the whole engine seems to shut down: like either a 
momentary lack of power to the fuel injection system or a sudden blockage 
of fuel flow. The whole bus shudders and shakes for one/two seconds and 
then resumes normal (smooth) operation. 

This is a tough one to debug because the problem never occurs during idle 
or engine revving and only randomly on the road...

I've already done full tune-ups and replaced the fuel and air filters.

I'm going to check:
1) Foreign matter in the fuel tank
2) Fuel pressure.
3) Systematic check of FI components.

My plugs are black--but not gunky or oily--could I be running too rich at 
times to cause random coughing ???

Other suggestions ?
 
---------------------------------------------------------
Morris Arthur < morris_arthur@unc.edu >
Environmental Sciences and Engineering
University of North Carolina