Intermittent Stumbling

[Tom Hierl <hierl@qedmbe.com>]

I have a 1987 5KQ which has developed an intermittent loss of power. 
After running for 15-20 minutes, it has severe hesitation after coming 
to a stop. Cold behavior is fine. Although it will hold an idle most 
of the time, there is no power. The situation exists for 15-30 seconds 
at which point the engine behaves normally again. This car has the CIS 
E3 injection and we have swapped a known good electronic pressure 
regulator which didn't help. The fuel pressures look OK when this is 
happening. The codes are 00. We have also changed the fuel filter.

Any comments or other things to try would be appreciated as the 
hesitation is getting dangerous as it usually happens in the middle of 
an intersection.

Thanks,
Tom