Hello All:
Thought I would post my PDF that illustrates the steps I went through to solve an extreme drivability issue with my 92 400E (260,000 miles)
Symptoms - engine stumbling, limp mode, harsh idle and stalling, horrible gas mileage
Previous corrections - New MAS, tested Throttle Acuator, new dist caps/rotors and plugs - no improvement
Test - confirmed vacuum leak in intake manifold - sprayed starting fliud in various regions of manifold while engine was running. Found engine to stumble/stall when sprayed near the front section of manifold.
Cause - broken manifold connector ring (gasket) on #1 cyl plenum. Remaining 7 gaskets were intact but extremely brittle and likely leaking.
EGR system 100% blocked - not sure that's a cause but was certainly not functional
Solution and additional mntc - remove and rebuild intake manifold assembly. replaced all gaskets, seals, vacuum lines and emission/vapor pipes. Cleaned all parts. Rebuilt fuel injectors while removed (washers, spacers, filters and pintle caps). Replaced small heater hoses at rear of engine while manifold removed. Repalced spark plugs, cleaned dist caps/rotors. oil change and coolant refill.
Result - WOW! my 400E is back! a 300HP sewing machine. no more stumbling or hesitation, no limp mode, smooth idle and mileage appears to be improved (still need to officially check)
Try clicking on the link below. It's a PDF of the photos I took throughout the process. I hope you can access it and I hope it helps.
https://app.box.com/s/qla96ib4yrtofnpnn4jy