QuestionQUESTION: http://www.allexperts.com/user.cgi?m=6&catID=807&expID=63082&qID=5078787
This is in continuation to the above thread. To summarize, the engine shuts off suddenly; if the van is running at some speed, it will normally restart itself. If it is not started by itself, I can crank the engine to start it again without any problem. I have done the following in the past:
1) I have checked the ignition by jiggling the keys and jiggling the wires under the steering column cover.
2) Cleaned contacts for ECM, fuse box etc.
3) Checked MAP and throttle sensor voltages
4) Cleaned throttle body, EGR valve and idle control valve
5) Changed speed sensor on transmission
6) Checked/taped all under hood wires
7) No codes!
During last week, the master cylinder went south. The van used to start slipping after some time while at a red light. But then it became suddenly bad as I needed to pump the brake to be able to stop the van. After getting it replaced, I have noticed that the frequency of intermittent shut down of engine has reduced a lot. Sometimes the van will go without any shut down the whole day!
With your expertise, can we establish a relation of master cylinder with the engine shutting itself down?
ANSWER: I don't see a direct relationship between the master cylinder hydraulics and the engine shut down. About all there is would relate to the brake system malfunctioning causing a brake warning light to illuminate on the message center and or cluster but there is no reason why that would shut off the engine unless there is short circuit in that pathway. You may have to wait further to see if the shutdown lasts longer than momentarily to then troubleshoot the situation.
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QUESTION: The brake warning light never came on.
I do have another observation and not sure if this should happen or not. When I pump the brake pedal while idling, the rpm goes up by 100-200 rpm and then drops to normal idle rpm. This was happening before and after replacing the master cylinder.
AnswerPumping the brake does bring the intake manifold into "play" due to the vacuum-assister power brake unit. So check that vacuum line's connections/condition but that variation may be related to the changing vacuum as you exercise the brake pedal. It may be an indication of a future issue with the brake booster unit air tightness.
