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Discussion Starter · #1 ·
Hey again!

Never did figure out my previous question, but hopefully the EVR solenoid was a red herring. The problem I'm trying to rectify is that, under heavy loads or heavy acceleration, the car begins to buck and lose power. I had read that this was likely the EGR system, so that's what I was checking out. Yesterday I connected the vacuum gauge to the EVR solenoid, and had a buddy check the reading while the car was actually in motion. Only once or twice did the EVR solenoid pass through any reasonable amount of vacuum. Then for curiousity's sake, I connected the gauge directly to the manifold and drove around. Well, when the engine is gunned, the vacuum initially drops hugely (10-15 mm Hg), then recovers if engine speed is held constant. When the car is bucking, the vacuum pretty much drops to ZERO. From what I've read, this doesn't seem right, everything says the vacuum should INCREASE as engine speed increases, with no mention of an initial drop in vacuum. As for dropping to zero...??? Any ideas/suggestions would be greatly appreciated. I'm pretty much at the point where I'm ready to go into the mechanic, and this seems like one of those problems where they can try a million things (and bill me for it) and not have fixed the problem. Thanks!

James
 

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Umm.....

Vacuum in the intake trackt is ALWAYS at its highest when the throttle is closed and the engine is at idle. As throttle opens, vacuum in the intake manifold decreases, engine speeds up. I would check you intake track for a vacuum leaks, most likey cause of creating a gutless wonder. You'ld be surprised how much trouble some of those stupid little lines can cause when they get a hole in them.

Matt 8)
 

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Vacuum to the EGR valve should be zero at idle. It should be increasing with RPM.

I have no idea if EGR valve problems can cause bucking. The most common problems with EGR are a stuck valve or if the vacuum is applied at idle it will idle rough and probably stall.
 

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Discussion Starter · #5 ·
Hey!

The EGR valve was good when I tested it, so I thought it was the solenoid that controls the valve, since it passed vacuum through to the valve only sporadically. However, after testing manifold vacuum while driving, and finding that it often drops almost to zero, I suspect a vacuum leak somewhere else (so that there is no vacuum to be passed thru when the solenoid opens). Not done testing all the lines and components yet, but there seems to be a leak within the cruise control servo, so that is my prime suspect at the moment. Thanks again, and any further suggestions continue to be appreciated!

James
 
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