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No Low RPM Vacuum, Problem Solved


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6 replies to this topic

#1 Dr. RX

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Posted 14 July 2004 - 09:53 PM

My 85 Turbo Wagon had some noisy hydraulic lifters (cam followers) on the driver side (cylinders 2 & 4), so last weekend I replaced them with new ones. After I put everything back together there was no low end power, seemed to run good at high rpms but not at low, and there was no power (vacuum) assist to the brakes at low rpms. The only thing that is connected with the vacuum system that I touched was the pipe that goes from between cylinders 2 & 4 up to the EGR valve. I speculated that the EGR valve might have gone bad so I replaced it. Things got a little better, but no much. I checked the old EGR valve witha hand vacuum pump and it functioned properly, so it wasn't that. I have made a visual inspection of every vacuum line and can see nothing that might cause any problem. The car ran fine with the exception of an occasional clicking of the lifters before, so whatever happened, it did so while I was installing the new lifters. I thought the new lifters might be keeping the valves open so I pulled #2 plug wire and the engine slowed down and sped up again when I re-istalled it, so I don't think it was that. It does seem to get better the more it is driven. It also seems to run better that more advance it has on the distributor (uumm doesn't the vacuum advance the distributor at low rpms?), but now it is as far as the distributor can be adjusted. Since I never remove the distributor, it should have maintained the same timing with the cam.

Does anyone have any ideas what might be causing the low rpm loss of vacuum??

#2 GLCraig

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Posted 14 July 2004 - 09:59 PM

Have you double checked the Cam timing?

#3 Dr. RX

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Posted 15 July 2004 - 08:58 AM

The cams are dead on, at least by the timing marks. They are exactly were the were before I replaced the lifters.

#4 Cougar

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Posted 15 July 2004 - 01:23 PM

Have you tried replacing the PCV valve? These can leak.

#5 Dr. RX

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Posted 15 July 2004 - 01:25 PM

Shipping pins (the little plastic things) were removed, but I didn't "pump" them, I figured that would happen under normal operation, but I did think about that after the fact. They have very little deflection by hand when I tested them by hand before installing them. I would think that if they collapsed that they would click, there is no clicking sound

#6 Dr. RX

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Posted 15 July 2004 - 07:57 PM

Problem fixed, I got a vacuum guage (something I've needed for a long time) and did a check, the needle flipped between 4 to 5 points from 0 to 5 on the scale, that told me that I either had valve timing problems or a leak in the intake manifold heat riser. Well I knew the heat riser was fine, so that left the valve timing issue. I pulled the cam cover off and could see the first three (#2 intake and exhaust, and #4 exhaust) valve pretty easy and they were ok, I couldn't see #4 intake, so a got my inspection mirror and looked. I had to look from several angles before I was convinced that it was not right (see attached sketch), so I got a long screw driver and pryed the follwer back into place, bolted everything back up, and now it runs great. My wife says that it seems to have even more power then before.

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#7 Cougar

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Posted 16 July 2004 - 04:11 AM

Good going. Thanks for the feedback.




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