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1988 Ford Ranger rpms dropping, power loss, backfire.
Video of rpms dropping:
youtube.com/shorts/O8GEPJ8kb9o?si=BTxfsp8HPBIZGf0J
Vehicle is a 88 Ford Ranger 2.9L 4wd. RPMs dropping while idling and driving as well as backfire while accelerating.
I have replaced fuel pump relay, both fuel pumps, fuel filter and file pressure regulator. I've also replaced the spark plugs and wires, distributor with tfi, map sensor and icm. I did a smoke test and didn't find any leaks. It seemed to settle down when I stepped on the bake pedal so I replaced the brake booster thinking that the booster had a leak but it right back to dropping.
Any thoughts are appreciated. Oh.. and I have access to a snap on mt2400 if that helps.
i can be wrong look at the map data and or voltage , look for internal vac leak i have done a few of those engine not so much the 2.9 more of the 3.0 4.0 ohv and the lower intake is a bit crazy also make sure the IG dist. performance is on point. look for oil or water leak around the lower part of intake
Morning, thanks for the reply. I'm worried that the issue is the lower intake manifold gasket. I replaced all the external gaskets including lower manifold gasket and didn't feel real good about it. I found a procedure to test the gasket. I pulled the pcv valve hose and plugged both ends. Then I disconnected the crankcase breather hose from the intake. With the engine running I held my thumb over the hose end looking for suction. Supposedly suction would be an indicator of an internal vacuum leak from the gasket. Instead of suction I got some air pressure building. Nothing crazy. My assumption is that this is normal but Google says that air pressure building could be a sign of the gasket not sealing properly. Any thoughts on this?
ill said it depends on the amount of feedback your getting ,because of the idle issue precent not sure if you did a comp test but came by a particular problem ,this problem i did a compression test and move on to other cylinder just to go back and run the same test on the same cylinder multiple times i was getting different readings it turns out to be a broken piston ring the leakdown test wont pick this up . hope this yield some result for you.
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