QuestionQUESTION: Hi,
any suggestions appreciated. 71 Ranchero with a 351. Ran fine for 2 weeks, suddenly started to idle roughly, then would be fine. After 3 days, would barely run, started backfiring. Replaced plugs, wires, points, distributor, rotor, coil, when timing couldn't get timing lined up, looks like timing chain jumped a few teeth.
Took a look, timing chain was slack on one side, quite a bit for some reason. Replaced chain and gears.
Timed engine, replaced ported vacuum switch, some of the vacuum line...have positive vacuum where it should be.
Car starts right up, sounds good...hit 40mph, starts to surge and occasionally backfire out the exhaust. If mashing the gas pedal, car runs right along to about 65 or 70, loses power, backfires, surges...
Any ideas welcome. I'm not sure what to do now.
ANSWER: Couple of thoughts, you did not mention as gas related repairs you may have done. Have you checked the fuel pump for constant pressure and have you done any carb work?
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QUESTION: Thank you for the fast response! Wow! I just found this page today, I've read a lot, it's terrific.
No carb work done, have not checked the fuel pump. I shall check fuel pump and fuel filter today. Any other ideas welcome. Was wondering if could be vacuum leak havent found.
ANSWER: Define what you mean by surge. It speeds up, it goes into a stall, its slows down and then revs?
Depending on what you call a stall, don't think it is vacuum leak.
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QUESTION: Thank you again. By surge, I mean at about 35 or 40 mph it seems to start to speed up and slow down, feels like it's loping or galloping along almost. it doesn't seem to actually "stall" but 'wants" to? I wish I could be more precise.
AnswerSounds very fuel related either fuel pump or a restriction. Only interesting point is that you can throttle up farther with no problems.
Backfire out the exhaust is usually excessive fuel, Backfire at the carb is too dry.
(post-ignition vs pre-ignition)
I would definitely check float level and accelerator pump cup condition.
