Intro 1972 Irish Green 1.7L; help needed with jerking engine |
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Intro 1972 Irish Green 1.7L; help needed with jerking engine |
andreic |
Oct 6 2018, 09:11 PM
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#1
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Member Group: Members Posts: 172 Joined: 21-December 15 From: Madison, WI Member No.: 19,479 Region Association: Upper MidWest |
Hello,
some of you may remember me. After owning for several years a red 1975 1.8L 914, on which I reinstalled the L-Jet, got it to work well, and have sold this summer, I am now working on a 1972 1.7L D-Jet which I got this spring. Photos attached. So far I got the brakes to work well (new front calipers from PMB were installed, and all four flex lines were replaced), replaced all fuel lines and the fuel pump, replaced all vacuum lines, new spark plugs, points, cap, wires and rotor. Also adjusted all valve clearances. I did a compression check and all was well, I got around 120lbs on all cylinders. What still plagues me are two engine issues. One is that when the engine is cold, if I rev it up it will make a loud noise that sounds like a bad rattle. It is only there on hard acceleration, and it goes away almost completely as the engine gets warm, say, after 10-15 minutes. I have come up with several ideas what it could be: exhaust noise from badly sealing exhaust ports; valve noise; or something else in the exhaust (the muffler is an aftermarket one, and I am not sure if there isn't something in it rattling). Another issue I have is that the car is not riding smoothly. It is hard to explain, but even if I am driving at constant speed, not moving my foot on the gas, it will jerk ever so slightly forward every couple of seconds, as if getting some extra power. The issue again is much more visible with the engine cold, but even properly warmed up you can feel it. It is stronger when accelerating than at constant speed; on acceleration the car really stumbles some times. When the engine is cold it can be pretty bad, enough that some times I worried if I would be able to climb a hill. I first thought it was ignition related, but after going through everything electrical I doubt it is this. (Replacing the spark plug, points, cap, wires and rotor changed nothing.) The car also seems a bit underpowered compared to my other one. I am starting to wonder if the two things (the rattle and the jerking) are not related, and if it could be a valve issue. By the way, once or twice in the span of an hour's worth of driving I thought I heard a mild backfire. Any suggestions on what could be the problem? Any help will be greatly appreciated. Andrei. Attached thumbnail(s) |
andreic |
Oct 12 2018, 09:26 PM
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#2
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Member Group: Members Posts: 172 Joined: 21-December 15 From: Madison, WI Member No.: 19,479 Region Association: Upper MidWest |
Well, that was optimistic.... Sadly it turns out that that was not the problem. I let the car cool down for a couple of hours, and then being happy that it was fixed I thought I'd take it out for another spin. All the old problems were back with a vengeance: backfiring, low idle, trouble revving up past 1000rpm. Removing the vacuum lines makes the idle slightly higher, but nowhere near as much as before.
So my guess is that there is some intermittent problem somewhere. When it happens, the car runs like crap when cold, and even warmed up idles around 700 rpm with the current setting of the idle screw on the throttle. What I saw earlier today was one of the rare moments when it ran well -- good acceleration, no hesitations, no backfires, and an idle of 1800 rpm. Then something went bad again and it returned to its old habits. This is driving me insane! Tomorrow I'll try to replace the condenser. Today I had put a new coil on it, so the coil is not the problem. |
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