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> Intro 1972 Irish Green 1.7L; help needed with jerking engine
post Oct 6 2018, 09:11 PM
Post #1


Group: Members
Posts: 130
Joined: 21-December 15
From: Madison, WI
Member No.: 19,479
Region Association: Upper MidWest


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.


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andreic   Intro 1972 Irish Green 1.7L; help needed with jerking engine   Oct 6 2018, 09:11 PM
914Sixer   Check the routing on the accelerator cable. Not u...   Oct 7 2018, 07:35 AM
JeffBowlsby   'trailer hitching (jerking) may be caused by a...   Oct 7 2018, 08:08 AM
Wyvern   Sounds exactly what I had with mine . Did all the ...   Oct 7 2018, 09:37 AM
Dave_Darling   One test is to unplug the throttle position sensor...   Oct 7 2018, 10:46 AM
andreic   Ok, things are weirder than I thought. After going...   Oct 8 2018, 10:03 PM
andreic   Actually here is a newbie question. Unfortunately ...   Oct 8 2018, 10:09 PM
JeffBowlsby   Fire coming outta the tailpipe usually means RICH....   Oct 8 2018, 10:54 PM
andreic   Hi Jeff, I don't know if the CSV leaks, but t...   Oct 9 2018, 03:26 PM
injunmort   have you checked timing. running hot like that sug...   Oct 9 2018, 04:03 AM
nditiz1   I am having a similar engine jerking, trailer hitc...   Oct 9 2018, 06:52 AM
andreic   Here is a photo of the exhaust pipe with white res...   Oct 9 2018, 03:18 PM
rhodyguy   MPS-buy a Mityvac Remove the dist cap. Look for a...   Oct 9 2018, 03:35 PM
rjames   As others have said, check the timing. Also if y...   Oct 9 2018, 04:14 PM
andreic   Well, I checked a few things today, but found noth...   Oct 9 2018, 10:23 PM
rjames   Well, I checked a few things today, but found not...   Oct 10 2018, 12:04 PM
914_teener   Couple of things come to mind: First check the MP...   Oct 10 2018, 08:25 AM
GregAmy   "help needed with jerking engine" Am I ...   Oct 10 2018, 12:27 PM
andreic   OK, still no success. I checked the MPS, and it ho...   Oct 10 2018, 09:37 PM
mepstein   Fuel filter All engine grounds Coil New fuel lines...   Oct 11 2018, 03:19 AM
andreic   One more test done today -- I tried to run it with...   Oct 11 2018, 09:53 AM
mepstein   One more test done today -- I tried to run it wit...   Oct 11 2018, 09:59 AM
andreic   One more thought. Could it be the ECU itself? Does...   Oct 11 2018, 09:55 AM
IronHillRestorations   I thought I read through all the posts, but I migh...   Oct 11 2018, 10:16 AM
ChrisFoley   The red mark you see on the front side of the fan ...   Oct 11 2018, 11:03 AM
injunmort   all suggestions are great, I would now swap coil, ...   Oct 11 2018, 11:48 AM
andreic   OK, finally some progress. I noticed on the instru...   Oct 12 2018, 07:42 PM
914_teener   OK, finally some progress. I noticed on the instr...   Oct 13 2018, 01:48 PM
mgphoto   #3 normal #2 vacuum lines are advance and retard,...   Oct 12 2018, 09:22 PM
andreic   Well, that was optimistic.... Sadly it turns out t...   Oct 12 2018, 09:26 PM
72hardtop   Check your fuel pressure. What you describe sounds...   Oct 12 2018, 10:20 PM
rhodyguy   Is the strainer sock in the fuel tank in good, fun...   Oct 13 2018, 07:23 AM
mgphoto   Head temp sensor lose, not screwed into the head t...   Oct 13 2018, 01:46 PM

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