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82 rabbit violent bucking and jerking

1467 Views 6 Replies 4 Participants Last post by  gberge
I have been up and down these forums, posted in facebook groups, and talked to pretty much every volkswagen tech in my area at this point so I finally decided to make an account and post. I bought the car for $800. 90k miles barely any rust and interior is in good shape. 1.7 CIS with a 4 speed manual trans. The first couple of days the car ran great but there was a little popping and sputtering so I did a tune up. Plugs, wires, cap, rotor, fuel filter and air filter. Then the car started misfiring hard under acceleration. Like extremely violent bucking and jerking. I haven't received my voltage regulator for the back of the cluster yet so I had no idea where my temp was at and a friend suggested the radiator could be clogged and that it could be getting hot and creating a vapor lock situation. So I flushed the radiator, replaced the thermostat and replaced the radiator cap that wouldn't hold pressure. Ran the car and used a temp gun to check temps. The car is not running hot at all. Still bucking and jerking. Messing around replacing the vacuum lines I found that with the vacuum advance unplugged the car would run great. No issues whatsoever. So next I timed the car, still bucking and jerking. It seems to only happen after driving for an extended period of time and I read that the car will only read from the 02 when it is warmed up so I unplugged the 02 and drove it. Still bucking and jerking. Last night I went through and replaced all electrical connections and grounds because I'm only reading 12v on the voltmeter on the center console. After doing that I'm still only reading 12v. Honestly I am at a loss here. When not in gear the car will idle and rev smooth as butter. Once you place a load on it it seems to be another story. It seems to mainly do it in second gear and if you keep your foot on it it will jerk like hell but it will power through and then shifting into third it will usually go away for awhile but eventually it gets to the point where it is jerking and misfiring so bad that it wont go anywhere. Anyone have any ideas? I'm sure I forgot some stuff that I have attempted. I have a full donor car for a 1.8t swap but would really like to get this 1.7 running correctly so I can drive the car until winter and then park it and start on the swap. Thanks in advance.

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I would do the following first.
Which type of plug did you buy? Because some plugs are not well liked by these guys, and you need to get NGK

Second thing it to verify that your timing is spot on. (pictures).

Once you have verified that base time is correct, and that your plugs aren't the issue I have also gotten bad new wires.

Then we can progress.....I had a 2 new out of the box sets of Bosch plugs that were bad from the get-go one set has 2 bad plugs, and the other but one.

Second thing to look for is Vacuum leaks these cars hate them, I would check all vacuum hoses for tightness and non leaking.
I have NGK's. Cant remember off the top of my head which plugs they are. I need to find someone with a timing light or last night I was reading about the trick where you put it in 5th and push it forward. I only timed it by ear so I cant verify timing is correct and I have actually verified with 3 different sets of wires that the issue is still present.

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And all vacuum lines have been replaced.

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I need to find someone with a timing light or last night I was reading about the trick where you put it in 5th and push it forward. I only timed it by ear so I cant verify timing is correct …
How in the heck do you TIME and engine without a timing light? I can do it for my Diesel because that is how it is done, but on a gasser???? Get a light!!! My guess is that by listening to it you have it advanced at idle and by the time you rev it up with a load on it, second gear shift point, it is way too far advanced.

You need to have it on the recommended mark at idle, so that may involve reducing the advance then going back and increasing the base idle to spec.

Just my quick thoughts on this one.
Bad valve cover gasket, broken oil dipstick funnel, bad Brake booster hard line (cracked) are also vacuum leaks.
Cover the things that changed before the bucking. Crossed wires?
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