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1984 VW Jetta GLi running rough. F.I. Problem?

My jetta has began to run pretty rough over the last few weeks. I did a compression test on it and it was 150 across the board. While looking at the plugs though, I noticed that one was black and the others were a beigey-yellow. I swapped the plugs around and it ran great. I assumed that the blackened plug was getting oil to it and fouling out from a valve stem seal. A week later the problem has reoccurred, a little worse actually. A friend recommended running a hotter plug until I could get around to changing the valve stem seals. I put in hotter plugs, new wires, cap and rotor. The symptoms are as follows: Runs rough (like it is missing on one cylinder) especially at idle, almost dies when taking off in 1st gear, it needs to be nursed along. It seems like it runs fairly ok when the rpms get up to around 2800, but any lower and it is bad, kinda lurchy. Anyway, if anyone has had a similar scenario and is willing to let me in on where to look next, I'd appreciate it. I think I'm leaning toward a bad injector possibly. I've heard about a method of testing these by using a jumper wire at the fuel pump relay, but I've forgotten the procedure. I would really like to get this back on the street. I've got 227K miles on it and I was under the impression that it was indestructible and I'm wanting it to at least make it to 250k. Anyway...thanks for any insight you might have. Bryan

Reply to
bryan gilbreath
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I'd be looking at whether you have a leaky fuel injector in with respect to that one cylinder or perhaps whether you have a problem with that spark plug wire just not allowing it to ignite properly. Look at the plug wires when it's dark out, then mist them with water and re-look. If you don't see anything wrong there then start looking into injector fuel problems (i.e. maybe it's just running rich in that cylinder). Beyond that it might be a leaky valve stem seal. Seems like those usually all go at once, though, but it is possible for one to go quicker than the others, I suppose...

Reply to
Bob Hetzel

Well, I'm pretty sure that it isn't the wire. I replaced the wires, plugs, cap and rotor last night and the symptoms persist. I think the crappy running must be in the fuel delivery. I was told, and I'm not sure if I'm remembering this correctly or not, that I should pull all of the injectors and lay them up on the valve cover, then bypass the fuel pump relay with a jumper wire and see what kind of spray pattern the injectors are producing. If one of them isn't doing a fan pattern, then it is most likely the culprit. I'm writing to see if anyone has used this test method before. Something about spraying gasoline makes me a little nervous. My other project car did the spraying gasoline with the added drama of flames so I'm a bit apprehensive when it comes to gas.

Reply to
bryan gilbreath

I've done it a few times. I always put the injectors into a plastic bottle to check the spray so the gas doesn't spray out over the engine. Before doing this, I'd recommend picking up a new set of injector o-rings (cheap). If you decide you don't want to pull them to test them, you could always add a bottle of Techron to your gas and hope for the best.

Chris

Reply to
Chris Z.

Definetly check the injectors for leakage. Also there are sleeves the injectors fit in and there's o rings there too. There is a air passage that runns alog the rear side of the head to cool the injectors. The age of the car would dictate new o rings. However the probles is most likely a leaky injector. Have you tried some injector cleaner? don't forget it contaminates the oil so you should change it after using two treatements.

Joe

Reply to
Joe R

Reply to
bryan gilbreath

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