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914World.com _ 914World Garage _ Intermitent bucking

Posted by: spiritedTreiber Apr 23 2005, 10:43 PM

My 1.8 FI likes to buck intermitently. Sometimes around corners, and sometimes going straight. Doesnt seem to matter what RPM it is at either. The engine has completley died a couple times from it too. At times it is a series of heavy bucks, or just one or two. I have a few ideas at what could cause it, but I was wondering if anyone else could come up with some more.

Posted by: jim912928 Apr 24 2005, 08:01 AM

Hi, my ljet runs as smooth as a baby's bottom! There was a short period of time that it would randomly feel like it was running out of gas or only on a few cylinders...then it would be fine. It was very intermittent. Turned out to be loose connectors on the fuel injectors in my scenario. I'd check all your electrical connections. I'd think if it were vacuum related (usually the cause of ljet issues) it would be more constant.

Posted by: root Apr 24 2005, 08:11 AM

I would look for an electrical fault first! like a loose 12V supply coil connection!

Posted by: lapuwali Apr 24 2005, 09:59 AM

From experience, it's either a coil connection or a fuel injector connection (at the injector). The injector connection is more likely if it just bucks, but never completely dies. If it dies, it's more likely the coil (or you have multiple loose FI connectors).

Check the wire into the connector, not just the connector to the injector or coil. Things can look fine, but still be loose. Try to pull the wire out of the connector.

Posted by: Cap'n Krusty Apr 24 2005, 11:51 AM

From experience, the FIRST thing I would check is the CHT sensor. Make sure it's tight and the connection to the harness is clean and properly made. Then I'd check the system grounds, then the wiring to the relay, then look for any loose vacuum connections and hoses, inculding the TWO seals on the oil cap. The Cap'n

Posted by: double-a Apr 24 2005, 03:46 PM

definitely sounds elecrical. my car (75 1.8) did this for awhile and it drove me nuts. i finally figured out what it was: bad plug wires. i replaced them with some nice bosch wires and it purrs like a kitten now. but also check your airflow meter and vacuum lines as well, because l-jet needs a tight vacuum system to run correctly.

~a

Posted by: elocke Apr 24 2005, 09:05 PM

Could be junk floating around the bottom of your gas tank.
Ed

Posted by: spiritedTreiber Apr 25 2005, 06:09 PM

Thank you for the suggentions everyone. Kinda gives me a good starting point to go from. One thing i thought it might be was points, or just the dizzy in general. It has a dual vac on it with regular points. It also has one vaccuum line off, but I dont see a line laying around that would go to it. Was wondering if a 009 with petronix would help it run any smoother. Have one layin' around.

Posted by: lapuwali Apr 25 2005, 06:29 PM

QUOTE (spiritedTreiber @ Apr 25 2005, 04:09 PM)
Thank you for the suggentions everyone. Kinda gives me a good starting point to go from. One thing i thought it might be was points, or just the dizzy in general. It has a dual vac on it with regular points. It also has one vaccuum line off, but I dont see a line laying around that would go to it. Was wondering if a 009 with petronix would help it run any smoother. Have one layin' around.

There's nothing really wrong with the dual vac, you get much better gas mileage with that. The points can be replaced with a Crane or Compufire unit pretty easily. The 009 is suitable primarily as a paperweight.

Posted by: Cap'n Krusty Apr 25 2005, 06:47 PM

Speaking, as we are, about distributors, have you checked the ground cable on the breaker plate? BIG possibility here! Repairs are possible, replacement of the plate is easy and better. The Cap'n

Posted by: spiritedTreiber Apr 25 2005, 07:23 PM

I will be sure to check out that breaker plate ground. Any clue as to where that 2nd vac line would go on the engine if I was to install it? Also, anyone know if the petronix from the 009 will fit in the dual vac? I know the cap and rotor are the same, but Im not sure about the rest.

Posted by: spiritedTreiber Apr 25 2005, 09:10 PM

Finally got a chance to have a good look around. Turns out I already have crane ign. in the dizzy. Cant find any open vac ports, or unused ones for that matter. Looks like what i think is the fuel press. regulator doesnt have a vac line to it either. Need a little help as to where the throttle valve switch is located though so I can check the ohms on it. The airflow meter tested good with just over 200 ohms resistance between poles 6 & 9 and also 7 & 8. BTW when i pulled the cap and rotor they were lookin pretty nasty, so i swapped them out. Maybe that had somethin to do with it?

Posted by: Reiche Apr 26 2005, 01:24 AM

The L-jet throttle valve switch is just that: a switch. It tells the ECU when the throttle is closed or wide-open, but nothing in-between. In between them, the AFM takes care of the metering. I would be surprised if your symptoms are related to the throttle valve switch.

Posted by: lylegd Apr 26 2005, 08:28 AM

Looks like there are many suggestions on things for you to check out so let's add one more to the list. The L jet FI uses an air flow sensor to provide a critical input to the computer. The air flow flapper inside this box can bind up by rubbing on the sidewalls of the air flowbox, thus causing the wrong signal to go the the computer. Check to see if it moves freely. Lyle

Posted by: spiritedTreiber Apr 26 2005, 02:30 PM

Thank you all for the helpfull hints. It appears to have been just the cap and rotor. The only other thing i really did was change the air filter, but the old one wasnt even that dirty. Put her all back together and took her around some nice windy roads around the area. No problem at all, but it felt like i gained 10-15 HP! Off to do the brakes on the front now.