81silverbullet

It has just started doing this regularly after I had a true dual exhaust put on. I doubt there is any connection here though, but it now occurs about every time. Anyway, what would cause this sputter when the ignition is turned off? It only lasts about 2-3 seconds, but that's all it takes...car sounds great, till I turn the key off.

Thanks for the help,

Steve

Fevre

Adding duals can lean out the a/f ration causing your eng to run 'hot', might not show up on the temp gauge but comb chamber temp will be higher which causes the plugs to be hot and ign fuel after shut down. might need to adj the carb to correct it esp if you had 2-1-2 with a cat and switch to true duals without cats.


[Modified by Fevre, 4:27 PM 10/17/2003]

81silverbullet

Thanks Fevre, I was beigining to wonder it the dual exhaust had something to do with this. I did have the 2-1-2 before and almost never had this occur at shut-down. Now it happens all the time. I've never adjusted a carb before...I have about every manual imaginable for this car, iincluding the shop manual. Is this too complicated for an amateur?? :skep: :skep:

Fevre

I know very little about q-jets, assuming that is what you have, and even less if it is elec controled. If it elec controled did you have a bung added for the o2 sensor? Again I know nothing about the elec q-jets so they might not even have o2 sensors. Might try contacting Lars the q-jet guru. :thumbs:

Wrencher

"Sputter, run-on, dieseling" all describe the engine continuing to "run" after the ignition is turned off. More efficient (and often leaner) combustion and resulting higher cylinder operating temperatures, and a residual fuel source can cause this. Often a slightly high base idle, inoperative idle stop solenoid, slightly rich mixture, advanced timing or any combination of these can cause it. Since you just installed headers, I'd go back and re-check the idle mixture and base idle (check that it's adjusted at the solenoid and not the stop screw), lowering it a bit if possible. Should be a pretty easy fix.

Hans

Fevre

BTW 2 things you can so short term until you can adj the carb: If you have a stick, push in the brake first then let off on the clutch just after you shut it off, takes a few times to get the feel. You can also retard your timing a few degrees, you will lose some power but it should get rid of the run on.

bloodvette80

i agree, i know that when i go on a good bag run and get my engine very hot, when i shut it down it may "diesel" thats because the plugs get so hot that they will actually ignite the fuel, even though the electrical is cut off, and theres no spark, the engine will still fire a few times. some people say it is carbon build up on the plugs. try take one out and see. also, if it is carbonned up, take your air cleaner cover off, bring up the revs a bit, and slowly pour a little bit of water into the carb. she'll suck it in and losen off the carbon and your problem is solved.

KenSny

Check the timing first - retard it a degree or two and see if it makes a difference. Going to true 2-1/2" duals from a restrictive 2" cat system required some tweaking of the carb on my car. The first owner had replaced the original 2-1/2" pipes with L48 2" pipes and a piece of crap cat..... It ran and sounded like someone blowing thru a tin can.



[Modified by KenSny, 6:17 PM 10/17/2003]

Marc80

Shut it off in drive. This will prevent the dieseling until you get the tuning right.