I have an 82 trans am 305. sometimes it diesels after turning off. it will do this when it's only ran for 5 minutes or even when its warmed up all the way. the idle is set correctly. if I adjust the timing it only gets worse and shakes. the plugs and wires are good as well as distrib. cap. o2 sensor was replaced not long ago. it will put out code 13. it runs great when driving. most of the time to start it I have to put my foot on the gas until it starts then it's fine. any clues why it's doing this and how to fix it? it is now putting out code 44. i've left the smog pump disconnected and tried pluging it back in to see if it made a difference.

 

Well this probably won't help, but my dads 1986 Caprice did that with the 305. Turns out the choke was not closing all the way, it stayed open just slightly and caused it to diesel. I had to spray the crap out of the linkage where it goes down into the carb. Hopefully this helps, but if it doesn't then best of luck to ya.

 

My buddies car had the same problem, but
we were unable to rectify the situation.. It
was very frustrating and embrassing..

especially when girls were around (haha)

So we slowly discovered to avoid any
deiseling, just turn the car off in "D"..
The converter locks up and seizes the
motor.. It has no ill-effects that I know
of, and saves the embrassment of a car
that doesnt shut-off.

Hope that helps alittle bit

 

Sounds like whatever supplies your fuel is leaking.
Carb or injectors.

 

I had this problem with another car, and it was doing it because of vacum leaks. Once they were fixed, it never did it again.

 

I've had this problem too on carb cars from time to time- the lower you can set the idle the better it will be, and the cooler you can run the engine the better the situation will get. Also, higher octane fuel and cooler spark plugs will help

 

before just replacing things... this is a 82 engine right? when was its last rebuild? do you always use good gas? does it burn any oil?

you could try some water... get a fertilzer sprayer the hand pump kind fill it with straigh water... start the car and and spray into the throttle bores while maintaning about 2k RPMs... you will need to fog it pretty good here after a few minutes you should really start to notice plumes of smoke out the tail pipes... that is good means its working clear the engine with a couple of quick revs and shut it off see if it still does it

 

thanks for all the good advice. from what I could tell the engine has never been rebuilt. it has 113,000 miles on it.we got it from florida off ebay for $600. the compression was a little high around 160-178 on all cyl.'s it sat for a long time in florida and hadn't really been driven. i can't find any vacuum leaks. I did have to put new valve cover gaskets on the old ones were not there anymore and oil leaking out. i turned the idle down. it runs at 400/500 rpms most of the time but runs fine. it's stop the problem so far. i'm a girl and it is embarrassing for me as well when it does that. thanks for all the advice. great help guys

 

it should be idling a bit higher than that around 700rpms warm

 

sometimes it does and sometimes it doesn't. when it first starts it won't but after 5 minutes it will most of the time. if it's cool outside it won't it stays low but doesn't ask like it's going to die.

 

o.k. the rpms have gone back to normal at about 600-700 on it's own. it is back to chugging a few seconds after turn off. could it be something with the ignition? i know the guy before had replaced it. he said it had an automatic push button starter that a lady had put on it.

 

Just one quick question, is the fan wired to come on when the key is turned on? the reason I ask, if it is wired into a direct power supply, when you turn off the car the fan wil continue to freely turn, when this happens it creats a small amount of power, just enough to have the engine fire over a few times...dieseling is then caused.

just a thought...

 

that isnt possible at all

 

it does come on as soon as the car starts and runs the entire tim untill turned off.

 

it is possible for the fan to be rigged that way... which isnt the way it is supposed to be... but it isnt possible for that fan to cause the car to diesel

 

i'll check to see where the wire leads ot and check it out. my 84 is like that but the guy who had it before installed a switch to turn it off and on. i've never looked closely at teh fan on my 82. thanks

 

I remember my car dieseling a few times when I had the fan connected to turn on when the ignition was on. When its still spinning right after shutting off the car, it acts as a generator and gives enough voltage for the plugs to fire a couple of times. This will be more pronouced if there is a problem with the carb or a vacuum leak.

 

Yes it is possable...in my quest to set my fan to run when the key is on also made my car diesel when shutting it off, the fan is like a little generator. I will now find one of those units that I can place in the radiator.

to test my theory just un-plug the fan, run it for a min, then shut it off...

 

Uhmm, the battery will provide more than sufficient voltage for the plugs to continue to fire but when the ignition is turned off the circuit to the coil/dist is open. It would have to be some wild hack to have the fan circuit wired so as to bypass the ignition switch and still fire the plugs. This fan-dieseling connection is just crazy talk.

Besides dieseling or run-on is not caused by the plugs continuing to fire, if they did that the car would continue to run normally. It's caused by air/fuel in the combustion chamber self igniting (in the absence of a spark), hence the term 'dieseling'. Lower octane fuel is more prone to diesel. Carbon deposits in the chambers on older engines can raise (slightly) compression ratios and cause hot spots that promote dieseling. The most common cause is a vaccuum leak. Chase that down and you'll likely find the problem.

 

i'll check thanks

 

my fan is bolted to the engine so that's why it comes on. I can't find any vacuum leaks. when it first starts for about 8 minutes it only idles at 500. when it reaches almost 220 where it stays at that temp. it runs normal at 600-700 but at 1100 in park. when I turn it off it makes a sound kind of like air brakes on a bus. it chugs for about one second, does that sound and spits gas up through the carb. you can see the gas come up and squirt all over the carb. sometimes it appears to have steam coming out of it or white smoke. it doesn't keep running. again it only last about 1-6 seconds maybe.??? by the way thanks for all the help.