Blitz21 Posted February 22, 2010 Share Posted February 22, 2010 Stock '73 Z. When I turn off my car, the motor will shudder and it sounds like its trying to turn over...I have no clue. I have a separate switch for the fuel pump, so it couldn't be something like fuel still getting in, and it'll only do it for about 5 or 6 seconds then stop. Quote Link to comment Share on other sites More sharing options...
leftover z Posted February 22, 2010 Share Posted February 22, 2010 Check your timing? Quote Link to comment Share on other sites More sharing options...
FlatBlack Posted February 22, 2010 Share Posted February 22, 2010 Isn't it just dieseling? Check to make sure your throttle is closing all the way. Quote Link to comment Share on other sites More sharing options...
MAG58 Posted February 23, 2010 Share Posted February 23, 2010 What's the mixture look like? Is it running rich? Lean? Quote Link to comment Share on other sites More sharing options...
jasper Posted February 23, 2010 Share Posted February 23, 2010 http://en.wikipedia.org/wiki/Dieseling Quote Link to comment Share on other sites More sharing options...
blue72 Posted February 23, 2010 Share Posted February 23, 2010 Beat me to it. I was going to say dieseling as well. It's been talked about on here plenty before. Quote Link to comment Share on other sites More sharing options...
Blitz21 Posted February 23, 2010 Author Share Posted February 23, 2010 Yup, got it figured out. It was dieseling. My timing is fine, and a little on the rich side. I guess I just have to run a higher octane, (running 89 now, guess I should go to 91, or be baller and go to 105 heh). Juuust kidding... Quote Link to comment Share on other sites More sharing options...
ArizonaZ Posted February 23, 2010 Share Posted February 23, 2010 (edited) I think that the dieseling occurs from carbon deposits in your combustion chamber staying hot and igniting the fuel mixture. You might want to try some "seafoam" to see if that helps Edited February 23, 2010 by ArizonaZ Quote Link to comment Share on other sites More sharing options...
JayBee280 Posted February 25, 2010 Share Posted February 25, 2010 wow you are usinging 89....ouch i feel it for the engine. I know the service manual say use 91 grade and in north carolina its either 93 or 89...so i go with 93 of course. Good thing figuring it out tho. helps alot for others Quote Link to comment Share on other sites More sharing options...
Blitz21 Posted February 25, 2010 Author Share Posted February 25, 2010 @arizona: I've used Seafoam before on my previous cars and it gave good results. I was thinking that or carb cleaner. @jaybee: Ah, that would probably make sense using 91. But I don't have any manuals so I wouldn't know and I've only had this Z for a month heh. Out here in Cali the highest grade we have is 91 but there are a couple pump stations that sell 105 for a ridicoulous price (the lowest I've seen 91 is $3.19 bleh). Anyways, I was planning to use 91 in my new motor (I'm having a L28 bored to 3.1 built etc. put in as we speak). Additionally, has anyone had experience with "octane booster"? Whenever I see it on the shelf of autozone I instantly think "ricer", but like anything, there could be some good to it. Quote Link to comment Share on other sites More sharing options...
T-Bone028 Posted February 25, 2010 Share Posted February 25, 2010 Blitz, if you are having a stroker being built and eventually being put in, and you have determined that the current motor is dieseling and not some sort of electrical/EFI issue, why bother troubleshooting/fixing? Not sure if this is also your daily driver, but me personally, I would take this time to sort through your car and make sure that everything else is up to snuff. That way, once your new motor is finished and installed, you wont have another million things on your mind that needs to get addressed before you feel comfortable taking it on the road. Just my 2 cents. Quote Link to comment Share on other sites More sharing options...
Blitz21 Posted February 25, 2010 Author Share Posted February 25, 2010 Thanks for the consideration T-Bone. While I am having a new motor put in, I'm just the kind of guy thats simply curious when something doesn't work right. It is my daily, and TRUST ME I'm taking all time I need while it's down to go over and replace/refresh everything. Quote Link to comment Share on other sites More sharing options...
jasper Posted February 25, 2010 Share Posted February 25, 2010 Hopefuly you read the link I posted. Run on/dieseling is caused by many factors. IT IS THE SUM,of all the possible causes. Usualy, there is not one cause. Engine temp/high idle/low octane/carbon build up/high compression/lean fuel mixture/ etc. ......all have a cumulative effect to cause this malady. This is one reason, why idle kickers were put on early 70's cars to maintain idle speed.Turn off ignition, throttle closed, not enough air for engine run on. Quote Link to comment Share on other sites More sharing options...
Blitz21 Posted February 25, 2010 Author Share Posted February 25, 2010 @Jasper: Yeah I read the link, thanks to wikipedia and thanks to the forum! Gotta love the wealth of knowledge. Quote Link to comment Share on other sites More sharing options...
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