Engine sputter after turning off ignition

[904Zster]

Thanks FreeZ for all the helpful hints. I will try all those suggestions, before I do anything more invasive.

I am suppose to keep notes on all that happens, since my mechanic is still fine tuning the car for me, and yes, I will take the car back to him with all these notes.

Now as far as the route of Sea Foam and gas additives that will help; Are there other good alternatives to Sea Foam? First of all, I went to my local Kragens last night and they didn't have it. They had things like Slick50. Is that a good alternative? Someone at work suggested kreen from kanolabs. Who carries these products? Anyone heard of this stuff?

I'm also intrigued by another suggestion of running a bit of water in the carb when the engine is running? I think this is something I picked up from an archived post.

The best suggestion from a coworker is to run the hell out of the engine on a open road in the morning. Yeh!!

Anyways, I'm learning a lot from all this great information. Thanks all.

[Arne]

Good comments here. I've got two things to add. One is that the early 240Zs ('70-71) definitely called for premium fuel. And that was in the day when there really WAS premium fuel. I don't know about the requirements of the later 240Zs when the compression was lowered a bit.

Second is that the idle speed spec on the early cars was 700-800 RPM. If your car is idling faster than that, I'd try dropping it down some. Although, a faster idle is a common workaround for worn carbs. Throttle shaft air leaks are less noticable at higher RPMs.

[thedevilz]

Not to hijack the post or anything, but my 72 240 also has this same issue. I would like to follow everyone’s suggestions, starting with the timing (also because my car though runs right, has for some reason no power in the higher RPM range...my little cousins civic could take me ...seriously :stupid: ). What are the correct timing settings for the car? My 240 usually idles at 1000, 1100. It has cams, not sure if this has anything to do with the high idle.

Thanks in advance.

[KDMatt]

Kragen didn't have Seafoam?! I find that hard to believe.

I, like many here, am also a "rookie" (only going on my third year of Z-experience here), but from what I can tell there is nothing that really compares to Seafoam... and it's sold in a lot of places... the corner gas-station by my college sells both Seafoam, and it's sister product "Translube." I don't really think there's an alternative that's as effective and has as reliable a reputation.

I don't mean to contradict you, but if all you could see is stuff like Slick 50, you were probably in the wrong section of Kragens. Seafoam is mainly a fuel additive, whereas Slick 50 is an oil additive. If it's anywhere, it'll either be on a shelf by itself or near stuff like Gumout... sometimes I personally still have a hard time finding it, and have to ask a sales associate.

'Best of luck to you gentlemen, Dieseling doesn't sound like much fun.

[Ricklandia]

1-Set the timing

2-set the idle

3-set the mixture

Perfectly said.

It was a hugely common problem back in the mid 70's when mechanics were forced to "de-tune" all those high compression, high horsepower engines of the late 60's - early 70's to deal with the switch to unleaded and lower octane gas. You retarded the timing in an effort to minimize pinging, but the consequence could be dieseling if you went too far. Richening up the fuel mixture also helped to avoid ping, but again exacerbated the dieseling problem.

Z-Train has it perfect; timing, idle, mixture