Stumble after acceleration...

Grand_87_national

I lika... do da cha cha.
Joined
May 1, 2016
I've noticed that after acceleration, if I snap the throttle blade closed, the engine will stumble, cut out, etc. It has never died doing this, and obviously, I can avoid it for sure. I would just like to see if it's a big deal, or perhaps if someone even knows why it does this. I have searched around on this forum, and found some mixed opinions in some threads of yester-year. Perhaps a blow off valve would help, (I know, I know, nothing "ricey", but the benefits to the turbo are palpable). It is a 1987 GN with a fresh engine on e85, trick flow 120lb injectors, 212/212 comp cam, ls1 maf, turbonetics 60 series, rjc fmic, g body parts 3" downpipe (internal wg), ported stock heads, currently on 20 lbs of boost (though it will do this after much less boost is made). My wideband shows 14.5-15 during light to no throttle, and will float up to 16 while coasting to a stop, 10 at wot. Anyone familiar with this? Thanks in advance.
 
Sounds like decel fuel cutoff to me. The lean wideband is indicating it too. Who's chip is it? You can ask them if decel fuel cutoff is enabled or not.
 
IAC set up correctly? Other than that you might be too lean on decel. Some chips have an antistall feature to help with that but if you already have a chip with that I'm not sure what else you can do.
 
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Sounds like decel fuel cutoff to me. The lean wideband is indicating it too. Who's chip is it? You can ask them if decel fuel cutoff is enabled or not.

I just purchased the car a couple weeks ago, so I really haven't had much experience with it... it's also my first turbo buick. Here's the chip...
 
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IAC set up correctly? Other than that you might be too lean on decel. Some chips have an antistall feature to help with that but if you already have a chip with that I'm not sure what else you can do.

I wish I knew.... how do you set up the IAC? is the lean spike during deceleration safe? If it's ok, I won't worry about it, I can avoid it.
 
Does it sneeze through the turbo at this time of lean decel? It won't hurt it. You can let off more gradually as you stated. Or blow off valve is an option.
 
No scantool?

I do have a scanmaster.... I just don't know how to use it. Lol. So far, I've been installing gauges (including a wideband) and haven't played with it much. It sits on the o2 voltage and knock retard values the whole time.
 
I do have a scanmaster.... I just don't know how to use it. Lol. So far, I've been installing gauges (including a wideband) and haven't played with it much. It sits on the o2 voltage and knock retard values the whole time.
You have a scanmaster that's good (y). If you do not have the manual for it I have attached it here. Just make sure its the 2.1 version. You can verify this at key-on. It will display 2.1 on the screen briefly. IAC is displayed on the 11th screen but don't worry about that right now. Start reading up on how to use your scanmaster, read the Vortex site linked above, and this http://www.turbobuick.com/threads/info-for-new-turbo-regal-owners.380856/

It's a lot to take in but we all started where you are at one time or another. The more you understand all the quirks these cars have the better the chances you will enjoy ownership. I think...:eek:. Lol.
 

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Thank you so much for the links! I did read some of the "tuning" section on the vortexbuicks link.... wow, lots of info! I do know it's a 2.1 because the first time I saw that on the "retard" side, I thought it was recalling a 2.1* knock retard from my last drive. Lol. I have a lot to learn.
 
With a chip designed for 25psi and you running 20, the amount of fuel is way too much, possibly resulting in a rich condition and sluggish stalling.
 
On a mass air car if the air is measured boost should be irrelevant. Spark timing would be an issue though.
True to some extend.
A 5.7 chip measures and tracks air flow to around 15 psi depending on setup, rpm and ambient, where the MAF value maxes out to 255. Anything over that is calculated.

If the car was set at 10 psi and still behaved the same way, the MAF would be suspect.

The operating condition does not match the fueling chip code. This could not be the issue but these are the facts.

In the end, without accurate data it's a moot point. LOL
 
True to some extend.
A 5.7 chip measures and tracks air flow to around 15 psi depending on setup, rpm and ambient, where the MAF value maxes out to 255. Anything over that is calculated.

If the car was set at 10 psi and still behaved the same way, the MAF would be suspect.

The operating condition does not match the fueling chip code. This could not be the issue but these are the facts.

In the end, without accurate data it's a moot point. LOL
Thats cool. I was thinking there was away to scale the airflow to get around the 255 max airflow problem.
 
My thinking was... since it does this on light acceleration as well, even 5 lbs of boost. Any time I'm in any amount of boost and I snap the throttle closed, it will spudder. That seems to me like it doesn't matter where my boost is currently set, because ad far as the computer knows, 25lbs of boost is right around the corner.... right? I mean, the computer doesn't know where my manual boost controller is set, so that shouldn't matter.
 
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