Engine sometimes dies when coming off the throttle

[buildit]

5.0L, TrickFlow Top End Kit, 75 mm TB/MAF

I had my car dyno tuned to make sure I wasn't lean ( I was a little). They corrected that with the chip, but ever since when I come off the gas at speed like to turn into my subdivision, the car sometimes dies completely.

I did the IAC test (got the car warm, unplugged it, see if it makes any difference). The idle did change when I did that, and got a little erratic.

I have set the TPS voltage previously (~.98) , haven't checked that again yet.

One other detail, while I was at the tuner we found that one of the injectors had quit...header for that cylinder was cold. I had 24# injectors in it. The tuner didn't have any 24#, so we we replaced them all with 30# and he corrected the MAF in the tune. It dyno'd fine after that and it ran ok coming home.

Any ideas?

Thanks!

 

[Rick 91GT]

Personally Id swap out the one injector.... I would play with the idle screw to see if you can bump it up just a little to get the TB open a little more, you may have to reset the tps I like to keep them around .92-.95 so it never sees 1v. Still could be the IAC.....

 

[jrichker]

See the "Surging Idle Checklist for help with all your idle/stall problems.

The quick and easy way to dump the codes is in there too, and all you need to do it is a paper clip! The first two posts contain all the fixes & updates. At last count there were 24 possible causes and fixes for surging idle/stall problems. I continue to update it as more people post fixes or ask questions.

 

[Dino Dino Bambino]

A faulty VSS could cause the engine to stall when coming off the throttle so you might want to look into that. The IAC is often falsely blamed for the problem so beware. You may replace the IAC and find that the problem's still there.

 

[buildit]

Thanks, guys.....I did replace all the injectors with 30# (i fixed my original post to be clearer). And I do have the VSS hooked up. This just started after the tune.....never had an issue with it before.

I'll try the base idle reset, thanks for the tip.

Any other thoughts?

Appreciate it!

 

[2002BLGT]

There are several things the tuner can do , and some things you can do as well , cracking the throttle plate to raise the idle speed just a little will help , the tuner can also add spark at idle , lean out the idle mixture just a little , and even clocking the MAF could possibly help depending on the set up you have