I just spent $3,000 on my motor to cure a problem I am having and I didn't cure anything!!!!!!!!

The car runs, Idles starts perfect. I hook my snap-on scanner to the car and get no codes.

The problem is when the car is at a dead stop and you put the peddle all the way down to do a burn out the car will break the tires loose for a split second and then fall on its face and die like it is shut off. The car comes back as soon as you let the foot off the pressure. I am not loosing fuel pressure I checked that.

I am really frustrated. I cured the hard start when warm problem but I still have the stumble when doing a burn out.

The motor is a 400 small block with a tuned port
I went with edlebrock aluminum heads E.T. they are a 73c.c. head.
I went with a roller cam from Comp.

I did a freeze frame on my snap-on scanner and this is what the results were.

@ 3500 rpm 02(mv) =789 integrate =128

closed loop exhaust= rich
tps(v)= 3.94 throttle(%)= 100
block learn= 128 ft cell= 4
iac postition =39 learned iac 40
O2 ready = yes O2 crosscount= 2
base pw (ms) =11.3 desired idle =713
decel enlean =no map(hg) =28.1
a/f learned =no spark advance(degrees) =13
map(v)= 4.58 knock= Yes
mat(f)= 113 knock retard (degrees) =6

Is it a concern that my spark advance is only 13 and the motor is sensing knock and the knock retard is 6 degrees???
Let me know what you think.
Thank you trever

 

I'll presume you're using a '730 since you reported a MAP sensor input. Have you increased the Accel enrichment versus MAP and TPS?

 

Vader,

Thank you for responding.

I am using a 1992 computer. I have craig moates programmer. up until now all I have done is change the cylinder volume to match my 400 small block and I changed the injector rate to 24 for the bigger injector. I have 24lb SVO injectors

Should I start by adding more to the Accel enrich versus Map???
also should I increase the TPS???
(what tables or were do I find both of these values)

Are you thinking it is not getting enough fuel???

Trever

 

I don't want to get too far away from normal "TPI Stuff" since this is probably best answered in the "DIY PROM" board, but we'll give it a try.

But before you go back to burning the next PROM, you might want to make sure the mechanical items are properly set. Regardless of the target idle RPM programmed, you should check/set the minimum air position and set it for at least 500 PRM on the bigger displacement. Making sure there is air moving around the throttle plates at the idle positon can reduce lean tip-in. Since your TPS should be a non-adjustable type, there's little to do there.

You also need to verify adequate fuel pressure - at least 43PSI standing, 37 running. You should also make sure the TPS has no dead spots all through the range. You can do that with either your scanner or a voltmeter.

If that's all good, Start looking at your tune. Increasing the base cylinder volume is a necessary step, as is matching the injector size. If you are using ethanol blended gasoline (and you probably are) you might want to decrease the injector constant by about 7%. If you are having a little longer cranking on startup, and some throttle tip-in problems, and generally lean BLMs, it should help. I've found that 5-7% is about right for E-10 fuel in the few that I've programmed.

Fine tuning the injector constant may help some general idle, cruise, and operating conditions, but you'll still need to tweak the acceleration "helpers" a bit. With the larger displacement, accel enrichment fuel should probably be increased. I'm guessing you're using the $8D mask, so I'll work with those addresses.

There are several Accel Enrich tables that start at $538. You may want to start with the table at $580 (Accel Enrichment PW Multiplier Versus Delta MAP) just to see if it makes a big difference. There is a similar table at $587 that adjusts tip-in PW multiplier Vs. CTS for a little more fine tuning.

Eventually, you'll probably have to work on the VE tables with the change of heads and cam, but you'll want to get the basic operation tuned and working well first.