first start tune...

[caffeine]

I've never found DFCO to be violent in any of my cars. Actually the opposite really. In OBD1 there's a setting to change how quickly the fuel is cut.
However even on the quickest setting it takes a few seconds after entering DFCO before the fuel is actually cut.

[caffeine]

Have you verified that DFCO is indeed the culprit by checking the injector PW during the situations in question?

[ericjon262]

Have you verified that DFCO is indeed the culprit by checking the injector PW during the situations in question?

no I haven't, I need to add IPW to my logs, keep forgetting... I have been assuming DFCO is to blame, because it only rears it's head at light loads, trans engaged, and throttle slightly closing.

[caffeine]

DFCO should never engage until the throttle is 99℅ closed and with factory settings it never comes on instantly when the throttle is closed

[caffeine]

With large injectors if the lag times aren't set up accurately enough it can feel like fuel cutting if the PCM is commanding low pulse widths but they aren't long enough to open the injectors. I had symptoms of that when I first started tuning my Firebird.

[ericjon262]

With large injectors if the lag times aren't set up accurately enough it can feel like fuel cutting if the PCM is commanding low pulse widths but they aren't long enough to open the injectors. I had symptoms of that when I first started tuning my Firebird.

I did put the lag times in on my base tune, they should be correct, I'm gonna email the company I bought them from to see if they can give me any more info. I did adjust for the minimum injector pulse width, so it definitely shouldn't be that, but it is possible.

[caffeine]

Keep in mind also that lag times are affected by fuel pressure. So if you're running a different pressure than they were originally rated for the lag times could still be off.

[ericjon262]

Keep in mind also that lag times are affected by fuel pressure. So if you're running a different pressure than they were originally rated for the lag times could still be off.

I'm at 43.5 PSI which is standard for my injectors.

[caffeine]

Yeah mine are rated for flow at 52 lb/hr @ 55 psi. But the lag time spec sheet they have lists the lag times for a lower psi and a multiplier to adjust for different pressures. I always thought that was odd that they didn't just provide dead times for the pressure that they're rated at.

[ericjon262]

ok, I replaced the IAC motor yesterday, I haven't had a chance to drive it with the new IAC yet, but the discs were very different between the old one and new one, hopefully that helps with the idle flare up, I'm gonna start it up when before I go into work tomorrow night and see how it does. I also picked up a 2 bar map sensor and am working on it's integration. I'm going to try to use a 3800sc bin file to run the car by changing the crank sensor resolution flag, and engine type flag, along with the other changes I made to the 3400 bin. my biggest concern is the dual knock sensor, the 3400 only has one, and there isn't a flag to turn the second one off. all I can do is turn the codes off and hope it plays nice....

in other news, I'm going to make a new harness for the car again, I'm going to try and input the 7x signal directly into the PCM with a hall effect sensor and use the ignition coil outputs for the LX5 shortstar for true coil on plug ignition. it will be interesting to see how this turns out, I'm very nervous, and excited at the same time, this could open a few doors for us if all of it works.

[caffeine]

Another PCM option could be the vortec 4200 PCM since that motor uses a 7x crank signal stock. I'm not sure what the cam signal is like though

[ericjon262]

Another PCM option could be the vortec 4200 PCM since that motor uses a 7x crank signal stock. I'm not sure what the cam signal is like though

I should be able to make it work on the 3400 PCM. if I can, that opens it up to almost anyone for minimal work.

also, I'm pretty sure the 7x signal the 4200 uses is the cam signal.

[caffeine]

No it's the crank sensor according to alldata. However the I4 and I5 use 58x crank signals.

[ericjon262]

No it's the crank sensor according to alldata. However the I4 and I5 use 58x crank signals.

weird.... for now, I'm going to stick with the 3400 PCM and see what I can do. there's alot available in there.

[3400-95-Modified]

I have a two bar map working on a 97 venture bit so you can do it on what you have and not need to move to the 3800 pcm