classic fast - car stalls during an electrical surge - tune file attached

[rwrows]

I'm new to this system. The car seems to run okay but not great. When I step on the brakes or turn the lights on, the car wants to stall. It's an 87 GN with a stroker and champion aluminum heads. I'm running alky and targeting about 22 psi. I was wondering if someone could take a look at my tune which I posted here:

https://docs.google.com/open?id=0B8Ec03TvqlNmRmw0Uldkd0NsQ1E

Thanks!!!

 

[Slow91z]

Is your fast power and ground wired straight to the battery?

 

[rwrows]

by the way, the battery and alternator are good. 12.8 while off and 14.58 while running. 14.2 with the high beams on.

 

[rwrows]

Is your fast power and ground wired straight to the battery?

i'm not sure. i will take a look now. thanks!

 

[pacecarta]

at idle whats the tps value? iac ?

tune looks fine

 

[rwrows]

at idle whats the tps value? iac ?

tune looks fine

here is a data log at idle. it was idling fine and eventually stalled from me pushing the brake pedal. And before that I turned on the crankcase ventilation fan thingy:

https://docs.google.com/file/d/0B8Ec03TvqlNmRkxGN2V0RHRrbzA/edit

 

[pacecarta]

turn the idle air screw in until the tps is at 9 or 10

also want to add the balancer ring must be way off .. I assume its a BHJ on that motor
timing base is set to 14degree in option file (normal setting is 10) ,
that means balancer is off 8 degrees , last one i saw like that was Joes silver car
the timing needs to be rechecked to see if the 14 deg was a carry over from his car or if it was indeed set based on your car


as for stalling with brake , make sure the vac booster check valve hasnt failed , it should store vacuum and just pressing the pedal shouldnt cause a major disturbance in the tune , but if the check isnt holding its like opening up a 3/8" vac leak


if you get the chance check the iac value , you still want to see it around 20 as you would have it set with a chip , if the IAC screw did back out which would cause the lower tps , it would increase the iac

 

[rwrows]

i actually disconnected the power brake booster vacuum line and plugged it. It still stalled when i stepped on the brakes.

at this point i am just happy i can drive it. i will fool around with the idle screw but will that just take the idle up 1250? i find that if i drive the car with 2 feet i can usually keep it from stalling. or should i just try to adjust the tps. how do i check the iac?

i'm starting to think it might make more sense to just take this up to you when i grab the GW

 

[Slow91z]

Adjusting the idle screw will not change the idle speed unless you turn it in so far that the iac is completely closed...once connected click view and then dashboard...you can see tps and iac and basically all readings there.

 

[DR BOOST]

power your map sensor from the 5volt reference wire that powers your tps. from the factory, the map sensor is powered by the dash gauge which is unregulated and fluctuates with things like brake lights and headlights

 

[norbs]

Could be many things going on here...timing is jumping all over the place ie from 15 to 30 degrees at lower rpm, fueling too rich and wrong iac blade postions, and injector open time vs voltage having a role in this, one of the drawbacks of the classic fast its more sensitive to voltage fluctuations compared to the xfi.

 

[pdzz]

Interesting, mine was doing the same. I ran redundant grounds, voltage right to the battery. Didn't seem to make it better. Upgraded to a 16 volt system, now it doesn't stall, but, have another issue.. Phil.

 

[Blazer406]

Guys..... don't forget to cover the basics first.... don't over analyze...... if the car has the basics covered... then step up the troubleshooting. Some have already alluded to it.... but:

1.) The IAC should be between 20-30 hot idling. If it is not.... I suspect this can easily be contributing to the stalling issue.
2.) Once you get the IAC happy, you need to go set the max TPS for idle on the clasic box. I don't think you can re-scale like the XFI.

If you ge the IAC happy.... and the TPS happy...... then start with other stuff to check.

I'd agree the timing table should be looked at.... the timing shouldn't need to vary much in the idle region.... the timing shouldn't be hunting much if any while the car is idling.

I see you have 900 RPM as the "target" idle speed when 181° and up. I don't know your combo... but is 900 high enough?

What AFR are you seeing right before it dies?

 

[pacecarta]

the hunting is a scaling setup in the idle speed error vs timing , his has a very aggressive timing vs idle rpm error ..why i dont know
on my car i run next to 0 timing change vs idle rpm error, set 0 at 80 to 2 degrees at 112rpm error

 

[Blazer406]

Why is the timing showing 15° some of the time...... he doesn't have that set lower than 25° as far as I can tell in the idle region of the timing table.

Looking at the log.... the idle is running higher than the idle speed vs coolant temp table is telling it to.... leading me to believe that the IAC is already all the way closed. Id bet the IAC numbers are 0 most of the time at hot idle based on this datalog.

The hunting timing isn't helping the idle..... I concurr..... what idle RPM does this motor like?

Id make from 99kPa and down ... over to 1600 RPM..... all timing cells in that region.... set it to like 32 deg or somethin close. you have 25 deg cells next to 40 deg cells while the car is sitting there idling at a steady state.

 

[pacecarta]

i explained the timing ...see above post
to see why look at idle functions .timing trim..
his tune has 10+ degrees trim at 112rpm idle speed rpm error

it could be his throttle blade adjustment , the iac motor could be bad or the iac driver(s) in the FAST box could be fried (common since all it takes to fry the driver is to unplug the iac while key is on)
having seen this car before i wouldnt rule out stuck injector or shorted injector driver or bad harness , but those issues were supposedly taken care of and the box was replaced

 

[Blazer406]

i explained the timing ...see above post
to see why look at idle functions .timing trim..
his tune has 10+ degrees trim at 112rpm idle speed rpm error

So this timing works in both directions? i.e. adds timing and takes away timing.... depending if the idle is too high or too low?

edit: Went and read the help..... it does work both ways as suggested.... I'd think like you say.... it needs to be almost flat.... maybe a couple degrees at the higher idle error......

 

[kidglok]

the jumps in the mappsi is making the AE fuel vs Map rate of change dump fuel in , you can see this by looking at the fuel lbs per hour. The AE vs Map is too aggressive for 83lb injectors at 4cts its adding 1.38ms of injector opening time- that translates to a lot of fuel. The FAST is looking for ways to compensate for this by the timing trim, as well as other things.

im wondering why your boost seems to jump around soo much with the tps staying the same, theres one point where it spikes to 4psi from -3. I would check that out and see whats up with your map signal. And 12.4 fuel #'s per hour is waaay off, mine reads 2lbs at idle

 

[rwrows]

Thanks for the replies guys. Yes the car does run super rich. I almost blinded myself and passed out in the garage. She puts out black smoke sometimes while driving too. It looks like there are a ton of things I need to do. Where the heck do I start? I'll take a peak around it this weekend. Any tips on what order to do things?

Appreciate it!

 

[norbs]

Thanks for the replies guys. Yes the car does run super rich. I almost blinded myself and passed out in the garage. She puts out black smoke sometimes while driving too. It looks like there are a ton of things I need to do. Where the heck do I start? I'll take a peak around it this weekend. Any tips on what order to do things?

Appreciate it!

Read the posts these guys have all the right idea's, mod your program so its less rich, timing stable and calibrate the IAC, while its running properly. If you can't do it I'll do it for you, but you need to set the Tb screw properly. You can run the timing offset high if you have everything else tuned in and stable, but I tend to limit that to 6 degree's max some other people like to run up to 12 degree's, but I find on my set up it tends to add instability to my idle.