i have a gen 7 dfi setup in my 67 its a 383 motor. the problem i am having is after the motor is warmed up the a/f ratio meter jumps from being normal to real lean and back again and so on.the correction starts at 5% and jumps to the max of 25%..it does this at idle and sometimes while driving.what should i be looking for?? i have checked for vacum leaks and found none and i have new fuel pump installed as well..fuel pressure is good..my intake port temp reads as high as 165 degrees at idle(is that too high?)any suggestions would be appreciated..
mike

 

A/F ratio meter ? That meter reads % ? If it is a NB meter that swing may be normal rich lean and then it sometimes sits a while. If you can read the NB volts in log you may see those swings.

 

thanks for the reply.its actually a wide band(lm1 hooked up to the dfi)..i forgot to mention that the car actually starts stumble and want to die from being so lean..

 

I assume speed density(MAP) ? Double check the header collector flange to ext pipe for leakage. If WB sensor near it it may explain.

How big is cam? If large cam specs consider idleing OL. A large cam and or smallish LSA can mess with idle quality.

 

yeah its a map setup...the cam is 224/230 and .510 lift so thats not very big..i will have to check the headers if it stops raining...thanks any other suggestions?

 

I know nothing about MAF other than there is a point where it cannot handle high flow requirements. That would show in your logs.

Does not Accel have a forum to post Qs?

 

Reading your issue, what I would check first is if it's actually too rich. If you are overly-rich it'll actually show as a lean condition because there aren't enough oxygen molecules left in the airstream because it's full of unburned fuel. I would check to first see if you're actually too rich and then go from there.

 

when this happens my lm1 meter says anywhere from 15.xx-19.xx a/f ratio..like i said it happens after the car is warmed up..its weird because lets say the car has been running for 10 minutes and it has reached operating temp it will be fine but the longer it runs the worse it gets...i'm kinda stumped

 

Again, often times it means that you're running too rich. You'd be surprised at how many people make that mistake.

 

Oh, and you didn't mention you weren't using your WB to help your Accel unit out. I assumed that at first. If the EFI system doesn't have a WB to deal with, then it can mess up on the fueling regardless. Why didn't you go with the integrated WB O2 that Accel offers?

 

thanks for the reply,ok assuming it is rich how would i know? i mean if my meter is telling me its lean then how else would i confirm its rich? and i didnt get the wb option from accel because it was expensive at the time and i alraedy had the lm1.
mike

 

So, without the integrated WB, how is Accel determining fueling? Just by the fuel map w/o any O2 sensor at all? That might be part of your issue then, as most of the tables will be worthless. You need at least a NB sensor to help guide the Accel system. Without that "all is lost" so to speak. You need some way for it to understand how to fuel. But, on the rich vs. lean. Easiest way is to go out in the country and make a good 1/4 pass and then shut down (carefully) at the end of it and then check your plug. If you don't know what to look for do a search on Spark Plug Reading.

 

the lm1 is hooked up to the dfi.in other words the lm1 is replacing the accel option for the wb...i have it wired into the dfi.

 

Ok, that's good. Then what I'd try to do is lean it by 20% or so in one area; i.e. maybe around the idle, since lean at idle won't hurt anything; and see what happens. I saw a car over-rich once by 40%, and when we leaned it out 20%, it finally registered correctly as rich, rather than lean.

 

thanks for the tip..i tried to lean it out a little at a time and it just wanted to stall..so im guessing that its reading correct..not sure what else to try..

 

What is your bypass air % set to at idle?

 

not sure what my bypass air is because my laptop just took a dump!! figures...i am trying to get a hold of another one...as soon as i do i will let you know..hopefully by tomorrow...
mike

 

ok, i took the car out for a short run today.so i started it up and let it idle for a good half hour...got it to temp then took it out for a run...i got on it pretty good,spun the motor to about 4800rpm..first time i did that no stumble a couple of minutes later the stumble is there...so i bring it home and let it idle for a minute or two then all of a sudden the fuel pressure drops to like 25lbs..the motor starts to stumble and finally dies..now i let it cool down and start it up again i rap the throttle fuel pressure stays like a rock,after it warms up i rap the throttle again and the fuel pressure goes down when i do that..it comes right back up though..i tried three different fuel pumps and the same thing occurs..im thinking fuel pressure regulator??? what else would cause this only when the motor is warm?? also i have good voltage at the pump, about 13.5v..even when i rap the throttle the voltage stays at 13.5...the fuel pressure is supposed to go up when i stab the throttle,right?? where else should i look ??by the way the air bypass is around 6% at idle..

 

Fuel pressure won't necessarily rise - for instance, from idle to 6500 rpm, mine is rock steady at 45psi. Only time fuel pressure should rise is if it's a boosted application. Sounds like your fuel pressure is the issue, though. Now whether it's the pump or the regulator is hard to diagnose. Regulator is cheaper of the two parts. So maybe I'd start with that. You might want to consider an external pump and regulator up on the fuel rail just before the return line.

Let me know if you figure out if its the regulator or the pump!