Is it natural to run really lean after applying initial load on the engine? My '89 F-150 5.0L does so, but only when engaging first and as I accelerate through first, and occasionally into second. It will smooth out once I get into a more "average" driving condition. I've done a few mods: intake, TB, bigger injectors, headers. Would those be my cause, or may it be that my TPS isn't signaling the comp quick enough. The last time I checked my TPS it read .8 volts at idle, and the Haynes manual says that it should read between .5 and 1.0 volts. (No ground probs here, I promise!!) It also says when readjusting the TPS to set it at 1.0volts. My fuel pressure is set at 45, using a Holley adjustable regulator. Is there anything else I can check for and/or adjust? Pumps are stock, maybe there?

Thanks again for all the help on the O2 sensor prob. It works beautifully now, thanks to ya'll.

Luke

 

If I'm not mistaken.....the TPS is ideal up around the .998 range.

 

Is the truck pinging or how do you know for sure that you have a lean condition just at that spot? If you do have a lean spot, it might take a custom chip to compensate for the mods. Lightning2fast knows alot about the speed density systems. You might try sending him an e-mail. I'm finishing up similiar mods to my truck and am wondering what I'm going to run into as far as driveability.

Randy

 

I have an air/fuel mixture gauge hooked up and it shows lean, as well as it chugs until I go to shift into second, which relieves the load.

 

Ahh. OK your using an A/F meter. I've thought about putting in one myself. What brand do you have? How do you like it? Is it easy to identify the air/fuel condition at the different engine speed/loads? One guy talked that they kinda fan back and forth violently during certain times and makes it difficult to determine exactly where your at.

FYI I have my fuel rail off and I put together a little test outfit to clean and test the injectors. I can vary the fuel pressure with the settup so I decided to check the flow at different pressures. I've got some tabulation and conversion to do yet to be able to make any real meaning out of this but I'll give you what I've got now.

19# injectors

30 psi- flows 154.5 cc per minute
40 psi- flows 190 cc per min.
50 psi- flows 216 cc per min.

I want to convert this all to lbs/hr and graph the results but with this info you can see that there was less volume increase by adjusting from 40 to 50psi than there was by increasing from 30 to 40. My truck (an 89 5.0 like yours) had the factory FPR before I put the adjustable Accell on. It was putting out 40 psi stock. I see you have increased to 45 psi so you have increased the potential flow available to the EEC by about 7%. By increasing to 50 psi you could gain another 7 % or essentially 14% increase of potential flow over stock. (I hope I'm looking at this right). I did notice a considerable increase in fuel force out of the injector at 50 psi and I wonder if at this pressure the pattern of the injector becomes less of a mist and more of a droplet which might not be good for proper burn. Dunno. I'm sure there are upper limits to where we can push our injectors before we have to go to 24# units to retain good pattern properties. Maybe someone will jump in here and let us know. I does appear that the flow increases would diminish rapidly above 50 psi- ie going to 60 psi would not yield another 14% increase in potential flow.

Sorry to get windy here but it might be possible to adjust pressure up again and see what happens to your A/F ratio. Being as you have the meter hooked up you could see what happens. You might be able to take care of that lean spot. My guess tho is that the truck will need to be chipped to program out that area as the fuel injectors have more than adequate ability to deliver the fuel load at the lower RPM's that your lean spot is. More than likely the EEC speed density just can't account for this.


Randy

 

Mine's a Sunpro/Actron gauge. It is pretty accurate in its readings. It might just be my setup, but I can actually see the change in mixture. I know it's supposed to be "100's of switches per second", but I see at idle a consistent back and forth, and as I increase RPM the "fanning" becomes more appearent. Hooking up a voltmeter shows the same.
As for the injectors and flowing, if ya haven't already, check out this tech article from Holley: http://www.holley.com/HiOctn/TechSer...l/Artcl07.html
It's pretty interesting.
I've tried bumping up the pressure more using a Holley Adj Regulator, and I'm not seeing any real changes. With Key On Engine On I'm at 45psi, and can't get it much higher than that with my regulator. Have thought about bumping up to the BBK adj reg, cuz it's adjustable up to 100psi, not that I EVER want to get that close!!!