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I need to adjust the fuel trim!

Performance mods and Advanced Stroker discussion.
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DaemonForce
I made it to triple digits!
I made it to triple digits!
Posts: 101
Joined: November 15th, 2013, 7:18 am
Stroker Displacement: 4.7L Super
Vehicle Year: 1983
Vehicle Make: American
Vehicle Model: Eagle
Location: Olympia, WA
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I need to adjust the fuel trim!

Post by DaemonForce » April 2nd, 2016, 7:06 pm

I have a very STRONG 4.7L on the bench and it needs to be tuned just to keep itself alive.
Block: 1989
Head: Casting 7120
Pan: 1983
Valve Cover: 1989
Intake: 1999+
Throttle body: 1996
Plugs: Champion 7034 (now fouled with carbon)
Fuel: Premium 92
Injectors: Dodge Neon 280155703
Fuel pump: Precision E16118

Wire harness is from a 1996 Cherokee equipped with a 5 speed from the factory. The only disconnected items are the downstream o2 and whatever harness combines the VSS with 4WD detection. There is no alternator, I'm working on it. The coolant temp sensor is impossible to find outside the junkyard and I have mine relocated onto the block. Throttle body is from an early 1996 Cherokee and the sensors were changed out to make use of it with the harness. The fuel rail is from a Grand Cherokee with a FPR and return line.

The whole system gets 40PSI steady but the fuel injectors are pulsing way too much at closed throttle as if it's at WOT. 16Hg on my gauge falls flat as the engine dies, which may indicate a vacuum leak, yet to be found.

This is a demo of my test bench.


Any ideas on how to get this under control?
   ,__,_____,__,       ~A-M-C YA!
//___}/,_ll,_\__\,_____
,l_/¯\_l__ll__l__/¯\(¤≡¤)
   (o))o))        (o))o))

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DaemonForce
I made it to triple digits!
I made it to triple digits!
Posts: 101
Joined: November 15th, 2013, 7:18 am
Stroker Displacement: 4.7L Super
Vehicle Year: 1983
Vehicle Make: American
Vehicle Model: Eagle
Location: Olympia, WA
Contact:

Re: I need to adjust the fuel trim!

Post by DaemonForce » April 2nd, 2016, 10:27 pm

Here's a quick update. I just changed my plugs to Champion RC12LYC and stock gapped them at 0.035" to make this safe. Well it fires up perfectly fine, idles ~2000RPM high, then slows down until it falls flat. I checked #6 and the plug is completely fouled black. I assume the rest are the same. What exactly am I doing wrong here? Are the injectors too big for this engine? They certainly seem to be pumping out more than enough fuel.

My TPS seems normal, it's a new part, along with my IAC valve. From the scanner my Absolute TPS% range goes from 18.0 closed to 78.4 WOT. Also, if I feather the throttle any more than 5-10%, it stumbles and backfires.
   ,__,_____,__,       ~A-M-C YA!
//___}/,_ll,_\__\,_____
,l_/¯\_l__ll__l__/¯\(¤≡¤)
   (o))o))        (o))o))

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gradon
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Stroker Displacement: 4.6/280ci
Vehicle Year: 1996
Vehicle Make: Jeep
Vehicle Model: Cherokee
Location: DC

Re: I need to adjust the fuel trim!

Post by gradon » April 3rd, 2016, 1:55 pm

I have a 96 w/ ax15 and 4.6l. I remember when stock, I had my rear o2 disco'd for whatever reason and it ran super rich. The rear o2 wasn't supposed to have anything to do with fuel trims on the 96, just monitor catalyst efficiency, but I think it does affect them. I have the rear o2 connected to a test pipe(no cat) with an anti-fouler spacing it away from the direct exhaust stream and it runs fine and doesn't set a code. I'm running colder ngk bkr7e plugs and ford all-blue injectors rated 24#@43.5psi(forget the exact higher rating on the 96's 49psi rail, but ~27#.) I can't get more than 15mpg but plugs don't foul. Oh yeah, I also have a switch that disables the VSS so I can go above 116mph(did 20 more) and if I left it disabled, the jeep would die at every stop or drop out when the clutch was pushed in(also think it idled worse). If you're gonna use a 96 harness and computer, you should have those sensors hooked up.

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DaemonForce
I made it to triple digits!
I made it to triple digits!
Posts: 101
Joined: November 15th, 2013, 7:18 am
Stroker Displacement: 4.7L Super
Vehicle Year: 1983
Vehicle Make: American
Vehicle Model: Eagle
Location: Olympia, WA
Contact:

Re: I need to adjust the fuel trim!

Post by DaemonForce » April 3rd, 2016, 3:26 pm

After heading out to Jeep Fest I started wondering about the o2 sensors. The one I have upfront is a pull but a missing downstream o2 will make this dump fuel this bad? Jesus...I think it's time for a new sensor.

I should probably fix my fuel pressure as well. I need to grab a returnless rail to test higher pressure. Really this should be higher than 40PSI.
   ,__,_____,__,       ~A-M-C YA!
//___}/,_ll,_\__\,_____
,l_/¯\_l__ll__l__/¯\(¤≡¤)
   (o))o))        (o))o))

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gradon
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Location: DC

Re: I need to adjust the fuel trim!

Post by gradon » April 3rd, 2016, 5:25 pm

You are using a 1996 pcm too? The stock injectors with that pcm were the grey tops: 23.2#@49psi(returnless rail). If you are using smaller injectors and the older, lower pressure return rail(30psi at idle, 39psi at WOT), no doubt the pcm is adding a bunch of fuel to reach it's stoich target. You should also have the obd2 connector in the harness to monitor fuel trims and see exactly what it's doing.
Edit: I just looked up the specs on those injectors: 22.5#@43.5psi. If you indeed have 40psi all the time, then they are now 21.6#. If at idle on the 30psi pre-'96 rail, they are 18.7#, which is 4.5# less than what that pcm is wanting. Your fuel trims are probably maxed rich and maybe even forced into open loop. If you get the 49psi returnless rail and pump, those injectors would flow 23.9psi, which should put you in the ballpark. I use http://www.witchhunter.com to calculate injectors and flows.

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DaemonForce
I made it to triple digits!
I made it to triple digits!
Posts: 101
Joined: November 15th, 2013, 7:18 am
Stroker Displacement: 4.7L Super
Vehicle Year: 1983
Vehicle Make: American
Vehicle Model: Eagle
Location: Olympia, WA
Contact:

Re: I need to adjust the fuel trim!

Post by DaemonForce » April 3rd, 2016, 11:27 pm

gradon wrote:You are using a 1996 pcm too?
The PCM I'm using is a reprogrammed test unit for 96/97 with the manual option. It would do well for breaking things in with the A-998 but I've decided to skip straight to doing the T-5 manual swap once this is in the car again. My harness comes from a strange aqua colored 12-96/1-97 Cherokee that ended up in the 205 Auto yard. It had no engine but the harness was unmolested and looked like a good starting point. It appears to get along perfectly with my PCM but I keep throwing a code for the evaporator control, which I'm guessing is the 4.0L version of EGR. I'll address that when I get the chance to weed through another Cherokee.
gradon wrote:The stock injectors with that pcm were the grey tops: 23.2#@49psi(returnless rail). If you are using smaller injectors and the older, lower pressure return rail(30psi at idle, 39psi at WOT), no doubt the pcm is adding a bunch of fuel to reach it's stoich target. You should also have the obd2 connector in the harness to monitor fuel trims and see exactly what it's doing.
No doubt it's the combination of low pressure and low # injectors that are screwing me here. I have everyone telling me the pressure is fine when it appears that I've been right to have concerns about this. My work week has just started and the weather has gone back to being sour but I should have no problem rounding up a returnless fuel rail by the end of tomorrow. I'm already curious what the new pressure will read.
gradon wrote:Edit: I just looked up the specs on those injectors: 22.5#@43.5psi. If you indeed have 40psi all the time, then they are now 21.6#. If at idle on the 30psi pre-'96 rail, they are 18.7#, which is 4.5# less than what that pcm is wanting. Your fuel trims are probably maxed rich and maybe even forced into open loop. If you get the 49psi returnless rail and pump, those injectors would flow 23.9psi, which should put you in the ballpark. I use http://www.witchhunter.com to calculate injectors and flows.
The return rail appears to rest in the mid/late 30s with the switch off. At idle, it's pumping a steady 40lbs and this is the condition being generated. It would appear that 21.6# is causing this massive rich+open condition, so it's absolutely critical that I get this closer to 24#. I may need to gather a set of the stock injectors to use as a control. Already choosing non-standard injectors was a real long shot but does nothing for me if there's no way to gauge where I'm at vs default. I'm going to keep all of this in mind as I sort this out. :cheers:
   ,__,_____,__,       ~A-M-C YA!
//___}/,_ll,_\__\,_____
,l_/¯\_l__ll__l__/¯\(¤≡¤)
   (o))o))        (o))o))

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gradon
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Re: I need to adjust the fuel trim!

Post by gradon » April 4th, 2016, 8:34 am

I bypassed the evap(not egr-like with exhaust vapors, but sucks fuel vapors out of intake manifold into a charcoal cannister, then a line runs to tank to deposit) by measuring the resistance of the evap solenoid and then putting a resistor across the plug with the solenoid disco'd. That code will not affect fuel trims. The plug should be high up on the passenger corner firewall. I can look to see what the resistance is if you like, but I think my 1/4 watt resistor is a little scorched(must still be resisting though).

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DaemonForce
I made it to triple digits!
I made it to triple digits!
Posts: 101
Joined: November 15th, 2013, 7:18 am
Stroker Displacement: 4.7L Super
Vehicle Year: 1983
Vehicle Make: American
Vehicle Model: Eagle
Location: Olympia, WA
Contact:

Re: I need to adjust the fuel trim!

Post by DaemonForce » April 4th, 2016, 11:00 am

I imagine the code is just an alert that effects maintenance more than performance. It looks like it keeps the dry part of the manifold DRY. Carburetion is a dated concept on this engine that has been replaced with what I'm trying to modernize here. Looks like I'll be setting up my classic charcoal cannister.
   ,__,_____,__,       ~A-M-C YA!
//___}/,_ll,_\__\,_____
,l_/¯\_l__ll__l__/¯\(¤≡¤)
   (o))o))        (o))o))

User avatar
DaemonForce
I made it to triple digits!
I made it to triple digits!
Posts: 101
Joined: November 15th, 2013, 7:18 am
Stroker Displacement: 4.7L Super
Vehicle Year: 1983
Vehicle Make: American
Vehicle Model: Eagle
Location: Olympia, WA
Contact:

Re: I need to adjust the fuel trim!

Post by DaemonForce » April 5th, 2016, 11:46 am

Well, I'm not much closer to getting this right. I need a fuel pressure regulator. Without one, I'm getting a steady 80psi. Not desirable. :lol:
   ,__,_____,__,       ~A-M-C YA!
//___}/,_ll,_\__\,_____
,l_/¯\_l__ll__l__/¯\(¤≡¤)
   (o))o))        (o))o))

User avatar
gradon
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Vehicle Model: Cherokee
Location: DC

Re: I need to adjust the fuel trim!

Post by gradon » April 5th, 2016, 12:46 pm

What pump do you have in there?

SIXPAK
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Re: I need to adjust the fuel trim!

Post by SIXPAK » April 5th, 2016, 2:47 pm

If thats a new build be careful you done wash out the rings!

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DaemonForce
I made it to triple digits!
I made it to triple digits!
Posts: 101
Joined: November 15th, 2013, 7:18 am
Stroker Displacement: 4.7L Super
Vehicle Year: 1983
Vehicle Make: American
Vehicle Model: Eagle
Location: Olympia, WA
Contact:

Re: I need to adjust the fuel trim!

Post by DaemonForce » April 5th, 2016, 3:24 pm

gradon wrote:What pump do you have in there?
Precision. Read the first post list.
SIXPAK wrote:If thats a new build be careful you done wash out the rings!
I thought about it but I'm not too worried. Engine wants to run for a maximum of 7 seconds. I'm more worried about the carbon fouling the plugs, injector pintle caps, intake area behaving like a carburetor draft zone and possible carbon buildup on the valves, pistons and rings. I'm already tempted to tear the head off over the weekend just to examine the potential damage. Should I start over with stock grey tops? I'm starting to think that's the best option. The only real problem at the moment is figuring out where I'm going to get a fuel regulator. I don't feel like dropping my tank and I want this engine to break in BEFORE dropping it into the wagon.
   ,__,_____,__,       ~A-M-C YA!
//___}/,_ll,_\__\,_____
,l_/¯\_l__ll__l__/¯\(¤≡¤)
   (o))o))        (o))o))

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