Missing under load

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easyrider

easyrider

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Well, I got the engine in and running. It runs good at idle and crusing at about 50. If I accelerate hard, it has a dead miss. It also misses with the throttle partially open in park. I've pulled the electrical connector off of the injectors one at a time (easier than pulling the plug wires) while a friend held the throttle open. It definitely made a difference on each cylinder when I pulled those. With all of them back on, it still sounds like it is missing to me. Occasionally under hard acceleration, all cylinders hit and this thing romps! I can't figure this one out. Any suggestions?

Tom
 
Maybe you could enlighten us exactly what it is you are talking about. Is it a go cart or what? Airplane? School bus?
 
Sorry RustyRatRod, I just installed a 2002 5.9L from a Dodge Dakota RT into my 65 Dart Convert. I used the wiring / ECU and fuse panel from the Dakota.
 

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If you mean pull the plug to see if its firing, no. I intend to do that tomorrow night when I get home. I did pull the plug wires one at a time, didn't seem to make much difference. While i'm pulling the plugs, I might as well check compression.
Tom
 
If the plugs look good install a fuel pressure gauge and see what you have for pressure at light load and WOT. Fuel pressure regulator senses engine vacuum. The lower the vacuum, the higher the pressure. IIRC low side is 50 psi, high side 65 psi.
 
easyrider said:
If you mean pull the plug to see if its firing, no. I intend to do that tomorrow night when I get home. I did pull the plug wires one at a time, didn't seem to make much difference. While i'm pulling the plugs, I might as well check compression.
Tom
Click to expand...

I meant for a possible indication of a specific cylinder miss, as well as an overall indication of mixture.

We know they fire, or at least most of them some of the time.
I was hoping it would help give an indication of going way lean or something like that mostly.
 
Did you wire in the DLC? You might be getting a trouble code. If you wired in the PDC you can wire one to the interior, or I think you could wire it off of the PCM. It may be worth the effort for future use.
 
One of the few things that will cause an EFI to hiccup is a stopped up fuel filter.

Usually under load misses like you describe is fuel. If it was light part throttle I would say secondary ignition like wires or plugs.
 
Did you retain the OBD2 connection. Might put a scanner on it, to start. I take it this was a running setup, transplanted. Was everything switched over?
 
Couple of things to look for,
I have seen crank sensor signals breaking up that feel like it is starving for fuel.

Also if the distributor was removed it needs to have sync set with a scan tool.
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1.Connect DRB scan tool to data link connector. The data link connector is located in passenger compartment, below and to left of steering column.
2.Gain access to SET SYNC screen on DRB.
3.Follow directions on DRB screen and start engine. Bring to operating temperature (engine must be in “closed loop” mode).
4.With engine running at idle speed, the words IN RANGE should appear on screen along with 0°. This indicates correct distributor position.
5.If a plus (+) or a minus (-) is displayed next to degree number, and/or the degree displayed is not zero, loosen but do not remove distributor holddown clamp bolt. Rotate distributor until IN RANGE appears on screen. Continue to rotate distributor until achieving as close to 0° as possible. After adjustment, tighten clamp bolt to 22.5 N·m (200 in. lbs.) torque.
The degree scale on SET SYNC screen of DRB is referring to fuel synchronization only. It is not referring to ignition timing. Because of this, do not attempt to adjust ignition timing using this method. Rotating distributor will have no effect on ignition timing. All ignition timing values are controlled by Powertrain Control Module (PCM).



As mentioned fuel volume and pressure need to be correct( 49.2 psi +/- 2 psi), with a high rpm misfire it could be running out of fuel. Run it with a gauge to make sure it doesn't loose fuel pressure when acting up
.On a 2002 Durango fuel system it has a in- tank fuel module,the fuel pump module containing the electric fuel pump, fuel filter/fuel pressure regulator, fuel gauge sending unit (fuel level sensor) and a separate fuel filter located at bottom of pump module.
There isn't a vacuum sensed regulator with a return line like a lot of engines have, just a single line from the module.
Not sure what you are using for fuel pump/regulation.
 
Plug wires, plugs, cap/rotor?

I've had issues with a 2002 van where it ran fine until it was under load. New set of plug wires cured it for me.

Just a thought.
 
I had a chevy blazer in the shop here recently that had a nice idle , on the test drive it had a misfire when you would try to accelerate quickly , as long as you accelerated normal it was fine.
I would have bet that it was a fuel issue, just felt like it was starving for gas.
Monitored fuel pressure gauge and was steady during symptoms, had my labscope hooked up to the cam and crank sensor and caught the crank sensor cutting out when it acted up.
I always try to make sure I am replacing a known bad part, it can get expensive guessing on these efi vehicles.

Here is a shot from the lab scope , bottom screen shows crank sensor in yellow when acting up. Green trace was the cam sensor :
 

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Thanks Guys for all the input. As of right now, I do not have a OBDII connector wired up. I went to Pull A Part today and got one from a 2001 Durango. The wire colors don't match my wiring diagram. The diagram only shows 4 wires. It doesn't show the grounds and the hot wire. I'm NOT hooking that thing up until I know what is what. If I knew the pin locations on the plug, wire color wouldn't matter.
I did pull the distributor, so I guess i'll need to sync it. That is a piece of information I didn't know. That may very well be my problem.
I'm running the 2002 Dakota fuel pump. I modified my tank so I could keep all the factory components. I have not checked fuel pressure yet, but I will.
Tom
 
Here's the diagram for my 2001 Dodge Ram 5.2. It wires into the PDC (fuse panel).
 
easyrider said:
Is DRB scan tool a brand name or a certain type?
Tom
Click to expand...

It is the name for the factory Chrysler scan tool
DRB, Diagnostic Readout Box

A lot of the more higher end aftermarket scan tools can also do this, We use a snap-on scan tool at our shop and its able to set sync.

A scan tool is the most accurate way to set it.
 
Ok guys, I wired up the data link and took it to the Dodge dealer and had the cam sensor synced. Didn't help anything. I checked fuel pressure. It reads 49 lbs at idle and only drops about 1 lb when I open the throttle. I changed the plugs and no difference. Maybe it is the crank sensor. I'm at a loss here.
Tom
 
Typically the fuel pressure varies with manifold pressure, that keeps the differential pressure at the injector constant, so the fuel delivery is always proportional to time of injector pulse width.

Is the pressure reference hose connected and leak free to the fuel pressure regulator? Also is the fuel return line working correctly? The fuel pressure should vary up to about 15 psi, depending on pressure reference for a normally aspirated engine. It should be lowest at idle, and increase as vacuum drops.

Fuel trims in the ECU get messed, if things are wrong. It might take a reset, after you fix something.

Please ignore my comments, they to not apply, and are incorrect to PO fuel system
 
Yes but, the fuel pressure should vary with manifold vacuum. It should be less at idle, and increase at WOT, if that is not happening something is wrong. A pinched return hose is an example. A 1 psi change that you suggested raised a red flag.

Please ignore my invalid comments, see below for correct information.
 
KitCarlson said:
Yes but, the fuel pressure should vary with manifold vacuum. It should be less at idle, and increase at WOT, if that is not happening something is wrong. A pinched return hose is an example. A 1 psi change that you suggested raised a red flag.
Click to expand...
His fuel rail does not have a vacuum actuated regulator. There is no return line on the later models.The pressure regulator is located in the fuel module inside the fuel tank.
 
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