If it's weak at low rpms, and has an idle stumble, and this gets better with the vac removed from the FPR, it is responding positively to more fuel, since the purpose of that vac line is to hold a constant fuel pressure vs. manifold vacuum, an if it references atmo pressure instead, the fuel pressure is relatively higher, thus it injects more fuel.

This makes me think of vac leaks as the culprit, but those are usually masked at higher rpms as the relatively small amount of leakage (if it's huge at idle, it won't idle) becomes percentage wise of the total air flow a less significant factor. I've had lots of single runner intake leaks, and you lose the leaking manifold path cylinder(s) at idle, and they come back as you raise the rpms. The worst offender was a Toy LC I6 F engine, where the alloy intake mani always warped, AND was hard bolted to the cast iron exh mani.

So I think you have some kind of combo problem, like an intermittent connection maybe in some of the fi wiring to injectors and/or sensors, OR some kind of fuel volume flow problem, like a gummy intake sock on the fuel pump in the tank, a pump that is too internally worn to give the required flow as the R's come up, a fuel filter that got quickly gummed by stale fuel (I've done that to myself), a kinked fuel line, or a you name it in the fuel system.

I've clogged injector intake screens, jacked the truck up with a fuel line pinched, had a rubber line start to lose the inner liner and have a loose flap restrict only higher flow rates.

I'd like to see the flow vs. time test. Remove the fat wire from the starter and splice a hose onto the rubber line feeding high pressure fuel to the fuel rail, over under the TB. Have the son activate the ign sw. in the start position for say, 15 seconds, and measure the volume pumped. I'll SWAG an estimate of max fuel required at WOT at 5500rpms, which should be the max required. I think I can find the calcs for fuel vs. hp, and I'll use 150hp at that rpm to swag it.

I have a growing notion that gasahol gums worse when it sits for a while.

Might try a dose of Seafoam...

I've routinely seen 23-2400rpms of stall speed in the converter, and about 200-300rpms of TC slip at 3000 cruise without a lockup converter. You want the lockup if you can find it...

Fast Eddy,

I can relate to the problems you talk about with the fuel system, I see happen it on the heavy equipment sometimes, However on this rig when we built the motor we also cleaned the tank and fuel lines, swapped in a new pump & screen and put on a new filter and we filled her up with new gas.(Thanks anyway- it's good advice! <img src="/forums/images/graemlins/kewl.gif" alt="" />

Me and a buddy, who stopped by to offer support (and hide the new box of bullets I just bought) got to talking about the problem I am having and we came up with a possibility, <img src="/forums/images/graemlins/scared.gif" alt="" />

If the ignition timing has to be advanced so much to make it run half decent, could the crank to cam timing be off, even if the marks are dead on? (say some previous owner swapped on the wrong crank gear) If this was true then the piston would be to far up the cylinder when the distributor fired the spark, and the combustion would technically be late (as in the timing be retarded)and the intake stroke would be shorter as well. This could explain the low power and popping when the base timing was set to 5 degrees. We wondered if we moved the cams one or two notches to the right technically putting the piston lower in the stroke, we might get our power back as well as our vacuum. (Note: No alcohol was injured or killed in the making of this theory!) <img src="/forums/images/graemlins/shame.gif" alt="" />

Doing this shouldn't hurt anything as this is a 0 interferance engine.

Before I got all crazy with theories I decided to make a few more practical checks,

1) Compression test: 4 of them checked @ 135 psi and 2 checked at 150 psi Spec is 130-150 psi with 20% max between them (The 20% is a rule of thumb thing) Based on the fact that this is a fresh engine with only about 4 hrs total run time, I think the results are fine.

2) Vacuum leaks: All the vacuum lines are new but thought, "Better safe than sorry"! I don't know how y'all
check for leaks but for me it's shaving cream <img src="/forums/images/graemlins/notooth.gif" alt="" /> (Not the gel crap, the good old fashion white fluffy stuff, a vacuum leak will suck a hole in the foam, hence a leak) I sprayed it on all the hose connections and the intake gaskets, ( I left the engine running and washed her down with electrical cleaner as a back up test) no leaks.

Well that left our conversational timing theory. I stripped down the front end (I'm getting pretty quick at it!) and rotated the cam pulley's one tooth to the right. Started her up and set the timing where I had the best running and most vacuum (it came up to 17psi from 15psi previously) Stall speed raised to 1700 from 1500. Acts like an improvement but the jury is still out.

Tomorrow, I'm going to go another notch on the cam teeth and see what happens. One thing I haven't done is reset the distributor rotor. When I move the gears one more tooth I will check how it lines up and may move it to correct for the adjustment.

On a side note: I decided to move the cam gears instead of the crank gear because the cam gears are a finer adjustment, the cams' turning one rev to the cranks 2 revs.

I'll let y'all know how it turns out. <img src="/forums/images/graemlins/confused.gif" alt="" />

One other question, How can I tell if I have a lock-up convertor. On the machines I work on, there is usually a green idiot light to let you know your in lock-up.

James

Serial number plate on the driver's side of the tranny--you're hoping for a P as the 4th digit.

Unless the transmission has been replaced with a later one, an '89 is unlikely to have a lockup torque converter. I believe those started mid-year '90 as a running change.

Frank

Let me bring y'all up to speed on what I done so far.

As far as advancing the mechanical engine timing (crank to cams) I tried advancing the cams one tooth and then two teeth. One tooth made a little better but two teeth made it fall on it's face.

I set the timing back to the factory settings and took the monty up town to the local garage. <img src="/forums/images/graemlins/ignore.gif" alt="" />

They put their sun machine on it and we found that #1,#3,&#5 were burning rich while #2,#4,&#5 were burning correct. On the analyzer occiliscope the peaks for 1,3,&5 were short & 2,4,6 were long.

We again sprayed down the intake with carb cleaner and found no leaks. (No gaskets sucking) The compression test for the engine showed all the cylinders to be relatively the same. 135psi - (spec is 130 to 150 psi) the heads and gaskets are good.

We ohmed out the injectors and they were all 15.7 ohms (spec is 13-18 ohms)

It appears the problem is in the one bank only. The mechanic is going to check my timing and if it is correct, he is going to advance the timing at the cam gears one tooth and see if the problem switches banks. Then he is going to advance just the left bank and see what it does.

It's got him stumped too! <img src="/forums/images/graemlins/confused.gif" alt="" />

I am trying to determine what could be at fault on only one bank.

Any suggestions? <img src="/forums/images/graemlins/confused.gif" alt="" />

James

If you have the valve timing correct, I'd think the mechanic is wasting time and effort playing with the cam sprockets.

I "think" the 3.0L injectors are bank fired, but they may be batch fired - I'm not sure. Either way, you'll probably find the problem in either the ECU or the injector wiring harness.

You only have one o2 sensor, so if it's within spec value, it will signal the ECU to open all injectors (whether batch or bank fired) for the same duration. A bad harness could shorten injector pulse time on one bank - since each bank of the injector power connections is joined inside the harness..... 2x 3-into-1, then 2-into-1 before the plug.

Check the connector at the firewall - cycle a few times, spray with electrical contact cleaner (Radio Shack has it).

Another remote possibility is that the injectors on one side are gummed up and sticking - although that might not show up on the scope, since the electrical pulse length is what is being measured - not the actual opening time.

IF - and I'm not certain - the injectors are bank fired, the problem could also be in the ECU or the harness.

If I had to bet, I'd suspect a bad injector rail harness.

Frank

I'd have to try swapping ecu's. That would eliminate stuff like iffy injector drivers. I think the 3.0 is batchfire, maybe by banks with 3 injectors per driver?.

I'll take your intake leak checks. They sound thorough.

I'll assume you've checked quality of spark as you rev it up.

That leaves a fuel hoodoo, right? Or a timing hoodoo. Can you get approx advance vs rpm?

And I'd still do the fuel flow quantity check...

To all you guy's who gave me suggestions, I want to say thanks! I finally got this girl ironed out. It ended up being two problems and timing wasn't one of them!

#1 was the ECM. The right side fuel injector driver was bad and according to Mitsubishi, sometimes when the driver craps it makes the injectors fire rich all the time. The ECM doesn't know this problem has occurred but it does sense a rich mixture and try's to lean it out. This results in the working bank running lean and the non-working bank running rich. Hence the retarded timing!
Note: This failure did not kick any codes because the ECM did not know it wasn't working correctly.

Swapped in a used ECM and the timing was corrected and she ran like a different motor.

#2 The fuel preesure regulator was faulty.
Once we got her timed right, she still didn't have as much pep as I thought it should. The fuel pressure was in spec but seeing how I had already purchased a new regulator I thought it couldn't hurt to replace it. BINGO, I don't know what was wrong with the original but once it was replaced she really came alive.

I tried a stall test but at 2000 RPM she spins the tires thru the brakes <img src="/forums/images/graemlins/evil.gif" alt="" />

I am tickled to have this ironed out. Everything seems to be working, she idles smooth, has a quick response and scoots right down the road.

The only thing I need now is a new EGR tube that goes from the intake to the exhaust. The one I have was broke at the flex, so I welded it back together but I don't know how long it will last. Any body got an extra one they would be willing to sell me or a suggestion of an alternative? <img src="/forums/images/graemlins/wink.gif" alt="" />

Well now I'm cleaning her up and checking the brakes (They ought to hold her for a stall test! Gonna replace the pads.) Then it's the ultimate test- 16 yr old driver! Go get em kid! <img src="/forums/images/graemlins/kewl.gif" alt="" />

Thanks again,
James <img src="/forums/images/graemlins/cheers.gif" alt="" />


03 F150 5.4 LS rear, factory
89 SWB Monty, 3.0 bored max,
auto trans, 31X8 tires (soon to be 31X12.50)
76 CJ5 Built to the max 258,headers,
3 speed, wide diffs, 33X12.50,(Our toy!)

I just cut the flanges off & plug welded them sealed, then ran them on a belt sander to flatten them to block off the EGR ports.

Ed