NDiNardi

I've been searching posts and everyone has had opposite hesitation problems than me. I have plenty of power in low RPMs but its once I get past 3,500 or so... hesitation, go, hesitation, go, its like theres a little gremlin pinching my fuel line every 1 - 1.5 seconds. If i slowly throttle up I can get up to speed, but any heavy throttle and that damn hesitation starts.

My AFM was messed with by the previous owner and i'm hoping to find out if there are any factory marks indicating what tooth was originally being held by the spring metal on the side of the AFM. I'll attach a picture below.

1. It appears that is as far ccw the gear has been turned
2. If you look closely, there looks to be a yellow dot on the gear. could this be a factory mark? or done by the person who was in here messing around
3. Does the factory mark need to land here? or at the spring metal of #2?

I belive the Idle Mixture Screw was tampered with also, it took 4 turns to tighten all of the way. In the Chilton's book there is a "Carbeurator Specifications" sheet that shows the factory specs to be 3.5 turns out. I have Injectors so would this setting also be true for me?

Work done so far..
Fuel Pump
Fuel Filter
EGR Temp Sensor(was broken)
Coolant Temp Sensor (to the ecu.... why not?)
Doublechecked timing marks on cams and crank
Timing is on 10deg BTDC

Thinking to check...
Throttle Position Sensor
Idle Mixture Screw
Air Flow Sensor

NDiNardi

Just did a fuel pressure test, loosing fuel pressure (below 20 psi) at higher RPMs.

Fuel pressure regulator?
Fuel Damper? PLEASE NO!!!!

bone collector

when is the last time you changed the fuel filter?? i would change it first before i went after the more expensive regulator and damper. From my experience inside of afm's there is no factory mark for the setting of the wheel. From your picture it looks like he tried to move the wheel 6 teeth. but it also looks like he moved it a total of 12 teeth then decided to come back to 6 based on the scratch marks on the wheel. this makes me wonder of it is even a 3vze afm?? i know the supra afm's are becoming a popular swap with the 3.0 guys and you have to move it 6 teeth. So I would look up the part number and see what comes up. happy hunting

NDiNardi

Holy cow, i did a test on my TPS and fuel pressure last night, also checked the idle speed screw(pulled it out and cleaned it off) and after putting things back together... i started the truck and it was billowing white smoke out of it.

I first did the fuel pressure test before anything. Drove up and down the street, got to high RPMs and lost over %50 pressure.

Then I ran the TPS ohm check and everything was good.

Then I pulled out the idle speed screw and cleaned it off and put it back in.

After that white smoke was pouring out of the exhaust.
It did just rain here last night and i drove it up and down the street once while the pressure gauge was attached at the cold-start injector.

After taking off the pressure gauge and putting the screw back on for the cold start injector,
pulling off the air intake hose and inspecting the throttle body valve, and checking to make sure i didn't have a major coolant loss(i didn't), the truck is actually idling low now haha! never got below 1000RPMs for a while!

I read in another post to take the idle speed screw out 1 full turn and work from there. Mine was out almost 4 turns. Now its about 2 turns out and like i said its idling between 600-800 rpms. Rough idle though, 1 turn out was too little.

Anyways, I think i'm in the clear so i'm going to go back to work on the fuel pressure problem. but can anyone think of what was up with the smoke? Was i possibly burning up something that got sucked into the throttle body like some dirt or something? Scared the CRAP out of me


Fuel filter and pump have been done this month. Fuel pressure test showed huge drop in fuel pressure on higher RPMs definately starved for fuel. I just got a new pressure regulator but if thats not the problem i dont want to waste money.

scope103

It sounds more like a blockage in the fuel line somewhere than anything to do with the FPR. When the fuel pump was changed, did you see anything in the tank? Sometimes work on the tank stirs up a bunch of crud, which gets pushed into the brand-new fuel filter clogging it. You could try disconnecting the aft-end of the fuel filter to see what drips out; if you get anything other than sparkling clean fuel I would a) pump a quart of fuel out through that line and b) put in another fuel filter.

While you're down there, try to trace each fuel line, looking for mechanical damage (kinks).

NDiNardi

Does this make sense?

After re-install the fuel tank

Testing the pump I cross b+ & FP on the DLC. Pump will run and run and run.

Once I start the engine and warm it up I hear the pump running then slowly stop, then the engine begins to stall..

The i hear the pump kick back on, sends some fuel to the engine and keeps it from stalling...


(I measured voltage during this and only saw a fluctuation of 12-12.5v while I didn't hear the pump, to 13v+ while I could hear the pump run ing)

There is never any power loss under 12v during this whole time. Also, this doesn't happen while testing with the DLC. So I'm kinda ruling out a bad pump.

Could my voltage readings be the ECU trying to lean out my mix?

Referencing the pictures I originally posted at the top. My AFM has been adjusted before, could this adjustment be what is causing this?

I know that turning the gear on the AFM will cause the mix to run lean or rich. And from looking at the scratches on the gear it seems there has been some major adjustments made.

scope103

The ECU does not lean the mixture with the fuel pump. The fuel pump runs all the time, at the same speed. When the pump stops, the engine will quit a few moments later as the pressure in the rail runs down.

So if you hear your pump "slowly stop," that sounds like a bad pump. Particularly if you don't see any significant voltage change when it does that.

Now if you never see the pump slow-down when jumpered, it could be something in the VAF/COR circuit. For that, you want to just listen to the COR; if it doesn't open, the pump will be getting full battery voltage, and it won't matter what the VAF did.

NDiNardi

What's the COR?

scope103

Circuit Opening Relay http://personal.utulsa.edu/~nathan-b...87fuelpump.pdf

NDiNardi

Alright!! Figured it out...
Fuel pressure vsv wasn't the issue, but im still going to replace it anyway.

Even though my fuel tank was empty when i began to work on it... the sediment was still in the tank. Opened it up and the fuel sock was covered in sludge.

So i took off the tank, got a couple 5 gallon buckets and put fresh fuel in them. Bypassed the FPR with a hose fitting and ran clean fuel through the lines a few times. Had a good return so the filter that was on there was working good!

I removed the plenum and all of the fuel lines and at the end of the line, just below the fuel pressure regulator, the bottom fuel rail screw was COMPLETELY CLOGGED! I also took a look inside the fuel hole and saw a wall of debri, i cleaned out what i could with small screw drivers and a few pipe cleaners with gas, blew the fuel rail out with a spare piece of hose into one hole and my thumbs over the others. Checked the dampner again while i was there and took pictures to post on how to check this without removing the plenum.

Got a new fuel strainer and filter and installed them, re-installed the tank, and it fired right up! No more hesitation, no more stalling, awesome idle. Took it out to the mountains today with the dogs and the kid and had a great day!

After 4 years of sitting in my driveway when i thought i had a headgasket problem, this thing is purring like a kiten and only has 151,000 miles on it! SWEET!!!!

bone collector

great news!!! good job figuring it out

ThatGuy1295

white smoke? fuel issue? Not likely.

NDiNardi

I know, I don't know if the vsv's for the fuel pressure and the EGR being backwards or if the fact that it rained very hard he night before we're causes, but I get no white smoke now. Well for like 40sec after startup but not while driving it any major amount. Coolant levels are holding fine and no overheating. Weird....