Your fuel pump is going bad your engine is running lean under a load my 87 was doing the same thing when I put a fuel gauge on I found out I was losing about 5 psi put a new pump in and the problem went away.

 

also please note the backfiring started a few hundred miles after setting the valve lash so this leads me to believe that it was something that eventually failed/or is failing. Fuel pump sounds like a good possibility as it has 227k on it and i think its the original FP.

just wanted to be a little more clear, the backfiring didnt start happening immediately after the valve adjustment.I think i drove approx 400-600 miles after the adjustment.

im now leaning towards..
fuel pump (with the mileage it has its probably a good idea to swap it out anyway)
knock sensor
ECM

 

To clarify my earlier post, I think what happened (to me, not sure if this happened to you) is I set the valve lash correctly but either over tightened the nut and it started pulling the aluminium threads out of the rocker or under tightened and it worked loose. Either way, ended up with a rocker with the threads stripped out and the adjuster nut and screw laying nearby. After my adjustment the truck ran great for a while (don't remember how long, this happened YEARS ago) then started running like crap.

This may or may not have anything to do with your present problems, just an idea.

Replacing the fuel pump sounds like a good idea weather thats the problem or not. Just a matter of time before it quits working if it hasen't allready.

Good luck.

 

steady 16psi from the brake booster line at idle .....electrical problem then?

gonna pick up a leakdown tester from Harbor freight anyway....probably a good idea to perform that test anyway.

 

What are you measuring at 16 psi ? and what's the booster line?

 

went through another can of carb cleaner looking for leaks...sprayed the intake manifold gasket just above injector #2 and the truck stumbled and wanted to die. Also sprayed some on the injector #2 and truck stumbled again.

Im hoping its as simple as a new intake manifold gasket and fuel injector o-rings!


*also tested the EFI sensors and they are within spec.

 

sorry for not being more clear...post updated. it was the brake booster line. I've heard if its steady then more then likely its not mechanical.

 

You mean you were measuring Vacuum from the Brake Booster line... Meaning you Saw 16hg(Inches of Mercury) steady on your vacuum gauge which is just slight below normal range for most automobile engines.

Normal Vacuum for most automobile engines is 18-22hg at idle.

16hg is low esp. if you said the engine is new?

A leaking intake manifold/Vacuum leak will show about a 4-7hg drop from normal reading but be steady. I'd more than likely bet thats your trouble area and likely the gasket was faulty or tourqed incorrectly during engine assembly.

 

Hmmm interesting thanks for that post very helpful.Yanked the intake manifold out ... what a PITA! Two of the coolant hoses were toast, they broke as I pulled them from the barb. Tested the knock sensors for ac volts and got nothing. Does anyone know if the 1st gens use resonance frequency knock sensors?

Fuel injectors were grimy and the rubber seals have seen better days. Sending them out to FIC tomorrow for testing and cleaning.

 

UPDATE

Got the injectors back from FIC, they look great. I also picked up the LCE Performance Fuel pressure gauge kit.

Will start reassembly this weekend.

so i've read a bunch of different things on the correct way to install gaskets and everyone seems to have a different method as to what worked for them.

From what i've read i believe the correct way would be to rub a little Ultra Grey Permatex around the coolant passages on both sides of the gasket, then torquing the bolts starting from the middle then working your way out.

Does anyone know what the correct torque is for the intake manifold?

Also does anyone know where i can buy the copper crush washers for the fuel filter? (i have a set of crush washers but all seem to have a different diameter and they are thicker)

Oh and the knock sensor tested good with my friends higher end meter.

 

ok folks i put everything back together and i still have backfire popping coming through the intake! frustrating.


i just pulled the valve cover off again and adjusted the valve lash to .008 intake and .012 exhaust, new valve cover gasket, new exhaust flange gaskets. Engine still idles nicely at 600-700 rpms.

when i had the valve cover off i noticed the cam gear sprocket mark was at 12 o"clock at TDC. I understand this should be at just before 12 o'clock, perhaps the engine builder installed incorrectly? how can i adjust how can i rule that out?

thanks

 

im thinking its a valve... i just put in new heads cams valves in my truck 3vze 3.0 v6 drove amazing for about a month then i started getting the same popping sound from the intake i refused to think it could be just that 2 months later after not driving it i took it all apart and the dam cams were warped had flat spots and #1 exhaust lobe was completly rounded out so it wasnt opening the valve, got parts from japanengine.com 800$ an now r junk only 1500 miles on them, i would check there dont doubt it, i ended up spending 500$ more on other stuff trying to solve the problem with no luck!

 

thanks for the post jorgs4x4....so your truck is still backfiring through the intake?

very frustrating problem, the truck has almost everything new on it.

 

Cam timing mark on a normal 22re set up should be at 12 o'clock at top dead center.

I suspect mechanical problems in your future...

Did you check engine vacuum again?

If you have an after market cam as jorgs mentioned that may be an area to look into as well.

Do you have a more "aggressive" camshaft in the engine? Trying going back stock.

Remember... Toyota knows best ^_^

 

cam and camshaft should be stock, i never gave the engine builder any request for modified parts/upgraded parts etc.

have not went back in to check engine vacumm since installing new manifold gaskets. its on my to do list

i checked all the terminals at the MAF, all checked out good, took the intake tube and elbow hoses off and thoroughly inspected them. a couple stress cracks but nothing that goes all the way through.

only other things i notices was the wiring to the ignitor was crisp and hard when touching and bending.

new fuel pressure gauge is reading 30psi at idle shouldnt this be 38-44psi at idle per the FSM? weak fuel pump?

truck idles nice at 650-750rpms, to recap the truck was running good before, truck gradually developed this backfire.

fuel pump may be on its way out, causing low fuel pressure, 30psi is probably enough to let the truck idle but it probably doesnt generate enough pressure when accelerating (if i recall i think the pressure goes up to about 40psi-44psi when revving)? is that a good theory?

 

browsed youtube last night looking at "backfire through intake" videos and although all were different engines none of them sounded like mine. It seems that when people refer to a “backfire through the intake” they mean after the acceleration the car has a loud pop bang through the intake.

my truc has a series of popping as im accelerating……..it sounds like a banshee when accelerating.

Maybe my terminology when explaining what it was doing was incorrect and that may be throwing people off?

 

Sounds like a banshee? Like a scream? Little pops and a scream/wistle while accel sounds like a pretty good vac leak to me. Spray around all seams and hoses with carb cleaner while idleing and listen for it to get rough and/or a dip in idle. Are all your vac hoses hooked up right?

 

yes thats correct.

i checked the engine vacuum at the booster and its a steady 18psi.

i rechecked the TPS and it appears that when i get to this reading 2.0.57mm (0.0224")IDL - E2< 2.3K< 2.3K
it reads open/infinite shimmed at .57

i unplugged the TPS and it idles up a lil but still pops under acceleration.

i think your right about a possible vacuum leak as a hear a slight hissing but its muzzled by the fan noise, where could it be. I already found and fixed the vacuum leaks between the intake manifold and head, lower plenum to upper plenum, and at FI #2 o ring seal.

One other thing i noticed was i had the fuel filter installed backwards. I've replaced and installed correctly. No difference. It was installed that way since i dropped the new engine in.

i guess im left with
a vacuum leak that i cannot locate
clogged cat
weak fuel pump

the hissing sound i think im hearing is coming from the distributor area.

 

You can tell if your exhaust is restricted very quickly with the vacuum gauge.

Hook up gauge and run the engine at 2k rpms and if the vacuum drops to zero or close to zero you have a resrticted exhaust.

 

thanks.....will try that tonight.

is it common for the vacuum advance diaphram to leak? I sprayed carb cleaner all over it and no difference.