Rough start, cant figure out anything. Advise please

so, 2kTaco 3.4 manual ext cab 4x4 trd. Sometimes, bout a third to half of the time, my truck will crank but it wont start right away. It usually starts on the second crank. Rest of the time it fires right up perfectly. I just removed and cleaned my TB and IAC valve. Still happens. I charged my battery, no change. Has a relatively new fuel and air filter. ive only had the truck for 18k or so miles and it has 202k miles. Plugs and wires are relatively new. I put iridiums in there, slightly more reisistant than OE, but shouldnt be enough to cause this issue.

anyone have any XP with this issue?

 

first thing is throw those plugs away and go get the oem denso dual electrode plugs, these engines need the dual electrode plugs to run right and stock plugs are all you need. performance plugs are just wasted money.

this is what you need: http://www.ebay.com/itm/6-PCS-L-xus...ash=item542113d4b3:g:EskAAOSw1S9WcoO1&vxp=mtr


after you put the correct plugs back in, if its still acting up, check your fuel pressures to see if the fuel pump is putting out enough pressure and holding that pressure for the correct amount of time after shut down

 

Personally I prefer NGK plugs, but regardless if he just replaced those with new parts, and he has gapped them properly, i dont think it is something that needs to be looked at.

Also the fuel pump primes the system within a second of key on. Remember our discussion on FPR functions? Having the FPR closed at key on/engine off would keep pressure in the line until the engine starts. Not the case with our engines though.

The only possibility fuel wise i can see is if you have a leaking injector, or your fuel pump is legitimately weak and not building pressure fast enough.

Just to be clear this isnt a starter issue? Because mine takes a extra try to click on sometimes too when cold, but when it cranks, it starts?

I want you to do something for me, can you get Ohm readings from your IAC? Youll need to check between the center ground and the two outer control pins, assuming its the same as the 3RZ, check the FSM wiring diagram. I think that is the culprit here, and you should have just replaced it. If you check out my no start thread, it shows you the issue toward the bottom of the page.

https://www.tacomaworld.com/threads/no-start-engine-is-getting-spark-and-fuel-fried-ecu.387148/

 

its more then just the electrode that's wrong with his plugs, he said the plugs he used are not the correct resistance, so that means he most likely isn't getting the correct spark from them either.

he needs to put the correct spark plugs in it first before looking for problems elseware

 

Not resistance, resistant. He mean the Iridiums are more corrosion resistant. Though still you're right, i dont like using any fancy Iridium plugs, by the time 20000 miles pass and they are due for replacement, they are going to be be covered in soot and other contaminants. Id rather pay $3 for a plug and replace it every other oil change. I use the NGK V-power OEM replacements, the best of the best. There are OEM replacement dual electrodes for the 3.4L as well.

@CodeSeven Keakar doesnt think youre getting spark, he thinks you should do that thing again where you stuck your finger in the plug wire and touch the plug. Just to be sure.

 

If the single electrode plugs are relatively fresh I would look elsewhere first unless you just want to get the correct plugs at the get go.
Because Toyota built the 3.4 with 3 Denso's on one side and 3 NGK's on the other I wouldn't worry about brand there.

Your fuel system should hold pressure after shut down, there is a spec for it. It will pressurize in a fraction of a second at start but if your injectors are leaking, that fuel is causing a super rich/flooded condition and a slow start.
The best way to check is going to be with a fuel pressure gauge and watch the bleed down VS spec, then isolating The FP and FPR. That said, fitting up a fuel pressure gauge to the 3.4 is a mild pain. A "poor mans" test will go like this. With engine running, open the gas cap and shut off the fuel pump. Allow the engine to die. This will remove most of the fuel pressure. Wait the appropriate time you feel causes the slow start and restart with the FP connected. If you are getting good starts than it's likely the injector/s are leaking.

"shutting off" the FP means cutting it's power in a way most convenient to you. I have a FP cut off switch as a theft deterrent, comes in handy for something like this.

 

close but not quite, I know you are just joking but I am thinking he isn't getting a "good" spark from them because they aren't the right plugs and on top of that may not be properly gapped

besides, when testing for spark, its better if you stick it to your tongue to test it lol

 

Ive used Liquid Schwartz in my fuel tank when having fuel pressure issues, it always does the trick.

 

Have you checked the negative terminal line on the batter? If there is a bad connection there then that could also cause this issue.

 

I believe you would.

 

The Taco pumps do not prime with only "key on".

 

Yes they do.

 

Wanna bet?

 

You remind me of my last girlfriend. Everything is an argument.

 

I'll take that as a no.

 

I find it suspicious that when i search for the sources of the images you post. The only other place they come up are from other forum posts you have made.

Otherwise, your using a schematic for the starter system. Its conveniently leaving out the IGN1 and IGN2 positions from the ignition switches which are linked switches. The fuel pump is switched via the EFI relay, which is controled by the ECU.

If its not too late, can we bet that you never post on TW again?

 

Suspicious? You will have to explain that.
Diagram above is from the FSM Advanced diagnostics volume. The part that says "Fuel Pump Control" must be a misprint. It clearly shows EFI and COR relay contacts in series with the pump.
Here's the whole enchilada diagram, find some fault with it.

 

lol. you 2..... but yes, Caligula. From what ive been told, Iridium material has slightly more ohm resistance than copper. but only say, 5 or so percent. where platinums have a resistance that's 50-70% more than copper. honestly, my truck runs just fine after startup. i really don't think it's the spark plugs.

ill have to reference back this post another time since it's new years and id rather get sh*t faced than mess around on these forums.

though I have been suspecting some sort of pressure loss as the culprit. whether it be fuel pressure, or cylinder pressure.

 

well there is a fuel pressure regulator "thingy" in the system. it works like a check valve to bleed off excess pressure and "hold" pressure in the system after shut down and if it goes bad, can cause fuel pressure leak down when its shut off.

I suspect its that or maybe leaking injectors which also cause engine off fuel pressure leak down and pressure loss

 

While I respect the technical expertise of both Caligula and Dirty Pool, I have to agree with Dirty Pool on this one.

I have a '99 Taco and a complete FSM (3 volumes) for 1999. The FSM shows a similar starting circuit for all engines, like Dirty Pool posted. With just the ignition on, power is not yet sent to the fuel pump even though the EFI relay has been triggered. The ECM receives 2 signals (power to the starter, and confirmation signal from the cam/crank position sensor). The ECM triggers the circuit-opening relay. The 3RZ uses the cam signal, while the 5VZ uses the crank signal.

I assume its a safety feature, in case of an accident, to minimize a potential fire.

Pretty sure this is why I don't have an 'instant start'. It consistantly has to crank for about 2 seconds before it catches.