Weak Hot Start

Well she fires off perfect yet again. I'll push it to 20 minutes and try again.

 

So after 20 minutes the truck start became a bit weak.

It looks like there is some improvement but something is still out of spec. All sensors check out now so it must be mechanical or ignition based now. Coil packs will be next on the list followed by new Denso injectors. May try the ACCEL coil packs if I can source them easier.

 

Well guys here is a small update. I have replaced the MAF and the idle has gotten better yet but the start issue persists. No change of coil packs yet. Have a URD fuel rail tap on the way to go with my liquid filled gauge. Something tells me an injector is sticking.
A side note for those with a 2TR-FE aftermarket EV-14 injectors are now available. I will be using them if the factory injectors are sticking or dripping.

I will keep y'all posted with updates as I figure this out.

 

Fuel rail tap made it but it looks as if I may need some fittings. Jegs order made for a 45 degree elbow.

 

Well I've installed a fuel pressure gauge and the bleed down rate is about .75-1 PSI per minute. According to the Toyota FSM this is acceptable. So last night I pulled the EFI fuses and cleared the fuel trims(I've been told pulling the fuses for over 5 minutes will do this).
I'm fairly certain I need a scangauge or ultragauge to see my fuel trims. I have a hunch this may get interesting quick. Thinking the engine is being told to run rich by one of 2 sensors.

 

Didn't I tell you to check the injectors? Can you buy a $70 bore scope from HF and snake it down the intake?. You will see real time leakage If they are leaking.

 

Injector leak down rate is way within acceptable values per the FSM. 42 PSI dropped to 25 after 30 minutes of sitting. I'm thinking old Air/Fuel ratio sensor or O2.
Replaced items that have helped so far:
- MAF
- Coolant Temperature sensor
- Reset EFI trims.
- I need an instrument to see fuel trims. Injector dribble doesn't help but I'd like to see what trims are before I invest in injectors. I have access to some high end bore scopes.

 

Sounds like a Coil pack breaking down when it's hot. Been stranded on the lake when my boat had this problem. It would only give problems when it was hot after running it down the lake

 

I agree. Coils will run me more than 4 injectors but I'd still want to check instrumentation first.

 

Yeah, you could always change one at a time and see which one is bad instead of buying all 4. I'd probably bet money that's the issue.

 

I'd rather do a full set. Plugs on cylinders 2 and 4 look good but cylinders 1 and 3 look soot covered but dry. I am burning oil too but my guess that's valve guide seals. Gasoline that's unburned could enter the crankcase and increase oil volatility and increase oil evaporation. More than one thing could be causing the same results.

 

I am debating breaking out the infrared camera.

 

Are you familiar with infrared cameras?

Not talking about an infrared thermometer.

 

I am, we use them all the time in the fire service.....and the electrical service

 

Educate me. What will the camera do?

 

Find a component that is storing excess heat or is not as hot as the rest of the same components. In electrical any additional resistance will show up as higher heat in the photos. So if one of the 4 coil packs is failing it will show up differently than the remaining 3. Also if a cylinder is rich and you are looking at the exhaust manifold it will be cooler than the remaining cylinders. Rich combustion is cold combustion. Too lean can possibly show up cold as well. Typically lean combustion produces greater heat because of the additional oxygen. The flame becomes an oxidizer flame (blue/white).

 

I plan on replacing all 4 plugs and moving coil packs from cylinders 1 and 3 to 2 and 4. If there is any carbon I will know which cylinders are affected. I want to see if the carbon on the plugs moves with the coil packs or if it stays with that cylinder. If the carbon moves bad coil packs possible. If the carbon stays it could indicate reduced compression in those cylinders or injectors sticking. The bleed down is way lower than the Toyota FSM allows so that is another sign pointing to coil packs possibly being bad.

 

4 new NGK IX iridium plugs installed and now I'm off to get her warm and play with the infrared camera.

 

Well chit. After looking over all 4 plugs and a 20 minute drive I can say I have one last chance at figuring out what is going on.

Cylinder 1: slightly lean
Cylinder 2: ok
Cylinder 3: slightly lean
Cylinder 4: slightly lean

Vacuum is still good at 21 inches at idle so no leaks.

Now for an interesting change. The fuel rail pressure finally dips at shut down. Idle is 41.5 PSI. When the engine is shut down the pressure immediately falls to 35 PSI and holds for up to 7 to 10 minutes. This could be the break I have been looking for. Ultimately the injectors are the oldest component on the truck that could possibly affect rail pressures. My guess is one pintle is hanging or sluggish to seat on shut down. 4 fresh injectors could definitely flow more fuel than 4 older injectors especially if the pre-filter within the injectors are plugging.

Guess the only way to be certain is swap them out with 4 fresh injectors.