Bimmernut

One more thing I didn't try yet, while the problem is happening, spay the iat w can of coolant that is used in electronics for troubleshooting. It wll chill the iat case. iForget the exact name but sure amZon has it. I spent 6 years w this issue.

2ToyGuy

If you have any canned air around, it's the same stuff as the component chiller. Just turn the can upside down. What comes out is icy cold, and won't damage anything.
Old trick E-Techs learn early on, so they don't have to carry 2 cans of the same thing around.

Be careful, don't get the liquid on your skin. You can get cold burns from it.

Good luck!
Pat☺

oldguyinoc

I read this thread, looking for an answer to my hot start problem (rough idle and gas smell after hot start).
Lots of reference material, good advice and band-aids, but no solution.
Because of the gas smell, I concentrated on the leaky cold start injector and failed Fuel Pressure Regulator Vacuum Switching Valve (Blue) theories.
After hours of researching the provided FSM and other resource material and testing the components, I noticed the Blue VSV had a strong gas smell.
I pulled the vacuum line at the Fuel Pressure Regulator and it was full of fuel !
I had a failed Fuel Pressure Regulator passing raw fuel through the VSV directly into the intake manifold.
$100 at O'Reilly's for a Std. Motor Parts PR126 and I solved my truck's excessive drinking problem.

jjswenn

Glad to hear you found a clear and concise failure that caused you problem. In my case, and many people’s here, we’ve tried tried numerous regulators and vacuum switches (blue), to no avail.

Everything on my truck is new, clean, and in perfect working order. Yes, the intake hoses, IACV, throttle body (LCE billet), upper intake, lower intake, thermo time switch, coolant temp sensor, are all new and clean, tested, swapped, and retested many times over. All the sensors are Denso, nothing from Oreillys or junk like that. I’ve chased signals to and from the ecu at the pins, swapped ecus, changed pigtail connectors, and everything works as it should. My airflow meter was disassembled, cleaned, tested, and I’ve swapped numerous units over the many years adjusting here there, but always returning to the factory settings. My O2 sensors are new from Denso, part numbers checked, rechecked, and numerous times swapped. I’ve had my truck over 15 years and numerous motors. The truck has always had hot start issues and the one solution that has actual helped is wiring a switch to the cab allowing me to activate the blue vsv on hot starts. Clearly Toyota missed on the temperature range for this heat soak condition. My truck is a 1995 22REC. Oddly, I’ve owned numerous 1986 4Runners though that did not have the hot start issue, which from the TSB, they should’ve had the issue. My truck also does not have the temperature sensor in the top of the thermostat housing, it only uses the ecu sensor adjacent to the thermo time switch under the throttle body.

The only reasoning I have is that modern gasoline has a lower heat capacity than way back when these systems were engineered. Modern gas changes states from a liquid to a gas at much lower temperatures causing our issue. Activation of the blue vsv helps the problem in my case by raising fuel pressure in the fuel rail, but even with that raised pressure my truck starts choppy when warm, even during colder seasons of the year. It clears up very quickly with the switch active though. I’ve learned to live with it. At some point I may put in a stand alone system that will run this beautiful motor better.

jjswenn

Many months and miles of driving… and my 95 22RE still has the hot start issue. This thread is long and there’s tons of history to it, so I’m gonna limit information for the sake of being redundant..

What I’m here for this time, is to talk/think about what type of heat shield I want to try on the fuel rail. I’ve played with the cheaper Amazon stuff and have it installed on my fuel lines coming into and out of the fuel filter, but there aren’t any really good options for shielding the actual fuel rail, which is what we need here to see any significant solutions to heat soak issues on the 22RE. So, I’m doing some research and looking for a product that will A) provide adequate heat shield to the rail, B) either be precut or able to cut/punch holes so that it fits tight enough and works etc, and C) well I don’t know here… but we just need it to work. Any ideas are good ideas here. Maybe you know of or have used a product I have not. I know LCE makes their anodized rails, and I see a market there for them to design a quality heat shield, but as far as I know, they do not make a heat shield for the actual rail. I believe the best cure for this hot start (other than the toggle switch wired directly to the idle up vsv I’ve had for a few years, and it works) is heat shield at the rail. The Velcro stuff seems like it may work, but it’s just too difficult sorta to get good coverage and have it not be a total mess. I’ve thought about that route many times. Idk.. Let’s hear what you know and have ideas for. Thanks

JJ in WA

oldguyinoc

Update to my prior post. Yes, my original fuel pressure regulator was bad, passing fuel directly into my intake manifold. Unfortunately, my replacement Standard Motor Parts PR126 regulator turned out to be defective (It does not hold pressure after shut-off, causing a long starter cranking while it builds pressure). I have ordered an original Toyota replacement #23280-35030.
Meanwhile, I checked the Air Flow Meter (device over air filter) resistances per the FSM and found an open circuit between E2 & Vs . I cut the silicone seal around the VAF plastic cover and popped it off. I then used contact cleaner on the potentiometer sawtooth pad and fine emery paper on the potentiometer contacts. The E2 - Vs reading and all other resistance tested within spec . I scraped all the old silicone off the cover and reinstalled it and used clear silicone caulk (Home Depot) to re-seal it. Stumble at idle when warm is gone.

jjswenn

Yep, months back when you posted about that regulator, I was wondering if you bought an oem Toyota part. None of the regulators from O’Reillys and autozone work correctly. I had the same experience over years with my issues. I bought a new regulator years back and always snag one when I see them at the yards. The genuine Toyota regulators will hold pressure for several hours after shut down. Gotta have the Toyota regulator

jjswenn

I wonder, though, if installing a aftermarket O’Reillys regulator would alleviate any of the heat soak issues. It’s been so long for me that I don’t recall how my motor behaved when I had one of those cheap regulators installed. I simply saw that it didn’t hold pressure after shut down, at all, via my LCE fuel pressure gauge on the cold start injector, I had that cheap regulator installed maybe a few days. By the way, the liquid/ glycerine filled measureman fuel pressure gauges on Amazon are fairly good. I’ve had one for years (0-60 psi, but they have several different versions and psi ratings, colors etc) and it’s still accurate and held up to my BS. I’m wondering if the cheap regulator may allow fuel to return to the tank (as they seem to do) and alleviate vapor lock we are experiencing. However, I’d suspect that without the cold start injector firing (as is a hot start) that excessive cranking may be necessary. IDK. Maybe something I try at some point. Again.

oldguyinoc

Yes, the Toyota regulator works like a champ according to my LCE cold start adapter bolt and 0-60psi pressure gauge. My engine now fires within 2 revolutions when warm.
You didn't address my free VAF Meter fix which I thought might be helpful.

pimacdaddy

Sooooooo ..... Did you ever find the culprit ? I've been having the same problem for years.

jjswenn

Yes and no. The culprit is the temperature range that either the ecu and/or temperature switch enable the Fuel Pressure Up switch (FPU) to activate, which in turn routes the fuel pressure regulator to atmosphere INSTEAD of motor/manifold vacuum. Which elevates fuel pressure from ~38 to ~43 psi, which pushes fuel vapor to be burned quickly. Toyota missed on this one. If you read further back in the thread, you likely read that there is a Toyota service bulletin for earlier models. The fix involved swapping temperature switches for a different range of fuel pressure up activation. However, it’s obvious they did not fix., as my vehicle and computer being 1995.

pimacdaddy

Yeah I saw that bulletin and the switch that was supposed to fix the issue isn't (and seem like it was never a thing) even available. What about the 4Crawler thread about by passing the vacuum switching valve?

https://www.4crawler.com/4x4/CheapTr...ne_Pix/10.html

jjswenn

right yes, so basically what you’re doing by bypassing the vacuum switching valve and plumbing the vacuum line straight to the Upper Intake Plenum, per 4crawler, is no different than how the vacuum line is already ran. You see, the purpose of that vacuum switching valve is to switch vacuum to atmosphere (or aka the intake nipple on the throttle body, depending on which year, and whether you have an early or late style 22RE throttlebody).
Hooking the vacuum line up directly to the intake Plenum does bypass the vacuum switching valve, but it doesn’t change what is actually happening. Vacuum is still occurring at the same upper intake vacuum port. What you WANT/NEED, is for the vacuum switch to switch vacuum on hot starts to atmosphere, this in turn eliminates vacuum at the fuel pressure regulator and raises fuel pressure to the ~43 psi required for not low rough idle at hot starts.

To simulate what I’m saying, next time you go to start the engine when it’s hot, pop the hood, and reach back there and disconnect the vacuum line that goes directly to the fuel pressure, regulator, plug the vacuum line up with something, and start the truck. You’ll probably experience something very different, and that, is what that vacuum switching valve for the fuel pressure system is supposed to do, but is not. Lame.

Also, try this.. aside from disconnecting the vacuum line from the fuel pressure regulator, next time you go to start your truck hot give it just a slight bit of throttle at the same time as you start the engine, as you would an old carbureted motor. Of course, once the engine fires up and things start you let off the gas almost immediately. I’ve found that my engine likes a little more air on these initial hot startups. . I’m guessing the boost in air as I hold open the throttle blade allows things to clear and burn off the vaporized fuel almost immediately. And it also has the tps communicating to the ecu and injectors to spray some fuel, which clears the vapor fuel. I’m sending a PM so you can call me

RAD4Runner

Like this:
I suggest you watch on youtube website itself so you see my parts list.
Also, please note that the glycerin-filled pressure gauge may have a fill plug which ends up on the bottom when gauge is upright (yes, lame). Mine leaked and now has less glycerin = less vibration damping effect.

jjswenn

Yes, exactly

pimacdaddy

Thank you for your quick reply. I actually notice that yes when giving gas to the engine when restarting the engine actually does help yes. I'll check my messages. By the way I have an 1986 22RE turbo truck.