Hard to Start when Engine is Hot

[morphius909]

'97, limited, 3.4L V6.

Just purchased a month ago.

I've been searching the forums, reddit and facebook. Seems to be lots of tips but thought I'd come back to the Original OG Forum.

Scenario:

-Cold Start: It starts fine. Idles around 1500.
-Hot Idle: Around 6-700. Smooth.
-No "Drivability Concerns". Lots of smooth power. No stumbles.
-No CEL

Issue: When engine is hot and go to park it, and come back say 10 minutes later, it's suddenly a bugger to start. Crank Crank Crank. Nothing. Pray to Jesus. Pray to Toyoda. It might start.

It just started happening.

I've:
-Cleaned MAF
-Cleaned TB
-Removed Plugs and wires. They are dry and Newer (BOSCH)
-Fuel Filter looks' shiny new (we live in Canada so

From looking around, it "looks like" the Coolant Sensor is new and the Fuel Filter under the truck is super shiny so I assume newer (we live in Canada/Alberta)

I know I should also look at:
-FPR
-Fuel Pump
-Fuel Pressure

What's the easiest to test first?

thank you!

 

[jgue467]

Going by the FSM - hard hot starts - supposed to check starter signal circuit and fuel pump control circuit (summary on pg196). Then onto pgs 321 & 327 for details on how to test each.

Could be the connections on either end also since you 've replaced some parts already.

Complete 4Runner Service Manual 1996-2002.pdf - Google Drive

 

[T4R2014]

I had a similar issue. Cold start was easy. I'd fill up with gas and then it would struggle to start. Issue went away once I cleaned the throttle body and IAC valve. The IAC valve in particular was very gunked up.

 

[morphius909]

thank you very helpful!

 

[loneshepherd]

I have had this same issue for three years on my 98 4runner 3.4 5 speed 4x4, I'm only now getting around to taking a look at it. Typically I don't notice it because I usually just drive to work, and come time to go home it's cold again and starts right up.

But on my days off, if I go to the grocery store, post office, get gas or whatever, the thing needs 10-20 seconds of cranking to fire up again between each stop.

So far only my TB and IAC are cleaned. There is often a notable smell of fuel. I did the injectors and pump on my 2runner and I really don't want to do them again on this one :banana:

Not to hi-jack, but keep us apprised of your progress. I also just watched a youtube video on this exact issue, and the fuel pump didn't completely fail, but it was just outputting low pressure, and amp draw from the pump was low as well. The car still ran just fine, but it wouldnt start hot :/

 

[morphius909]

I have had this same issue for three years on my 98 4runner 3.4 5 speed 4x4, I'm only now getting around to taking a look at it. Typically I don't notice it because I usually just drive to work, and come time to go home it's cold again and starts right up.

But on my days off, if I go to the grocery store, post office, get gas or whatever, the thing needs 10-20 seconds of cranking to fire up again between each stop.

So far only my TB and IAC are cleaned. There is often a notable smell of fuel. I did the injectors and pump on my 2runner and I really don't want to do them again on this one :banana:

Not to hi-jack, but keep us apprised of your progress. I also just watched a youtube video on this exact issue, and the fuel pump didn't completely fail, but it was just outputting low pressure, and amp draw from the pump was low as well. The car still ran just fine, but it wouldnt start hot :/

I need emotional support so feel free to keep in touch.

And yes I saw the same video, Pine Hallow Diagnostics?

My next step will be :

-Clean IAC
-Check Starter as noted in manual
-Check Fuel Pressure and Fuel Pump as stated in Manual
-Maybe Parts Cannon and change out the FPR
-If everything else fails, parts cannon and Change Fuel pump lol

 

[phattyduck]

-Removed Plugs and wires. They are dry and Newer (BOSCH)

Unlikely to be your current issue, but you'll want to get the right NGK or Denso plugs in there when you can.

-Charlie

 

[loneshepherd]

I need emotional support so feel free to keep in touch.

And yes I saw the same video, Pine Hallow Diagnostics?

My next step will be :

-Clean IAC
-Check Starter as noted in manual
-Check Fuel Pressure and Fuel Pump as stated in Manual
-Maybe Parts Cannon and change out the FPR
-If everything else fails, parts cannon and Change Fuel pump lol

Haha yep that is the one I watched. I am doing fourteen hour shifts right now but this weekend I'm going to reclean my IAC and dump the injector cleaner in my tank since its super cheap - why not.

A while back when working on my other car I rented a couple different fuel pressure testers from Autozone and oreillies and neither had the right adapters to connect the guage in-line. The one the dude used in that video is ~200 on amazon :s, so I'll save that for next week when I have time for someone to come do it for me.

 

[pluton]

Pure guess: Temp sensor. Remember that the gauge temp sensor is different than the computer temp sensor, which is the important one.

 

[Calm8809]

I'll actually double up on that temp sensor. Chased this problem on my mom's 3.4 for a month. New fuel pump, pressure regulator, even took it to the shop and they said it was a bad injector. It was the water temp sensor all along. There's two of them. The one you're after for the computer is the one up front. I personally spent the money and got one from Toyota.

 

[2TH4IST]

I did mine (ecm temp sensor) when I did my tb/water pump. Oem toyota is the way to go.

 

[Atimm693]

You can check the temp readings with a scan tool. I've heard that suggested a lot but never actually found an issue with one.

I'd look at the fuel injectors first. Many times a poor hot start is an injector leaking into the intake, flooding the engine. Not an issue on a cold start as it has time to dissipate, and a cold engine needs more fuel anyway.

First get a fuel pressure gauge on it. See if it holds pressure after you shut the engine down. It won't if an injector is leaking.

Second get your scanner out and see what the fuel trims look like. If you have a dribbling injector, you will also likely have fuel trims pretty far in the negative, the PCM will be pulling fuel. In severe cases you may have a fuel system rich code.

 

[truckmike26]

Pure guess: Temp sensor. Remember that the gauge temp sensor is different than the computer temp sensor, which is the important one.

A good guess. On the previous gen 3VZ-E, the computer temp sensor circuit increases the fuel pressure accordingly to combat vapor lock for hot soak starts. My old '94 struggled with hot starts until I replaced that sensor. Hot starts are perfect now.

 

[alexperrucci]

I did mine (ecm temp sensor) when I did my tb/water pump. Oem toyota is the way to go.

Do happen to have the part # for that?

 

[2TH4IST]

89422-35010 is the part # for a 2000 sr5 5vz. Buy only from toyota, to many fakes on fleabay and chinazon.

 

[spartacus]

.Temp sensor gasket/washer. 90430-12221.

 

[loneshepherd]

Since my initial response to this thread I've been running injector cleaner for four tanks of gas now, two of the smaller sized bottles in each tank, and yesterday and today after running several back to back errands of varying time in between I just realised my issue is basically gone. I never really put any stock in that stuff but I cant argue with the results, especially considering that I havent had time to to try anything else to fix it.

 

[morphius909]

Since my initial response to this thread I've been running injector cleaner for four tanks of gas now, two of the smaller sized bottles in each tank, and yesterday and today after running several back to back errands of varying time in between I just realised my issue is basically gone. I never really put any stock in that stuff but I cant argue with the results, especially considering that I havent had time to to try anything else to fix it.

That's great to hear.

I'm now dealing with a misfire issue

Yesterday cylinders 1-3-5
Today 1-2-3.

Praying it's not a head gasket issue.

Haven't really noticed the no start during heat soak lately. One thing disappears ...another appears lol