HELP 99 taco won’t start when 90+ degrees..

Alright so I’m sure this has been covered in here about a thousand time but I’ll tell you what I’ve got goin in and if it sounds familiar and you can point me in the right direction or a post that covers this I would greatly appreciate it. I have been looking a bit but I just don’t have a ton of time to spend on my phone browsing right now

so my 3.4 runs great when I first fire it up or it sits for an hour or two. However when I start it right after running it in any temp above I’d say about 80 degrees outside I have a problem with it chugging like it’s over fueling itself. Sometimes if it’s like 90+ and I just shut it down it won’t start at all. It will just crank and crank. I do have the dreaded PO171 code so that could have something to do with this. The last owner said they replaced the maf and the fuel pump. I replaced the tps and got rid of that code. It didn’t want to start today at one point and I had some intake cleaner so I sprayed into the air box towards the maf and the truck finally started and ran but it did chug for a about a mile after I got going. Just not sure what to do next? Any help would be greatly appreciated! Also I can answer any questions about this that might help me get to a solution.

thanks all

also anyone close that has a topper for a first gen (mines a 1999) that would like to trade for something let me know. I really want a topper for my truck but can’t afford to buy one for a while. (Buying a house)

 

I haven’t looked at anything else since the tps. I work for a ag company and we are in harvest right now so... anyone have a direction or anything that might help?

 

when you try to start it what do your engine temps look like?

 

1. Edit the title and remove "help" since that's reserved for those that are stranded, stuck, etc. Your title could lead someone to believe you're out stranded somewhere with a no start issue

2. Your front bumper pads are installed incorrectly

3. I hope you find the help you need

 

Maybe it’s your fuel pressure regulator or possibly a faulty injector. Not really too sure

 

It chugging possibly sounds like your not getting enough fuel and may be something to do with your injectors. I’m just going on a limp here though so take what I say with a grain of salt

 

Maybe try a new coolant temp sensor

 

How many miles??

Have the injectors ever been serviced or changed.

Cold starts are fine because the spark plugs have time to dry

Shut the truck off the injectors bleed into the cylinders fouling the plugs .

Your intake cleaner increased the volatility enough it fired getting things running .

Once the spark plugs were cleaned some what it runs better till the next hot start.

I would inspect the spark plugs if you have not done so.

There is a big saga ( thread) here about this same problem it was found by bore scoping the fuel rail

 

I've seen this exact same thing before. Diagnostics on EVAP is exasperating. Before you hot start, try the gas cap off trick. If you get a big hiss taking off the gas cap and it starts normally after, tank pressure sensor and VSV may be flooding engine on hot start.

 

I put help because it has stranded me twice while I’ve been on a time crunch. So I’m good. second I didn’t install the bumper so I didn’t even know or know they were. Thank you for pointing it out I will look into it.

 

I will give this a try. We have a couple mild days but I think we are gonna be hot again Tuesday so I will give her a shot! Thank you!

 

it has 282k I have no clue on the injectors or plugs. I was gonna start working through and servicing it here real soon. If I took the injectors in to be tested they could tell correct? Is there a way to test the injectors myself? Thank you for the info! I will definitely give them a look.

 

There should be a clear flood crank mode built into the PCM. Put the throttle to the floor with the key off then crank her over for a second. This should disable the fuel injectors from adding additional fuel. release the throttle then try to start normally.

 

I had a similar problem some years ago with my 3.4. The engine would start and run fine cold. However, after it warmed up it would run rough and could be hard to start. I ended up replacing my injectors. I don't remember the codes I was getting. There is a known issue with the original injectors where the solenoids get weak or grow a resistance over time. Somebody in another thread pointed to MotorWest for reconditioned injectors. MotorWest states that they no longer recondition the original injectors because of the solenoid issue. However, they do sell reconditioned densos. It might be worth mentioning that I had similar symptoms when my coils were going out.

 

I did see about the motor west injectors and I am definitely going to look into them. 200 for recon denso injectors really isn’t bad. I’m gonna try to get them tested somehow. Thank you for the info!

 

This is interesting because I just had some cleaned and flow tested by MotorWest. They even included my old seals, caps, o rings, etc. Maybe I'm misunderstanding reconditioned vs flow checked and cleaned.

 

How does that work on a cable controlled throttle a signal via the TPS to the ECM to disable the fuel??

How would one know if that system has failed causing the injectors to not open ??

I could see with a drive by wire system maybe .

 

what kind've hiss should I be watching for? Intake of air or exhalation of air? I do get a hiss when I take the gas cap off but never paid attention to which it is, intake or exhalation.

I'm having the exact same issue, it appears to be hot start flooding based on observations.

Is there a way to tie into the fuel injector rail with a gauge and isolate that portion of the fuel injection and see if it bleeds down? Ie: injectors are leaking?

Also where is the tank pressure sensor? I will check that possibility.

I was thinking about starting a thread on this given what I've done to the truck so far but found this thread.

`96 2.4 manual trans. new tacoma owner.

 

You got the charcoal cannister under hood like this?
Tank pressure sensor is on top of gas tank.

 

Welcome aboard @atticus finch
If you have suction or negative pressure when taking off gas cap you have the wrong cap or the one way vent on cap is clogged.
OEM Toyota gas caps are vacuum vented to prevent implosion of tank and vac lines/ fuel hoses.