Won't start on hot days

[geohil]

This should be a simple one - but I'm stumped. Don't know if I need just the S/C crowd or not, but my truck will not start and idle if it has been sitting in the sun on a 90+ degree day.
Here are the specks:
1997 4Runner Limited
1st gen supercharger
URD 6 injector kit
2.2in pulley
Downey headers, OEM CAT, Magnaflo exhaust
Snow performance meth kit

Issue: no codes have been thrown but will not barely start, will not idle, and die on hot days while engine is below NOT.

I've tired:
changing my map
cleaning my MAF
pulling and cleaning my injectors

Things to note:
have not changed spark plugs in 75K (they have been sitting in my garage for over a year....I'm lazy I guess)

Any thoughts from you guys are welcome - please!

 

[A.Wilson013]

I don't think it will help, but the plugs seem like the cheapest/easiest thing to check out. =)

I really have no idea though man... That's weird.

Do you have a OBDII scanner? Can you read the fuel trims at startup?

Perhaps a wideband AF gauge? What is it reading when it's dying?

 

[kball]

What do you mean it won't start and idle? Which one? Does it start and then barely idle and die or does it not want to start at all or both?

On cold days it acts perfect? Once you get it running on hot days is it fine? Only thing that comes to mind for me as far as heat affecting it is maybe your throttle body is really gummed up and the heat makes it real sticky. Have you ever cleaned the TB or IAC?

These trucks don't have MAP sensors so what did you change?

 

[geohil]

kball
Sorry - to clarify it will eventually sputter to life but will cough and sputter between 300-500 rpm until it dies. Did this for about 20 minutes of restarting until finally I was able to get the truck to hold 3000 rpm with my foot on the gas. Eventually it did settle in and get back to normal.
MAP - as in fuel map....sorry
The TB has been cleaned and does get cleaned almost every time the water/meth system kicks on (nozzle is on the intake tube).

Has a new TPS sensor from a year ago...but where the heck is the IAC? Idle Air Controller, right?

A.Wilson - I have both a wideband which was reading AFR's in the single digits while it stumbled, and a OBDII (DashCommader) where my fuel trims were all over the board. At least the short was...but isn't that more of an sinusoidal wave anyway? I've done the dyno tune and have used this map and setup for many years with little to no issues. The only thing that has changed is the ethanol in the gas, and I'm not sure if that could have any effect, or if it atomizes differently at high temps or not? I know my intake temp was reading 119 degrees which I don't like.

All I know is it was frustrating waving to my coworkers as my 4Runner coughed it's way to life after the 70th start.

 

[Dirtyfingers]

Have you tried cleaning the idle air valve? That could be it as well.


EDIT: Sorry kball I didn't see your suggestion there

 

[kball]

Well if the TB is clean from the water injection then I don't know. IAC is below the butterfly valve.

I would think if it's not the TB it must have something to do with the fuel mapping. When it finally starts does it smoke?

 

[A.Wilson013]

A.Wilson - I have both a wideband which was reading AFR's in the single digits while it stumbled, and a OBDII (DashCommader) where my fuel trims were all over the board.

To be honest, I don't know much about the fuel trims other than that to a real mechanic, they can tell you a lot about what's going on in your engine... lol. Was hoping you could post some numbers and perhaps get some more/better input.

As for the AFR in single digits- your truck is obviously loading itself with fuel upon startup... That's not right, and is most likely the cause of the stumbling. Upon starting it should be right around 14.5ish... regardless of the ambient temp.

My question for you is... How long has it been doing this? Are you SURE it only occurs when it's hot out, or has it just started in this latest heat wave, and the temperature is completely irrelevant? Basically... If you try to start it up now that it has cooled down (a bit) outside, does the problem persist?

I would think if it's not the TB it must have something to do with the fuel mapping. When it finally starts does it smoke?

I imagine he's running the URD piggyback... If that's the case, his fuel mapping should only be effected under boost.

 

[geohil]

Kball - honestly I didn't look. Sitting in the cab of an un-air conditioned truck with my temper as hot at the weather the only thing I remember is the smell of unburned gas. That alone says you are probably right. Just not sure why it's happening now and not in previous years. I'll hit the IAC, install the new plugs, and I have new NGK wires as well just for fun. If that doesn't work the. I guess map is next.

 

[geohil]

It pretty much is just the latest heat wave - but just waked to the vehicle and it started fine. Outside temp is 82 and it's in the shade.
Correct on the URD piggy back.
Only question on that is the use of the 318cc injectors on the URD 6 kit. Can that throw off idle?

 

[geohil]

A.wilson - I will park in the sun tomorrow and see if I can start my PLX logging tool to get hard numbers tomorrow.

I really do appreciate the help. Nothing more frustrating then being stumped.

 

[geohil]

Well if the TB is clean from the water injection then I don't know. IAC is below the butterfly valve.

I would think if it's not the TB it must have something to do with the fuel mapping. When it finally starts does it smoke?

The more I read about the IAC, the more I think that might be the cause. The water/meth mix won't touch the carbon that appears to build up on these over time. I'll pull it apart this weekend and get some pics of how dirty it is.