tc

I am having a very annoying issue with my truck now that things are getting warmer the last couple weeks.

When it's warm out, and the truck is under heavy load, it will sputter and die. If you pop the hood and let it sit for 10 mins or so, it will start up and run OK for a while. It seems to happen mostly at altitude (going over passes), when it's hot out, and at lower speeds. Coolant temp gauge reads right in the middle, and the coolant doesn't seem to be boiling (no reason to believe gauge is incorrect), although there is quite a bit in the overflow tank.

It also seems to be pinging/knocking a lot.

Fuel tank, pump, and hard line from the filter back was replaced last Sept
O2 sensor replaced a month ago
Fuel filter was replaced this week (what a PITA)
Plugs, wires, cap, rotor are about a year old
Seafoam and fuel injector cleaner after fuel filter replacement last week

Reading ovrdrive's pinging post gave me some ideas to check, but wondering if anyone has had something similar.

I haven't pulled codes, but I don't have a CEL. (which seems awfully strange)

Thoughts of what to check first?

tc

Anyone think it could be vapor lock?

tc

Nobody has any ideas?

Lysmachia

BUMP! Anyone? This is a PITA and any ideas would really help us.

95RunnerSR5

have you checked the timing? and the air/fuel ratio? it may be getting too much fuel and not enough air since the warm air is less dense than cold air and your problem is when its hot outside. just a few ideas

Lysmachia

Lemme ask troy. Oh and we just did a code check. No codes were thrown BTW...

dcg9381

So does it have spark when it dies? IE - is it missing fuel or spark when it won't run.

I've seen ignition components get hot and then fail.. when the cool off, everything is OK. Really annoying and hard to find problem.

Might help if you knew what it was that was preventing it from running:
spark, fuel, or air.

reggie 00

Had a coil do that, was a pain in the rear.

That's what came first to mind reading this.

when it ides pop off the line feeding the fuel rail see if gas comes out when you have it cranked over.

just cause it is newer doesnt mean it wasn't made on Friday @ 445 pm

tc

or 420 ...

I am pretty sure it's fuel, (when I was changing the fuel filter and tried to run it with the gas line still crimped off, it acted EXACTLY the same) but I'll look into it more specifically next time it happens. Where exactly does the fuel line go into the fuel rail? (Probably a good place to check fuel pressure too, huh?)

95RunnerSR5

the fuel line is on the passenger fuel rail at the firewall end, there is a pretty large bolt holding it in, i think 19mm? you should be able to get to it with just the plenum out of the way

Lysmachia

I thought fuel injection doesn't have vapor lock.... Can it?

And if it is Vapor lock - how does one "fix" it?

Four Runner

Injectors going south?? Replaced or Flow tested lately??

ORS

Sounds like this has been a real pain.

If you haven't already, you really need to check fuel pressure. Vapor lock can happen if fuel pressure is very low. This could also be fuel starvation. Since you've had some work done on the fuel system, it could be related.

We suggest getting a hold of a real fuel pressure guage w/ the right fittings. This will have a fitting that will connect to the cold start injector port, it makes checking the fuel pressure easy. Should be 36-42 psi.

It could certainly be ignition related or even something else, but start here, it's the next best step.

A few thoughts on the fuel:
-once we saw an improper fuel pump installation. The pump fell out of the brackets in the tank and was still wired and plumbed. The truck was fuel starved because the pump intake was getting smashed against the bottom of the tank.
-this can also happen with a smashed fuel tank (don't know how we know that )

If the fuel pressure is OK, try borrowing a "noid" light and check to be sure all the injectors are being fired properly. Bad power/grounds can effect this. It would probably run poorly all the time but worse when hot.

Let us all know what you find.

tc

Thanks Mike - talked to a friend of yours (Darryl) at a local meet yesterday and he suggested the coolant temp sensor too.

I about ready to let you know I'll be dropping the truck off for a 3.4 swap LOL (no - seriously, I was JUST about to call you!)

Zealot

As much as I am aware of, fuel injected engines can not have vapor lock. Due to the fact they are a pressurized system. Just for a safe bet have your injectors cleaned and if needed replaced, it might not be the solution but it will help. Contact Dr. Injector, they're one of the best.

locked stock 84

try: www.autozone.com diy!

Schump

wrong.
my 914 used to get vapor lock when it got hot, and it's fuel infected (bosch D Jet-aka the 1st fuel injected Porsche...mine's a 73 2.0)
anyhow, Porsche decided to mount the fuel pump under the sheet metal in the engine compartment, and guess what....... when the air cooled motor got hot, so did the air around it!... and consequently the fuel pump, so much so that it would vapor lock when hot (that's what i'm told, anyhow.)
To fix it, Charlie moved the f pump to under the gas tank right next to the steering rack. No worries on that now.
I just wish fixing the terminal cancer problem was so easy! (duh, rust, a factory option on 95% or 914's, esp those that lived in the NE for most of their life be4 u bought them...as a naive but porsche hungry high school senior....who soon bought a MIG and learned how to do sheet metal fab and weld!)
hope that helps.

thook

Any updates on this problem? Or you just not going to deal with it and put in the 3.4?

Reason I ask....
My '92 3.0 has started to do the same thing it seems. I recently put in a new water temp sensor with a new connector, last year a new TPS and recently a connector...sensor properly adjusted testing fine, new O2 sensor less than a year ago, plugs less than a year old, wires not very old, fuel filter not very old, pretty new FP regulator, just cleaned TB, vacuum lines all good, no EGR...so that's moot, timing is dead on, new rotor and cap, it has a new KS and connector, numerous things. All of these repairs and replacements have been done within the course of over year and less, but not to resolve this problem. This is new. The vehicle did sit for a while here and there because of a wreck in Jan. and whilst some of these repairs were being made, but not for terribly prolonged periods...meaning periodically it did run and you could get around, just not great. NOW, it's running really good up until after it's reached operating temperature and been running about approx. 20-30 min.'s and then try to go somewhere. Right when I got to the hill leaving my house and started up it just died..... like the rug had been pulled from under it with no warning. Then, it will start right back up and "Sputter, sputter.....die!" I eventually did get it going again, made it up the hill, and then dead again. Only this time it won't go.

To me, it seems like something is being cut off....like the fuel, maybe. Except that you can hear the fuel pump running when the key's on and motor's not running. Plus, last few days when I've had it apart and cracked the fuel lines there was pressure with lots of fuel. I've not gauged it because I don't have one. Anyhow, applying throttle has no affect once it starts to chug and die. That's why I think fuel. But, I don't know. I'm stumped....and frustrated.

I'm going to try and start it up again here in a little bit after it's cooled off and see if anythings changed magically. Maybe fairies have rallied to my cause in my absence and sprinkled some dust on it.

tc

No, I need to check the fuel pressure still. I did replace the air filter and it hasn't done it since, but it's been a little cooler. It happened two or three times on the way down to Castle Rock on Sunday, so I think it's more temperature related than altitude related.

I agree - with mine, applying the throttle actually seems to make it die faster.

x2 for stumped and frustrated - if I had the money a 3.4L would definitely be going in as I'm not sure I'll EVER know that it was fixed and be able to trust it again...

AxleIke

3.4 SWAP!

I may have to start up a fund or something for this, just so i can see it go in.

Other than that, sorry that the damn thing is being such a pile. Let me know if you need anything.