2000 3.4L 4Runner only idles

[twicepipes]

Hello,

I am working on a 2000 4runner limited 2wd 3.4L. This is a friend of mine's vehicle with 260k on the clock.

Initial problem: Waterpump failed ( was replaced previously with TB at 110k) and the temp gauge red lined before it was shut off. No signs of head gasket failure, all cylinders read over 150 psi. I've replaced the water pump and all timing components. Ran a cooling system pressure test and all is well on that end.

Remaining problem: After overheating, the engine will now only start and idle. Any throttle applied off idle will cause sputtering and backfiring through the intake. Before the overheating event, it ran fine. I believe the sputtering is what cause the driver to stop the vehicle when it overheated.

With quick, short throttle blips, it will rev to any RMP and sound somewhat smooth. With steady application of throttle it just spits shudders and backfires through the intake.

I have checked the TPS ( checked this with analog meter), CrankPS and CamPS with an ohm meter and all specked out fine.

With the engine idling, unplugging the MAF kills it.

Also, there is a slight hint of gas smell in the vacuum line to the FPR. Its there, but just barely. Could overheating kill the FPR?

Right now, everything is back together and.. I'm not sure where to go from here.

I've been searching threads for hours, but it seems that similar situations were not resolved or there was no follow up with results.

Any direction or help is greatly appreciated. Also, there are no CELs.

 

[kball]

My guess is you're off a tooth or two on the timing.

 

[twicepipes]

I've done quite a few timing belts, this one was done right. All the marks were inline with the old belt on as well.

There was no change in how it ran before or after the new water pump/ TB instal.

 

[tvpierce]

Is the MAF Sensor plugged in?

 

[twicepipes]

Everything is back together.

It barely starts with it unplugged

Right now it starts and idled normally.

 

[AntleredRuin]

Sounds like the FPR went bad.
Mine went bad right after I bought my 4Runner. It would start ok, but any real throttle and it'd stall out.
My FPR was actually dumping fuel into the intake baffle through that vacuum line. I think the check valve in it went bad.

$30 shipped for a used OEM from eBay, and 55k miles later, still going strong.

 

[twicepipes]

Well thats where i'm leaning.

I don't have a vacuum gauge, but I can place a vacuum line on the FPR and suck in, and it never holds suction ( for what thats worth).

*There is no change in how it run with the vacuum line it removed from the FPR. *

I just drove it around until reaching operating temp. It actually drove and made it up the hill and down the street and back.

When I got back it seemed to rev a little better but still very choppy. I could hear a miss through the exhaust for a few seconds after putting it in park and then it cleared up.

:shrug:

EDIT: I also checked the maF with the ohm and volt meter. All looked good.

Later I am going to swap out the TPS with the one from my 4runner just to rule that out.

 

[gamefreakgc]

TPS is a good place to start.

You'll need a fuel pressure tester in order see for sure if it's the FPR or something similar. Fuel delivery issues are rare, but likely someone else said they do happen from time to time.

 

[DaMonkey]

Could overheating kill the FPR?

absolutely. i have not looked at fuel line routing because hot gas does not seem to be a problem in these, but if temps went red line, that can boil fuel in the lines fast and take out FPR.

it's just interesting to think that was the first thing driver noticed was stumble from fueling prob. not impossible at all, just interesting and something to think about.

along the same vein may be intake air temp sensor could have been knocked out by the heat.

i think the key is that the driver noticed the stumble after it got hot, so the problem sounds like from the overheating and not anything wrong from timing belt and wp install.

good luck.

 

[alumarine]

Have you checked for codes?

 

[twicepipes]

No check engine light is on.

I'm looking for an easier way to check fuel pressure without opening up the fuel rail..

Sorry for the typos earlier.. appreciate every ones advice.

 

[twicepipes]

**UPDATE

The problem was resolved by replacing the fuel pressure regulator.

Runs like a top now.

Thank for all the help.

 

[tvpierce]

**UPDATE

The problem was resolved by replacing the fuel pressure regulator.

Runs like a top now.

Thank for all the help.

Thanks for posting back with your results. Helps folks in the future when researching a similar problem.

Good job tracking it down.