Please help me diagnose this! So, in January my 4runner suddenly began to bog/stumble (and generally stall) whenever the motor is cold and any throttle is applied (even in park/neutral). I have to let it idle and warm up for at least 15 minutes before I can drive it because after it stalls it won't start again until it sits for 15-20 minutes at least; it'll turn over but it won't catch.

After it warms up it acts fine and pulls alright for a 3.0. It seems like even after coming up to temp, the hotter it gets the more power it has.

Now that the weather's warmer, it still runs rough, but doesn't necessarily stall in gear; it will go into gear without stalling, but it literally doesn't accelerate any. After driving around the block for a few minutes it pretty much suddenly starts to pull and run normally. It lacks power too, I have to merge onto the highway going around 35 mph and it can't hold 75 on flat ground

Gas mileage is piss poor, of course, but even more so than usual (<12 mpg)

New plugs/wires
New fuel filter
Tried a different AFM as well as TPS because it was suggested
The fuel pump does run when the ignition is on and the vane in the AFM is moved.
Unplugging the cold start injector doesn't make any difference in how it runs.
Took the TB off and cleaned it out as well as the coolant passage.
The timing belt was replaced in December along with all the belts

1990 4runner 3.0, auto.

Here's a video showing the problem:

http://www.youtube.com/watch?feature...&v=93owwzdbi7M

Yeah, I know, it's a POS Toyota 3.0 and I should expect nothing more.

Can't find any vacuum leaks. No CEL codes, there is a stored transmission one for the VSS #2, but I have been told that's completely unrelated to what's happening.

I did determine that the EGR is faulty, but I removed it and blocked off the port on the intake manifold. That didn't resolve my stalling/bogging issue, but it did have noticeably more power after it warmed up. Putting it back on didn't really change anything.

It was suggested that it could be an issue with the fuel pressure regulator, but I don't really know how to test that

Thoughts, ideas, suggestions? I'm ready to burn this thing to the ground.

 

You're symptoms would indicate the mixture isn't rich enough during the warm up period of the engine. This could be cause by a faulty coolant temp sensor, cold start time switch, or wiring between a sensor & the ECU. I'd check the coolant temp sensor first. FSM in my sig has test procedure.

 

+1 for TNRabbit I would add possibly an AFM issue. I had a Ford Probe back in the day that did the same thing, turned out to be a faulty AFM.

 

+2 on coolant temp sensor. Test it (page 10)
http://www.ncttora.com/FSM/1990-1995...e/troubles.pdf

 

+ 3 on coolant temp sensor.... also... when was the last time u changed your o2 sensor?

 

Ats the ECM connector I get around .001-.002 volts when it's supposed to be .2-1 volt.

Should I just assume that the Coolant Temp Sensor is bad? The motor's still too hot to test it right now.

 

Did you follow the diagnostic chart on that same page? Start with step one and check for voltage at the terminals shown.

 

I did, and the coolant temp sensor tested bad.


I replaced it and it runs a little better after it gets nice and warm, but it still bogs down/has no power.

 

Why do you have the EGR vacuum connections capped off? Are they capped off at the throttle body? Are you sure that you have all your vacuum connections correct? What brand of wires are these? My 3.0 ran like crap with new wires from autozone. Changed them out for NGK wires, and it ran fantastic.

What do you have your timing set at? Has it ever run correct since you did the timing belt? Is the distributor maxed out in one direction or the other?

 

I had the EGR removed and blocked off temporarily to see if it would make a difference. It didn't, so all those lines have been reconnected.

I used whatever the Napa premium series wire is (Gold?) and replaced the crappy Autozone ones installed by the PO. I also used Denso plugs gapped to whatever the factory spec was. When I did the plugs/wires, I found out that it was only running on 5 cylinders because of a bad wire, if that matters.

I don't know, a shop did the timing belt. ASSuming they did it right, it should be at the stock 10 deg spec.

It hasn't run correct since the timing belt was done, but I don't know if it ran any better before. I have only owned the vehicle since August and let it warm up everyday before driving it.

I think the motor is about done anyway; it's got noisy valves, leaks/burns a lot of oil, and seems to have a slight intermittent knock. After a (presumably rough) 200k miles.

I'm just really frustrated right now with this thing.

Before I got this turd, I paid for a pre-purchase inspection at a local shop (different one than the one that did the timing) who found nothing major wrong with it and assured us that it was an "excellent deal" and that "it would be good for another 100-thousand miles..." Of course that's as-is where-is, no guarantee, buyer beware, but I'm still not majorly impressed because things keep going wrong. I doubt they looked it over two well because they didn't even notice that it was only running on 5 cylinders during the inspection/test drive.

Thanks.

 

Just an update.

It did seem to run stronger yesterday until it died while driving.

I heard a clunk from in the engine bay while driving and it stalled. I killed the headlights and put it in neutral, but couldn't get it to start again. It still turns over, but slower than usual and with a lope. There's nothing externally/obvious wrong and I ran out of time to mess with it. I did check and I didn't run out of gas/oil/coolant.

It's sitting at a shop now, so I guess I'll wait and see what they say. Threw a rod through the block maybe?

 

Idk.. I'd imagine a puddle of oil under the truck if a rod came thru the block... Prolly a spun bearing, but no way to really say without tearing into it... Good luck!

 

I just heard from the shop, I guess they've had a lot of trouble this week and just got around to looking at it today, but there's nothing "major" wrong with it.

Quick diagnosis shows that it has spark, but the fuel pressure is too low for it to run. I guess I should do a happy dance, a fuel pressure regulator or fuel pump is a lot cheaper than a spun bearing or a thrown rod

 

Things aren't looking as good as they were initially, I guess it sheared the crank key and there's a bolt from somewhere in the oil pan. I'm guessing it was (poorly) rebuilt sometime in the past

We're gonna replace the crank key, pull the bolt out, and hope that it runs.

Time to sell it and move on.