Engine troubles - need advice
 

Hello!
Recently I have been running into engine troubles. I have a 2000 limited 4WD with an auto trans and the 3.4L V6.

The other day when I was trying to leave work, my engine began running a bit rough. I made it to the intersection across from my work and I stopped at the light facing uphill, maybe a 10-15% incline if that. When I stopped, my idle began dipping down and struggling to get back up. It would go from like 600 ish down to like 100-200 and kinda of go up and down in that range. As soon as the light turned green, I gave it some gas and it stalled. I panicked a bit, so I hit the brakes, turned the key off and restarted it. I managed to just barely get up and around to head down the hill to my work turn - the car was running very rough and had barely any power. As I was heading up the drive to my work, the engine stalled again. I tried restarting but had no power to go up the hill (just a slight incline again). Luckily some of the guys from my work noticed and towed me into our lot. In the lot, I parked in a spot and just let my car idle. It sounded somewhat like drag cars with modified cams - kind of like these YouTube . For a second I was like that's kinda fun but also realized I have a major problem. I figured the problem was probably something to do with fuel - and the fact that I was missing my second 02 sensor - the one right between the cat and the muffler. So I went to advance auto and got some BG44k and an 02 sensor. I put in the BG and the engine almost instantly started running better. A bit of running on the road I noticed there was a smell similar to old boats or dirt bikes - but the engine was running better. I then put in my 02 sensor and figured problem solved for now.

That was a couple weeks ago. However, I recently did some offroading with a buddy and had pretty much the same problem. After going through a puddle (not the first - we had splashed through like 5-6 others before and had no problem), I turned to head uphill and got the same loping and lack of power. Enough that once again, my engine stalled. I restarted it and this time it started running normally - a bit rough still - but enough that we were able to get off the trail. I noticed on flat ground and downhill it seems relatively fine. It is only uphill that the power really starts dogging, and it gets the sort of missfire - loping issue. I put more fuel cleaner in, and that helped once again but I am just worried this is going to come bite me again and I will get stranded somewhere or worse.

A couple things to note-
No CEL or codes either time
I did do some readings the first time it was running rough - noticed it was getting random misfires - but didnt trigger CEL
Newish plugs and wires (new enough they shouldn't need to be replaced yet.)
Applying throttle while engine was loping/missfiring didn't seem to have much effect. Only increased average rpm of maybe 100.
All maintenance is relatively up to date - oil change, battery, fuel filter, timing belt/pump, plugs, wires, etc all within 1-2 years
I believe it is running slightly rich - occasionally it is smellable
Seems to have lower power while driving until it reaches about 3000 rpm, with a noticeable increase in power - almost like turbo lag
I have not done anything like ISR or Deckplate mod - but I do have a lift with 33's

I am going to start with pulling plugs and wires and just seeing how they look. If anyone has had a similar problem or has any advice I would appreciate your comments - I consider myself mechanically handy but I do not have much experience with complex engine issues.

It could be a number of things. The spark plugs, bad fuel, throttle body might need cleaning, dirty maf etc..I had bad gas once and had to clean my entire fuel system, tb, and maf to get it to run right. This issue will probably just take time to figure out unless you take it to a good mechanic who has seen alot.

Dying at idle is almost always a clogged Intake Air Control valve. That's the greenish-grey contraption that sits on the bottom of the throttle body that has two coolant hoses and one vacuum hose running to it. It would be good to take it off (remove the entire throttle body) and give it a good cleaning. Focus on the valve that opens and closes. Note that it will require a new gasket and the 4 screws on it are prone to stripping so use your best set of screwdrivers and apply pressure. The check and cleaning will only cost you a couple of bucks for a gasket.

You don't have to drain the coolant either. Disconnect the throttle body off the plenum and then lay a towel under it. Remove the hoses one at a time and prop them up so they don't spill. It's the highest point of the coolant system so it won't flow out. You can do this after checking your plugs, which I'm assuming will look completely fine.

Dying at idle would definitely point to the IAC but the OP also had issues while driving. Sounds like a fuel delivery problem to me. I wonder if the fuel pump is on it's last legs. When going uphill, the fuel pump needs to overcome gravity with the pressure it's creating. On flats, the fuel pump has an easier time providing fuel to the engine and on downhills gravity is actually helping deliver fuel to the engine.

That's a good point, and the IAC would not create pending misfire codes. Lack of fuel would.

Now if only we had a way to read fuel pressure on these darn engines...

With all the good advice I would also add take the timing cover off and make sure the timing marks are good. Also when I had a bad injector, my truck sounded like it was going to backfire. It took a while but the cel finally threw p0303 which led to a new oem injector.

I thought about making a video of reading fuel pressure by tapping into the driver side fuel rail but I'm still not sure I have the right fitting to make it work. This is the way the FSM shows how to do it with their "SST" connecting a gauge to the fuel rail.

You can get a banjo fitting on amazon for about 9.00 i have one put figured out my problem before using it. With a fuel pump problem reveal it self by put it in 1st gear and take the rpm up to about 2,500 to 3,000 and hold it to see if the pump can keep up with the demand all little upgrade would make it work harder.

:moon:

Great advicehttps://babang.xyz/assets/5/o.png

Easier way to check fuel pressure:

https://www.toyota-4runner.org/3rd-g...ml#post3392028

Did this last fall and it worked perfectly.
Just need the fuel line fittings from a junked runner/tacoma.
Good luck!

Thanks for all the advice guys! I’ve been busy with work this week and haven’t gotten a chance to check much yet but I’ll keep you guys updated!

With the incline symptom, I wonder if the fuel pump could be sucking crap from a low spot in the tank?

A new fuel filter might be money well spent.