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Discussion Starter #1
Hey everyone, hopefully one of you will be able to shed some light on my situation.

2000 4Runner 4x4 5 speed 190,xxx miles on odometer.

The problem is that my engine will not idle until it is up to operating termparature. As soon as I start it in the morning, it runs for 1-2 seconds and then the idle drops to nearly 0 and it stalls. Once the engine stalls it is very hard to start again, and I have to wait about a minute to try and crank it again, otherwise it will keep cranking with no results and I am afraid of overheating the harness so I decide to wait. To avoid this, I have to give it gas and hold it above 1500 rpms to allow it to warm up. Basically compensating for the cold start system that is either not working, or having a hard time. I am thinking because it is flooded after it stalls initially, I have to wait for some fuel to evaporate before starting again? I get very poor gas mileage as well, and there is strong pinging at low rpms when driving, especially up hill. It has a misfire, and sending misfire codes for cylinders 2&3 which share a coil pack. I live in Hawaii so the weather is generally pretty humid and warm, no real COLD starts. I bought the 4Runner pretty cheap with the idle issue. At first I was thinking it would be a simple fix, maybe a vacuum leak somewhere or a bad sensor. However since I have owned the 4Runner for two months, I have since replaced:

Both coil packs
All fuel injectors and seals
IAC valve
ECT (back of head)
Cleaned throttle body
Changed all vacuum lines
Cleaned egr
Air filter
Coolant flush
Oil change

I have done all of this and still have not benefited at all. My truck might idle a little better when up to temp the before I bought it, but the cold start issue has still not improved at all. Starts and stalls and is hard to start immediately afterwards. Once up to operating temperature it runs okay. However before it is up to temp, the engine has little to no power. Also once up to temp, it will stall when coming down from a high rev. For example engine breaking and then throwing the gear box in neutral will cause the rpms to drop beyond idling range and the engine will stall almost every time I test this scenario. I have had it compression checked and cylinders 2&3 both have low compression. Around 70 if I am not mistaken. I understand that is dangerously low and will most certainly have an impact on engine performance. I am thinking that there are some burnt valves on the exhaust side of the engine causing my low compression readings. My main question is whether or not bad valves and compression would keep a 3rz from idling at all upon start up, or if it should still idle. I am more than willing to pull the head and swap it out, but for now I am a bit puzzled and worried I may be over looking something very simple. Or, it’s simply mechanical and that’s it. I am capable of replacing shims if the head looks to be in good shape. Just wondering what some of you might think about the engine simply not idling and warming up on its own. Fuel? Spark? Air? Or just blown head.


1998 T100 SR5 2WD
13,691 Posts
Welcome to the forums! :)

You didn't mention anything about cleaning the MAF. When you replaced the different sensors, did you go with OEM or did you use aftermarket parts? No mention of testing the fuel pressure or fuel pressure regulator. Did you inspect/test the fuel filter? It should be located just under the air intake manifold. ;)

Do you know if this vehicle has been in an accident before? ;)

Did you perform a leakdown test? That can rule out a lot of things without pulling the head. The valves will tighten up on the 3rz over time. ;)

One of the best diagnostic tools is to use an OBDII scanner and see what the sensors are reporting. Temp, fuel trims, spark advance/retard, etc. Bluetooth dongles can be had fer cheap off of Amazon/eBay and used in conjunction with yer smart phone/tablet/laptop. You can also git stand alone versions that you can graph the data over time. ;)
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