I've a '99 4Runner 4x4 SR5. Started running really rough on idle and check engine light came on and began flashing whenever I went over 2000RPM. It only pulled one code when I ran it PO304 so I changed out the spark plugs and cables. The rough idle is a little better and it has a bit more power but its still shaking and engine light still flashes when I go over about 2000rpm.

 

There have been quite a few have problems with injectors 98+ 4R's after 20 years creating the symptom you have, but its best to eliminate coils, wires, boots, correct dual prong ground electrod NGK or Denso plugs ect., before changing injector(s).

 

Either a clogged injector or you have a coilpack taking a crap. Move one of the coilpacks and if your cylinder misfire code moves, then you know. if not, then go with the fuel injector. I had this happen to my cousin's 4Runner and after swapping out the injector in question, it was good to go.

 

My vote is always injectors. I had 2 of my original injectors go bad, and then the replacement set had a bad injector too.

the injectors aren’t very hard to get to. You can swap them and see if your cEL code moves.

 

Adding to the 'injector' bandwagon. I had one go bad on my '99. It first did it on a very warm day, worked fine when cool or merely warm, very rapidly progressed to not working at all.

I ruled out ignition issues by swapping coil/plug/wire (helps that my wife as a '96 to borrow parts from) - with no change to the miss on #6.

Worth ruling out all that before taking the intake off to get to the injectors.

I'd also warn against the various cheap knockoff 'new! OEM!!!' injectors on eBay. I tried a set and they were crap - very long crank to start each time 10 seconds - getting worse, cold or warm) and an uneven idle. I returned them for a fullr efund ASAP and put on a set of junkyard Toyota injectors.

 

Question for the guys talking about injectors going bad, were you able to determine if they were just clogged or actually shorted/open internally?

 

I think my set of used junkyard (Camry?) injectors were $75 for all 6. It was cheaper to just swap out and be done then spend for diagnostics from Witchunter which is like $25 per injector.

 

Def cheaper. I only ask to know what to look out for. It'd surprise me if the wiring itself was going bad but even Denso turns out the occasional lemon no doubt.

Would think a quick test for resistance between the 2 pins would determine if the coil is shot or if nozzle is clogged. If clogged I'd personally spend the extra $ for cleaning and make sure I'm getting all my ponies out of the engine, but either way works.

I've also had a bad injector right out of the box, from Rockauto. For 22RE. Want to say it was Beck Arnley but not positive

 

Testing coil resistance is a clue to wether your injector is good or bad. Applying voltage to the injector and listening for the click is a way to test the pintle is moving. Both the coil and the pintle are non-serviceable parts.

the problem with faults in our generation and style of injectors is they often fail during heat soak. So cold, even slightly warmed up, they work fine. It’s when they’ve sat on a normal operating temperature engine for a bit that they show their failures. In order to replicate this test, you’d have to bake your injectors in an oven to 200+* for a while and then test their resistance. Personally I’ll buy some eBay injectors for $10 each rather than chance the 3rd degree burn waiting to happen diagnostic test.

 

Mine was still working when cold, just stopping at lower and lower engine temps. I would have guessed that electrically it would ohm out the same when removed (when it was cold and presumably 'working'). But my wife was curious and checked it with a multimeter and it had a large difference between it and the other 5. I forget the readings.

Since then, I grabbed a second set of spares at a junkyard. So now I have the 5 working original ones, a junkyard set on the car now, and another junkyard set just in case.

FWIW the first set I took off the car in the junkyard still has pressure in the fuel system. I don't know how long it had been since it was last run, it was wrecked. But it wasn't just fuel in the rails leaking out, when I first pulled the fuel rail partially off the injectors, fuel *sprayed* out. Makes you feel good that they aren't leaking, at the very least.

 

Makes sense, like an ignition coil usually presenting when warm. News to me on injectors though, esp Denso

Woman who can read a multimeter, now that's wife material