montypower

Trying to eliminate the dreaded CEL!!! My 4runner is 1999 Limited. It sat for the last 7 months or so... and I just started driving it the last couple weeks (2nd tank of gas). It has approx 130k miles.


Current maintenance done:
Oil Change, Injector Cleaner, Air Filter, Iridium Plugs (used 10k miles), Toyota Wires, Toyota #5 Coil Pack (CEL was indicating misfire on 5 & 2).


Issue:
The computer was bringing up a miss-fire code on Cylinder 5 & 2. I'm hoping that replacing the coil pack did the trick. --- Today I borrowed my mechanics computer scanner. Everything was looking fine while driving around... there was an occasional misfire on Cylinder 1 but the rest was good.

But the CEL would start blinking anytime I gassed it hard (especially on the hwy). The scanner was showing that the engine timing was being advanced, then not dropping down (like it should), thus the CEL starts blinking. My question:


WHAT CONTROLS THE ENGINE TIMING? WHY WOULD IT NOT BE DROPPING DOWN (staying advanced)?


-- Side note: My first tank of gas resulted in 6.8 mpg!!

AgRunner06

The computer controls the engine timing on the 3.4L. I think your timing is supposed to advance when you have your foot in it and then drop back down when you ease off. Is it just not dropping down when you ease off? I could be mistaken.

Also change those plugs back to the stock plugs. Toyota stuff likes stock plugs. Dealerships can also blame your problems on the plugs if they like. That could be the source of your misfire.

I don't think your fuel filter is the problem because of your mileage.

The O2 sensor also controls fuel mileage.

The only thing I can really think of is maybe a faulty ECU.

Otherwise I don't know.

montypower

Yes. When it's rev'd up... then let off. The timing stays advanced, even while it's at idle.

Just replaced all the plugs with new NGK Iridium, pcv valve, fuel filter, cleaned mas... no change. I was thinking about doing the O2 sensors, but there is no code being thrown to indicate such.

Any other thoughts?? I'm going to keep replacing stuff... Timing Belt, Water Pump, etc. More injector cleaner. --- Will a bad cam or crank sensor cause these problems?

MTL_4runner

What exactly was the CEL number (that will help narrow it down)?

I assume there was no CEL issue before it sat and now there is?

Have you reset the ECU (just pull the fuse or negative battery terminal for 10 sec)?
Does the light still come back?

Did you ever empty the gas tank after sitting that long?
I would pull down the fuel tank and dump it out just to be sure there is no bad gas issue going on.

You might look at a few of these and see if they are similar:
https://www.yotatech.com/forums/show...ighlight=p0303
https://www.yotatech.com/search.php?searchid=862081

montypower

Here are the engine codes:

P0300 - Random Missfire
P0302 - Cylinder 2 missfire
P0305 - Cylinder 5 missfire

These codes have not changed since I first started driving the truck. Since then:

I replaced the plugs (cleared the computer) - Same codes came back
I replaced the wires & coil pack (#5) Toyota parts - Cleared/Same codes came back
Next: PCV, fuel filter, cleaned MAS, Air filter, new plugs (iridium) - Cleared/Same codes came back

It seems to run fine. And it's not a major missfire, otherwise I wouldn't be driving it. But the gas mileage is terrible. Any other ideas???

AgRunner06

Does the 3.4 have an Ignition Control Module? If so, I'd look there next before going to the ECU.