Hello everyone. I am new to this board and hope I may get some advice. I have searched throughout the forum and there are many similar posts, with good results. I have tried everything to get rid of this problem. My truck likes to hestitate when I accelerate. Only once in awhile. Not consistant at all. Also when I barely give it throttle. Here is a list of evrything I have done.

1. Seafoam 2. Plugs & wires. (Not the coil packs) 3. Throttle Position Sensor 4. MAF cleaning. Twice to make sure. 5. Throttle Body cleaning. (Removed when done) 6. Fuel Filter 7. O2 and A/F sensors. 8. Air Filter (k&n)

None of these have helped with the issue. My only thought now is injectors. Oh it is a 3.4 V6 auto also. I am at a loss now. Oh and all these parts came from Advanced, nothing from Toyota. Not sure if this would matter.

 

Could be injectors, but they'll often throw a misfire code.

What plugs are you using? These engines seem to like Toyota OE, NGK, and Denso for plugs/wires/electronics/O2 & A/F sensors.

You've checked all the vacuum lines, intakes tube, etc. for cracks or loose connections?

 

Not sure on the plugs, I will have to check. O2 & A/F sensors are Denso. I have looked all over, but I could have missed something. Also, when this all started a code never popped up. I also found a hole in my air box after the filter. My MAF was just nasty. Now I am wondering with all that nasty crap getting in could have clogged an injector. I did put a obdII on there and there was a code for O2 sensor running rich. That's when I changed those 2 sensors. Seems like after I change something it runs good for about a day then goes right back to this hesitation. What about the fuel pressure regulator? It only hesitates when I am barely on the gas. Under 2000 rpm.

 

Did you clean the IAC valve on the throttle body too?
Seems doubtful that the dirty air would cause the injector to get clogged, but the tips of the injectors do get dirty over time from the combustion process and it can affect performance.

 

No did not clean that. Would that cause the slight hesitation? I guess I will try anything at this point. I will rip it all apart tomorrow and see what happens
.

 

IACV helps control idle speed, but some have had improvement in situations similiar to yours after cleaning.

Have you ran any injector cleaner through the fuel system?

 

I have ran some more seafoam through it. Is there something better to use. It seemed to help, but I can make it hesitate by barely pushing the pedal. I have heard that if overfilled with fuel to much the fuel gets caught in a canister and that would make it run bad. I have been overfilling alot because I think it is a small tank. Lol.

 

Not sure amout the canister bit. I don't overfill.

I use Seafoam or Chevron Techron about a tank or two every 6-9 months...works for me.

 

I think I may pull some injectors this week.

 

Highly recommend Witchhunter for injector testing and cleaning...about $21 per injector plus shipping.

 

Update*********

So I have done a few additional things since my last post. I replaced the ECT sensor and cleaned the throttle body again and cleaned the IAC. I still have a hesitation!!!!!! Still no code being thrown also. I also noticed while in park that when I bring the RPM's up to 2000-2100 it will fluctuate +/- 200 rpm. I tried to hold it there long enough to possibly throw a code, but it will not. I am ruling out injectors, because I would think that if I had a bad one I would feel it throughout the RPM band. Now, what I am wondering is if anyone out there ever had issues with there CAT Converter. My exhaust is leaking from the down pipe I believe. If my CAT was becoming clogged would it make the engine hesitate? I have also went from getting 20 mpg's to about 14mpg's if I am lucky. Here is a list of all the troubleshooting I have done since the problem started.

Replaced spark plugs and wire. ( did not replace boots or coil packs)
Cleaned MAF (several times to make sure)
Replaced both O2 sensors.
Replaced ECT sensor
Replaced Throttle position sensor.
Cleaned IAC
Put injector cleaner through fuel. ( several times )
Replaced fuel filter

Any help would be greatly appreciated. Thanks!!!!!

 

Have you checked for any vacuum leaks yet?

 

No I have not checked for vacuum leaks yet. I will tomorrow. I believe I just need some throttle body cleaner and spray it on the vacuum lines and see if the engine bogs down correct? I am going to get underneath and smack the CAT to see if it is rattling or if I can hear loose pieces.

 

Explain the hesitation. Is it a popping or studdering noise, or just a general poor performance?

 

When it first started it backfired. Now that I have done all this work to it. It is more like the engine is studdering. Not much of a noise. When it happens it feels like the vehicle is starving or flooding of fuel.

 

OK, so I am really starting to get irritated with this 4runner!!!!!! Anyways I ended up cracking my valve cover the other day and now I am leaking oil on my manifold!! Anybody know where I can get a used one cheap. Also, back to the hesitation problem. I think my CEL or system is not working. The light will not come on upon start up, also when the obd2 scanner is attached it says something about how not all reading can be read. Not sure what that means. I will hook it up tomorrow to get what the wording means. Also, are there any experts here that may be able to read all the numbers during live data?