2.7 4 Banger Hesitation

I always go OEM if Possible. Fuel Pump was Not Cheap.

 

And Again Thanks Guys for all the Help and Insight as to possible Culprit. I want this fixed as I am Giving it to my Son and just want it to be safe and reliable. It has been for me thats for sure.

 

I wonder if hooking up a scanner and recording live data would give any insight. Maybe a sensor reading is off when the hesitation starts, like the air or coolant temp sensor. Or maybe you could check the fuel trims. Or possibly the timing is being retarded (causing hesitation) because of a flaky knock sensor.

 

I had a spare OEM one from another engine that had 50K miles on it. Just happened to have it laying around.

 

Issue seems to slowly be getting worse. Heat in Phoenix doesn’t help. Going to Have a friend take a look at it and try and help out...

 

Does the 99 have an igniter mounted somewhere under the hood? Sometimes these go bad and act up when they get hot. The igniter relays signals between the coils and computer. If the computer doesn't receive a signal back after each spark it will cut fuel to the injectors.

Do you have a tachometer and does it act up (suddenly drop) when the hesitation starts? This would indicate an ignition related problem (igniter, cam/crank sensor) rather than fuel.

 

Yes have a Tach. When It starts to Hesitate the Tach starts jumping all over as the engine Sputters.

 

Like it's not matching the actual engine speed? Based on that, I'd bet it's definitely something in the ignition system. The tachometer gets its signal from the igniter. I don't have the wiring diagram for your year, but that's how other Toyotas work from this era. Check your igniter. I've heard of people pouring water on the igniter when it acts up to cool it off. If that solves it then you know. And aftermarket igniters can have these problems right out of the box. You're better off getting a used Denso one from a junkyard.

 

I thought replacing Coils would do the trick. Where is the igniter Located?

 

As the Tach Goes Down so does the Engine Power. Then the Tach Will Go up again and engine seems to have power increase also. Then it lags again and Tach Drops down

 

Do you have manual or auto trans? Like in a manual if you were in gear and the momentum of the car kept the engine at 2500rpm but the tachometer fell to zero suddenly that would be a sign of an electrical problem in the ignition system. If the tachometer still gave the correct engine speed even as it stumbles then it could be fuel or still ignition related.

Usually Toyota mounts igniters on the strut tower. It's a square metal box about 3x3 inches maybe.

Cam or crank sensors are also things that can act flaky when they get too hot. If the computer doesn't get the signal from the cam sensor it won't fire the coils, but I'm pretty sure your tach would drop quick if this happened. The tach is basically reading the rpms based on the coils firing.

 

It’s an automatic when it first started happening I actually thought it was a transmission problem as that’s how it initially felt as if the transmission was slipping it has gotten progressively worse since the 1st time it happened. I wish I could video tape it and post it up here.

 

And this happens with a steady pedal. Usually around 2k. As I Steadily accelerate and get to 2k and above Truck starts to Buck. I never try to start reving the motor at all. Power decreases and then increases pretty fast and then back down again without moving the Gas Pedal. Tach jumps in unison with power increase and decrease. Just today it started because I Sat at a long light. Give the Truck a break for a half hour and it Runs fine. I think I Need an Exorcism as I think my Taco is Possessed.

 

If you have coil packs then you don't have an igniter box. it's built into the plug wires. You could run a check on the TPS yourself and see if that is dying. then take it to the dealer and have the ECU checked.

 

If the igniter is built into the coils, and your coils are new then all you can do is check for loose/broken wire connections.

Based on it failing when sitting in traffic I'd still lean toward something electronic failing like the cam or crank sensor. These are tightly wound coils of wire and when they heat up and expand a little they can partially short out, so the computer doesn't get a clean signal.

Have you scanned for any codes?

 

No have Not Scanned. Have Not thrown any CEL’s.

 

Happened with out even being caught in traffic. May have even heard it Back Fire too

 

My Friend is going to Hook up a Scanner to it, and drive it around and see what he can Find. No CEL’s at this time. I drove it on freeway today for a While and it started acting up without being in traffic. It is getting more frequent. Temps are on the Rise in Phoenix so its happening more.

 

Also mentioned.

Clean the throttle body and pull the idle air control solenoid and look at it see if it's all carbon up and clean it put it back see if that did anything if not I would change the idle air control valve and check EGR

 

Going to be doing this on this fine Weekend.