Pre-runner sounds like it's running on two cylinders on start up

Hi all !!! This is my first post. I have a 2001 2.7 liter pre-runner. A couple of days ago in the morning, got in my truck, started it up and the truck sounds like it's running on two cylinders. When I press the accelerator the engine hesitates & stumbles. After a 15 minute warm up I attempted to drive it but the truck shakes and feels likes it's going to stop running. After another 5 minutes or so of driving the truck runs fine. This problem only occurs in the morning after the truck has cooled down.

I have looked all over the Internet to find some insite on this problem but all I run into is a lot of confusion. My pre-runner is we'll maintained and has never given me any problems. It has 195,000 miles on it. Tune-up done 4 months ago, new spark plugs, oil and air filter. Coil packs inspected and look good no visible cracks.

Check engine light on with P0300, P0302, P0304 & P0402. I know what the codes mean. A buddy of my told me he had a similar problem with his vehicle and said it might be the EGR. He said try and bypass it and see how it starts. He was thinking EGR was stuck open letting to much exhaust back into trottle body. And after the truck got hot enough the EGR would close. I bypassed the EGR but that did nothing. Any suggestions

 

what are the rpms at when started? high? low? normal?

 

RPM's while warming up in the morning at about 1000 maybe a little over. After its warm it drops down to about 700 or so.

 

I'm going to check and try to test a few parts this up coming weekend ( TPS, IAC, EGR, O2 sensors) and see what I come up with. I'll keep you posted....

 

Hello again Tacoma World. Well I spent some time on my truck this weekend and removed the EGR valve, TB, TPS, IAC valve, MAF sensor, VSV sensor and spark pugs. This is what I found.

- EGR checked out fine. No carbon build up and functioned properly
- Throttle body and IAC valve a little bit of carbon but not much. Cleaned them with some TB cleaner everything ok.
- TPS sensor. Used multimeter to check ohms. It tested ok.
- MAF sensor. Just cleaned it out with some CRC Mass Air Flow cleaner.
- VSV sensor. Looked online and found a post on how to test it. It read to bench test the sensor by applying 12 volts to it. Just make sure you have the polarity correct. The VSV has two terminals. Verify the polarity by testing the plug with a multimeter. When you apply 12 volts to the VSV sensor your suppose to hear it click. The VSV is a small green sensor with 2 small vacuum lines and a 2 wire plug. Its underneath the throttle body intake manifold. Its a real pain to remove it. I found out afterwards that if the VSV sensor goes bad, it will not affect the vehicle with the problem I having currently. But it could be the reason why I have a code P0402 for EGR since this VSV is connected to the EGR.

Replaced all four spark plugs(again) with OEM Denso part#

$2 K16R-U11 Denso 3120 Spark Plug

K16R-U11. Part # from the dealership is

$6 90919-01164 Toyota Genuine Spark Plug

90919-01164

Put is all back together, started it up and it did the same thing. Engine was stumbling, shaky idle and hesitated when I accelerated.
I plugged in my OBDII and it now displayed P0303 (misfire on cylinder 3) Previously the codes were P0300, P0302, P0304 & P0402.
I was puzzled for a moment. Then I decided let me swap the #3 coil with #1. I cleared all the codes, started my truck and it ran the same way(As I figured it would) check the codes again and now I have a P0301 (misfire on cylinder #1)

I was still puzzled by this. So I just said the heck with it I'm going to buy a new coil from the dealership.
Well I installed the new coil and the truck is running good thus far. It starts up real quick, no more hesitation when I accelerate
and no more engine stumble. The number #3 coil did have a very small on the rubber boot that I did not catch on my first inspection.
But I don't think it was the crack on the boot. Just the coil itself was starting to go bad.

I'm still a little confuse why I had all these codes come up the first time on my OBDII. I guess with the #3 coil being bad it set off other codes as well. I really hope this information can help someone else that might encounter this same problem. I'll give you an update later after I drive the truck a little more.

 

not sure why all the codes came up? clear all the codes and drive it...it they pop back up then youll know where to look

 

Hello all, This is a very late follow-up in regards to a post I made back in June 2015. I wanted to share this information with everyone in case you happen to come across the same problem I had. Hopefully this will save you a lot of headaches, time and money. I finally figured out what was wrong with my 2001 2.7 liter prerunner. I was having unexplained misfires that would come and go. Many mechanics I talked to, taken it to, even the Toyota dealership could not figure this out. I could not find any info on the net either. Well the problem was the cylinder head. I was starting to loose a little coolant but not much. I had to add a little coolant maybe every 4 months.

I though it was the head gasket but it wasn't. The head had very small hairline cracks on the underside of the cylinder head next to each spark plug hole in close proximity to the exhaust valves. Very small amounts of coolant was seeping in over night so when I started my truck first thing in the morning, it would misfire but then go away after the coolant burned off. I finally found a great independent Toyota mechanic not far from my home here in Los Angeles. He found me a used cylinder head for $500. A new head from the dealer was $1200. With that coolant seeping in the exhaust side of the head, coolant destroyed my two catalytic converters also. California model Tacos have to have two cats.

I had them replace some other needed parts as they had my truck apart. It runs great now. I bought this truck with 34,000 miles on it, never had any mechanical problems and this cylinder head problem happen at 200,000 miles. My mechanic told me that he's seen this problem before maybe about 12 times in he's 40 years in business. He also assured me that I should be able to get another 200,000 miles. Because every other vehicle he fixed with the same problem never came back. Hopefully he's right.

 

Any chance the cracks in the head were the result of over-tightening the spark plugs?

 

I torque the spark plugs to 14lbs according to the Toyota service manual. I ask my mechanic if he thought over tightening the plugs would result with cracks on the head but he said no. He said you got to figure, there's going to be some defects out of the hundred of thousands of heads that are out there. The 3rzfe engine is not only used on Tacoma's but also on T100's and Camry's. Well that's what he said.