Engine hesitales when lugging

First, I purchased an '01 4x4 about 3 years ago and love it! My first truck and I have no idea how I made it so long without one. However...
It has a standard transmission with the 3rz engine and over 195k. For the last few months this problem was been getting progessively worse. When under power at low rpm's and the engine luggs out, it hesitates/stutters severley. Once the rpm's are high enough the problem goes away. I thought it might be the fuel filter, so I changed that pain in the ass part, no fixee.

There was NO CODE for months, so we tried to clean the throttle plate. On my way home I tried to "push it through" the rough running,which finally made the check engine light came on. For the next few days if I lugged it for long enough (about 1 min) the check engine light would flash for about five seconds, then go out. The codes it gave were:
Random cylinder misfire
Cylinder #2 misfire

We changed the plugs and switched the coil on #1 and 2 to see if the code would change to cylinder #1 misfire, no luck. New code though:
EFR insufficient flow

Checked for codes again yesterday. Two "incomplete" codes that I can't quite remember:
O2 sensor something
Cat converter something

After searching this forum, I realized perhaps the drop-in K+N filter I added might be an issue. So today I purchased some MAF cleaner, I'll let you know how that goes. Note- I have checked all the hoses and wires and a can't see anything obviously wrong with them.

Has anyone experienced this or a similar issue? Does the diagnostic plug in the engine compartment take more precise/accurate readings? Is it worth having the dealer check that plug (don't wanna unless I have to)?

Thanks in advance all you Taco lovers!

-Hackjob

 

As a rule, lugging an engine is bad. You're producing just enough power to keep it alive but the 'lug' is it almost dying. Downshift.

That's not saying your engine doesn't have issues, but ALL engines will be without power when it's borderline not running.

Also when the engine is lugging, it's not burning fuel like it should. That means more unburnt fuel through the exhaust system, that means doing damage to O2 sensors, cat's etc. And that will throw codes. Once the engine is up to speed and running correctly the readings are correct and the codes stop. The computer doesn't know what is going on, all it knows is a sensor is reporting the wrong info.

 

Okay, maybe I wasn't clear enough. The emgine is hesistating /stumbling at low rpm in all gears. From a stop, I have to give it excessive throttle to get enough power to move, I have to rev the engine and "drop" the clutch to get past the "bad" section of the power band. It then stumbles at the low end of every gear. 20-25 mph in 2nd, 28-32 in 3rd, etc. When driving, if I let off the trottle to account for the ebbs and flows of traffic, when I acceleate again, the stumbling occurs, unless I'm at very high rpm (generally a gear lower than traffic speed would dictate). If I am driving in 4th at 40mph, and I press the gas, the engine lurches, sputters, and shudders untill almost 50, then vroom- the engine seems fine once it hits a certain rpm (don't know, no tach), then when I shift into 5th, same deal till around 60 mph.

Also, I tried MAF cleaner, no change.

-Hackjob

 

Has the 02 sensor been changed?

 

Spark plugs?

Not sure on the Taco but I fixed a similar problem on my Subaru and boat motor.

 

What tire size? If im in 4th at 40 with mine, its definitely lugging. I have factory gearing and 31's, im probably in third until 50.

The weathers decent so im in the mustang, ill check rpms when i have the truck out next.

After that youre on to basic tune p, and always have to ask how much clutch time you have, whats 'excessive' rpm to you etc.

 

Without seeing the truck...
My guess is going to be a clogged catalytic converter. Especially if the truck did not have regular tune-ups. I would have a good mechanic look at it though. Because this sounds like one of those problems that you throw parts at when you should've took it to somebody.

 

Drove the truck in today with my scanner running (no tach in the dash). From a stop the engine doesn't really wake up until 1700-1800 rpm. With my tires I *can* cruise on flat ground light throttle in 4th around 40 but its borderline. I spend most of my around town driving in 3rd until 50-55. In 4th around 55 I'm only turning 2700-2800rpm.

Redline is around 5500-6000rpm I think, so cruising at that rpm seems about right to me.

 

It sounds to me like a bad upstream O2 sensor or a clogged cat. The O2 sensors are a general maintenance part so you might as well change them first and maybe look into pricing a replacement cat. Spark plugs are cheap and a fouled plug can cause some of these symptoms. Make sure if you get plugs you get NGK brand. Otherwise, it might be time to let a good mechanic give her a look. I have the same engine and tranny, so I'll be interested to hear what fixes it.

 

Update- Got new codes last week.

Random Cylinder Misfire (x2)

I tried to take the pipe off the header so I could see how she ran without the potentially clogged cat. Unfortunatley, one if the bolts was so rusty we couldn't get the nut off, even with the torch. We didn't have time to attack it from the other side, but I plan on having another go at it this Friday, I'll let you all know how it goes.

-Hackjob

 

Well, I did'nt have any luck getting the cat detached from the header, but we did seperate the pipe at the seam between the two cats. It got lots louder but didn't improve performance any. I have ordered the upsteam O2 sensor and will swap it out this fri, I'll let you all know how that works out.

-Hackjob

 

Hey again,

I'm starting to notice that the problem either starts or gets much worse after the engine heats up to operating temperature. I'm starting to heavily suspect a problem with the EGR system, possibly the valve. If the O2 sensor doesn't fix it I think I might try replacing the EGR valve. Has anyone else out there had similar problems with the EGR system?

-Hackjob

 

Hello again,

Well, I changed the upstream O2 last friday, and there has been no improvement. I wanted to make sure I went the 50 miles it takes for the computer to recognise a new part before I posted that. I now am really thinking it might be the EGR vaccum solenoid. I'm gonna try changing that as soon as I can order the part (early next week I hope). Will advise as the situation develops.

-Hackjob

 

Hackjob, are you still having these problems or were you able to find a solution?

 

Yes

I replaced the EGR vaccum solenoid, to no effect. I have it scheduled to be looked at by a mechanic I trust this coming Tuesday.
I'm gonna have him pull the cat from the header to see if it is clogged first. I tried to do this, but one of the bolts is so rusty, he's gonna have to cut it off and replace it, which I don't have the tools for.
If that doesn't yield any resuts, I think the next step is to replace the EGR valve, after that, I'm at a loss. If you have any ideas, I'd love to hear them! I will try to let you guys know how it goes Tuesday night or Wednesday.

-Hackjob

 

Just had some info from my on experience k&n filters work great unless you over oil them it will cause stumble and hesitation until you clean the Maf sensor another thing that will cause hesitation under load are bad spark plug wires . Hope this helps

 

Hey all,

Sorry it took so long to get back to this post, but ya know, life happens.

I finally fixed the problem with my engine! It was a bad coil pack. If you remember in the first post, cylinder #2 was showing a misfire code, so I swiched it with the #1 cylinder, but the code didn't change. Well, that was the problem, I it changed it out, and the truck is runnin' great.

I guess the lesson here is, a little knowledge can be a dangerous thing. Since I was working on this car with my friend (who is an experienced mechanic), when I had the idea to change the coil with the #1 cylinder, it didn't show a misfire code on #1, I was like "that coil must be fine!" he said it might be occuring to fast for the computer, and I was like "too fast for a computer, no way" well I was wrong. The next mechanic said the same thing, and that stuff like that can totally happen too fast to read. Lesson learned.

Anyhow, thanks to all who tried to help, and I hope someone else can learn from my mistakes.

-Hackjob

 

Thanks for checking back and explaining the issue. Oftentimes this does not occur and those with the same problem are left hangin'

 

I've been having some issues with lack of power too. I've been going through the same steps you have so far. I think I'm going to get my coils checked. How many miles do you have? Mine is coming up on 50k but I've taken mine off roading so much my engine bay is stained brown.

 

My truck has about 195k. If you think it is a bad coil, they are around $80 at advance auto. I recommend just buying one and trying to swap it around. When I finally figured out my problem, I asked the mechanic if I should replace all the coils and he said they only replaced one at a time as necessary.

Good Luck!

-Hackjob