"Heated Exhaust Gas Oxygen (HEGO) sensor - voltage signal indicates "lean" (Bank #1).

I've had this code for a while now, in fact I've had it since I had the code for the bad ICM unit, which I successfully replaced with the help from the fine folk on this forum. After replacing the ICM, coil packs, and plug wires, the truck ran like it was brand new, so I ignored this code.

However, recently when I punch the gas, the rubber tubing tieing the DPFE sensor to the exhaust manifold would detach and I could hear air hissing. I figure that maybe the DPFE sensor is bad, but that would trip its own code 326 and 327. I had no such codes, so I can assume that the DPFE sensor is okay. So to fix this problem I screw clamped the rubber hose down on the exhaust manifold nipple like tube, and now it does not blow off.

But what I have now is very, very weak acceleration, and when I punch it, especially going from 1st to 2nd gear, I hear a hissing noise like air is either escaping or something is clogged. It almost reminds me of a blown head gastket, but I know its not that.

I personally think it is my cat. converter AGAIN. I've already replaced it once, but I ran the truck on the new cat for a few lenghty test rides trying to figure out what was wrong...when I eventually figured the truck was only running on 2 cylinders because the ICM was shot. This means I ran my new cat with fuel being dumped in and it being colored a bright, cherry red. I am sure I messed up the new cat because of this idiotic move on my part. I can even hear parts of the new cat rattling around inside the new cat.

So I think this is my problem - a messed up cat. converter AGAIN! I think that my original melted down also from all that fuel being dumped in too, but I wish I would have caught on that the ICM was shot before I wasted $100 on a new cat. converter.

Who votes that I just mash out the insides of the converter and throw the thing back on? Can I do this?

And what about this code? Could it also be contributing to acceleration issues?

 

Simple, fix you vacuum leak, you code is not a sensor code. It means the sensor is detecting a lean code that 9 times out of ten is caused by a leak in the intake. By intake I mean anywhere between the MAF sensor and the intake valves.

Sounds to me like you need to do some diagnostics. Sorry you wasted your money on a cat, none of you issues point in that direction, you came up with that on your own. Forget about EGR as well, you have no codes indicating an EGR problem, so if you came to the conclusion this is an EGR problem, you have been doing so based on false information.

The code is not contributing to your acceleration issues, its trying to tell you what the problem is. A lean condition will mess up your vehicles entire operations and will make it slower than a dying dog.

Pull your entire intake off, replace all gaskets, replace all vacuum hoses, and clean your MAF, if the problem is still present, chances are you have scorched the intake valves due to the intense heat a lean condition generates.

Don't ignore lean codes. My brothers engine suffered valve damage because he ignored his lean code.

 

My cat was toasted because of an ICM that was non-working. Fuel dumped into my exhaust system and it turned cherry red melting the internals of the cat. converter. The problem is, I thought it was purely an issue of the cat. converter being clogged, so I simply replaced the cat. converter before realizing there were deeper issues. Unfortunately, I ran the new cat. converter on several test runs before I realized it too ran cherry red and most likely was toasted also. Like I said before, I can actually hear the internal parts of the new cat. converter rattling around within the structure itself. So I am very suspicious my new cat. converter is clogged also. I finally figured out what the "deeper issue" was, but unfortunately not until after I drove around with my new cat. converter being subjected to lots and lots of heat.

When cat. converters are clogged, back pressure gets screwed up and acceleration can be affected.

However, with that said, I will definitely take your advice and clean my MAF sensor. That is easy and free and it could very well be causing some issues as it has never been cleaned. I may even take the EGR valve out and clean it up too.

But I have a feeling the root of the problem is that cat. converter, but this time, I'm not buying another one. I am going to gut the one I have and simply put it back on.

 

Excessive exhaust back pressure likely caused the line to blow off the DPFE sensor.

Hook up a vacuum gauge & do the restricted exhaust test.

 

That's what I'm figuring. I dont have a vacuum gauge. I think that test also calls for VERY specific rpms and I have no rpm gauge.

What do you think about just gutting the cat. and putting it back on? I'm also worried about the condition of the muffler seeing as how the internals of 2 cat. converters have broken down and probably tried to make their way through the muffler.

Also, a very important question I think. Would a clogged cat. converter cause the lean code I'm getting?

 

Here is a link to a vacuum gauge tutorial with moving graphics, so look up the restricted exhaust scenario for an exampe of what the vacuum gauge will illustrate.
How to Use and Interpret a Vacuum Gauge

The quick/poor mans check, is to hold your hand over the exhaust pipe opening while someone revs the engine, to see if exhaust flow is puny.

A clogged exhaust isn't likely causing a lean code, but it sure can cause power problems when you rev the engine, not to mention the extra heat the poor engine will have to deal with!!!!

I suppose you could gut the cat while you run down the root cause of your problems, but expect the computer to turn the CEL on for cat conveter efficiency below spec & if you have emissions inspection, you'll have to replace the cat & drive it to clear the code before inspection.

Gutting the cat will uncalibrate exhaust back pressure & may cause driveability problems, so you'll not likely want to leave it that way & doing this isn't lawful, so it isn't recommended you do that.

Find & fix the root cause of the problem & replace the cat converter if need be.

 

Thanks for the advice. I dont think this truck has a sensor on the cat. There is a pre-cat. converter oxygen sensor I think, but a clogged cat or a gutted cat should not turn on the CEL. I am probably wrong on this, but saw no sensor on the original when I replaced it and hooked nothing up to the new cat. converter, so I would assume no way for computer to recognize clogged or gutted cat. Unless the computer picks up info from the pre cat converter oxygen sensor, I cant see how it could be informed of the operation of the cat.

Interestingly, I did have a conversation with the guy that did my last inspection and curiously asked him what he would have done in terms of the inspection if I would have just "straight piped" the exhaust from the manifold straight to the muffler and he said it would automatically fail the inspection because a converter is damanded here in North Carolina. However, he did admit to me that they are not interested in the least about what is inside the coverter as long as it is there. The truck is a 94 so there is no emissions test, just a quick look at stuff and their done.

 

If you have the California emissions set up on your year/model, you may have a post/after cat O2 sensor on/in the exhaust pipe, after the cat. It monitors the cat converters efficiency & will turn the CEL on if the cat is removed, gutted, or isn't doing it's thing.

 

I do agree, that running a straight pipe till you can solve this is a better approach, however, the clogged cat is not causing your problem, the problem is being caused by the lean condition, and the lean condition has also clogged you cat, if it is in fact clogged.

You need to fix the lean condition, and then sort out what is going on, you do not have an O2 sensor issue, and I see no indications that you have an EGR problem, I think you have a massive intake leak. Based on the location you describe, this fits.