Hey All,

Hoping maybe someone else has been thru this same issua and ca share their experience. Currently getting p0404, p0405, p1404 codes, relating to the EGR valve readings. I've only got a low-end scanner, and no way to command the EGR during troubleshooting.

But I'm wondering if anyone thinks that there could be a wiring issue that could be part or all of the problem, and not the EGR valve itself? I ask, because I've changed the EGR valve probably 5 or 6 times so far, and this last time, the codes started popping backup maybe a little over a week after the latest new valve assembly.

I don't have access to the probes needed for my voltmeter at this time, to start probing all of the wires, but do have a good local shop that I would entrust for the job if it seems like there could be a wiring problem.

But I did purchase the EGR from the parts store with a lifetime warranty, so at least I've been able to get a new one the last few, without having to buy outright again.

Engine performace does seem to be affected currently. So I think there is really something not right at the moment. MPG has dropped, and I seem to notice a small stumble at cruising speed every once in a while, very briefly.

Would like to hear your thoughts on the matter. Thanks!

 

A very common problem is chunks of carbon break loose and lodge in the pintle valve, which holds the valve open slightly. Along with setting DTC's and turning the SES light on, the symptoms can include stalling at idle, hesitation on acceleration, or a stumble at steady speeds. If carbon chunks are the problem, this gasket has a screen that breaks them into smaller pieces that won't get stuck in the valve. Most auto parts stores have the screened gasket, or can get it for you, typically the cost is under $10. (your 98 uses the triangle shaped gasket)
Dorman Products - Search Results


If that doesn't correct the problem, the DTC's will need to be diagnosed in the order they are retrieved. Here is a list of diagnostic flow charts for DTC's: https://blazerforum.com/forum/tech-a...agnosis-26408/

 

Thanks for the response. Will removal and cleaning of the valve solve anything, or are there carbon chunks always flowing thru the system? I have had success in the past simply swapping valves entirely. But last time at the parts store, the clerk suggested that maybe I have another issue, if I'm indeed going thru these valves yearly at best, and in the case of the last one, having trouble a week after install.

I do know that the gasket that comes with the part I've been getting, is not screened. But I have been using the Dorman brand valve, after having the 'house' brand one only last a couple months the first time before re-lighting the SES. To date, my 'fix' has been just getting a new valve each time, after cleaning did not seem to make any difference. But now I'm curious if I might have an underlying matter that I've incorrectly diagnosed as simple valve replacement. The truck only has 78,xxx miles on it, and I'm probably on my 6th or 7th valve, which seems silly.

So far have not experience any stalling, or noticeable hesitation. And a very infrequent 'stumble'. I will need to make note of the 'order' of the codes next time I scan. I was able to remember them in numerical order, but that's probably NOT how they were, in all honesty.

More to come later. Thanks again.

I will check out the diagnostic flow charts, but being winter time, I may send it into the shop instead

 

There is a steel tube that runs from the rear of the engine, up and along the driver side rocker arm cover, then into the intake manifold near the A/C compressor. The tube has a braided insulation material around it. When the EGR valve opens, exhaust flows through the tube, through the valve, and into the plenum, and burned. The accumulation of carbon is normal, and not a whole lot can be done about it, except maybe try another brand of fuel. Certain fuels tend to produce higher levels of carbon than others. The carbon deposits break loose and flow through the EGR valve. The screen pretty much pulverizes the carbon so it's not an issue.

If the SES light is on, there's probably a piece stuck in there now. Try cleaning the valve with carb spray first, but don't move the pintle, (it will break the gear inside the valve). If the light shuts off, you shouldn't need to replace the EGR valve again once the screen is installed. I service a fleet of vehicles with 4.3's, one of them has almost 400K miles, and several in the 200K to 300K range. All have the original EGR valve... with a screen

 

I don't have a 'usual' fuel brand, pretty much whatever I might be near when the need arises, so I doubt that I'd be able to point at any specific brand as causing me more than the next.

Will try a quick remove and clean as you suggest. I will admit to playing around and moving the pintle on previous ones that I ended up replacing, usually when I would get frustrated and the cleaning didn't seem to resolve anything. I'll also stop by the store and see what they can do about getting an EGR gasket with screen like suggested. I would be thrilled if it were that easy. Honestly, I've read the various flow charts for each of the codes, and don't yet COMPREHEND what they are trying to tell me. As much as I feel I should be able to understand the function of the system better, it's just not 'clicking' for me yet.

Should I clear codes before I remove and reinstall, or will the light go out if the problem is resolved?

Thanks again for the input.

 

Clear codes after you remove, clean, and reinstall the valve.

 

Fwiw, I cleaned my egr valve and it seemed like my acceleration picked up. My gasket was not screened either.

 

Well, so far so good. I decided on Saturday Am that I would take a run to the salvage yard, and grab a different EGR valve, so I could swap out and see if I was still having issues, just out of curiosity, and since they can be had pretty cheap.

Found another '98 to pull one from. Cosmetically the housing looked different than the Dorman ones I had been getting at the parts store. Wondering if maybe I have an actual OEM part now? Had a bar-code type marking on it, I don't know. Anyway, once I pulled that from the engine there I was greeted by a very clean underside. Virtually no blackend coating on the pintle end. The gasket under that was not screened by the way. I don't know what kind of mileage this salvaged valve may have seen, of course.

So when I got home, I pulled the current EGR that I had, which was maybe 3 weeks to a month old, and while it did not start out with any malfunction, about 1 week into it, I started getting the p0404, p0405 and p1404. They were in that order on my scanner, actually, FWIW.

No visible carbon particles in the "new" aftermarket EGR, but it did have a fairly thorough coating of black. I took it off, and sprayed it with carb cleaner. And I did pick up a screened EGR gasket kit which I was going to use under the next aftermarket EGR, since I did buy the lifetime warranty for that part. But before that, I decided I would quick try the salvage yard piece. Installed that, cleared the codes, and started the truck.

No more SES light, and it has not re-lit since. Have made a few local trips as well as some highway driving, and as I started this post, so far, so good. So I still have the aftermarket EGR which I suppose I will go exchange for a 'new' one, since it's warrantied. But I'll probably just run the salvage yard piece for now and keep the fresh aftermarket one on the shelf for if/when I ever need it.

I suppose I could still try reinstalling the cleaned aftermarket one, to verify that it wasn't just some sort of blockage, but I'm tempted to leave well enough alone with it as-is right now.

I was surprised at how clean the salvage yard piece was on the pintle side. especially compared to my 1-month in service unit. Although I did experience an injector issue soon after install, but after the initial EGR codes registered, and the truck was running terribly rich for a bit there. But is there anything that can be done to reduce carbon build-up as a whole? Fuel brands were mentioned early on as being a factor. My typical drive is 30+ minutes each way to work and back, so the engine doesn';t have any issues like short trips not getting up to temp or anything like that.

 

The valve should only open when cruising at a steady speed with the PCM in closed loop. If the valve doesn't seal tightly, it will constantly have exhaust flowing through it. That can cause a hesitation on accel, stalling, misfire, surging, hard starting, carbon build up on the pintle, crappy fuel mileage, AND set a code. Sounds like you've got it under control now. Keep an eye on it and let us know if there's any problems with it.

 

So is the flow in at the pintle, and out the other hole, or do I have that backwards? Still trying to learn a little more about it for future reference.
But hoping that I won't need to work with this valve again for quite some time.

And thank you a TON for sharing your knowledge so far, it was VERY appreciated!