99 GMC Suburban - EGR Issues

You need to clean out the passages in the intake. They are likely full of carbon and crud, which is what is causing the problem. Pull the valve off and use some stiff wire or cable to run down the passages. Once you have it cleared out go get a can of SeaFoam or GM top cylinder cleaner and run it through the engine. That will dissolve more carbon and allow it to blow out of the engine through the exhaust. The easy way to use either one is to pull the brake booster line off and allow the engine to draw the cleaner in. Let it draw in about half the can or until the engine stalls. Then shut off the key and let it set for 20 minutes or so. Dump the rest in the gas tank. Now start the engine and take it for a drive to burn off the cleaner and blow the crud out. It will generate a LOT of smoke and spray soot and carbon out the tailpipe. DON'T USE IT IN A GARAGE or enclosed area. Make sure the tailpipe isn't aimed at anything that you don't want covered with carbon and crud.

Hey Steve... no Kleenscreen suggestion??

I put one in my 95 Blazer about 1 year/10,000 miles ago at your recommendation and haven't had an EGR problem since..

Thanks again!

mac

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He could add one. The V-8 intake is just a bit different in design so carbon chunks are usually not the big problem. It is usually the passages themselves.

I looked into the passages to see if there was any crud. I stuck my fingers in there. The insides were black. However, there was no real thickness to the black stuff, just a light coating. I have some trouble believing that this would cause the problem ... but I suppose it is possible.

Thanks Dan

You would need LONG fingers to reach down to the head/intake area where the carbon builds up.

OK, so it looks like Steve was correct. The new EGR valve fixed the problem for two months .... WooHoo. The check engine light is on again. A few days before the light came on, I was starting to feel "EGR" like problems (a little surging, particularly at lower RPMs). So it looks like those EGR passages need cleaning. I did not read the OBDII code yet ... but I'm all but certain it will be a P0404 code.

I don't really want to run Seafoam or GM Top Engine Cleaner (TEC) through the engine since I'm kinda worried that all that burning crud could cause problems. I'm guessing that like it or not, I will have to do the cleaning anyway.

From what I read, after running TEC through the engine I will need to change the plugs and the oil. I am also kinda worried that it could hurt the catalytic converter ... all that smoke going through the converter does not sound good to me.

So as a preliminary fix I got one of those Klean Screen gaskets. I will clean the valve carefully with carb cleaner (without getting any cleaner into the electronic portion) and see if that buys me any time. If that does not work, I'll get the cleaning done.

Thanks again, Dan

The gasket will stop the carbon chunks from getting into the EGR and sticking it open.

The TEC won't hurt anything. It DOES generate a bunch of smoke when it goes through but it won't hurt anything (provided you don't decide to do the cleaning right after the neighbors put all their clothes out on the clothesline, or in the middle of a BBQ with friends, then you may have a problem ;-)).

Yes on the oil, The plugs wouldn't have to be changed unless one of them bridges with carbon after the treatment. The reason for the oil change is to flush out all the carbon that will go past the rings.

I do the treatment every other oil change on the 97 and the 02 just as a prevention. Also do it on a lot of other vehicles. It really helps.

Good Luck.

For sure!! Steve turned me on to the Kleenscreen gasket a few years ago, and it stopped the EGR problem completely... I bought 2 so I'd have a spare and so far the first one is still working great..

mac

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So are you saying this screen gasket for the EGR valve stops the P0404 code from being tripped? Wondering about that since that code indicates a misfire on cylinder 4. It is interesting to see others having the same code though. My '99 Suburban has done this for years, but only if it doesn't get a good running every so often due to my wife using it as a daily driver. Get on it a few times a month and it never throws the code when under stress during a climb mainly at highway speeds. Don't get on it every so often and the same code will throw and it will miss like mad for a few seconds until it clears out and then go on about its merry way.

I've always attributed it to being a weak cylinder and getting deposits on the valve(s). It has over 120K miles on it and keeps on going strong.

Kevin

No idea about that code, sorry.. but the screen keeps carbon from getting TO the EGR valve, so it doesn't bind up..

Our 95 blazer would get a "check engine soon" light and idle very badly and have no power brakes at low RPM.. Had the EGR valve replaced and it the problem went away for a while, then came back.. I cleaned the little pin in the valve and the problem went away again but came back.. Steve recommended the Klean screen to replace the EGR gasket and the problem has been gone for about 2 years..

mac

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P0404 is EGR Circuit Range/Performance.

Nothing to do with cylinder misfire. That would be code P0304

Ooooops!!! That would be correct, P0304 is my usual code if the engine doesn't get "driven" every so often. 8-) I was even questioning myself while reading the P0404......

OK, I verified that the code was indeed P0404. I bit the bullet and did the top engine cleaning. I went to the GM dealer and tried to buy TEC. They told me that it is not made anymore and gave me the "new" replacement called "Upper Engine and Fuel Injector Cleaner" - #88861802. I rigged up nice little funnel arrangement and slowly poured the stuff in through the brake booster line.

Ultimately I poured the whole container in there and let the truck sit for an hour. I started it up and it did the white smoke thing. I decided to drive the truck rather than smoke out the neighbors. It did seem to make a lot of white smoke. I also did some driving at wide-open throttle. I forgot just how anemic the old 5.7 really is. In any event, I can't tell any difference. . The engine still had some EGR like symptoms ? stumble/surge when you give it a little gas ? just off idle. Otherwise the truck runs OK ... not great ? but OK. I will change the oil tonight ... spark plugs seemed to be OK

Next, I took my previous EGR valve that I had cleaned with carb cleaner ? lots and lots of carb cleaner. I put that in with the Klean Screen. I also cleared the P0404 code (so the check engine light is out ? for about a day or so). I can already tell that the "cleaned" EGR valve is no good. The engine still stumbles/surges when you give it a little gas ? just off idle. So ? I went to the store and bought another EGR valve. I already know that when I put the new EGR valve in the engine will not stumble/surge at all (since I have already done this ? twice before). .

My best guess is that none of this will have any long term effect. In two months the new valve will be fouled. It would be great if the cleaning and/or the Klean Screen solves this problem. Only time will tell.

Thanks, Dan

Dan.. I had different symptoms, besides the "check engine soon" light, the real rough idle and no power brakes at idle, nothing else was effected.. The truck ran fine except at idle, brakes were normal unless at idle, (and after the first pedal push and release), and the fuel economy was normal..

I took the EGR valve out twice and both times the pin was frozen from carbon.. After putting the Klean Screen in, it's been trouble free for about 2 years now.. Hope yours is too!

mac

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OK, I put the new EGR valve in. Of course the truck runs correctly now. No stumble/surge at any RPM. Idle is very smooth. Most likely, by June 19 the new EGR valve will be fouled.

I believe that my engine is making lots and lots of carbon. This is obviously what is fouling the EGR valve. I also believe the top engine cleaning and the Klean Screen are most likely irrelevant. It's not chunks of carbon fouling the valve. If this were the case, I should have been able to clean my old valve (i.e., wash the chunks of carbon out) and the valve would have worked again ? but it didn't.

So my theory is that the gasses flowing though the EGR passages simply foul the EGR valve ? within two months. Whether the passages are clean or not, those "toxic" gasses are going to flow through the valve causing it to foul. I'm guessing that either i) the engine is basically worn out or ii) there is something wrong with the way the intake manifold is installed.

This truck has had a lot of problems (way too many). I bought the truck new it now has 118K miles. It is pretty much always "broken". It runs ? it's just never right. The "service engine soon" light was mostly on for the last 80k miles. No matter what I fix ? it does not last and that service engine soon light comes back on within a month or two. For the most part the truck really never ran right. My wife drives it most of the time and she does not really notice or care. I usually hate driving the thing since it usually runs crappy. I went through the whole random misfire fiasco ? too much to detail here.

Anyway, once I got the injectors changed the engine finally ran OK and life was good (for a few months). But then it started leaking coolant. Of course it was not the water pump ? again ? this time it was leaking coolant from the block, at the intake manifold. So the local mechanic changed the intake manifold gasket and the leak was fixed. But its been EGR hell ever since. I took it back a few times ? again too much to detail here.

So I wonder if it is possible to screw up the installation of an intake manifold and cause all kinds of horrible fumes to flow into the EGR passages. If this is possible, perhaps I need the have the intake manifold done again (only correctly this time). In the alternative I could try to make some sort of bulk purchase of EGR valves (since I will need 6 of them every year).

Thanks, Dan

Yes it is possible to screw up the intake gaskets. Do you notice and white or blue smoke from the exhaust? If your not using coolant or oil at a rapid rate I would guess the gaskets are OK.

It is also possible that the valve you purchased just failed.

The gasket is mainly to keep chunks of carbon from sticking the pintle open. The top end cleaner dissolves the carbon and allows it to blow through the system. It also cleans the valve heads, rings, and passages where the carbon likes to build up.

Yep, I'm sure the TEC cleaned the combustion chambers. This is certainly not bad. I'll bet there was carbon in there. But it does not really make a noticeable difference when you are driving. The TEC did not clean the previously fouled EGR valve and I was unable to manually clean an earlier fouled EGR valve with carb cleaner (i.e., an entire can of carb cleaner).

I installed a brand new EGR valve and of course the engine runs "perfectly" ? or at least as good as you could expect from a 1999

5.7l Vortec. The truck does not seem to be using fluids or blowing oil smoke from the exhaust. It seems to run perfectly fine (with a new EGR valve) ? so I am a bit puzzled as to where all this carbon is coming from. I should probably talk to the local mechanic. He spent a lot of time on this truck (as did I). I mean, I bought a darn code reader six years ago just so I could figure out why the service engine soon light was always on. And I used that code reader a lot over the years. The local mechanic fixed lots of problems over the years at very reasonable prices. But this EGR thing has just sucked. He lost a lot of money trying to fix this truck (cause I kept bringing it back)? I'll be lucky if he agrees to work on it again (I wouldn't if I were him).

I took a drive this morning and I actually enjoyed driving the truck. If you press the gas pedal (even just a tiny bit) you feel some acceleration. That is, the truck actually responds. Once the EGR valve starts to go, you just don't feel the responsiveness and often it is opposite of what you want (i.e., you depress the gas pedal and the truck actually decelerates or hesitates or surges ?). With the new valve, the truck feels 500lbs lighter ? it's like a whole different vehicle. It can even go up hills without dropping out of overdrive.

The drivability issues I have with this truck are kinda my fault. The

5.7liter engine was never really adequate for a vehicle this size. I really knew this when I was buying the truck. I should have bit the bullet and sprung for the 2500 with the 454 engine. Of course the 2500 is super major overkill for my needs (and gas mileage would probably be worse than the 5.7l ? if one could actually imagine that) but at least I would have been happy with the power output.

So for now the truck is technically "not broken." Since it is garage kept, it looks almost brand new. It took it to the car wash, cleaned up the wheels and tires, cleaned all the glass and vacuumed the interior. So if I left it in the garage for the next six months and didn't drive it ? it would be pretty and "not broken" for six whole months. But alas, we are going to drive the thing. I will post an update when I have something new to report.

Thanks, Dan