Insufficient EGR flow and no 4000rpm surge

[Dalamar]

Hey guys, I've got a 96 SL2 with a code for insufficient EGR flow. The valve is less than a year old and there are no carbon blobs visible in the ports under the valve, though I did clean some out of there when I originally changed the valve.

Based on that, and the fact that it does not surge to 4000rpm if started with the EGR valve off, does this mean the port is clogged with carbon somewhere within the intake manifold?

I've read that if one feeds compressed air into the EGR port, that it should be possible to feel it coming out of the throttle. I tried forcing air into it (with a gas station tire hose, as I don't own a compressor) and did not feel anything from the throttle. There was a lot of air coming out around the sides of the hose, which I guess means that it couldn't pass through the port.

If the EGR intake is clogged would that result in my DTC, and if so then how do I go about cleaning it?

[Dalamar]

Also, I guess I should note what's been done to it lately. I got it inspected a couple of months ago but I can't recall if it didn't have the code then, or if I just got around it by having that sensor Not Ready during the inspection.

Anyway, since October I've changed the plugs and wires, EGR valve, ECTS, EGR and TB gaskets, and air filter. I have cleaned the throttle body, IACV, and TPS.

[Dalamar]

Hmm, well today I pulled off the TB and looked inside the intake. It looks like there's mud in there, particularly in the EGR runner entrance, which was completely filled. I scraped some gunk out of it, and sprayed carb cleaner in it from that end. It just pools there because it's so clogged.

So I have to find some way to clean it out, or take the intake off and clean it that way. I know that's the only way I'll ever get it truly clean, but I'm not sure yet what's involved in doing it.

[fdryer]

Your descriptions seem accurate about a thoroughly plugged intake manifold passageway for exhaust gas flow requiring removal from the engine. Unless someone else has a better way of cleaning a plugged passageway, removal and soaking in ammonia can loosen this sludge build up.

[madpogue]

With both the EGR valve and the TB off, put a rag in the manifold just past the EGR runner, to block the chamber runners off. Then try a shot of compressed air into the port at the EGR valve end. ___MAYBE___ the "sclerotic tissue" will get blown out the TB hole.

Or, if you think the bulk of the obstruction is toward the EGR valve end of the passage, do the opposite; leave the valve off, and run compressed air down that passage from the TB end.

**MIGHT** avoid from removing the manifold.

[Dalamar]

Okay, through repeated soakings with carb cleaner, and scraping with a hanger wire, auger, and a plastic drain cleaner, I've gotten it open at least some. I scraped out everything I could see at the top, and I can now spray carb cleaner in through the top and have it eventually come out the EGR end. I have to believe there's more in there, but how much I don't know.

It occurs to me that the right angle fitting that screws into the bottom of the manifold looks like it would probably lead to the EGR runner shaft, and might allow me to clean more gunk from the bottom if I removed it, but I can't be sure of that as I don't know what it is, or what that hose goes to. I'm also concerned that if that hose does in fact enter the EGR runner, that the hose may have gunk in it as well, and so it might benefit from cleaning. Is this worth investigating?

Would it be worth dumping some seafoam into the EGR runner and letting it sit overnight, to perhaps loosen up whatever is left?

I've attached a picture of the connection I'm talking about.

Thanks for the replies - I wouldn't have gotten this far without this forum.

[Dalamar]

Hmm, apparently the picture didn't get attached properly.

[jpeters2]

That hose is the hot water supply to your heater core. No connection to the EGR system.

[Dalamar]

Ah, thanks. It just looked like it went into the side of the intake. No need to mess with it then.

[1996SaturnSL2]

[QUOTE=Dalamar;1622969]Hey guys, I've got a 96 SL2 with a code for insufficient EGR flow. The valve is less than a year old and there are no carbon blobs visible in the ports under the valve, though I did clean some out of there when I originally changed the valve.

Hello, I also have a 96 SL2 with the "insufficient flow" code. The engine still runs like new and I get great fuel mileage with 178K miles on the clock, but I can't pass a SMOG test until this is fixed. I installed a new oil and filter, EGR valve and gasket, thermostat, water pump, tried running every type of fuel system cleaner with every fill up, have sprayed the throttle body and under the EGR valve and still keep getting the P0401 code. I also tried removing the EGR and starting the engine a few times to blow out the carbon from the passages. The engine did not race to 4000rpm and very little if anything came out from the passages below the EGR. I hate to do it, but must I remove the intake manifold? What passage/s will I find that is clogged or restricted when I remove it?

Are there only four passages in the intake manifold (for the four pistons) that must be cleaned before re installing it?

Also, my coolant reservoir tank does not really hold high pressure due to stripped threads on the tank, but it does not leak or overflow, the level always remains the same at the safe level. Will not having pressure in the reservoir affect the EGR system flow?
Thanks for any help.
Dan

[fdryer]

1-With the egr valve removed and engine running, what rpm are you seeing? Generalizing doesn't help. If the engine doesn't rev up then the intake port of the intake manifold is caked up from years of carbon buildup. You'll only have to remove the intake manifold once to clean out the port.

2-The cooling system has no effect on egr valve operation. Something may be wrong with your cooling system as all cooling systems will boil over when the system isn't sealed. The coolant cap is a pressure and vacuum valve. When working correctly, the cooling system will heat up and generate pressure. The cap seals to keep pressure high enough to raise the boiling point of coolant. An open system that isn't sealed will simply boil sooner because of the lack of pressure. If your cooling system doesn't boil over with a broken seal from stripped threads on the container then either the thermostat is running cold or missing.