jimp2001

Sometimes my Service Engine Soon Light turns on while I'm crusing. It does not record a code on the computer. I can shut the light off by pulling over, turning the car off for a minute, then turning it back on. If I leave the light on and keep driving, it shut itself off. Anybody have an idea of what is going on here? It's happened about 5 times in the past 2 months, and by the time I can grab a paperclip to get the code from the ECM, it's gone!

Here are the mods I have done to help diagnose the problem:

Open Element Air Filter, IAT sensor installed in cleaner base
Deleted AIR system, removed smog pump and control valve.

Thanks,
-Jim

sqzbox

With your mod's I would suspect it might be a EGR code (32).
It seems wierd that the code would disappear though. I would check the battery cable connections, starter, and ground to the body and computer.

jimp2001

I only tried to grab the code once, and figured it was the same code after that...

So I just checked it again and came up with a code 32... What can I do to resolve this problem? Assuming the removal of my AIR system is making it throw the code.

I know that some people burn new chips to have the EGR turn on at some rediculous temp, that way it never tries to turn on, and will never throw a code, however, I have not yet purchased the equiptment to burn my own chips.

-Jim

PhLaXuS

The removal of the AIR system on an LO3 wouldn't cause that. Quick fix is to pop off the EGR valva and check for Crusty Carbon Bits <-- (sounds like a new cereal!) The real way to check it typically involves a hand operated vacuum pump and a multimeter...

Could also be as simple as a line cracked in two.

jimp2001

I know I dont have any vac leaks... I'll pop off the EGR this weekend, what do I have to do? just clean out all of the carbon in there?

I also heard that you can clean out carbon deposits by misting water into the throttle body when revving the car while its hot. Should I disconnect my exhaust before the cat (so I dont clog my cat with carbon) and give that a shot as well?

-Jim

PhLaXuS

Gotta love old school tricks! I took about a cup of water and slowly dribbled it into the throttle body while holding the engine at about 3000 RPM. It surprisingly doesn't bog down all that much. I'm under the assumption that the hot carbon when flash cooled cracks off so it could shoot out in little bits and clog the cat. Mine was gutted by a former owner so I cannot say if it's necessary -- never hurts to be safe.

I doubt the water trick would clean out an EGR valve due to the layout of the manifold. Cleanign it the "proper" way is easy enough, though. Remove it and you'll see a small pintle -- kinda like a float needle sticking out the bottom. Gently hit it with a block of wood, rubber mallet, etc and the little bits of carbon will fall right out.

Before replacing mine on the engine, I wire brushed the EGR passageways in the manifold and started the engine for a few seconds to blow out any remaining loose bits.

It shouldn't really be necessary, but Autozone/Advance Auto Parts sells a replacement EGR gasket for about $2. I'd recommend grabbing one just in case you need it and returning it otherwise. I've removed about three LO3 EGR valves and the gasket was always good even after years of use.

I may run some SeaFoam through the crankcase & top end this weekend before changing the oil if I find this is a good idea. I'd love to pull the heads and really make certain everything's clean, but that's too much $$ and time that I don't have right now...

jimp2001

I'll do it all this weekend... I have to do valve seals anyway...

Thanks fo rthe help

-Jim

PhLaXuS

After reading up a bit on SeaFoam, it looks to be a decidedly bad idea to run in the crankcase -- so that I'll skip. I think I'll run some through the throttlebody/brake booster line and go smog the Turnpike!

jimp2001

so I popped off the EGR valve today... It was clean for a 16 year old car. Wasn't siezed or anything. I banged it around a bit and got a few pieces of carbon out, but nothing crazy. I'll post here again if it throws a code.

-Jim

PhLaXuS

If you're still throwing the EGR code, go grab a hand-operated vacuum pump. I got an Actron (I think it's model CP7830) from Advance Auto for $40. It's got a pump & gauge combined and measures up to 30" vacuum. With it, you can tap into various parts of the EGR system and make certain everything's OK.

Hopefully, this fixed it, but I went through several EGR valves and a lot of irritation trying to find the problem. In the end, I just needed the right tools for the job.

sqzbox

PHLaXuS, What did the right tool tell you what the problem was?

1989karr

I had the same SES problem. Turned out to be a EGR vacuum solenoid. Perhaps that's the problem? But difference is that I got me a massive......2.8

PhLaXuS

To the best of my knowledge, there is no one piece of diagnostic equipment that you can hook up to any thirdgen and have it tell you what's wrong in the EGR system.

You just have to start at one point in the system and work your way to the end. I first attached the gauge to check mafold vacuum at idle and at ~2500 RPM. Then, I checked it hehind the solenoid for no vacuum at idle, but >12" (I think it's 12") at 2500 RPM, etc... I also manually powered the solenoid a few times to make certain it worked as it should.

Just get a vacuum diagram of the EGR system and an electrical schematic. It's a pretty simple system, but looks complex because it's a mix of electricity & vacuum and snakes all around the engine compartment.

jimp2001

I have a vac pump, valve opens and closes without a problem.

At worst, I'll burn myself a new chip to disable the EGR and buy a block off plate.

What sensor(s) is/are used to determine the EGR is working properly?

PhLaXuS

On an LO3, I'm pretty sure the ECM only looks at the MAP sensor to see a manifold pressure change when EGR is commanded. I think that's it, but there may be more to it than this, so I'd like someone to corroborate it for me...

As far as testing, if you cleaned the valve thoroughly and it holds vacuum for a decent period of time, then it is most likely not at fault. If you feel like more troubleshooting, you'd need a vacuum gauge to test the rest of the system. The PROM trick does work, but you will be making your engine more susceptible to detonation. Either make certain the engine stays cool or run a higher grade of fuel to keep your timing close to where it is now.