Can bad EGR cause smoke inside engine?

[smagnotta]

All,

I started my 87 Turbo for the first time in a week today and it started out normal, no color or smell from the exhaust, no pinging or sounds, vacuum normal, no codes thrown. The idle was a bit high (1100 RPMs) and stayed high for 4 minutes.

It warms up and then idle is rough, idle is low at 400 RPM, car is barely running, car misfires, vacuum pressure goes way down, black smoke comes out of the exhaust, a pinging sound from the intake manifold and EGR side of the car, and then of all things exhaust smoke inside my engine bay! OK this is not normal. I look and the smoke and the pinging is coming from the driver's side of the engine where the intake manifold and EGR parts are located.

The EGR parts are the original, and it is time to replace all of them, but does it make sense for exhaust to come out of that side? Perhaps the intake manifold is leaking and this smoke is revealing this?

Any thoughts?

Thanks,
Sal

Edit:

From wikipedia:
Exhaust gas recirculation (EGR) is a NOx (nitrogen oxide and nitrogen dioxide) reduction technique used in most gasoline and diesel engines.

EGR works by recirculating a portion of an engine's exhaust gas back to the engine cylinders. Intermixing the incoming air with recirculated exhaust gas dilutes the mix with inert gas, lowering the peak combustion temperatures and (in diesel engines) reducing the amount of excess oxygen. Because NOx formation progresses much faster at high temperatures, EGR serves to limit the generation of NOx. NOx is primarily formed due to the presence of oxygen and high temperatures.

 

[Nick M]

While the Wiki info was half correct, don't use them for really anything. Yes NOx is formed from high temps. It happens when air (nitrogen and oxygen) are superheated. Such as in the engine, or in the upper atmosphere.

Look for a vacuum leak. There is a vacuum routing diagram on the underside of the hood. Check it out to see that all the EGR vacuum lines are hooked up in the right spot.

If you have exhaust smoke in the engine bay, you are either leaking oil on something hot, or an exhaust leak. A leak at the exhaust manifold will pull in air, giving a false oxygen sensor signal, making steady idle difficult. And steady cruise too. Any exhaust noise?

 

[smagnotta]

Any exhaust noise?

No exhaust noise. There is some kind of vacuum leak for sure. It's pure exhaust smoke in the engine bay, not burning oil smoke.

The smoke is coming from the intake manifold / EGR side of the car (driver's side).

When I heard the pinging noise I thought it was rod knock but the car does not vibrate. Also, on cold startup, there is no pinging or clanging. It takes about 5 minutes to start the pinging.

 

[smagnotta]

Symptoms of a bad EGR and I have all of them:

Last 2 weeks:
1- Rough idle
2- Missing, misfire
3- Detonation, pinging
4- Black exhaust smoke

Before:
5- Car stalling after acceleration; i.e at a stop sign (had this intermittently for months; replaced the ISC, cleaned the throttle body and it still happened).

The engine has 125,000 miles and the EGR parts are the orginals, so I think I got my use out of them.

I will replace the EGR parts regardless, and look for any leaks. Some use a "smoke" machine to track down leaks that are hard to find or you cannot hear. Is there any other way to do this?

 

[Nick M]

You have to look at them and see what is hooked up correctly. An EGR test is usually with a vacuum pump and DVOM.

Rough idle is from an EGR valve that is hanging open for one reason or another. Detonation is reduced from EGR, not increased. Perhaps you have a very large leak at the valve and you are pulling in air from the valve, giving you a lean condition, causing your symptoms.