EGR Delete - Will I benefit?

[Schurkey]

I have a stupid EGR question for this old thread. On my OBD1 92 5.7, does the ECM know if the EGR is even functioning?

Yes.

Not directly. There's no EGR "exhaust flow sensor" or EGR pintle-position sensor. The ECM assumes the EGR is/is not working based on how the engine responds. Therefore it can still set EGR code(s).

 

[Supercharged111]

Not directly. There's no EGR "exhaust flow sensor" or EGR pintle-position sensor. The ECM assumes the EGR is/is not working based on how the engine responds. Therefore it can still set EGR code(s).

That's fair. I know in the TBI trucks it watches the MAP sensor for that, I'm not sure what inputs it considers in the Vortecs.

 

[someotherguy]

That's fair. I know in the TBI trucks it watches the MAP sensor for that, I'm not sure what inputs it considers in the Vortecs.

IIRC during closed loop, steady state cruise (throttle hasn't changed X% in a certain amount of time) the PCM will command the EGR open to test by then watching the O2 sensor reading in order to see if the EGR made any difference in rich/lean (it should go a little lean.) If not, then it'll set code 32. This is why so many people can drive around with a bad EGR and rarely set a code, because the conditions to get to the test are picky. If one does mostly stop/go driving you're unlikely to meet the criteria for the test to run.

Richard

 

[evilunclegrimace]

Hey guys,

Just looking for some information and advice - I have a 1997 GMC K1500 with a 5.7l Vortec and 4l60E. Currently have a Blackbear performance tune on the way, cold air intake and 2.5" straight pipe. My truck has 480k KM on it.

Very shortly (spring or sooner), I plan on doing some motor work. I've already swapped in a newer 5.7l Vortec with only 160k km and it is clean. The truck is noticeably more powerful and runs a hell of a lot better. I have long tube headers on order and plan on putting the largest cam possible with stock Vortec head clearances and possibly boring .030 over.

My question: I've seen and watched EGR deletes done on these old trucks. Some people claim you will have more power and slightly better fuel economy by deleting the truck, but I don't see that being possible. The EGR is recycling unburned gas, theoretically making it have better MPG than without. Will I actually gain anything from deleting the EGR? I would guess that performance gains would only be 3 - 5HP, but I don't know much.

NO

 

[Erin]

IIRC during closed loop, steady state cruise (throttle hasn't changed X% in a certain amount of time) the PCM will command the EGR open to test by then watching the O2 sensor reading in order to see if the EGR made any difference in rich/lean (it should go a little lean.) If not, then it'll set code 32. This is why so many people can drive around with a bad EGR and rarely set a code, because the conditions to get to the test are picky. If one does mostly stop/go driving you're unlikely to meet the criteria for the test to run.

Richard

From what I noticed in my 94, I had to be cruising above 50, and the truck around operating temperature, for it to set code 32.

 

[PlayingWithTBI]

From what I noticed in my 94, I had to be cruising above 50, and the truck around operating temperature, for it to set code 32.

Yep, IIRC the engine has to be up to operating temperature and cruising over 45 MPH with light throttle for the ECM/PCM to open the EGR.

The EGR was invented because manufacturers couldn't meet NOX emission standards with the old technology 2 way pellet Cat. It was not developed to increase/decrease MPGs.

 

[b454rat]

I had the EGR tuned out on the 99 Tahoe I had, didn't ask but was tuned out lol, but I didn't notice a difference....

 

[L31MaxExpress]

IIRC during closed loop, steady state cruise (throttle hasn't changed X% in a certain amount of time) the PCM will command the EGR open to test by then watching the O2 sensor reading in order to see if the EGR made any difference in rich/lean (it should go a little lean.) If not, then it'll set code 32. This is why so many people can drive around with a bad EGR and rarely set a code, because the conditions to get to the test are picky. If one does mostly stop/go driving you're unlikely to meet the criteria for the test to run.

Richard

Almost all TBIs I have messed with watch for a rise in intake MAP to determine if the EGR is active, not 02 voltage.

 

[L31MaxExpress]

NO

I absolutely had added power and mileage with the EGR turned off in my 97 Van. Vortecs have a tip-in stumble when the EGR opens near 100% opening at like 2 mph at part-throttle from the programming. It is really not all that noticeable until you enable it again after it has been off for a while. The loss of-low speed power especially at part throttle has you dipping further into the pedal, which burns more fuel from having to rev the engine higher with more throttle opening. On the highway at steady speeds the PCM commands very little EGR opening, so it contributes very little to highway mpg. Even at WOT if the engine is not in PE the EGR valve is basically wide open as well.

TBI engines I have had my hands on also seem to do better on fuel with it deleted. More torque, less throttle, more vacuum, less fuel delivery.

 

[Supercharged111]

Almost all TBIs I have messed with watch for a rise in intake MAP to determine if the EGR is active, not 02 voltage.

I had assumed he was talking Vortec here.