7.4 EGR bypassed

[JimRMac]

I just bought a 97 c2500 Suburban with 7.4l. PO removed upper intake to replace fuel regulator and twisted the EGR tube closed while trying to disconnect it. He's been running the truck that way for a couple of years. He just unplugged the pigtail on the EGR valve. Truck seems to be running fine. This truck wont be a daily driver but I do plan on towing with it. What harm is being done to engine/exhaust components leaving it like this? Second question: I see replacement tubes on Ebay running anywhere from $35 - $80 for a new one vs. $200+ for a stock used one. Anybody have info on these new replacement tubes?

 

[someotherguy]

I just bought a 97 c2500 Suburban with 7.4l. PO removed upper intake to replace fuel regulator and twisted the EGR tube closed while trying to disconnect it. He's been running the truck that way for a couple of years. He just unplugged the pigtail on the EGR valve. Truck seems to be running fine. This truck wont be a daily driver but I do plan on towing with it. What harm is being done to engine/exhaust components leaving it like this? Second question: I see replacement tubes on Ebay running anywhere from $35 - $80 for a new one vs. $200+ for a stock used one. Anybody have info on these new replacement tubes?

Haven't seen the replacement tubes, got a link?

Furthermore haven't seen factory new ones available (discontinued) unless there's been a change in supply. Link to those would be helpful, too.

As far as running without a functioning EGR, that will result in higher combustion chamber temps which can (and usually) does lead to preignition, aka spark knock. This will cause the PCM to pull timing back and lose a little power. Excessive spark knock leads to engine damage. A custom tune can compensate for this by changing the spark advance tables. Or, just fix the EGR...

Richard

 

[1998_K1500_Sub]

A custom tune can simply disable the EGR from being enabled altogether. On a 1998 it's a simple change to one ECU parameter, the other OBDII systems are likely identical.

 

[Schurkey]

Not emissions-legal, will fail inspection if that's done in your location.

Increases NOx emissions.

As said, often leads to "ping", "knock" or detonation, which makes the knock sensor crazy, which reduces power, reduces fuel economy, and reduces throttle response.

 

[JimRMac]

I dont have to worry about issues with an inspection, not required where I live. The new tubes on ebay are aftermarket, none have name brands except for one made by Dorman. The Dorman one is about $80. I figure the used factory tubes are high since this is a discontinued factory part. I'll probably just replace the tube, providing I can get it loose from the exhaust manifold. THAT looks like a fun job!

 

[1998_K1500_Sub]

Buy the equipment to remove it from the tune, and then it's out of the picture forever.

Afterward, you can use the equipment to tweak the ECU as you wish... e.g., remove the "flutter" from your gas gauge, that's a popular problem, via ECU tune. Change your shift and TCC lock/unlock speeds, power enrichment enable delay, etc.

This tool works on 1996 and later.

@df2x4 and I have both used it, possibly others. It can be bought through many channels.

No, I don't work for them.

14005 Jet Performance Dynamic Spectrum Tuner Programmer – Jet Performance Products

jetchip.com

 

[someotherguy]

I dont have to worry about issues with an inspection, not required where I live. The new tubes on ebay are aftermarket, none have name brands except for one made by Dorman. The Dorman one is about $80. I figure the used factory tubes are high since this is a discontinued factory part. I'll probably just replace the tube, providing I can get it loose from the exhaust manifold. THAT looks like a fun job!

Thanks for the heads-up on the Dorman part. Last time I looked for this item (years ago) I don't believe anybody was offering them. The Dorman part # for the Vortec 7.4 EGR tube is 598-169 - which by the way is currently $65.49 on amazon.

At the moment there's one listed on amazon "used - like new" for only $40.

Richard

 

[Keeper]

Dorman 598-169 Dorman EGR Tubes | Summit Racing

Free Shipping - Dorman EGR Tubes with qualifying orders of $109. Shop EGR Tubes at Summit Racing.

www.summitracing.com

I just installed one of these last week on a 7.4 that had the original twisted up. No issues.