Shaky Idle?

[2seater]

I would have to look at the idle speed command in the chip to tell for certain, but it is in the 600-650rpm range in drive, warm.

 

As for the moisture in the EGR passage, I would venture that is condensation. If not fully warmed up, it wouldn't be unusual, even though it is ahead of the catalytic converter, there is still plenty of water vapor in exhaust gas. There is no possible connection from that port to the cooling system.

[heygibb]

On 8/30/2017 at 3:30 PM, 2seater said:

 

 

As for the moisture in the EGR passage, I would venture that is condensation. If not fully warmed up, it wouldn't be unusual, even though it is ahead of the catalytic converter, there is still plenty of water vapor in exhaust gas. There is no possible connection from that port to the cooling system.

 

Good observation. The EGR passage definitely collects moisture. When my idle was sketchy, my exhaust was full of white smoke until it warmed up...a clear indicator of moisture. After I blocked off the EGR, the white smoke/moisture problem went away.

 

[2seater]

I know it is counter-intuitive, but a properly working EGR usually helps fuel mileage, especially at cruise. I have blocked the EGR on a couple of different cars, one was a Saturn and the other a 4 liter Ford Ranger. Both had failures of the system, the Ranger had a terrible lope at idle and while the Saturn idled well, just off idle stumble made it almost un-drivable. Blocking the EGR did cure the drivability, but the Saturn lost 2-3mpg, due to the timing constantly retarding due to knock during cruise. This was a work car driven in a 70 mile loop each day and I kept track of everything I did to monitor the mileage, fuel additives, snake oil, cruising speed etc... The mileage drop was immediately noticeable and a scanner showed what was happening while cruising. The Ranger does not use a knock sensor, and has always had abysmal fuel mileage since new, so there was little to tell if the engine liked it or not, but the plugs were bone white. I suspect the lousy timing control is part of the reason it gets such poor mileage. In any case, the EGR systems were repaired on both vehicles, the Saturn mileage returned and the Ranger now ran without a hiccup. If I understand the theory correctly, introducing semi-inert exhaust into the intake, requires the throttle to be open further for similar power, reducing engine pumping losses from less restriction in the intake tract.

 

Watch the knock counts in diagnostics while driving and see if you get knock counts at light to medium steady cruise. If nothing shows up, it may not care about the lack of EGR. For the record, the early L27 3800 with the aluminum TPI manifold did not use EGR, but GM added it back in for later models. Must be a reason.

[Ronnie]

I put a block plate under the EGR on my Blazer, 4.3 when I first got it with 31,000 miles. It accelerated fine and idled well. The problem I had was at cruising speeds in high gear I could feel a surge on level ground. It was under warranty so I took it to the local dealership. My friend who worked there knew exactly what was causing the surge as soon as I told him about it. He said the EGR was causing it to run too lean. He told me the cure was to put a block off plate under the EGR but he said he couldn't do it at the dealership. He suggested the 5/32 holes in the plate to keep the ECM from setting a code. To make sure the EGR wasn't defective he installed a new one but the surge continued until I installed a block off plate under the EGR. Installing the plate hurt mileage about 1-2 mpg but it was worth it to get rid of the annoying surge.

[2seater]

I know I am getting off topic but it's funny that my sister had endless trouble with the EGR in her 4.3 Blazer way back when also. The mechanic she always used (non-dealer) would clean it out and get it to run better but he suggested she always run premium fuel to avoid the issue. She swears that it worked better that way. Some systems are simply bad designs and there are many of them.

[Ronnie]

The 4.3s are bad about building up carbon on the valves and pistons. My friend who worked at the dealership recommended going to the floor and let it shift 2-3 gears at least once a month to keep the carbon blown out. He told me that when he replaced the EGR in 2002 and I've never had a problem with carbon. I've never ran anything but regular gas in mine. Overall my '99 s10 Blazer has been a great car. I wish I could buy another one just like it... like it was in 2002 that is. :)