Hello to All! Been browsing the BB for some time now and picking up a lot of good info. But I have run across a wierd problem with the EGR on my TBI, but could not find an answer for it.

So here is the issue it has. History on the 92 TBI (this is a 350 from a p/u), rebuilt the motor .030 over, put in a comp cam 12-388-4, run an open element air cleaner, thorttle spacer, every thing else is stock. The computer is from a 92 Suburban. Bought a harness from Howell, and dropped the engine in my jeep. When I got the sensors and seleniods for it, the EGR selenoid had broken nipple on it, so I just plugged off the vacuum port on the TB. It would run ok, but would set a 32 at highway speeds, did not bother me much. I noticed a slight ping under a pretty good load, so decided to replace the selenoid and hook it up.

Here is what happened.......
Idles fine. Give it enough throttle to get it to about 1000-1200 rpm, and the valve opens. Wont run worth a crap unless I get the R's up. If I keep it in the 1000 rpm range, it will almost die. I let the engine idle, and the vavle will close, and stay closed until I just brush the throttle again. I check the valve, it does not stick. So I take a vacuum gauge and connect it to the output of the selenoid. At idle, no vacuum signal. At about 1000rpm, a vacuum sig is present for just a second, enough to deflect the needle to 20, but only for an instant. Then I hooked up a line to the EGR itself and gave it a suck to open it while it was running, and ofcourse it stumbled at idle. When I quit sucking, the valve closes, and it runs fine. I put the everything back to normal, rev it up to the point the vavle opens, then disconnect the input to the vacuum at the selenoid, and the vavle closes.

Where I am confused is, the vacuum gauge on the output of the selenoid is only present for a instant, so why is the valvle staying open after the vacumm signal is gone. When I used the sucking vacuum, the vavle did close when I let go. Could the sig from the ECM be pulsing the signal so fast that the vacuum gauge cant pick it up?

One other thing that may matter for t/s purposes. I have a manual tranny with a speed sensor from Howell, no shift lamp, no AIS. The ECM came from a auto tranny set up.

Any help would be greatly appreciated, and sorry for the LOOOOOONG newbie post guys.

 

Someone on the BB must know the answer to this one....

 

well... even if the valve was staying open, it would run good at all rpms but idle and, possibly WOT. EGR staying open al teh time only makes for a harsh idle but when the throttle opens, the engine smooths out. I found all this out when the electronic EGR on my s-10 was improperly instructed to open by the ecm (just unplugged it to fix that one!). A bad egr staying open will only cause trouble at idle, At higher rpms, the egr is open anyhow. The solenoid, however, could be causing the valve to open eratically. I dont know what effect that would have on you but if it runs ok w/o the egr hooked up, then the solenoid or its operation is to blame.

P.S. Try over at general tech, they may be of more help.