I've just started driving around after a fresh engine rebuild. From the start - when cold seems to idle fine and has part throttle misfire/giveout/stumble. And it's just slight throttle, very slight, like 10%. After that it runs great, lots of power. When hot, idle is hunting like +-200 rpm. Where should I look first? I guess all bets are off since it's pretty much got new everything. Vacuum leak?
Doesn't matter if there's load or not - slight throttle is bucking/stumbling pretty bad.
Thanks in advance.
[This message has been edited by cebix (edited 10-24-2019).]
Ok I think it was the EGR. It's a brand new one. I disconnected and plugged its vacuum line and the problem went away.
What should I do temporarily while i wait for a new one - should I leave it in the manifold as is and just plug the vacuum? Or should i block off the EGR intake-exhaust path too?
It sounds like the EGR valve is too aggressive. It's dumping too much exhaust gas back into the intake, which chokes the engine.
The EGR valve is normally closed; the vacuum pulls it open. So disconnecting the vacuum line and capping it off will disable the EGR.
If you can't find a less aggressive EGR valve, you may be able to address the issue with a custom EGR gasket. The idea is to use a gasket with a smaller hole, to restrict the gas flow. You may need to tinker a little to get the proper hole size. I'd also suggest using a metal gasket for that.
If you can't find a less aggressive EGR valve, you may be able to address the issue with a custom EGR gasket. The idea is to use a gasket with a smaller hole, to restrict the gas flow. You may need to tinker a little to get the proper hole size...
Makes me wonder if cebix is currently using an aftermarket EGR valve with an incorrect washer/orifice installed.
Patrick, you might be right. It's the Standard EGR from rockauto, the $40 one, brand new. It doesn't look like the one in the picture, it's flat at the mounting base. I had no idea of this problem, maybe I can fix it then. Thanks.
EDIT: Yes, it looks exactly like the one in that thread. I didn't receive those washers with it though... I also don't have the original EGR and no way to figure out what diameter orifice should I use. Any ideas how to figure it out?
[This message has been edited by cebix (edited 10-26-2019).]
Yes, it looks exactly like the one in that thread. I didn't receive those washers with it though... I also don't have the original EGR and no way to figure out what diameter orifice should I use. Any ideas how to figure it out?
If the aftermarket EGR valve you bought is supposed to be adaptable to different applications, then you need those washers with the different sized holes (or you'll need to make a washer with the correct sized hole). In regards to which washer/hole size to use, I was in the same situation as you... and my "solution" was less than ideal.
Years ago I had to replace the EGR valve on an '87 duke, and if I remember correctly, the EGR valve I was replacing was an aftermarket unit with no numbers on it to go by. I ended up just guessing as to which "washer" to use with the new unit. I didn't feel very comfortable about that.
[This message has been edited by Patrick (edited 10-26-2019).]
