I have been fighting the EGR for 2 months now tring to get my truck to pass emissions. Basically I think what it boils down to is the EGR is not getting enough back pressure from the exhaust. If you remove the vacuum line from the EGR, I have good vacuum there. But if I "T" in with the Vac. gauge at the EGR I dont get but -2 vac. What I believe is happening is when the EGR opens the back pressure drops and the Modulator doesn't stay closed causing a vacuum leak. Modulator has been tested on another truck and works fine.

Any Ideas on fixing back pressure? I tried a 1 inch restrictor plate and it didn't make a difference. I had to basically totaly block the exhaust to get a -5 vac reading.


Edit: Compression readings are 140-80-145-55, probly got some burned valves.

New Compression Numbers 160-160-165-125

Im thinking maybe I have an internal crack in the head causing low pressure to EGR?

 

With those compression numbers the last thing I'd be worrying about is the EGR.

 

Yeah but it runs fine. I just want to pass emissions.

 

You're not gonna pass emissions with those CR's I promise you. When the engine has CR's that low you are not generating enough pressure/heat in the cylinder on the compression stroke to properly atomize (vaporize) the fuel/air mixture. The fuel is going to remain in droplet form due to the lack of pressure and heat and come right out the engine to the catalytic converter. Once this unburnt fuel comes in contact with the catalytic converter it is going to cause the catalytic converter to overheat and eventually fail. You are not going to be getting a good enough Air/Fuel ratio for the catalytic converter to operate correctly even if the unburnt fuel wasn't destroying it. You need to fix your compression issues before you hope to ever pass smog. Sorry to be the bearer of bad news, but like you said, you've been struggling with it for a while, and this is why.

 

You got two dead holes dragging you down. You have to fix the valves or rings and probably both. It may seem to run right but its not.

 

Yeah the low compression is causing low combustion temps which leads to high hydrocarbons..

I'd be looking to rebuild it..

 

My problem in high combustion temps. Here are the emission numbers.


25/25

HC-119
CO-.58
NOX-3626
CO+ CO2-14.7


50/15

HC-114
CO-.59
NOX-3790
CO+ CO2-14.7

I ran some seafoam through it since I took those compression numbers. Im going to try and check them again tonight.

 

New compression numbers are much better. Still a little low on one.

160-160-165-125

Any why Im not getting enough back pressure at EGR? Clog in the head? EGR itself is clean.

 

Your egr is probably the problem. It can be 1 of 2 things. pull vacuum on the valve and see if the motor dies or stumbles real bad. If it does not then your passages are plugged. If it does then is a vacuum issue. You way over thinking the process. If you have vacuum at the valve then you tee it in and you have no vacuum, then the valve its self may have a ruptured diaphram. The vacuum side of the bpv is sealed so your vacuum should not drop off.

Http://916smog.com