Ok, I have failed Emissions becasue of NOX.

I hooked up a gauge to the line from the line that goes from under throttle body to EGR SOlenoid and I found out Im getting very little Vacuum, (getting 2 hg when i should be getting around 10hg at 3,000 RPMs) can anyone help me out? Why am I getting so little Vacuum from Throttle Body to EGR Solenoid. I have cleaned out the passages and I have replaced the lines. HELP!!!

 

your timing could be off. Also try getting a small bottle of propane from the hardwere store, and spray it around your vacc lines, if the idle changes, you have a leak

 

TTT

 

My timing is fine....any other suggestions?

Can it be my Throttle Body?

 

 

Hello?

 

Is this a TPI, I assume?

That sounds wacky. That port should pull full manifold vacuum at all times. The EGR solenoid, run by the ECM then "vents" some of the vacuum to bring it down to whatever it needs to run the EGR valve (venting all of it, none of it or some of it, depending on how far open it wants the EGR valve to be open). The "vent" is what looks like an unused vacuum port on the EGR solenoid.

First thing I'd do is to plug your vacuum gague into the port on the bottom of the TB directly- don't patch into the EGR vacuum lines for this test. Start the engine and check vacuum. It should be full manifold vacuum- 15-20" or whatever your engine is capable of pulling at idle. If not, you've got something REALLY weird going on.

Now do the same test again but by patching into the EGR line between the TB and the EGR solenoid. Patch in near the solenoid end. Disconnect the vacuum line between the solenoid and the EGR valve itself. Start the engine and let it idle. You should now be pulling very little vacuum at the patch-in point since the solenoid should be bypassing all the vacuum out the vent. Now put your finger over the vent tube and you should be reading FULL manifold vacuum again. If not, you've got a leak somewhere in the lines or maybe internally in the solenoid.

See where we're going with this?

OK, let's say it all checks out. You have no vacuum leaks in the system up to that point AND we know that the solenoid is at least working in the "bypass" mode.

Beyond that I'd check the operation of the EGr valve iteslf BUT I think the valves can not be "bench tested" with a hand vacuum pump like earlier valves can (they have a vacuum bleed built into them that will outrun the vacuum you can supply with a hand vacuum pump). We dead yet? Nope. Hook up a vacuum line to the port on the bottom of the TB DIRECTLY to the EGR valve. Leave the end of it off the valve itself until you get the engine started and running. Now take this vacuum line and shove it onto the EGR valve vacuum nipple. The engine should almost immediately start to run rough and might even stall. This is good- it means the EGR valve itself is capable of opening and working correctly when given vacuum.

SO....... now you're down to only a few things it CAN be. The EGR solenoid is shot, the wiring to it is shot, or the ECM pin-outs that supply activation voltage to the solenoid are shot.

One word of caution...... depending on exactly how you tested for vacuum at the EGR solenoid previously it's possible that the system itself is functioning correctly, but that the way you did the testing is invalid. Maybe. You see, all TPI engines from about 1987-up have an EGR valve sensor that actually tests to see whether the EGR valve is opening up when the ECM commands it. It's a temperature sensor built into the base of the EGR valve itself and it clicks on when hot EGR gasses are actually flowing past it. If your EGR valve were not actually opening you WILL get a check engine light indicating EGR malfunction after you drive around for a while. You didn't mention you were experiencing that so I offer that you may actually have nothing wrong with the EGR system at all and that your high NOx readings are due to something else.

 

It is a TPI and I hooked up the vacuum gauge directly under the throttle body. Everything else is fine, EGR Valve is new, EGR Solenoid is new, and my Catco cat has about 5K on it.

Im only getting about 2 Hg, i should be getting at least 10 hg.

I've taken it to a mechanic and they said they also were only getting about 2 hg and that I should clean out the Throttle Body with Carb Cleaner and it should be fine, if not replace it. I cleaned it out real good and Im still getting low vacuum and I highly doubt replacing it will fix my problem. I do have an Airfoil on the Throttle Body, but that shouldnt affect vacuum...Can it?