Westers Garage has been doing programing for me for some time. Have an 89 K1500 with 7747 computer, used to run Edelbrocks TBI to MPFI conversion system but changed to Vortec heads and Edelbrocks Hi Flow tuned port setup, TB flows 785cfm. This is an older problem for me even with the original Edelbrock tune, the check engine light comes on in cruise on the highway- code 32 which seems to be a common problem. I have been told that the GM EGR valve is a 'balanced' valve and since my exhaust works so good its screwing up the valve with not enough back pressure. I looked into part numbers and the '91 vette EGR is different than the Camaro EGR valve, I was thinking that since the vette exhaust is so much better than the Camaro it may work for me- also the vette plumbing is similar to mine in that EGR tube comes off the header. The code was shut down so the light wouldn't come on, but it seemed to impede EGR function- right now under heavy throttle there is pinging, with the code off pinging was present even at moderate throttle. In the past I used 94oct all the time and now am using 89oct- so if the tuning wasn't great the 94oct is now no longer a crutch. My mechanic suggested that I get a 'universal EGR' with the disc orifaces and experiment with the disc's- I really don't want to tear down the manifold multiple times. I know there is alot of experiance out there- hope you can help me out. davefarr@telus.net

 

Here's what I know about "stock" gm egr systems. You have a dual pressure egr valve 89 TBI truck. In a dual pressure egr, exhaust pressure (back pressure) flows up the center stem of the valve and opens a check valve within the top of the egr and does not allow the vacuum source to open the valve. So in this part of the valve operating range if back pressure IS present, the valve will not open. So the opposite is true to open the valve, if there is a lack of back pressure, then the vacuum applied can open the egr valve. So in a good flowing exhaust system, the only bad egr side effect can be a valve that opens when it shouldn't. I usually see egr failures as being a valve that opens just off idle, always because the stem gets carboned over=stem carbons over, no backpressure=applied vacuum will open valve.

So my suggestions are; manually pull valve open with your fingers on the diaphram with engine idling, look for a big rpm drop=valve is flowing of rpm falls & starts to run rough. Check for vacuum at solenoid if equipped, or at ported source. Check solenoid for electrical power. Ohm solenoid for cont. Something in neighborhood of 12ohms-don't quote me on ohm spec, I have to look up.

Ok if all these are ok. Its more complicated. In most stock gm tbi trucks, the way I see the ecm knowing the egr opened is by commanding egr open & looking at oxygen sensor. ECM is expecting a rise in o2 voltage. So now if all items are good mechanicly you need to look at the scan data. It could be the tune is really lean at cruise and egr opening doesn't provide much o2 enrichment.

I don't see any benefit to changing egr valves from Camaro to Vette.

All this is probably meaningless if you aren't using the original egr valve. But it may help you figure out other dual pressure valves.


edit- Vortec heads require an external egr supply tube on stock applications, I don't think these heads have internal egr supply ports. Do you have an external egr supply? Do the manual valve opening first. I have a Vortech headed HT383 TPI set-up running around on 87 octane & no egr in a 93 K2500 SDPC intake and no ping. I can send you my .bin if you want to look at it.

second edit- From my search, Vortec heads don't have an egr passage within the heads, you must have an external supply tube so if you don't have a supply, start there.

 

Thanks, this is great. The EGR is routed externally off the passenger side header and as per Edelbrocks TPI intake like the vette and probably the same as your SDPC but you have it blocked off. I have to pass emissions so I kept it. I will have to datalog- there doesn't seem to any dyno here that is capable of reading emissions and what the computer is doing. What is your compression ratio- mine is 9.5:1, 19lb ford yellow top injectors at 55psi at idle vacume line pulled, current cam is stock vortec with lobe separation of 111deg. Please send me your bin and I can forward it to Lyndon for study- whats your total advance, I believe he has mine at 28deg at 2000rpm which my mechanic thinks is excessive.

 

I already had this engine through emmissions, passed with flying colors CO 0.00, HC 52ppm, NOX ~655, my NOX # may be a little off, quoting from memory, I'd have to call the owner to get exact numbers. In CT we have strick emmissions standards, this was an ASM test on the dyno. Brought to test untouched! As driven daily. Now the motor is a bone stock GM HT383 with 24lb ford injectors, 43 psi fuel pressure,SDPC intake, no egr, tubular manifolds, stock replacement cat from NAPA. As far as timing, if total advance is only 28 from a zero base setting, thats not excessive. Now I'm running a 730 ecm with a 700r4 trans so keep that in mind when you see the bin file, regardless the tables should help out.

 

Dave, did you get get your EGR problem resolved? I have the same code show up also. This is on a 95 1500 with Vortec heads and headers. I've been told the same thing about not enough backpressure but have been unable to come up with a fix. Also do you or anyone else know how to download the Bin fom my chip to my laptop?
Thanks, Walt

 

went thru emissions last week and the nox showed real well, so i actually think that the valve is working, check out the same listing under TPI some interesting info.

 

Did it stop throwing the 32 code? If so, what did you do to stop it
from doing that?