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I love my Chevy Chevette!
Posts: 7
Joined: 04/11
Posted: 06/05/13 06:13 AM

whats up,cause this is whats going down,please help? have 1989 c4,replaced heads with eldobroks 202 aluim heads. the old 194 heads did not have heat riser ports ,new ones do.! will that have an effect on my emmissions. because i cant seem to pass 15 mph NO{PPM} MAX IS 545.MY LEVEL 544.PASS OK. AT 25 MPH MAX NO{PPM}502. MY LEVEL 789,I HAVE REPLACED JUST ABOUT EVERY THING,EXCEPT ??????. IF YOU COULD PLEASE HELP !!!!. THANKS VETTESTER.  

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My first time was in a Chevy
Posts: 129
Joined: 03/13
Posted: 06/05/13 03:30 PM

the EGR supply on these come up over the valve cover in the tube ...
the egr valve is vacuum actuated.. and controlled by the ECM via an EGR solenoid mounted near the EGR valve..

do you have a vacuum gauge??? that you can tee into the hose between the EGR solenoid and the EGR valve to verify that the EGR valve is getting vacuum signal when you are driving the car...

i am taking that the speedo is working.. and that you can see MPH on the scan tool when you are driving..  as the EGR will not be commanded open at idle..  and it will not be commanded to open unless the vehicle speed is above 20 MPH..  viewed on the cluster and on the ECM via a scan tool..

so... do you get EGR vacuum as you test drive the car...  gauge should be on the windshield..

when you apply direct vacuum.. and have the engine revved up slightly .. does the EGR valve actually open... this is more than likely a back pressure type of EGR valve.. where it needs exhaust back pressure before it will close a valve in the EGR valve and then it will respond and open when vacuum is applied..

do you have a scan tool... i think we talked about this before..

warmed up at idle...

RPMs.. 450 to 600 RPM
TPS 0.53 volts at idle..
IAC 20 to 50 counts.. Idle air Control...
ECT 195 to 235F coolant temp unless you have chipped the ECM....
IAT 65 to 90 F running.. depending on ambient temp.
MAF  0.6 grams per second at idle.. or is it 6 grams per second..

block learn... 128
intergrator..   128..

injector pulse width 1.2 to 1.4 MS at idle..

O2 cross counts..  at 2500... over 20... is expected..  

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My first time was in a Chevy
Posts: 129
Joined: 03/13
Posted: 06/05/13 04:13 PM

i did some editing..


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I love my Chevy Chevette!
Posts: 8
Joined: 02/13
Posted: 06/10/13 08:35 PM

By any chance did you blow a head gasket with the old heads?
  The reason I'm asking if the cat has anti freeze in it you emmissions will suffer.


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