'89 PU, code 32's EGR failures and high flow exhaust
Question:
I’ve got a ‘89 GMC PU with a 350 that I recently installed a Edelbrock Tubular Exhaust and a Flowmaster CatBack system on. Oh, by the way I made a trip to Midas for piece of 3" pipe flared on one end that just happens to be the same length as the catalytic converter if you know what I mean. Sounds good, runs much better. Now for the problems: gas mileage got a little worse,10.5 combined city and highway, seems to run a little richer (which explains the poor gas mileage), and my real concern, code 32’s. Code 32 translates to a EGR failure. I’ve replaced the EGR valve and O2 sensor. The EGR solenoid checks OK. The EGR valve is a backpressure type and AC Delco says the backpressure EGR valves do not like high flow exhaust systems because the EGR valve needs the backpressure to operate properly. The code flags the "check engine light" only at highway cruise so it sounds as if its not opening. I know I can’t be the only person in the world who has put a high flow exhaust and thrown the cat in the trash on this popular type and very common GMC/Chevy truck and experienced a "code32". I’m considering reprogramming my chip to lean it out a little and to possibly mask or disable the code 32 from causing the "check engine light" from coming on but that is my last resort. I’m also wondering if leaning out wouldn’t cause the light from coming on because maybe the richness is what is causing the problem to begin with. Any ideas would be appreciated. Reply to e-mail is preferred. Thanks, Ron
Response:
What causes the code 32 is that the ECM is supposed to detect a decrease in manifold vacuum from the EGR opening. If it does not detect this, code 32 is set. The EGR flow relies on a certain amount of backpressure to open the valve and to cause exhaust flow. Without it, it won’t work right. How do you know it’s running richer? A high-flow exhaust should not affect the O2 sensor. If it puts out more exhaust fumes, well of course it will because you removed the converter. I would suggest putting the converter back on, or a high-flow performance one on if you wish. You do of course realize, removing the catalytic converter is illegal. — Robert Hancock Saskatoon, SK, Canada Home Page: http://members.home.net/hancockr – Hide quoted text — Show quoted text – > I’ve got a ‘89 GMC PU with a 350 that I recently installed a Edelbrock > Tubular Exhaust and a Flowmaster CatBack system on. Oh, by the way I > made a trip to Midas for piece of 3" pipe flared on one end that just > happens to be the same > length as the catalytic converter if you know what I mean. Sounds good, > runs much better. > Now for the problems: gas mileage got a little worse,10.5 combined > city and highway, seems to run a little richer (which explains the poor > gas mileage), and my real concern, code 32’s. Code 32 translates to a > EGR failure. I’ve replaced the EGR valve and O2 sensor. The EGR > solenoid checks OK. The EGR valve is a backpressure type and AC Delco > says the backpressure EGR valves do not like high flow exhaust systems > because the EGR valve needs the backpressure to operate properly. The > code flags the "check engine light" only at highway cruise so it sounds > as if its not opening. > I know I can’t be the only person in the world who has put a high > flow exhaust and thrown the cat in the trash on this popular type and > very common GMC/Chevy truck and experienced a "code32". I’m considering > reprogramming my chip to lean it out a little and to possibly mask or > disable the code 32 from causing the "check engine light" from coming on > but that is my last resort. I’m also wondering if leaning out wouldn’t > cause the light from coming on because maybe the richness is what is > causing the problem to begin with. Any ideas would be appreciated. > Reply to e-mail is preferred. Thanks, > Ron
