After converting from carburetor to throttle body injection system I have a persistent code 32 EGR failure. After a few years of replacing all the system components, spending a lot of money, and paying more to have the problem misdiagnosed, I believe the problem stems from a lack of exhaust backpressure.
In a nutshell the TBI ECM is pre-programmed with specific parameters regarding EGR flow. The ECM gets it’s pressure feedback from the MAP (manifold pressure sensor) by triggering the EGR Solenoid to allow flow from the EGR into the base of the throttle body and into the manifold. The ECM reads this pressure change, if the pressure change does not match the parameters the ECM triggers a code 32. The stock 1990 K1500 I pulled my system off of had a restrictive exhaust and high back pressure. The open exhaust on my 77 truck with headers and high flow mufflers creates very low back pressure. The result is an EGR pintle that does not open properly & lower than normal pressure change reading in the manifold when the ECM commands the EGR solenoid to open.
There are several apparent solutions.
1. One solution is to get your prom chip reprogrammed with wider parameters by a company like TBIchips.com. That way you can keep the EGR and have it work properly to get the benefits of improved highway mileage and emissions.
2. Another solution is to have the EGR function eliminated from their prom and then install a block off plate on the manifold port. I know a couple people that have had success and don’t feel their mileage has decreased. Their rigs are for offroading and emissions testing restrictions aren’t tight in the area where they live.
3. I’ve read of a few people have drilled out their EGR pintle with torch bits, only one confirmed successfully, and he couldn’t remember the torch bit size. That supposedly allows a quicker flow through to the manifold to meet the ECM parameter. It requires patience as you try one tiny torch bit size at a time then test driving to se if the code light comes on. If someone is successful with this method please post your results and bit size.
4. A few guys have apparently changed out EGR’s from positive to negative backpressure units. I have not attempted this.
4×4 Mecca Archive of the above file: [level-extreme] EGR.txt [/level-extreme]