My (new) 97 OB has a working EGR (I think) and a bad BPT. The BPT was bypassed and the EGR seems to still be working - no CEL as long as I've owned it (1,000 miles). I bought a new BPT just to make things right. I hooked up the new BPT (yes, properly) and 10 minutes in, it threw a CEL (not sure of the code, but I'm certain it was EGR). I put the old BPT on and bypassed it again - CEL went away. This left me totally confused because based on what I see, the BPT is not needed - but I KNOW that's not the case.

 

My next hunch is the solenoid under the EGR that switches the BPT on/off. How do I check if that's bad. What is that part called? I swear I am mechanically savvy, but I've never had a car with this much vac. controlled stuff. I hate vacuums

Forgive the ignorance, but what exactly are you calling BPT?

Forgive the ignorance, but what exactly are you calling BPT?

 

Backpressure transducer

it's the little guy in the square

Edited May 13, 201015 yr by tricked919

You think these are bad go work on an early 90's Honda or Toyota. Vacuum hoses out the wazoo!

 

It would help to know the actual code that is being set. Most EGR related codes are two trip fault codes which means that you have to make two consecutive drive cycles with the fault present before the computer sets the code. Usually circuit codes are immediate upon starting.

 

The EGR solenoid valve is probably the one you are talking about, it is the only one in the vicinity of the BPT. It controls vacuum ON/OFF to the EGR solenoid. It can be tested with a multimeter but I'll have to look up how later on. It's just a resistance check, but I don;t know the values off hand. You can test the connector plug for continuity to ground to rule out grounding issue. (will prevent the solenoid from operating properly)

 

 

On a side note... I didn't know MSD made ignition coils for these cars. I'll have to look into those a bit.

Edited May 13, 201015 yr by Fairtax4me

Two thoughts- if the EGR passages are restricted somehow (carbon build up?) perhaps defeating the BPT gets enough flow to fool the computer. You could pull the valve and check to see if it's plugged up.

 

Check the diapragm of the EGR valve for a vac leak.

 

Is the exhaust backpressure normal? (i.e. you still have your catalysts?)

 

Nathan