Fubared idle issues

[ftawizard]

Was wondering if some one can help with my issue .....
I have a 95 mx3 with I believe a bp engine 1.8 ...... Mazda guy told me engine was swapped from original and after research it looks like a bp 1.8 .... It's suppose to have a 1.6 ...

Anyways I'm haveing an issue with the idle ..... I checked for leaks and have swapped egr three times and fuel filter and oil and oil filter ...... I had to put original ecu back in the car with original harness ..... The engine light still comes on and after repeated scans it keeps say egr positioning sensor check circut failed ..... When I unplug one vacuum line off of the fuel rail regulator it idles fine ....... However when I am driving and I'm brakeing ..... So I got clutch and brake pushed down...... it idles up and down .... Any ideas what may be wrong? Anyone? Some help would be much appreciated please and thank you

[mor500589]

im having the same problem on my RS but im pretty sure i narrowed down the problem to Possible solutions yet to try.

1:
PRC solenoid valve no.2
at the bottom there is supposed to be a hose attached to it that goes to the Pressure Regulator but is somewhere else now

2: EGR solenoid valve is not sucking air...

[Josh]

SO I always had this same problem in my 95. I could never figure it out what the little bug was. I even swapped to the 93 harness and an BP ecu and still had the issue. thought it might be the Throttle position sensor and readjusted thought it might be the egr so i changed that did nothing so i took that out all together.

sounds like a vacuum leak to me, or a bad vacuum sensor somewhere.

what distributor are you running? the internal coil off the B6 or an external? and there is a vac line to the airbox that NEEDS to be hooked up or it can idle funny like this. the other thing to check would be your Alternator output, a weak one can contribute to the issue. until i upgraded mine to a millenia alt my rpms would drop every time i stepped on the brake and or came to a light to stop. another thing you could check but should have thrown a code is the o2 sensor, it can cause it to idle funny as well. If you do a bit a searching on the forum I know this has been talked about a lot in depth and you may be able to find some useful info. you may have to start a series of elimination on all your sensors. test and move on to the next.

If I were you and you have a BP in there I would swap back to the other harness, sensors, and make sure you had the right VAF, as to not hinder the performance of your motor. although timing on the B6 and BP are the same the fuel maps are different. and the BP revs to 7200 instead of 6500