Hello all, trying my luck again since I had no response on my last post and I really need your help please!
And sorry for any stupid questions as I am still learning.
Basically I just got my 1995 Rx7 fd engine rebuild from a professional shop that works on rotarys and literally changed everything, nothing was used from old motor including water pump and thermostat, but didn’t change fuel pump, injectors, twin turbos and sensors as the car was working well before rebuild but compression was low but drivable. Car is on pfc ecu.
Now the car is smoking like crazy if we hit to around 3k rpm and keeps going even at idle with gray and white smoke but when increasing rpm it turns to very dark gray almost black.
Funny thing is that I can leave the car running at idle for a long period of time and light throttle with any smoke at all but once hit mid rpm show starts and if I turn of the car a start it back up in a couple of minutes with engine warm smoke stops again.
I went to speak to who build it regarding the oil control ring pinched or backwards spring but he sad it’s impossible as smoke should start immediately and not gray to black smoke.
took it also to a tuner and set the air to fuel checked for vacuum leaks and sensors but had no luck.
Also need to change oil for the 2nd time by only testing cause it’s getting all with fuel.
My hope is a leaking/stuck injector and almost my only hope but the car idles fine apart from staying a bit high idle.
please any recommendations and thoughts will help me a lot.
posted pictures on the previous post
Thanks
Malcolm

 

wrong section. several replies in the other thread. https://www.rx7club.com/new-member-r...build-1166551/

i'm guessing u weren't getting the answers u were looking for. i'll move this one to the 3rd gen section. how long after the rebuild was done that this issue presented itself? they will smoke after rebuild due to all the lube used during assembly. maybe oil is getting in by the turbos. anyway, good luck figuring it out. hope it's not something that will need another tear down.

 

If you are getting dark grey/black smoke and your oil is getting diluted with fuel very quickly, then it sounds like fueling like you mentioned. Do you have a wideband to check A/F ratio? It does sounds like you may have something not reading properly causing an extremely rich condition such as a temp sensor or the MAP sensor. or a setting possibly changed in the PFC.

 

Thank you very much!
yes got a couple of replies but really wanted to try posting again to try my luck if anyone had same problem.
The thing is that at first it used to smoke at idle guessing it was all the lube from the engine but after that it calmed down and gets crazy when accelerating mid rpm.

 

Thank you for your reply!
Unfortunately I don’t have a wideband yet but tuner did attach one to see the A/F but when it came for high rpm he actually couldn’t tune as the car was smoking a lot.
Can I ask a stupid question? The tuner found that the map sensor was not getting proper vacuum at first which it had rough idle also but then he connected properly and idle sounded good and picks rpm freely, but also noticed that he attached it with the same vacuum of the blow of valve with a T. Could it maybe be that is why car is not smoking at idle at first but when hitting mid rpm bov piston opens and map sensor gets wrong reading?

Thanks again
Malcolm

 

Sounds like you need to track down all the vacuum lines and make sure they are in the proper position. Those should not share a source of vacuum and shouldn't even come from the same side of the manifold. The MAP sensor should have a dedicated source coming from the UIM just behind the throttle body, the BOV should have a vacuum from the turbo side of the UIM right where it bolts to the LIM. You said you are running twins, are they sequential still or did they get rid of the rats nest and run them in parallel now?

 

Thank you.. Yes I will fix that first thing cause both of them are taking from behind the throttle body.
They are parallel, no rats nest and was done from the previous owner way before the rebuild.
It’s very confusing at the moment and frustration.