94 850 Turbo running rich and idling high

skloon · Post by **skloon** » 28 Jun 2017, 09:36

My 94 850 has been RN and manual swapped, Other than catless and running only a front o2 sensor all other is stock I am trying to get it running well before tuning it, the issue is it blows black smoke when I get into boost- engine and turbo were fine beforehand, and when at idle it will puff black smoke too- the other weird thing is when it is coldish it will idle at 2900 rpm- I have tried my original ECU as well as one from a 95 turbo manual and a 95 850R automatic- I get no error codes other than transmission related have checked for vacuum and boost leaks but fnd nothing I did repace the 02 sensor with a new bosch one to no difference

Post by **bmdubya1198** » 28 Jun 2017, 16:48

Have you cleaned your IACV?

Sommerfeldt · Post by **Sommerfeldt** » 29 Jun 2017, 01:19

Which transmission related codes are you getting with the other ECUs?
Also, the rear O2 sensor is the "diagnostic" one, and if it hasn't been deleted correctly, that will definitely cause you to run rich and blow black smoke. bmdubya's tip is good for the idle issue though - if it's stuck or clogged, it an cause some weird, hard to trace stuff.

- S

Post by **misha** » 29 Jun 2017, 14:21

Rear 02 sensor is diagnostic one but it plays a role in air/fuel mixture and fine tunes it.Since you allready removed cat you just need to disconnect it.
If it is disconnected it will not make problems except check engine light.If you removed cat and you left 02 sensor connected it will make problems with mixture.

I guess that you don't have problems with o2 sensors at all.High idle and rich mixture,together,are pointing to a large vacuum leak.Vacuum leak means that you have unmetered air comming into the engine.It is that large that iac valve could not compensate by closing air flow.

Post by **rspi** » 29 Jun 2017, 19:26

Double check the turbo for shaft play.

Sommerfeldt · Post by **Sommerfeldt** » 30 Jun 2017, 01:50

misha wrote: 29 Jun 2017, 14:21 Rear 02 sensor is diagnostic one but it plays a role in air/fuel mixture and fine tunes it.Since you allready removed cat you just need to disconnect it.
If it is disconnected it will not make problems except check engine light.If you removed cat and you left 02 sensor connected it will make problems with mixture.

When my rear 02 sensor went dead, it most certainly made problems. Rich mix, black smoke, CEL and limp mode. So... not sure you can just yank it out of there, misha.

OP, also make sure your coolant temp sensor is in working order. That thing will cause high idle, at least, even though it might not cause you to darken the neighborhood skies with unburned fuel.

- S

Post by **misha** » 30 Jun 2017, 04:23

Yes....IF it is dead and you leave it connected.It gives false reading,almost like bad Maf.
If you disconnect it's connector...all you get is check engine light.
Right now,when he don't have cat anymore,he can disconnect it and also...he can connect his rear 02 sensor into front o2 plug without problems.The only condition is that he don't have a leak in exhaust system,especially at flexi pipe.That could also be a reason for rich mixture.
Trust me,i've tried it numerous of times on Volvos and other cars with success.

skloon · Post by **skloon** » 30 Jun 2017, 11:42

The weird thing is I have a tuned me4.4 ecu- it is set for a huge turbo and different injectors, if I use this ecu it starts fine and idles like a champ of course it throws smoke like a worn out bus but I dont have the idle issues

Vazfx16 · Post by **Vazfx16** » 30 Jun 2017, 11:51

One thing that is not an obvious thing to check, is that coolant temp sensor. I had a similar issue, I found that the connector on the sensor was bad so was not giving the ECU the proper temp. This caused the idle to go really high (1500 rpms). I took me a month to figure this out. I bought two new sensors, then finally realized it was the plug. Please check out the temps sensor

skloon · Post by **skloon** » 30 Jun 2017, 12:16

is this the sensor low on the front of the block ?