Running VERY rich and IAT

454cid · Post by **454cid** » 03 Apr 2022, 18:47

96 NA 2.4L, under 100K miles.

I've noticed black smoke, and soot on the tail pipe. MPG is not great either, although I haven't actually calculated a number recently, but if I didn't know better, I'd think I had a hole in the tank.

Car enters closed loop pretty quickly, but as coolant gets warmer it gives up and goes back to open loop.

At first STFT is like 25% and LTFT is I don't recall, but lower. After going back to open loop, STFT is 0 and LTFT is .25%. (POINT 25).

ECT seems fine, responds normal after changing thermostat a couple of months ago. I have no reason to suspect it's bad.

I'm using the 850 OBD2 app on my phone.
When scanning the Mototronic ecm, I notice the "Ambient air temperature" is way low.... like SUPER low, although it does change. I never paid attention to this because I don't care what the ambient temperature is, I can tell it's cold out just fine. Dash outside temp digital display seems to work okay. Then is occurred to me, maybe this "ambient air temperature" is actually the IAT (Intake air temperature) and is being reported as "ambient" due to a language difference between the programmer, and I.

I see "Air Intake / Charge Temperature Sensor" on Rockauto, but doing a search on the forum, I'm unsure if my car is actually supposed to have one or not.... and if it does, it's behind the bumper someplace?

I did get a couple of codes.... P0131, and P017something, but have since reset them and I'm waiting to see what happens. I do have missing, but much better since I changed the rotor and cleaned the cap.

Post by **erikv11** » 03 Apr 2022, 22:10

I don't have an answer but here is a start: According to misha who is very reliable, 850 NA cars don't have an IAT. Here is some info on IAT https://www.matthewsvolvosite.com/forum ... hp?t=78051, you can check your car for it but probably don't have it.

You are correct IAT is not the same sensor as for the ambient (outside, shown on the dash) temp.

454cid · Post by **454cid** » 04 Apr 2022, 00:21

erikv11 wrote: ↑03 Apr 2022, 22:10 I don't have an answer but here is a start: According to misha who is very reliable, 850 NA cars don't have an IAT. Here is some info on IAT https://www.matthewsvolvosite.com/forum ... hp?t=78051, you can check your car for it but probably don't have it.

You are correct IAT is not the same sensor as for the ambient (outside, shown on the dash) temp.

Yes, that's one of the threads I found. I guess I'll have to look under the bumper tomorrow..... weird place for it, Though. Unless it's just the 850 OBD2 app giving me wonky results, some sensor is telling the ECM the air is -75F to -1**F! If that value is being used to calculate fuel, then that's going to be the cause of the car running pig rich.

I'm used to IAT sensors being right in the air intake.

Post by **abscate** » 04 Apr 2022, 04:31

I believe the ECU uses a temp sensor built into the MAF on some models, worth digging into

Post by **erikv11** » 04 Apr 2022, 09:46

There is definitely not one on the intake. My NA lives across town but II may be by there today I can check under the bumper. I'm wishing I had looked 5 years ago and added it to that thread! I have done two NA engine swaps and don't remember ever seeing one though.

First thing I'd try is swap in another Bosch MAF from the junkyard and see what happens to the reading. 95-98 P80 all use same MAF, turbo or NA.

454cid · Post by **454cid** » 04 Apr 2022, 13:16

Took a look under the car today, and found the dash temp sensor. I unplugged it, and it went to "Lo" on the dash. Unplugged the maf, and removed it from the housing. That's definitely different than a GM MAF! I was hoping maybe I'd see a thermistor in there, but the plug is only 4 conductors. I did a poor job of spraying Deoxit on the connector as I was running out of time.

Post by **misha** » 04 Apr 2022, 17:12

P0131 is front o2 sensor code.
The other one is probably p0172 since it's running visible rich.

No IAT on 20v n/a.

Code reset will reset the CEL but not the fuel trim.
Disconnect negative battery cable for about 10-15min and that will reset ecu,code and fuel trim.

Perform a re-learn procedure of ecu after re-connecting battery cable and see how things are going.

Those obdII apps are NOT reliable and we allready had a member from France who got a code for something his car doesn't even have.

Vol-Fcr is needed if the car have M4.4 management or some proper diagnostic tool which can read engine codes in P xxxx format.

xanthefin · Post by **xanthefin** » 05 Apr 2022, 00:58

IAT sensor you are looking through OBDII (Generic OBDII) Live data is not on Motronic section as there is none. This "OBDII" is made for any car and not just Volvos so its all around section and not divided per car or per model as that would be nightmare to make.
# I add now info text which can be seen when clicking on live item about this on live data section on coming update as its good info for volvo Mtoronic user not to mix in future.

ECU reports to that (PID: 0F) is using standard conversion of that generic OBDII command's answer. On Motronic case that equals actually Ambient Temperature sensor output directly as i tested on bench quickly as whats going on here.

This comes to Motronic pin A35 if its there (in Volvo books called too as "Outer temperature sensor").

If it goes under 7C some diagnostic functions are disabled.

I give that if you using old version and wifi there was typo which did give wrong results like on OBDII.

If you want read P xxx codes as suggested you refer at scan only as "OBDII Standard". It then reads P xxx codes as any other OBDII app does. Otherwise (i prefer you do) you read codes in Volvo way (EFI- code) and select Motronic to read code so you get text form what code means and more accurate.
If there is problems i like to know so i can check and fix.

Example link to that french. I suggest to check raw data before making comment was it app or was it totally legit for other reasons. Facts first.

I seen some other readers to use wrong conversions on some live data items so i been fixing them show correct or more realistic like what Volvo tool does.

454cid · Post by **454cid** » 05 Apr 2022, 11:55

xanthefin wrote: ↑05 Apr 2022, 00:58 IAT sensor you are looking through OBDII (Generic OBDII) Live data is not on Motronic section as there is none. This "OBDII" is made for any car and not just Volvos so its all around section and not divided per car or per model as that would be nightmare to make.

I'm using the Motronic section. It shows large negative values labeled Ambient air temperature. If I use the OBD2 section IAT is blank.

I give that if you using old version and wifi there was typo which did give wrong results like on OBDII.

I'm using bluetooth, and am unsure how to update to a newer version.

454cid · Post by **454cid** » 05 Apr 2022, 12:00

misha wrote: ↑04 Apr 2022, 17:12 P0131 is front o2 sensor code.
The other one is probably p0172 since it's running visible rich.

Yes, I think that's correct.

No IAT on 20v n/a.

Given that I'm getting a reading, and we're in different countries, I figured there was a chance that North Amercian cars had one.

Code reset will reset the CEL but not the fuel trim.
Disconnect negative battery cable for about 10-15min and that will reset ecu,code and fuel trim.

Perform a re-learn procedure of ecu after re-connecting battery cable and see how things are going.

How do I do a "re-learn"?

Vol-Fcr is needed if the car have M4.4 management or some proper diagnostic tool which can read engine codes in P xxxx format.

I'll have to Google Vol-fcr. I do have an old pro-level scanner, but I don't have the European cartridge to access Volvo specific things, just straight OBD2... which may be of some use.