'98 Volvo C70 2.5T atmospheric pressure sensor and high consumption

[sleddriver]

@sleddriver
.... that would be the worst case scenario, to be honest.
The price of having the wiring harness replaced by a workshop is an economical total loss. I'd have to find someone to do some patchwork. I myself do not have the knowledge or the possibility to do so.

I'm not talking about replacing the whole wiring harness. Not by any means. The insulation will flake off about 6" or so from the end, where it's least protected.

Given you removed the sensor then drove the car and noted an improvement, that indicates you need a geniune sensor. Perhaps from a junk yard.

[SvenGWK]

Thanks for the suggestions! Then I'll try to get the ECU out. I hadn't opened the box yet. The " new" sensor should arrive on Tuesday. In the coming week, the temperatures will finally rise above the threshold of frost, and then my fingers won't hurt so badly when I do handicrafts.
I'll keep you updated!

[SvenGWK]

Today I received the used, but original sensor (BOSCH).
Installed it instantly and it looks really damn good! It Seems the other one actually has a problem, even though it worked on the power supply.
I have now seen a plausible value of 99kpa at 4.6V.
However, there were more error codes today. Bench 1 mixture too fat and MAF low input. I don't know when they were thrown, maybe yesterday when the engine went out in the idle gas (was without sensor).

I have checked what the ECU sees from the MAF:
870rpm (idle) - MAF Load 0.5V; 4.8kg/h
2100rpm - MAF Load 1.2V ; 35,2kg/h
3240rpm - MAF Load 1.6V ; 64kg/h
840rpm (idle again) - MAF Load 0.5V ; 6.4kg/h

The readings were all taken in the parking lot, I can't make a test drive until tomorrow.

Does that look plausible?
I assume that Uref=5V are here too (not have measured, it is raining ^^)
But the 1.6V/64kg/h at 3240rpm seems kind of low, doesn't it?

Wouldn't a 2.4-litre engine have to inhale something around 200kg/h? (if you don't consider the effects of the turbocharger...)

[precopster]

On P2 turbos at idle around 12-14kg/hr. Not sure at those higher revs. Looks like MAF is the next culprit

Do a battery reset first to clear all data then check readings.

[SvenGWK]

With the other MAF sensor I have the same problem. The machine apparently gets false air, but it depends on the engine temperature, I noticed. When the engine is cold, the MAF sensor measures approximately 14kg / h. When the engine is warm, it is only about 4.5kg / h. Does that make sense?

[SvenGWK]

A theory (Sorry if it's nonsense, I do not know much about it ...) :
The cold run control is inverted. How do I get the idea?
When the engine is cold, idle rpm is lower than when the engine is warm. The MAF sensor measures the real airflow. When the engine is warm, the cold run control gives air somewhere behind the MAF sensor, which the MAF sensor does not see.
Result: MAF sensor measures only 4.5kg/h but engine gets enough air to run.
The lambda probe is ready for use at this time and detects a mixture that is too lean. The control unit is adding more and more gasoline, long term trim then rises to 25% and the yellow light turns on.
Possible cause: Something was wrong connected when replacing the vacuum hoses?
How exactly is the cold run control implemented in the vehicle?
Or maybe I'm completely on the wrong track?

[RickHaleParker]

.

28: EFI-422 (P107) Atmospheric pressure sensor.


Diagnostic trouble code (DTC) information EFI-422

A2301616 Condition
Diagnostic trouble code (DTC) EFI-422 is stored if the engine control module (ECM) receives a signal from the atmospheric pressure sensor corresponding to a height above sea level of over 6.500 m (low signal) or under 780 m (high signal).
Diagnostic trouble code (DTC) EFI-422 is stored if the signal is unstable for 25 seconds (sporadic signal).

Substitute value
The engine control module (ECM) adopts a height of 0 m above sea level.

Possible sources

Signal too high

• short-circuit to supply voltage in the signal cable
  open-circuit in signal cable or ground lead
  short-circuit to supply voltage in the power cable
  contact resistance in terminals
  short-circuit to supply voltage in air conditioning (A/C) pressure sensor power cable
  short-circuit to supply voltage in fuel tank pressure sensor power cable
  short-circuit to supply voltage in accelerometer power cable
  defective atmospheric pressure sensor

Signal too low

• short-circuit to ground in signal cable
  short-circuit to ground in power cable
  open-circuit in power cable
  contact resistance in terminals
  short-circuit to ground in air conditioning (A/C) pressure sensor
  short-circuit to ground in fuel tank pressure sensor power cable
  short-circuit to ground in accelerometer power cable
  defective atmospheric pressure sensor
  defective air conditioning (A/C) pressure sensor
  defective fuel tank pressure sensor.
  defective accelerometer.

Signal sporadic:

• loose connections
  contact resistance in terminals
  defective atmospheric pressure sensor
  defective air conditioning (A/C) pressure sensor
  defective fuel tank pressure sensor.
  defective accelerometer.

Fault symptoms
Poor performance at high altitude
can cause starting problems at high altitude.

[SvenGWK]

Thank you, but this problem has been eliminated. The newly installed sensor (from junkyard) works perfectly, the error is no longer reported. But there is obviously a false air problem which occurs after reaching the operating temperature of the engine. It can be deduced from the data of the MAF sensor.

[RickHaleParker]

How exactly is the cold run control implemented in the vehicle?

Bottom of the air box. Control valve maybe stuck or somebody knocked of the vacuum line or leaking.

[SvenGWK]

I took a look at it on youtube, but it's obviously not installed in my vehicle this way anymore.
Anyway, today I removed the airbox cover and tried to "strangle" the engine.
I wanted to see if I could find a leak that way.
The problem is not only to be read off at the air mass meter, but also physically present.
If the car was parked overnight and the engine is started, the MAF sensor shows plausible values.
When I close the inlet, the engine goes out, there is a significant negative pressure in the air intake hose , which causes it to visibly contract.
When the engine is warm, hardly anything flows over the MAF sensor, but to keep it closed still makes the engine stop, of course - it then measures zero and the ECU cuts the fuel.
However, if I disconnect the MAF sensor and then block the inlet, the engine will keep running FULLY NORMAL. When the engine is warm, there is only a minimal negative pressure inside the hose, which is barely enough to affect the hose in any way when keeping it closed.
So the engine is able to get 100% of its air from somewhere else.
I have squeezed the hoses that go in at the end of the intake hose (there is a also sensor) . With the thick hose there was a minimal speed change when released.
Opening the oil cap does not cause any rpm changes.
There is also no negative pressure there.
I conclude from that, when the engine is warm, OK - actually after 2-3 minutes in idle gas, something opens up where the air comes from. And much more than a torn hose could deliver.
What could that possibly be?

(At the engine, crankcase ventilation, vacuum hoses and timing belt were replaced before the problem occurred, if this is a useful information)