2003 V70 T5 Hesitation:Is it MAP sensor, 02 sensor, or both?

vulvu · Post by **vulvu** » 11 Sep 2013, 11:04

Hello fellow volvoists,

I've got a problem with hesitation and cannot figure out which one of the sensors in the topic is the culprit. I wouldn't like to just change sensors until a faulty one is found, perhaps one of you can help me to find the problem. I try to be comprehensive. Thanks in advance!

Symptoms
Occasional hesitation with light(ish) load, slow speed, around 2000-2500 RPM for one year. Last 2 weeks, severe hesitation, the car went once into limp mode, reduced power (like the car had some 90 HPs...). Hesitation takes place also in highway speeds now and can last quite long, around 2000-2500 RPMs, again. If RPMs get higher than ~2300, there is a strange sound under load, which could be the turbo wastegate operating hard. When there is is no load (i.e. revving on a parking place), the sound is not there. When I park the car, it feels unusually hot inside the engine compartment. Idle is nice, not rough.(Silly me, I didn't read OBD graphs when the hesitation first begun

)

Suspects
* Throttle body, maybe not: When hesitation starts, changing pedal position doesn't end it. Also, test OBD graph of throttle position shows a nice curve.
* MAF sensor, definitely no: I misinterpreted an OBD code and replaced the unit.
* Vacuum leaks, maybe not: I checked with butane and I didn't find any leaks. Also, OBD long term fuel trim is too negative. Positive would indicate a vacuum leak since ECM would try to compensate with extra fuel.
* O2 sensor(s), no. 1 culprit: OBD graph looks really suspicious, see graphs.
* MAP sensor, no. 2 culprit: OBD scanner doesn't get any reading, see graphs. I checked with a multimeter, there is supply to the sensor. Also, I checked with a vacuum pump the sensor, reading stays allways zero.

OBD data
Error codes:
* I've only read "P0127 - Intake air temperature too high". If I reset it, it stays away for a while and then it comes back. Hesitation occurs even when the code is not there.

Things which are wrong in the graphs:
* No MAP reading (top/blue): It stays zero
* SHFRFT1/Short term fuel trim (bottom/red): There should not be 2 figure readings normally, I believe.
* LONGFT1/Long term fuel trim (bottom/green): It is -15% (lean condition/false lean), it sould be a 1 figure number.
* O2S11/O2 sensor in exhaust manifold (bottom/blue): It's current, I'm not sure how to interpret it. However, I saw earlier a lamba=2 reading for the sensor.
* O2S12/O2 sensor after catalysator (bottom/yellow): There should be nice oscillation present in the graph. Oscillation is not there even when idling with A/C etc. switched off.

Graph 1: Vertical bar where hesitation begins.

Graph 2: O2 after catalysator is totally wrong.

OBD curves, questions
* Range of throttle position reading is from 12% to 85%, is it normal for this car? That is the range reported be OBD.
* If a O2 sensor is OK, should one always see nice oscillation ~1/s, despite that some other component/sensor is broken?
* There is no OBD reading for MAP (it stays zero). There should definitely be a non-zero reading, shouldn't there?

If there was a MAP reading, I would go and replace the O2 sensors. But with no MAP reading, I'm not sure at all. Can behaviour of the 02 sensors be because of a faulty MAP sensor? Or could it be something else than MAP/O2s? Any help is greatly appriciated.

Cheers,
Jani

Post by **chrism** » 11 Sep 2013, 11:55

Is P0127 the only code you're getting?

Does your car have separate IAT and MAP sensors (which would be side-by-side in the intercooler tube just before it enters the throttle body)? From what I've read, on some Volvos like the "R" models, a single double-duty sensor measures both IAT and MAP.

If you are measuring resistance through the MAP sensor and don't get any change in reading even though you you've run the pressure up and down with a vacuum pump, I'd be suspicious of that sensor.

Output swings from the O2 sensor may just be an effect of the other fluctuations like mixture and ignition advance, rather than actually being the cause. You aren't getting any fault code for the O2 itself, correct??

vulvu · Post by **vulvu** » 11 Sep 2013, 12:31

That's right, P0127 is the only code I'm getting. IAT and MAP are in one 4-wire package.

If you are measuring resistance through the MAP sensor and don't get any change in reading even though you you've run the pressure up and down with a vacuum pump, I'd be suspicious of that sensor.

Well, I didn't, yet: I just removed the sensor and applied vacuum/pressure several times to it and watched OBD scanner. I need wire supply to the sensor, redo the test and see if resistance changes. Do you happen to know the exact wiring diagram for the 4-wire socket? I've got wiring digram of the car, but it only shows connections to ECM. One can make an educated guess, but still..

Output swings from the O2 sensor may just be an effect of the other fluctuations like mixture and ignition advance, rather than actually being the cause. You aren't getting any fault code for the O2 itself, correct??

Thanks, that's what I hoped to hear

(No, there are no codes for 02 sensors) I'll retest the MAP as soon as I can and report what I found.

Post by **chrism** » 11 Sep 2013, 16:03

Whether it's right or wrong, I looked at diagram TP3998202 at:

http://www.volvowiringdiagrams.com/?dir ... 20Diagrams

Scrolling to page 62 you'll see that:

Pin 2 = green wire
Pin 5 = violet
Pin 3 = green/white
Pin 4 = violet/white

It's not at all descriptive as to which pins feed which functions (air temperature or air flow). But I think P0127 refers to intake air temperature.

Have you tried cleaning the sensor with some of that MAF spray cleaner - may be worth a try.

Also check fuse #12 in the eng compartment fuse panel. I think I saw where that has something to do with the MAF.

BTW - I'm not so sure using a vacuum source is the right method to check the sensor as it's measuring airflow vs air pressure.

Good luck!

vulvu · Post by **vulvu** » 12 Sep 2013, 11:16

I finally found the MAP connector wiring diagram (for Facet replacement sensor):

http://img.findpart.org/images/820/820880.jpg

Measurement showed that MAP sensor is fully functional. The strange thing is, that MAP reading in OBD scanner is still zero. Maybe it is a wiring problem from MAP to ECU. Strange is also that ECU doesn't report a MAP fault.

chrism wrote: P0127 refers to intake air temperature.

Yes, it does. In this car there is a thermo sensor in MAP too. MAF sensor it is not, since I've already replaced it. All fuses are OK.

Good luck!

Thanks Chris, I think I'm going to need it...

Post by **chrism** » 13 Sep 2013, 17:04

"...Measurement showed that MAP sensor is fully functional...."
Understood. How was that measurement performed?

"...Strange is also that ECU doesn't report a MAP fault...."
True, but it reports an IAT sensor fault. And are you not saying that MAP & IAT are both measured with the same sensor? If they are both measured with a common sensor then wouldn't it be probable that one function of the sensor (IAC) would fail before the other function (MAP)? The likelihood of both functions failing simultaneously seems pretty remote to me. Have you done anything to test the IAT part of the sensor?

"...The strange thing is, that MAP reading in OBD scanner is still zero...."
I'm wondering if the test equipment is 100% compatible to the car's system. Is the scanner showing separate IAT response?

"...In this car there is a thermo sensor in MAP too. MAF sensor it is not, since I've already replaced it...."
So are you saying your car has both a MAF and a MAP sensor??? (I seem to be missing something.) If you replaced the MAF sensor, where did you source it?

vulvu · Post by **vulvu** » 04 Oct 2013, 10:43

I'm sorry I've been a way for a while... I'm back to the problem again.

chrism wrote:"...Measurement showed that MAP sensor is fully functional...."
Understood. How was that measurement performed?

I used a vacuum pump to produce positive and negative pressure. The sensor was attached to a power supply. The range of readings looked fine on multimeter, so the sensor (the vacuum part of it...) is at least not completely dead.

chrism wrote: "...Strange is also that ECU doesn't report a MAP fault...."
True, but it reports an IAT sensor fault. And are you not saying that MAP & IAT are both measured with the same sensor? If they are both measured with a common sensor then wouldn't it be probable that one function of the sensor (IAC) would fail before the other function (MAP)? The likelihood of both functions failing simultaneously seems pretty remote to me. Have you done anything to test the IAT part of the sensor?

Yes, both variables are measured by the sensor. Now that I read your reply, I think my brain did produce a fart. Of course temperature part of the sensor could be faulty - I thought about that while a go, but somehow I negleted it.

Anyhow, it feels too hot inside the engine compartment after a ride. Also, the fan starts after parking despite that it's around 5 C / 40 F now. A good guestion is that if "IAT too high" is an egg or a chicken.

"...The strange thing is, that MAP reading in OBD scanner is still zero...."
I'm wondering if the test equipment is 100% compatible to the car's system. Is the scanner showing separate IAT response?

That could well be the case. Still, another tool reports that boost pressure feature is not supported by the vehicle (or reading it, at least). IAT reading is there.

"...In this car there is a thermo sensor in MAP too. MAF sensor it is not, since I've already replaced it...."
So are you saying your car has both a MAF and a MAP sensor??? (I seem to be missing something.) If you replaced the MAF sensor, where did you source it?

Yes, it has both sensors. The MAF came from FCP Euro and is an original Bosch part. (Go figure that it's cheaper to buy parts to Euro cars from US, including postage!)

I also did an O2 test with my OBD scanner. The result was "pass", but I don't know if one can trust the result much.

Hesitation has grown worse now. I still suspect a vacuum leak and I'm going to recheck for them again. If non found, it's time for a new MAP sensor. Or then I'll give up and take the car to the shop...

Jani

vulvu · Post by **vulvu** » 06 Oct 2013, 08:53

vulvu wrote: Hesitation has grown worse now. I still suspect a vacuum leak and I'm going to recheck for them again.

Gotcha!

I found a massive tear in the rubber hose just before intercooler intake by visual inspection. I did blow butane around the area when checking for leaks for the first time. Apparently, it starts to leak enough only after a certain engine load limit. I did the butane test when idling.

I put self vulcanizing tape (great stuff, BTW) around the tear and good bye hesitations. It's not completele sealed, though. So the car sounds like a horny cat between 2000-3000 RPMs.

A new rubber hose and it's going to be case closed.

Thanks Chris for you discussion. It did help me to keep on seaching for the fault.

Cheers,
Jani

p.s. The problem is probably connected with an old problem with this car. More than a year ago I had to replace the radiator fan. A transistor inside the fan control box was short circuited and the box overheated. Now, the rubber hose is routed close to the box and the hose seems to have suffered heat damage which has detoriated it. Furthermore, the control box has a sharpish corner just where the hose passes it. I susped that a service quy has removed (to replace spark plugs) the hard tube which takes air from turbo outlet to intercooler by pulling the rubber hose downwards. A weak hose + a sharp corner = damage. At least, heat damage is there for sure.

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