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2006 Volvo XC90 4.4l V8
6 Posts
Discussion Starter · #1 ·
2006 Volvo XC90 4.4l V8, 181k miles
P0174, P0171, MAF question, help please
I have been fighting these 2 codes for over a week.

This is what I have done so far:
(all genuine Volvo parts. All of these parts were faulty)
new oil cap “O” ring
new oil dipstick with new “O” rings
Removed crossflow air manifold.
New vacuum hoses to the inlet manifold (underside of crossflow manifold)
new inlet manifold gasket
new crossover air manifold gaskets
new PCV valve and Emission Check Valve
new vacuum tank
cleaned MAF sensor (although it didn’t look dirty).
put everything back together.

Clear codes. Start engine. Idle for 15 mins or so. No codes. Shut off engine. Let sit for a 1-2 mins. Restart engine. Let idle. Within 1 mins the codes come back. However, the engine runs perfectly, easily revs to redline. No stutters, no hesitations, no backfires. Nothing.

Log engine PIDs with Torque Pro.
MAF (cfm) is 42 – 43 at idle, approx 675 rpms.
MAF (cfm) is 138 – 140 at approx. 2,560 rpms.
Is the MAF suspect?

Any advice would be greatly appreciated.

2006 Volvo XC90 4.4l V8
6 Posts
Discussion Starter · #2 · (Edited)
Rectangle Slope Font Plot Line
2006 Volvo XC90, 4.4L, AWD, 181k miles. Starts, runs, drives very good.
I am asking for help/advice in solving this nagging problem: P0174 current fault, P0171 pending fault.

1. KOEO, connect scanner, clear codes with scanner. Rescan for faults, no faults.
2. KOER, drive approx 15 mins, 40 MPH max, some stop and go, pull over, park leave engine on
3. Idle for a few mins, exact 2 codes return

What I have done so far:
1. New vacuum tank (broken hose port) top rear of engine, passenger side. TEST DRIVE. Same codes.
2. New PCV valve and related hoses. TEST DRIVE. Same codes.
3. New air crossover manifold gaskets to intake manifold. New gasket, inlet manifold (30720333). New PCV hose located under the crossover air manifold. TEST DRIVE. Same codes.
4. Clean, bench test MAF. TEST DRIVE. Same codes.
5. Replace MAF with known good one, same MAP on gen2 Prius. TEST DRIVE. Same codes.
6. SMOKE TEST. Remove air filter box with MAF. Seal off inlet side of throttle body. “Tee” into throttle body to brake booster vacuum hose to smoke machine outlet. Turn on smoke. Could not find any leaks. Repeat SMOKE TEST. No leaks.
7. Reinstall air filter box and air snorkel to throttle body. Seal off air filter to keep smoke from coming back out to outside. SMOKE TEST. Minor smoke from snorkel to throttle body. Remove snorkel. Add small amount of silicon to throttle body where snorkel seals. Reinstall snorkel using new hose clamp. SMOKE TEST. No leaks. TEST DRIVE. Same codes.
8. Disconnect MAP sensor pigtail. KOEO. Test Vdc supply from ECU to chassis ground: 5.05vdc. Test ECU ground in MAP pigtail: good.
9. BENCH TEST. Remove MAP sensor from car. Bench test MAP sensor. Attach +5vdc (120vac to 5vdc, 400ma adapter) to MAP pin (ECU supply pin). Attach adapter ground to MAP sensor ground pin. Attach VOM multimeter to read MAP voltage output. Attach hand held vacuum pump to MAP vacuum port. Pump vacuum from 0psi to 26.57psi, and log the inHG readings on vacuum gauge.
10. Find other standard 1 BAR MAP sensor voltage/psi tables. Graph 2 standard MAP tables and my MAP table from 9. (See attached graph). My MAP differs quite a bit from standard. Search for MAP table from Volvo or anywhere else. Could not find any. Denso K0F-A9521-00 079800-7350.
11. So, took a leap of faith, and bought a used MAP sensor (MAP2) from eBay. BENCH TEST MAP).
12. Add MAP2 to graph. MAP and MAP2 look the same.

Getting ready to install MAP2 on vehicle, but, I don’t expect the faults are going to go away
Any help or advice from anyone here that understands my write up will be greatly appreciated.

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