'04 XC Engine Misfiring-Further Updated (Moisture ruled out - possible defective coils, bad MAF) Topic is solved

[jimmy57]

The 2002 and later that use electric throttle assembly with ZERO processor circuits inside have great reliability but the connector is not durable. I never unplug them unless it is not avoidable. If the engine comes out the throttle gets unbolted and sits somewhere with harness plugged in on it. The throttle adaptation occurs if you turn the ignition on w/o starting engine and wait a bit over 45 seconds to then hear it open and closes twice during the throttle position sensor sweep and range test. There have been a number of throttle issues fixed with new repair pigtail on throttle and 4 new repair wires with new terminal for the wires at ECM plug. Volvo sells 5 inch long wires with the terminal already crimped onto wire. There was a harness from throttle to ECM to replace the whole set of wires but I do not think that is available and was a part the tech hotline for dealers had control of. It might be worth a try asking at the dealer parts dept or calling Tasca. In most cases cleaning terminals and dielectric grease fixes connection issues but not here. VW Audi had the same hypersensitivity issues with the ETA and had some special expensive connector glue. I have had one car with the issue but it did set 91B7 and the pos sensor correlation codes at different times along with reduced eng perf message. I un plugged it and used my tiniest pick probe and pushed the two leaves of terminal closed and then applied copper paste with a tooth pick to keep thee being enough so as to conduct between any other pins. I then did ECM base plug spray cleaning and then inserted fully and removed ECM 5 times to "scrub" connections and then spray cleaned and dielectric grease. That car was fixed and stayed fixed for the 3 more years they owned it. There is more anxiety engineering in the throttle circuits than anywhere on that car (the newer radar cruise likely have even more of this) to assure that there is no way the throttle ever overdelivers compared to accel pedal position.

[jonesg]

Sounds like defusing a bomb.

[E Showell]

So my independent Volvo expert purports to be a little stumped as well. He claims no communication from TB and asserts it is a failed throttle body. (This is the used TB I got from Harry's). First thing he says is the TB is wrong part # for car. Current TB ends in 553. He says it should be 554. I took the TB out of same model at Harry's. Also, the TB I took out of the car had the exact same part number. I am certain the one I took out of the car was original to the car.

Independent Volvo specialist advises changing TB wiring harness as well, even though he can't tell me definitively the harness is bad.

I feel like he's firing the parts canon at it, since he can't say for sure this will fix it. He does however "guarantee his labor," whatever that means.

Frustrated. He seems to be strongly suggesting the wrong part # is the problem, when I know the issue results from something else, since the car has had the "wrong part #" throttle body off the factory floor.

He did remove the ECM to check for corrosion. Said the pins looked pristine.

[93SCMax]

Would it hurt to reinstall the original TB? Otherwise you are suggesting you have two bad TB's (original and junkyard replacement).

Your Indie suggests you have the wrong TB PN but also wants to change the wiring harness?

Can't you use your VIN to confirm the correct TB PN? If you are the original owner of the car, the factory didn't put on the wrong TB. I'm assuming you have the correct PN, but the used one is faulty...otherwise the harness got messed up somehow. Any ideas?

[E Showell]

I suspect it is and always has been a harness, not TB issue. Perhaps I was unclear. I have no paperwork suggesting the throttle body was ever changed prior to me swapping in a junkyard unit.

The part numbers for the junkyard unit and the factory original TB it replaced are identical, both ending in 553.

Independent Volvo specialist seems to suggest installation of wrong TB at factory (PN should end in 554 per him) is genesis of problem 16 years later -- at least that's where his logic leads (unless I am fundamentally misunderstanding something he's saying) which is certainly possible.

He could flash me the proper software for $350, but it could already be loaded and it doesn't seem like he can determine that without first loading it, so I could spend $350 for nothing.

As the youth would say, sounds a little sketch.

[chrism]

So a question for your mechanic would be, “If the car had the wrong TB P/N installed since who knows when, then why did it run perfectly fine for numerous years and then suddenly go bad?”

[E Showell]

Exactly. That's why I said sketch.

[abscate]

So a question for your mechanic would be, “If the car had the wrong TB P/N installed since who knows when, then why did it run perfectly fine for numerous years and then suddenly go bad?”

You guys with your logic and science thingy think you know everything. You just need a bigly mechanic to fix it.

Evan, have you reached out to yagger on the software load?

[RickHaleParker]

You guys with your logic and science thingy think you know everything.

If we thought we knew everything we would have no questions. Perhaps you thinking of the irrationals that "know" they are right even when they are not correct.

[E Showell]

Back from mechanic. Had him install new Volvo TB harness and new XeModex TB. Car is running like a top. Still don't really know what the problem was since it was cheaper to install both components at the same time, I could not do a truly scientific method single variable analysis.