"Engine Performance Reduced" with No Start Issues and Faulty Thermostat

[rl0089]

So my wife and I recently picked up a 2006 XC90 2.5T and love it! However we've run into a few issues so far in our 2+ weeks of ownership.

Most commonly is no start when attempting to start for the first time, usually in the morning when it's still pretty cold out (between 20 - 40 degrees). I thought it may be battery related so we replaced the old Volvo battery with a new one. Other issues I've noticed is the temp gauge does not get up to temp, usually sits around 1/4 and at one point didn't move at all, prompting a coolant sensor failure message. So, the thermostat housing is already ordered and in route. Car has ~112,000 miles.

Fast forward to today. My wife tries to start the car first thing in the morning with no luck, it cranks but doesn't fire. She tries two or three more times waiting between attempts. She finally gets it to start but receives an "Engine Performance Reduced" message followed by a CEL. The message and light only lasted about 5-10, after the car warmed up the light and message both disappeared. And once she got to work, 10-15 miles, the temp gauge was at the middle position (actually a hair over). Could the thermostat/coolant sensor housing being faulty have anything to do with the no start/reduced performance issue? I have February break off from work so I'm planning on a major tune up, filters, plugs, clean MAF, TB, replace PCV system, replace Timing Belt, thermostat housing and maybe the water pump while I'm in there.

Hopefully they are all related and will stop once the work is done. I have heard there can be issues with the ECM? Could someone elaborate on that?

Thanks!

[rl0089]

Anyone?

[hoonk]

Could the thermostat/coolant sensor housing being faulty have anything to do with the no start/reduced performance issue?

I have heard there can be issues with the ECM?

Yes, If the coolant temp sensor sends the wrong temp to the ECM the engine may have a hard time starting or fail to start at all. For instance if the ECM thinks the engine is -40 degrees, too much fuel will be injected and the engine may fail to start. A good first step would be scanning with Vida or an appropriate scanner to give you real time values and any stored codes.

Don't worry about your ECM. CEMs were supposed to have been prone to water intrusion in some earlier xc90s, but that does not apply to your year.

[hoonk]

clean MAF, TB,

I have heard of many problems created by "cleaning" an air mass meter. I would avoid doing that if it were my car. Throttle body cleaning is helpful, just make sure to use a new gasket and clamp the pipe back on properly.

[rl0089]

I appreciate the info on the t-stat, ECM. Thanks.

I have heard of many problems created by "cleaning" an air mass meter. I would avoid doing that if it were my car.

Is that a Volvo thing? On my Saab with a MAF you are advised to clean the MAF periodically to remove oil and dirt build-up. When dirty, they're known to produce a lean condition with, combined with their notorious sludge, can do some nasty things to the engine. I'd think that removing oil would be a good thing.

[hoonk]

On my Saab with a MAF you are advised to clean the MAF periodically

By Saab?

Many Mass air flow meter designs include a burn off function to "self clean" themselves. It is possible some cars have problems with contaminated MAF's - especially cars using oiled aftermarket air filters.

I don't clean air mass meters because Volvo does not recommend that at any time in their service schedules and I don't see "dirty" air mass meters making cars run bad. Unless a manufacturer specifies a service procedure I don't do it without the customers request or approval. It's very difficult to explain to a customer (or your wife) why they need a new ~$300 air mass meter after a service when the car ran fine before. My matra is - if it ain't broke, don't mess with it - cause it might be broke when you are through with it!

I'm sure every forum has threads expounding how cleaning their AMM gave them better gas mileage, more performance, lower ET's, and their wife, dog and kids love them more now. They are sure of it because performance was measured with their butt dyno and MPG was measured by barely touching the gas pedal the week after. However in my humble opinion all that happened was ~$9 +tax was transfered from their wallet to a retailer selling the product.

[rl0089]

So with the week off from work, I tackled the t-stat housing.

It was pretty obvious that the thermostat/sensor was causing some trouble. Since we owned the car in late March, I believe I saw the gauge at the midway position once, after the car had been sitting at idle for awhile on a somewhat warm day. On the highway it would plummet to the resting position all the way on the left like the car wasn't on. And we would occasionally get the P0116 code (I think that's what it was). So I went ahead and replaced it. Just some advise for anyone who may be doing this job in the future:

-Access to the thermostat is partially blocked by the power steering pump. If you want to remove and replace the entire housing in one piece, the pump needs to be moved, which means the serp belt needs to be taken off. I'm sure that leaves plenty of room to get in and out but I did it a different way considering I didn't have the correct torx bit to relieve the tensioner on the serp belt (t60 I believe).

-If you are careful with the gaskets and keep everything clean you can do this without removing the power steering pump.

1.The t-stat housing is two pieces sandwiched together with the t-stat in between and sealed by a gasket. Removing the old one, you take the outer piece off first and then the inner. As soon as you begin to remove the torx bolts holding the two pieces together you can feel the pressure of the t-stat between the two pieces. Like I said before, the entire unit will not fit with the pump there, so I removed the outside piece first with the t-stat, and then the inner piece, the piece that mates to the engine and has the sensor.

2.Replacing is the reverse of removal but because of the limited space, it can be a pain to get the housing lined up correctly with the gasket and two bolts. I tightened the top bolt by hand and then fished around for the bottom bolt, which is out of sight because of its placement on the bottom of the housing and because the power steering pump kind of sits right in front of where one would have clean access to the bolt. To get it tight I used a long 1/4" extension extended under the pump. The hardest part is getting the outer piece aligned because of the tension caused by the t-stat. To keep the gasket and torx bolts in place I used a light coat of vasoline on each and used trial and error to get the t-stat in the correct position. Note that the piece has to be tilted down to fit into the cavity where the housing is so the t-stat will want to fall out. It took some time but I was finally able to get it all in and aligned properly. Finally the bottom torx bolt on the outer housing is a pain to get to because it sits right next to the power steering pump. I used a very short torx and a very tiny 1/4" ratchet to get it in.

So it was an annoying job because of the limited space but not too difficult. Hope that description helps anyone needing to do the same!

Oh and now with the new housing in the temp gauge is in the correct place (matched with the correct temps on the torque app) and this morning we had a clean start so I think we solved both problems! Next is the preventative maintenance stuff, t-belt, PCV, cleaning and flushing fluids. Thanks for the help all!