I sure thought the fuel pump relay would be it

[jblackburn]

I believe the WOT issue is unrelated. I believe, but i am not sure, so this is the best i can reason:

In fact, the way you describe the hiccup, it sounds more vacuum or "over boost" related to me, and maybe the engine is cutting power for a second to dump the boost off before it can build up too quickly to harm something.

A vacuum leak would also explain why it stalls with the MAF taken out of the equation. As I recall you had a P0172 and a couple other O2 sensor codes that usually show up with vacuum leaks on these cars. There have been several posts like this and I have spotty phone service at the moment, so please correct me if i am wrong.

[belyle]

That's correct, I did have an O2 sensor and burning rich code. It did not throw those codes during my testing this morning though. Probably just didn't run long enough. From what I've read, I don't think a vacuum leak would cause a total engine shutdown. I have also seen some folks with a bad TPS with the same symptoms as my car, especially it dying after a longer drive time.

[anmartin44]

Go through and tighten all the clamps on the intercooler hoses and check for cracks on the bottom sided of the intercooler. Have you done a compression check? I had a car that ran fine at idle but crapped out under load. It was dead on two cylinders. that happened due to my brother-in-law's wife running it 2 qts down on oil. Probably not what you got going on but might be nice know what your compression is anyway.
A significant vacuum leak can make your car pass out for sure. Unmetered air gets to your system and throws off your fuel air ratio.

What's the condition of your turbo?

Have you ever changed your fuel filter?

[Pauloil]

Sorry for my apparent ignorance. I'm an engineer (mechanical), so I know that there is a huge difference in off the shelf stuff for certain things. I just never have mucked with picking certain brands of stuff for my maintenance items in my cars. It sounds like Volvo is a little more discerning than my old Toyotas...

I picked up copper core autolite plugs (not bosch, but Napa didn't have non-platinum bosch in stock), a new cap and rotor, and a set of plug wires. The cap and rotor are both echlen (Napa branded) and despite advisement to go with Bougicord, I picked up the Beldens. I grabbed those for two reasons: one is that they are immediately available and the Bougicords were special order. Second is that the Beldens are 1/2 the price.

I also picked up a can of carb/intake cleaner and new hose claps so I can clean out the IAC. I'll post back with results.

One thing that nobody has addressed is why it would be running perfectly fine and then just die. Replacing the fuel pump relay got it running again, but now it runs crummy. Maybe the fuel pump relay wasn't bad to begin with?

put in bosch plugs, get bosch cap and rotor, and new volvo wires. let us know if this helps

[jgray850turbo]

I didn't have exactly the same symptoms with my 95 850 turbo, but had several frustrating stalling, hesitating, no start conditions, ESPECIALLY at WOT(warm oper temp?). Most of my conditions went on to varying degrees over a two year period and I tried all sorts of tshooting and parts. I basically adapted my driving to what the car would allow, until it wouldn't start at all and I diagnosed the Fuel Pump as the problem. Replaced it expecting it to 'just' start again, but it eliminated all my other problems as well. One thing I think is of note is that, when I removed the old pump the hose was not FULLY connected to the pump. I think it had shrank a bit over time or the pump dropped in the craddle, but because of age, it was 'trained' to stay right at the tip of the pump nipple. My thought is, when it built pressure in the tank from heat and jostling or from the pressure of the pump, it would allow a loss of fuel delivery. Testing rail pressure while car is stationary may not give the whole story. It was only about 70 bucks and an hour job, couldn't really hurt at your cars mileage. On the side, I'm running Bosch Coppers, cap, rotor, BUT I do have the Belden 'Edge' wires and have been really happy with their performance. Sorry to ramble, hope you get it worked out.

[Chefbob1]

My daughters car was acting strange....stalling, surging, dumping her at the side of the road...I would get it towed and it would start up at the shop everytime.....There is another relay that controls the fuel injectors...it resides under the shroud on top of the fan...it was functional but the connecting block was very corroded....we fixed it and the car has been trouble free...try checking that part...might do the trick...

[belyle]

So, I go away for a week and ended up with a bunch more suggestions. Thanks, all!

I went back to Redmond today to work on and pick up my car. It spent Christmas at work since I didn't trust it to get me home. In the meantime, I ordered and received a new MAF sensor and new vacuum elbows. I printed out the vacuum elbow instructions from IAB and the vacuum line map. After a bunch more research, my gut was telling me vacuum, but I've been wrong (a lot) before.

This morning, I removed and cleaned the MAF sensor and its connection. I took apart the intake and cleaned the throttle body thoroughly. I cleaned the connector for the throttle position sensor. I cleaned the connector for the IAC. While I had the intake apart, I cleaned up all of those hoses with some carb cleaner and rags.

I added a couple of clamps to my vacuum lines, one on the line that goes to the air intake just downstream of the MAF sensor, and one to the line that connects just under the throttle body/IAC area (the larger diameter line). I checked out all the elbows in the system, and they all looked like they were in great shape. I believe that the ones in the injector area were replaced when I had the PCV redone about 10k miles ago.

I looked for vacuum leaks everywhere. I kept the car running and sprayed starter fluid on all the joints and tees in the system. I sprayed along all the vacuum lines. Nowhere caused an increase in RPM.

After reconnecting everything, I cleared the codes and went for a test drive. The car started rough at first but then smoothed right out. I drove around the block ~1 mile and pulled codes. It had thrown an MAF sensor code P0102. I checked and the connector was not quite dry from cleaning. I dried it out and test drove some more and everything was A-OK. No hesitation at wide open throttle (WOT), no stumbling at idle.

I drove it home with my oh-so-patient wife following me just in case. No problems at all. My problem is that I have no faith in my car now. I don't feel like I really did anything to fix anything today. I still have the brand-new (Bosch) MAF sensor that I can install, but I'm not sure if it would do any good, or if I should just return it and get my $150 back.

What I need right now is someone who knows what the vacuum lines should look like (the routing) to come over and help make sure that everything is routed correctly. I have the vacuum diagram, but it doesn't make any sense to me. It seems like I have one more thing connected to the vacuum tree than is shown in the diagram, but I can't really figure out what's wrong with the whole system.

And now, I noticed that I have a slight coolant leak at or near my upper radiator hose right on my radiator. I'm very strongly considering selling the car and being done as a Volvo mechanic.

[cn90]

Just put in the new MAF sensor and see how it goes.

Another culprit (for no-start or stalling ) is ECT, new ECT is $40.

[belyle]

I put the new MAF sensor in and have driven about 50 miles around town since. No hesitation or stuttering, or lag at wide open. I'm not 100% that I've solved the problem since I didn't have any symptoms before it died the first time, though. No codes on the computer, either, and before it was throwing a couple (O2 and rich condition) pretty quickly. So... maybe problem solved.