'96 850R Very low mpg, very low power.

bmessina · Post by **bmessina** » 26 Nov 2012, 11:09

Hi - Previously posted on another board, but I'm spreading this around to hopefully get some more ideas.

The car is generally very low powered throughout the rev range. Will not rev above 4.5k RPMs or so, 0-60 in about 30 seconds. Trip computer and math at the pump are giving me 7 - 8 mpg. No CEL, and the only code I was able to pull (using the LED/OBD pin diagram method) was 233 (P0172 Long term idle air trim). I've since fixed 2 small vacuum leaks. No smoking out of the exhaust. Amazingly enough, the car passed a CA smog test in this condition.

Replaced front O2 sensor
Replaced fuel injection relay
Replaced fuel pump (found a walbro kit in a T5 at the junkyard)
Replaced catalytic converter
FPR tested, not leaking
Car won't idle with MAF unplugged, but will run if I keep my foot on the gas.
Fuel pressure is about 44psi at idle, dips to about 39psi when I rev the engine (this was before I replaced the fuel pump)
Replaced Coolant Temp Sensor (gauge stays at 3pm)
Ignition tune-up: Plugs (gapped correctly), wires, cap, rotor from IPD
All turbo hoses replaced w/ silicon
TCV replaced w/ IPD HD unit, associated vacuum hoses replaced
CBV replaced w/ stock Mitsubishi unit, vacuum hose replaced
PTC cleaned
PCV system replaced using IPD kit
Fuel filter replaced
ICV cleaned

Exhaustively checked for vacuum leaks via pressure testing - There are certainly no large ones left. Not large enough to cause this much of a problem, anyway.

Sorry for the book, I've been working at this since I got the car almost 2 months ago!

Post by **jblackburn** » 26 Nov 2012, 12:08

Does it rev to 4500 with no power at all with your foot on the gas, or just rev that high in park if you hit the gas?

I think it might be time to head to a junkyard and get a mass airflow sensor for a few bucks. I'm not sure it will cure your problem, but it seems to be the only thing left in the equation that you haven't tried already.

While you're at it, grab a throttle position sensor as well. I doubt this one is your problem if it revs and downshifts properly and is just low on power.

bmessina · Post by **bmessina** » 26 Nov 2012, 12:19

4500 is in gear, foot on the gas. The revving in park is sluggish, but I don't think I've seen how high it will go.

Yeah, that's pretty much what I was thinking on the MAF. The only problem is that my local yard wants $40 for it plus core! I'll probably just suck it up and go check for one this weekend. They have a kind of return policy so if that's not it I'll just bring it back.

It is downshifting and revving as well as can be expected right now. Which is to say, normally.

Thanks!

Post by **precopster** » 27 Nov 2012, 05:54

This is really rare in whiteblock Volvo engines but have to ask if compression has been checked? Get some numbers from the engine and publish them here.

l'm beginning to suspect the computer. Something sure has it fooled into thinking that your engine's running well and I don't know if the MAF will help, though if I were you it would also be next on my list.

bmessina · Post by **bmessina** » 27 Nov 2012, 10:55

Compression has not been checked. The idle and running is smooth and even (just slow), so I've been coming at this from the perspective that whatever is wrong is affecting all cylinders. There's really no reason not to do the test though, so that goes on the list for this weekend. The motor has about 120k on it, fyi.

bmessina · Post by **bmessina** » 10 Dec 2012, 21:05

Checked compresion tonight, and measured resistance/voltage values on several sensors.

Compression was 170-175psi across all cylinders.

Resistance on all fuel injectors, TPS, ICV, and CPS all check out to spec. Also, the plugs all looked the same:

Got it all back together, turned the key (but didn't start it) and noticed the trans arrow in the dash was flashing. Car started fine, arrow kept flashing, and the check engine light came on. Checked for codes via a generic OBD reader, nothing. Checked all the connectors I touched, they were all good. Car seems a touch more responsive, but now has a bit of a random stumble on the road. Shifts fine.

I'll have to get my pin reading circuit back out and see what codes i can pull via that method.

bmessina · Post by **bmessina** » 12 Dec 2012, 11:46

Flashing arrow persisted yesterday morning, but was gone for my evening commute. It did not make a reappearance for this morning's commute either. The Check Engine light has persisted, though, even through clearing the codes (via the same generic OBD code reader).

I'm getting a backpressure tester (via the O2 sensor port) soon, so that will be my next check. I'm basically only testing to see if the muffler is plugged, though I don't think it is.

After that, I guess I'll be looking for a spare ECU to test.

After that, I'll be checking values at the ECU harness to check for a wiring issue.

After that... I don't know yet!

Post by **jblackburn** » 12 Dec 2012, 11:53

All that black soot on the plug looks like it's running super rich.

Did you try the new MAF sensor, or are you skipping that

bmessina · Post by **bmessina** » 12 Dec 2012, 14:42

Yeah, with that fuel efficiency I don't think there's a question that it's running rich. It's just... why.

Did not pick up a new MAF to swap. I get good readings off the current MAF via the OBD plug, and I tested the sensor against the voltage values found in the technical manual. It was well within spec. WIth that, I can't see how it would be causing a problem.

Post by **jblackburn** » 12 Dec 2012, 14:47

Gotcha