Does anyone know the difference between regulators on:

1999 SOHC 2.5

1996 2.2

 

?

 

Working on a 99 Foz for a friend of mine that doesn't have much money.

Started with a non-responsive front O2 sensor, her parents dropped the money on a spankin new one from the dealer. Put that in, now I can see fuel trims (they were solid 0 before). Car is running pig rich and ECU is pulling -29% (yes, negative) trim at idle. Front and rear O2 sensors both reading 0.85V or higher constantly.

All other sensors reading normally. ECT reading normal on scanner. Fans turn on properly at 204° and turn off at 194°. Runs 190° when driving. After 20-30 seconds a idle fuel system switches to OL-Drive then fuel trims 0 out, and idle starts to bounce.

No vaccum leaks.

Vacuum line to the FPR is clean, no fuel in it.

Am thinking injectors are cruddy or FPR is clogged and forcing fuel into the thing.

 

Going to put a pressure guage on it tomorrow, and see if my high fuel pressure theory is right.

If It is the FPR I have a few for the 95-98 2.2 and I'd like to try and swap one on to test. Just not sure if it'll fit.

Yeah, I'd check the fuel pressure to confirm what is going on and that the regulator is working properly when you remove the vacuum line from it.

 

All the stock regulators are 1:1 ratio, so as long as it physically fits it should be interchangeable.

Fuel pressure is spot on. 35 psi at idle, 45 with the FPR vacuum line off.

 

Found a TSB for MAF sensor. The MAF on this one has been cleaned but I will pull it out of the housing and try to get a closer look at it this weekend. I unplugged the MAF and it did run better.

Have to try and find what the normal airflow should be for these. It looks like its close to the correct range but I don't have another of these to compare with.

Anybody know what the flow rate should be (99 SOHC 2.5) at Idle and at 2500 rpm (in Nuetral)? G/sec or lb/min. G/sec is a bit more accurate but I can use either.

Fairtax,

 

I usually see 5-8 G/sec @ idle and about 25-40 G/sec at 2500-3000 rpms under load. These are number off the top of my head from what I recall driving in but let me verify those numbers on the drive back home today.

 

Rob

Cool, thanks Bob. I figured I would ask you about this since you have the scanguage.

 

The MAF flow under load varies too much. It's going to change drastically depending on if the car going up/downhill, but if you could check at 2,500 rpm sitting still that would help.

Also, could let me know the engine load calculation (%) at idle?

Thanks!

Cool, thanks Bob. I figured I would ask you about this since you have the scanguage.

 

The MAF flow under load varies too much. It's going to change drastically depending on if the car going up/downhill, but if you could check at 2,500 rpm sitting still that would help.

Also, could let me know the engine load calculation (%) at idle?

Thanks!

 

FT, here are my numbers during idle and 2500rpm and they are consistent over time:

 

idle  3-4gm/sec

2500rpm (no load) 10-12gm/sec

 

engine load percentage at idle - think its around 5-7% but I'll check that number again tomorrow morning to be sure.

 

Rob

Thanks! I'll have to check again this weekend, but it seems to me this car was reading 6-7 g/sec at idle. It wasnt too happy to idle properly though, so it was difficult to get a solid reading.

 

Gonna see if I can find a used one locally. The made in China cheapos are only about $25 on eBay... but I'm not sure if I trust that kind of high quality.

FT,

 

just checked the numbers this morning:

 

MAF numbers at idle remain the same & at 2500 rpm (no load)

 

Engine load - consistent 2 to 2.4% @ idle

 

Rob

Thanks Bob.

 

I'll have to hook the scanner up to it again and recheck just to be sure but I think this is the right track.

Idle was a bit jumpy but its reading about 6.5-7 g/sec at idle. 14.5 g/sec at 2500 rpm.

Engine load around 5.5-6%.

 

I did look up factory specs and the FSM says idle air flow should be 2.2-4.0 g/sec at idle. 12ish g/sec at 2500.

Engine load is supposed to be 1-3%.

 

Found out Subaru sells just the sensor element for about $70. Much less than the whole sensor/housing assembly for $225. The plastic housing part costs more than the damn sensor! So anyway, they're getting a MAF from Subaru and gonna pop it in there next week.

sounds like the reason the fuel numbers are so rich as those numbers are slightly high. Could the fuel line clamps be lose as well?

 

I bet the TPS could use a cleaning as well. Also, Subaru can sell a portion of the sensor only?

 

R

Right, MAF flow directly affects fuel. If the MAF flow is high it'll get tons of fuel and the O2 sensor readings will be rich.

 

Computer pulls fuel trim negative to compensate for the rich reading from the O2, but in this case it can't pull enough. It's maxed out negative at idle and still reading over 0.9v from the O2 sensor.

When driving the difference is less and fuel trims are closer to -15, but still a problem.

 

TPS isn't an issue, it's reading properly. No way to clean that anyway, its a sealed unit.

 

This is the replacement unit Subaru sells: http://www.scoobyworld.co.uk/catalog/product_info.php?products_id=1351

Edited March 3, 201511 yr by Fairtax4me

my mistake, I intended to say IAC, not TPS. Had TPS on the mind from reading a post on forester.org