Need help diagnosing a problem on a Tleg

macipusy · Post by **macipusy** » Wed Oct 14, 2009 1:01 am

The car is a 93 Turbo Legacy 4EAT

Basically the car has no power starting off...especially when you floor it. The car barely wants to go, even when you shift the AT into first.

It feels like it is bogging and I can hear loud pops or booms coming from the engine bay. It does not pop when in park and reving, but bogs when you floor it quickly.

I checked compression and seems good as well as fuel pressure.

Any ideas what to check next?

ericem · Post by **ericem** » Wed Oct 14, 2009 2:10 am

Have you done a tune up yet? Plugs,wires, PCV valve? Clean intake etc?

My car was similar ended up doing a turbo swap with intercooler runs amazing. I wonder if your problem is similar.

tturnpaw · Post by **tturnpaw** » Wed Oct 14, 2009 3:36 am

cracked knock sensor possibly or the engine temp sensor for the ecu.

magicmike · Post by **magicmike** » Wed Oct 14, 2009 3:57 am

yes, check cel codes. Also, possible clogged cat.

Post by **Legacy777** » Wed Oct 14, 2009 5:38 pm

Yeah....ECT or knock sensor. Sounds like it's back firing under load. I'd suspect ECT.

What is your fuel mileage like?

macipusy · Post by **macipusy** » Wed Oct 14, 2009 8:24 pm

Definitely sounds like a backfire under load, but from the front of the car.

macipusy · Post by **macipusy** » Wed Oct 14, 2009 8:50 pm

The fuel mileage I don't know since the car is barely drivable on the street.

ECT is the engine coolant temperature sensor....right?

log1call · Post by **log1call** » Wed Oct 14, 2009 9:11 pm

Recommended action here is a tune-up, check all the vacumm hoses and pipes, then check fuel pressure AND flow and engine vacumm. Checking the engine vacumm should include a check for a blocked cat.

Then you start suspecting and checking sensors.

macipusy · Post by **macipusy** » Wed Oct 14, 2009 9:32 pm

Here is what I did check so far:

Fuel Pressure....35-40psi

Compression...120,120,110,130

TPS....within resistance spec....2.2kOhms to 9.2 kOhms

Coolant Temp Sensor....warmed up...within resistance spec .3-.4 kOhms

replaced coil pack

checked vaccum...19Hg

Swapped plugs and wires

Next I will unbolt the exhaust when the car cools down and report back

log1call · Post by **log1call** » Wed Oct 14, 2009 9:41 pm

Those compressions look too low and the variation is a bit much probably. That being said, it's probably not the problem.

Have you checked all the vacumm hoses?

You can check the exhaust for blockage using the vacumm gauge too, no need to disconnect the pipe.

macipusy · Post by **macipusy** » Wed Oct 14, 2009 11:24 pm

I didn't go through all the hoses....I looked at the usual suspects and also hooked up my boost gauge to see idle pressure....it was just the same as my 91....19Hg at idle

Just disconnected the DP and still the problem persists.

Seems to get a little better when the car is warmed up, but still has no power.

When I rev it in park and floor it, the RPMs rise ok to 4K then stutter a bit for a second or two before going up to redline.

log1call · Post by **log1call** » Thu Oct 15, 2009 12:29 am

You should check for trouble codes.

It sounds like a lean mixture causing a backfire out the inlet, which is why I reckon ther will be aa hose leaking or off.... although it could also be cross firing, but not likely on one of these.

Do you have coil on plugs or wasted spark ignition?

cj91legss · Post by **cj91legss** » Thu Oct 15, 2009 1:17 am

Hey just go out on a limb and check your fuel pump.... mine was doin the same thing for like a year and i was gettin pissed... finally the pump died on me one night after work and i got stranded for an couple hourstil a friend was able to come help...

log1call · Post by **log1call** » Thu Oct 15, 2009 2:31 am

That might be a good idea.

When you check fuel pumps you need to check the flow as well as the pressure. They can have enough pressure but it can die away when you have your foot down and the flow can't keep up. That would make it run lean.

cj91legss · Post by **cj91legss** » Thu Oct 15, 2009 2:39 am

exactly, i would try to get on it, and if i eased into throttle... i could get up there. When i tried to floor it i would hear POP POP like the intake was backfiring....

Dynamic Entry · Post by **Dynamic Entry** » Thu Oct 15, 2009 6:14 am

+1

I replaced my fuel pump this week with a walbro and my low-power/hesitation/backfiring-under-WOT-issues have been alleved significantly

but that said, there are a few other variables that changed also

206er · Post by **206er** » Thu Oct 15, 2009 7:40 am

were your compression tests taken with open throttle and a strong battery?

macipusy · Post by **macipusy** » Thu Oct 15, 2009 4:26 pm

Compression was done with all fuel injectors unplugged and spark plugs out, good battery and cranked 6 times per cylinder. I compared the values to my 91 TLEg and they were close enough.

The fuel pump was the first thing I did...I forgot to mention that.

I also checked the ignitor and fuel injector resistance.

I checked the timing belt for skipped teeth as well.

macipusy · Post by **macipusy** » Thu Oct 15, 2009 4:27 pm

What is the procedure for testing fuel flow?

log1call · Post by **log1call** » Thu Oct 15, 2009 10:14 pm

Ha, you put a fuel hose in a bottle and turn the key. There is some specific figure about how much per minute but as long as the fuel comes out as a full diameter of the hose and with a bit of force it will probably be Ok.

Have you checked for codes yet?

If you have a spare MAF meter you should try swapping that.

The symptom sounds like lean burning, which makes the fuel burn so slow that there is still flame in the cylinder when the inlet opens the next time. It could be lean because of air leaks, dirty injectors, sensor troubles or fuel shortages but it sounds like we have covered the fuel.

Have you tried going for a drive and pushing it till it plays up then stopping and pulling the plugs to see if they are running lean?
You may find it's just one cylinder which would point to an injector.

macipusy · Post by **macipusy** » Fri Oct 16, 2009 1:31 am

It was definitely the MAF....just swapped it over from my 91 and it runs perfect.

Thanks for all your help guys.

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Need help diagnosing a problem on a Tleg

Need help diagnosing a problem on a Tleg