good boost, no power

george · Post by **george** » Fri Feb 21, 2003 3:12 am

1993 turbo auto with 90K miles. Tranny is fine except for a soft 3rd
gear shift. Thinking of trying the resistor higher shift pressure thing.

Porblem:
sort of complicated symptoms but hear me out.

For a month now the engine seems to bog down at low RPM and medium
boost (medium acceleration, half throttle). re 2,000 to 2800 rpm with
5 inch vac to 4 lbs boost engine power seems flat. As soon as the
rev's hit 3,000 power comes on nice. When its bogging it seems to
surge slightly, apparently only noticible to me, the Subaru mechanic
I'm sure thinks I'm going nuts. I also noticed a slight hissing sound
when on boost. Mechanic said my up pipe may be leaking but I can't
hear any exhaust noise otherwise ($500 experiment I want to be sure
of). Gas milage has dropped 70+m / tank but may be from hitting it
harder now with the flat spot.

I have replaced, fuel filters, spark plugs and wires, valve timing
belt, air filter, and had a injector / engine power flush treatment.
No change.

1-What and when, triggers the fuel enrichment loop? Is it gradual or
on off?
2-The hissing sounds more like a intake leak to me but can't hear
where its coming from when buddies hit the gas with me under the hood.
3-Turbo seems to be working fine, lots of boost at low RPM and steady
at 8 to 9 PSI all the way up when I've got it to the rug.
4-Should the transmition be down shifting in this situation and if so
what triggers this, throttle position, engine vacuum / boost,
transmition torque, ?? I bought the car last Sept and didn't have the
boost guage until a couple months ago. I remember the tranny not
downshifting too easily but the engine 'had' lots of low end grunt.

Any clever ideas?

Thanks
George

dorj76 · Post by **dorj76** » Fri Feb 21, 2003 6:48 am

Finally someone with the same problem...

I don't seem to have that hissing sound though...but i'll check.

this problem showed up after i had my timing belt replaced. I had the timing double checked so its ok. I also changed the fuel filter.

At around 2800 i get the hesitation (surge) and i'm at 4-5 PSI boost.

Last week i burned 20 Liters of gas for 100 Km.

Some days it pulls better but not as well as before.

Haven't found the problem yet...

IggDawg · Post by **IggDawg** » Fri Feb 21, 2003 2:17 pm

tranny downshifting is triggered mainly by rate of change of throttle position. I can ease it up to 70% throttle and keep it in 4th with the TC locked. but if I stamp it down to 50-70% throttle it'll downshift sho' nuff. I think there's some absolute limit at which it downshifts no matter how fast it got thee, but quick throttle changes are what tell the tranny to downshift.

I reccommend changing your plugs. the whole "moodyness" thing was what led up to my hesitation problem. The moodyness was the first thing I noticed before it went downhill. see the sticky at teh top of the forum. plugs are cheap, and if you're not running NGK plugs, you should be

. just about everyone's hesitation problems are due to something somewhere in the electrical system. plugs, wires, and recently someone swapped their alternator and that fixed it. so I bet you're in the boat with the rest of us. start with the plugs.

dorj76 · Post by **dorj76** » Fri Feb 21, 2003 2:33 pm

What plugs do you guys recommend?

This summer i put in NGK Iridiums and man what a difference that was. I can't beleive they're already done but you never know.

With my opened up exhaust and MBC, should i go colder? if so by how many?

what is the exact plug gap that i need?

IggDawg · Post by **IggDawg** » Fri Feb 21, 2003 2:44 pm

The NGK V-power plugs are what everyone swears by. off the top of my head I wanna say 6BKE111 or something like that. someone correct me.

You don't need to go colder unless your combustion temps are up. Read: more boost. don't worry about it until you've had to disable your fuel cut

. if you haven't then you're not running that much boost that you'd need to change the plugs.

As a side note, I'm running the same setup as your car. Straight pipe, MBC... running around 10-11 lbs. And she gets up to speed like nobody's business. the plugs were what was holding me back in my car. now I have to be careful that I'm not going over 100 mph when I go to pass someone.

dorj76 · Post by **dorj76** » Fri Feb 21, 2003 2:50 pm

can you tell me the gap i need?

Is it an easy DIY job? Access is different than a straight four

IggDawg · Post by **IggDawg** » Fri Feb 21, 2003 3:27 pm

yeah. you'l need to move your washer fluid tank tho. otherwise it's DIY. gap is .038-.043. IIRC.

vrg3 · Post by **vrg3** » Fri Feb 21, 2003 4:20 pm

It can also be a little easier to do if you disassemble part of the intake.

You'll need long extensions for your wrench. I haven't tried using one of the u-joint-type extensions, but they'd probably help, too, as long as you don't mess up the torque.

mikec · Post by **mikec** » Fri Feb 21, 2003 4:40 pm

Don't try to do it without removing anything. I did that (it was my first spark plug change), and I think my knuckles are still missing some skin. It CAN be done, but the frustration and contortions necessary aren't worth it IMO.

That gap (.038 - .043) sounds right. I split the difference and went with .040.

george · Post by **george** » Fri Feb 21, 2003 7:51 pm

Thanks,, I'm picking up some NGK plug this afternoon. BKR6EGP was what he had. These are platinum with the skinny electrode. Are these ones OK?

I'm noticing more now that the power is RPM related, locked it in 2nd and loaded it up, its dead until it hits 3000 then it hits hard. Do plugs normally effect low RPM, high or all?

george

boostjunkie · Post by **boostjunkie** » Sat Feb 22, 2003 6:47 am

george wrote:1-What and when, triggers the fuel enrichment loop? Is it gradual or
on off?
2-The hissing sounds more like a intake leak to me but can't hear
where its coming from when buddies hit the gas with me under the hood.
3-Turbo seems to be working fine, lots of boost at low RPM and steady
at 8 to 9 PSI all the way up when I've got it to the rug.
4-Should the transmition be down shifting in this situation and if so
what triggers this, throttle position, engine vacuum / boost,
transmition torque, ?? I bought the car last Sept and didn't have the
boost guage until a couple months ago. I remember the tranny not
downshifting too easily but the engine 'had' lots of low end grunt.

Any clever ideas?

Thanks
George

1. Depends on how far in the rpm range you are. When I'm cruising in 5th, the car goes into open loop mode (fuel enrichment) at something like 1/20th throttle. It's almost always in this mode. Lower gears take more throttle input.
2. Have you taken out the intake smorkus? My car makes that swoosh sound whenever I'm even CLOSE to boost.
3. Sounds like the turbo's spooling just fine.
4. Don't know about this one.

See my post about the "unexpected cure for hesitation." You might want to try testing your ignition system and alternator . . . Also, I would definitely go with the NGK v-coppers. I'm running much more boost than stock and they haven't given me any problems.

george · Post by **george** » Sat Feb 22, 2003 3:30 pm

The engine is stock re the intake smorkus?
Tested the vacuum hoses with 5 lb air in the hose at the intake,, no leaks. If I do the same for the back end of the exhaust will I hear a leak? I know there are water drain holes but if I put enough air in I should hear if my up pipe is leaking I hope. Its impossible to hear the leak from under the hood when the engine is loaded and on boost. May sound stupid but I'm sure this hissing noise is leaking air in or out somewhere screwing things up.
How can I check the intake manifold?

boostjunkie · Post by **boostjunkie** » Sun Feb 23, 2003 9:22 am

Get a vaccum gauge and hook it up directly to the intake manifold. With the engine at normal operating temps, the gauge should read between 17-22inHg . . . lemme know what readings you're getting and whether they're fluctuating . . .

george · Post by **george** » Mon Feb 24, 2003 3:59 am

17 cold, 15 hot. Vacuum is steady. Vacuum at 60 mph on the flat is about 10 but like I said before I can go into 5 lbs boost with very little increase in power until the rev's hit 3K.
I hooked up a temporary vacuum / fuel pump tester guage as a vac / boost gauge. Masures up to 10 lbs boost and my stock controller holds it to 8 to 9 anyway. A bit ugly but it works.

geo

boostjunkie · Post by **boostjunkie** » Mon Feb 24, 2003 5:04 am

"A low, steady reading usually indicates a leaking gasket between the intake manifold and throttle body, a leaky vaccum hose, late ignition timing, or incorrect camshaft timing.

Check for slow return after revving the engine by quickly snapping the throttle open until the engine reaches about 2500rpm and let it shut. Normally, the reading should drop to near zero, rise above the normal idle reading (about 5inHg over), and then return to the previous idle reading. If the vaccum returns slowly and doesn't peak when the throttle is snapped shut, the rings might be worn. If there is a long delay, looks for a restricted exhaust system (muffler or cat). You can check this by taking off the exhaust and re-test."

Taken from the Haynes Manual for the legacy.

george · Post by **george** » Wed Mar 19, 2003 2:20 am

I can't beleive this but I had the car in to fix an oil leak and they found the left cam out by one tooth. Car runs much better!!!

Gas milage is back up (for this car anyway), 25 USmpg at 70mph.
Vacuum at idle is 19 ish. Had new timing belt installed anyway even though it wasn't due.
Thanks

Geo

entirelyturbo · Post by **entirelyturbo** » Wed Mar 19, 2003 5:25 am

george wrote:I can't beleive this but I had the car in to fix an oil leak and they found the left cam out by one tooth. Car runs much better!!!

How much worse did it run before? I'm 98% sure my car is on-timing after I did the timing belt, if you can tell me it ran okay and now runs much better, then I'll be 100% sure like I wanna be...

boostjunkie · Post by **boostjunkie** » Wed Mar 19, 2003 5:37 am

george wrote:I can't beleive this but I had the car in to fix an oil leak and they found the left cam out by one tooth. Car runs much better!!!
Gas milage is back up (for this car anyway), 25 USmpg at 70mph.
Vacuum at idle is 19 ish. Had new timing belt installed anyway even though it wasn't due.
Thanks

Geo

WOAH, the Haynes manual was right!!

entirelyturbo · Post by **entirelyturbo** » Wed Mar 19, 2003 8:21 pm

boostjunkie wrote:WOAH, the Haynes manual was right!!

for once...

george · Post by **george** » Thu Mar 20, 2003 12:39 am

I guess the best discription would be the engine felt soft, like it was down 20 or 30 hp. I have a boost guage so I noticed I was into the boost much more when driving normaly. I bought the car 15K ago and it overheated slightly?? with my wife driving just before it went soft. (Coolant tank cracked). The car definitly was strong before it overheated then started to give the flat soft band symptom after. Is it possible the belt was damaged or soft from the heat and skipped a tooth? The Sub garage said the belt looked OK but we decided to replace it anyway.

I'm thinking the heat caused cam seal to fail. Anyway thanks again.

entirelyturbo · Post by **entirelyturbo** » Thu Mar 20, 2003 5:09 am

That's good enough, I'm 100% sure now!!!
I don't think the belt skipped a tooth, unless someone can report it running poorly all of a sudden. The person who did the last timing belt probably put it off a notch, and I can't call them idiots, because it's a little hard. Of course, that was my 1st timing belt change ever in my life, but thanks anyway, glad you got your problems fixed...

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good boost, no power

good boost, no power

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