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  #91  
Old 06-15-2010, 05:50 PM
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Re: Help!! I'm going to get hit by a semi truck!! Random stalling, stumbling idle

Quote:
Originally Posted by Trevor View Post
I sincerely apologise to members for the typo in the second added paragraph within my last post, where it is surely obvious, in view of the earlier text, that I transposed ECU with TCU. This I have hastened to correct.


Gee, Trevor, it sure wasn't that obvious to me

Thanks for trying to clear that up!

Keith
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  #92  
Old 06-15-2010, 06:16 PM
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Re: Help!! I'm going to get hit by a semi truck!! Random stalling, stumbling idle

I have very carefully gone through this complete thread in an effort to logically asses the issue. These clue are significant. ---

#5 --- Modifications on car:
-ECU tune 1v5, octane switch NOT installed, no stock ECU to swap out

#46 --- Found the wire from the ECU to install the 87 octane map switch last night as the car has tune version 1.5. May try to make the switch and try out the car in that mode (still running 93 octane gas and vice versa.

1) The TCU should be replaced for a trial period, with a correct stock standard unit, known and proven to be OK.

2) All connectors and wiring associated with the TCU, should be checked, with special emphasis regarding anything involved during previous removal and modifications to the TCU.
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  #93  
Old 06-15-2010, 07:02 PM
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Re: Help!! I'm going to get hit by a semi truck!! Random stalling, stumbling idle

Quote:
Originally Posted by oab_au View Post
Chris, Mac says that the engine clears up and runs fine over 4000. So that rules out a lot of things like a blocked exhaust, and a lot of mechanical troubles.
It really seems to me to be a spark timing or mixture problem, caused by, air leaks, fuel delivery??????

Harvey.
So whats the backfiring through the intake from then? Pre-ignition would be the prime suspect, but how could the signal from the crank sensor come prematurely? He has verified doubly that the crank and cam timing are correct.

I think it may be time to swap in a stock ECU and see what happens......
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  #94  
Old 06-15-2010, 07:28 PM
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Re: Help!! I'm going to get hit by a semi truck!! Random stalling, stumbling idle

I'll do my best to summarize here, I know that this is now the never-ending thread. Believe me, I have spent at least, one hundred hours trying your suggestions and those of the dealers', along with my own. I have also spent over $1800.00 in parts, labor and tools. I am really trying very hard here, so I hope you guys don't feel like I am wasting your time. I sincerely appreciate all of your help and I cannot even begin to tell you how much I have learned in the process. I would love to get this sorted and trust the car enough to come to one of the meets to thank you all in person, (sorry to those down-under, I can't afford to travel that far right now.)

First, the stalling is gone, fixed by the new MAF. So, the issue(s) now are the rough idle (not surging or stumbling, just rough), soggy feeling and sound at lower rpm operation. The issue may still be present at the higher rpms, but it feels and sounds smooth above 4000 rpm with good power. Another trait of the issue is the backfiring. Upon decel, the instant I open the throttle again, it will pop loudly. Still getting poor gas mileage. The car has been reliable for short trips, starting and driving with no stalling or hesitations.

Also, the blow-back from the MAF/snorkel connection has likely been resolved. I found that the Subaru tech forgot to put the o-ring in when he installed the new one. I installed the o-ring and corrected the problem. I will unbolt the airbox lid and re-try to see if I am still getting any blow-back.

Is 19 inches of vacuum correct at 600 rpm?? Or 21 inches at 1500 rpm? Are these too low?

-Mechanical timing and cam keyways= good.
-New coils (6)
-New TPS
-New CTS
-New LH O2 sensor (after it threw that code once)
-New MAF, factory Subaru part
-Vacuum pressures as stated just before = goodish?
-Fuel pressures as stated just before = good
-3 different sets of plugs including the factory set = same running condition
-K&N filter replaced with stock
-Dealer claims 170 psi min compression for all 6 cylinders. (I may check this myself later, seems suspiciously high.)
-New upper manifold gaskets
-Removed manifold and replaced all vacuum lines
-Sprayed propane, carb cleaner and starting fluid around engine bay with no surges in idle rpm.
-Seafoamed intake
-3 STP injector clean treatments
-Tried octane boost, no change
-New EGR vac lines
-Cleaned upper EGR pipe
-New gaskets for TB, IAC, and oil breathers
-New PCV and fuel filter (both autozone parts if it could matter)
-Purge recovery system is bypassed and capped at top of TB after the nipple broke off the solenoid
-Car has ECUtune 1.5, Stebro muffler, resonator delete, perrin crank pulley, 82,000 miles and is a 1995 L-AWD model
-No Codes other than the O2 and purge vapor code, as the solenoid is unplugged.

-Spoke with longassname about ECU who advised to check Fuel pressure for injector leak and to check for head gasket leak. The results from the fuel pressure check and the vacuum pressure needle not fluctuating at all, tell me that theses issues are not present. Yes/No?

Will by-pass aux. air to see if it could be leaking.

Does anyone have an extra stock OBD1 ecu I could try????

Chris, will try removing the O2 sensors and running to see if there is in fact some blockage.

Thanks,
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1993 968 Coupe 6-speed, 80,xxx miles black, H&R springs

Last edited by macadamianut; 06-15-2010 at 07:32 PM.
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  #95  
Old 06-15-2010, 08:10 PM
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Re: Help!! I'm going to get hit by a semi truck!! Random stalling, stumbling idle

Honestly... a compression test followed by a leak-down would be my next steps were I in your shoes

Tom
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  #96  
Old 06-15-2010, 08:51 PM
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Re: Help!! I'm going to get hit by a semi truck!! Random stalling, stumbling idle

Quote:
Originally Posted by SoCal LS-L View Post
So whats the backfiring through the intake from then? Pre-ignition would be the prime suspect, but how could the signal from the crank sensor come prematurely? He has verified doubly that the crank and cam timing are correct.

I think it may be time to swap in a stock ECU and see what happens......
Refer also #92. On the basis of logic and now with two of the same mind, it is time to swap the ECU and check all the associated connections and wiring.
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Last edited by Trevor; 06-15-2010 at 08:54 PM.
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  #97  
Old 06-17-2010, 05:19 PM
oab_au oab_au is offline
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Re: Help!! I'm going to get hit by a semi truck!! Random stalling, stumbling idle

Quote:
Originally Posted by Trevor View Post
I have very carefully gone through this complete thread in an effort to logically asses the issue. These clue are significant. ---

#5 --- Modifications on car:
-ECU tune 1v5, octane switch NOT installed, no stock ECU to swap out

#46 --- Found the wire from the ECU to install the 87 octane map switch last night as the car has tune version 1.5. May try to make the switch and try out the car in that mode (still running 93 octane gas and vice versa.

1) The ECU should be replaced for a trial period, with a correct stock standard unit, known and proven to be OK.

2) All connectors and wiring associated with the ECU, should be checked, with special emphasis regarding anything involved during previous removal and modifications to the ECU.
Fixed it for you. So you don't lead people astray.

Harvey.
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  #98  
Old 06-17-2010, 05:56 PM
oab_au oab_au is offline
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Re: Help!! I'm going to get hit by a semi truck!! Random stalling, stumbling idle

Quote:
Originally Posted by SoCal LS-L View Post
So whats the backfiring through the intake from then? Pre-ignition would be the prime suspect, but how could the signal from the crank sensor come prematurely? He has verified doubly that the crank and cam timing are correct.

I think it may be time to swap in a stock ECU and see what happens......
Well I still think it is a lean mixture problem, caused by, an unknown air leak, or fuel delivery.

The symptoms of a bad idle, getting better as the engine speed increases, and backfiring through the inlet, are all a sigh of a lean mixture.
Chris, a lean mixture burns slower, still burning when the inlet valve opens, to cause a backfire into the inlet manifold. A very retarded spark will do the same, but it won't get better as the revs go up.

I would go all over the engine, at idle, with a stethoscope listening for a leak.

Harvey.
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  #99  
Old 06-18-2010, 08:00 PM
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Re: Help!! I'm going to get hit by a semi truck!! Random stalling, stumbling idle

Quote:
Originally Posted by oab_au View Post
Well I still think it is a lean mixture problem, caused by, an unknown air leak, or fuel delivery.

The symptoms of a bad idle, getting better as the engine speed increases, and backfiring through the inlet, are all a sigh of a lean mixture.
Chris, a lean mixture burns slower, still burning when the inlet valve opens, to cause a backfire into the inlet manifold. A very retarded spark will do the same, but it won't get better as the revs go up.

I would go all over the engine, at idle, with a stethoscope listening for a leak.

Harvey.
I believe he mentioned the backfire thru the intake had been corrected?

In all fairness, it may just seem that it runs better at 4000RPM, as at that speed anything less than catastrophic misfire is heavily shrouded by engine speed, and also the IRIS is open to help the air along the lengthened track.

Some careful spraying of starting fluid along the intake system should help identify any intake or vacuum leaks..... however I think that given the symptoms and the amount of new equipment he has already installed and eliminated as a cause, engine management should be scrutinized and a stock ECU at least swapped in to see if anything changes.
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  #100  
Old 09-10-2010, 07:14 AM
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Re: Help!! I'm going to get hit by a semi truck!! Random stalling, stumbling idle

I know someone with similar issues on an non-SVX. Was this ever solved?
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  #101  
Old 02-09-2011, 02:33 PM
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Re: Help!! I'm going to get hit by a semi truck!! Random stalling, stumbling idle

Not entirely, but the car is running (dare I say) well.... The real culprit in the stalling and rough running was the MAF. Also, I went back to the OEM spark plugs- I mean the ones that originally came with the car 16 years ago. Runs much more smoothly with those in. At one point in the process I shot the car with a 12 gauge filled with "part-shot" which included:

-6 new coils
-new CTS
-new TPS
-new breather gaskets, hoses
-new PS o-ring
-new vac lines - all
-new TB and by-pass gaskets
-new left side O2 sensor

At any rate the majority of the issues have been resolved by the great advice from you all and a large money-injection. I am thinking my residual issues popping from decel and re-opening throttle are from oddball ignition as a result from my exhaust. I have a stebro muffler and ditched the resonator. I am going to live with it, and its kind of entertaining anyway.

Thanks,
Mac
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1995 SVX-L AWD, green, 98,xxx miles, ECUtune 1.5, mazda RX-8 wheels with subie center caps, stebro muffler, resonator delete, koni inserts, perrin crank pulley, hella 500 off-road lights, power-slot rotors and .....
1993 968 Coupe 6-speed, 80,xxx miles black, H&R springs

Last edited by macadamianut; 02-09-2011 at 02:41 PM.
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