Strosek

Hi, I'm trying to diagnose a 993 with very low power output. Here's the situation.

Power is way down...feels like a 100hp car but runs and starts smooth.
Engine is brand new fresh 3.8 rebuild with best of everything so it's not a mechanical problem... Engine was gutless before rebuild as well....
New wires, plugs, injectors and air flow meter,distributors rebuilt
Tested cylinder head temp sensor is OK
Tested fuel pressure is OK air and fuel filters new
Engine runs on one coil at a time so both are OK.
Feels like it may not be getting Timing advance but not sure how to test...

Check engine light is off.
I have a Bosch hammer but don't have the obd connector so can't use that yet....

Any help would be appreciated.


Thanks

driveline

Whats your compression? Real compression test not just theoretical.
Does the engine turn over easy?
How old is your gas?
Are both coils hot? Crank and see.

Now are you reving it? Its not a chevy 350. Its way cooler.

Strosek

Engine is new and has full compression. Before rebuild compression was down a fair bit and getting tired hence the rebuild.
Fuel is new
Both coils work tested by removing one coil while running then the other...RpMs drop but engine remains running.
Engine turns over great no problem... Just gutless way way down on power. I have a second 3.8 So I know what this should rum like.

Strosek

Remember this is 99.99% a preexisting problem.... Power was wayyy down as it is now before rebuild as well.

driveline

I only asked about compression if there was an assembly problem. This is troubleshooting so it takes methodical steps. This one is difficult because so much has changed. I would have to treat a tired 3.6 and a fresh 3.8 at the same power as not necessarily having the same cause, but the coincidence is hard to ignore. Was the motor dynoed before it was installed?

If there is good compression and smooth running it sound like a fuel delivery problem. What about fuel pressure under power? If pressure is dropping under load it could indicate a filter restriction or low fuel pump output.

Finally is the Varioram working? Could be when it revs over 4000 RPM it is actually air starved because it has not changed to the shorter runners. I am not a H6 expert but I have been around many engines. Beyond this you probably just need to keep posting your progress and people can chime in.

Read Varioram explained. Look at mode #2). One guy hooked the vacuum canister wrong and only made ~180 hp.

http://www.instant-g.com/Products/36...sion/VRAM.html

Good Luck,

joel
96 c2 iris blue

Strosek

Hi,the motor runs a tiny bit better since the rebuild but the lack of power issue still remains... This is a preexisting issue.
This is not a varioram intake 993, it has the black composite intake and the resonance flap which works fine and the power loss is much larger then if that would not work. No dyno test was ever done.
Fuel pressure tested at idle and was fine, fuel filter is new.

It feels like the ignition timing isn't advancing and I know this motor has very low base timing so if it didn't advance power output would be low but don't know how to test for that...

Thanks very much for your help I appreciate it really.

95_993

Is the throttle advancing/opening correctly/fully? Just a thought since you are not having classic signs of ignition issues, etc.

Strosek

Throttle plate movement was checked and is fine. But thanks

AKTUNG

Make sure distributor belt is good in dual distributor unless your coil test took this into consideration.

Livefreeandrive

Can you borrow a DME/ECU from another car?

Strosek

Distributor was rebuilt with new belt and bearings... Also like you said my test would have confirmed that indeed they both are working fine. Car sounds great at idle just super sluggish and also the exhaust is all new so not a plugged cat or anything... Honestly feels like a 100hp. tops!

A second DME to test would be ideal but I have none. Are you thinking the DME gone bad is a possibility?

Thx

Strosek

Would a DME from a 964 work in a 993? I actually do have a 964 dme if it would work.

Thanks

techman1

Whatever was re-used should be tested.

I recall a beater with a clogged catylic converter that had similiar symptoms.Do you have another exhaust system that you could test on it?

You sound like a shop, can you put it on a lift, and check temp on all 6 exhaust? I know new injectors, but if all temps are close, you have verified all injectors are firing , plugs are sparking and no intake runners are blocked. (A theory, never had to try it)

pp000830

[QUOTE=Strosek;10413186]the motor runs a tiny bit better since the rebuild but the lack of power issue still remains...QUOTE]

t seems to me that running the OBD Codes and looking at the real time OBD data should tell you something.

I noticed your comment above. I may be misinterpreting it but, If the engine pre-rebuild ran at X perceived performance and the rebuilt engine runs at X + 15% you may be looking at all there is.

Your last step is to take it to a qualified technician who can go throu the diagnostic program steps and see what is up.
Andy

Strosek

Hi, I'm not a shop just trying to help a friend with his car as I have a bit more knowledge then he does.

Injectors are all firing and no intake blockage...

The motor had no power before the rebuild and has no power after the rebuild... I drove the car before and after so I know first hand... Its a preexisting problem for sure. I also built a custom 3.8 motor for my 964 so I know what this should run like.

We've ordered a connector the hammer so hopefully it will show something I was just hoping to get some ideas as too places to check and tests to run. Feels like the timing is not advancing to me.

Thanks