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Discussion Starter · #1 ·
I already posted this on Central, but figured I'd put it up here, too:

I've been having some problems with roughness at idle and hesitation under initial load, but no CEL.

I did have an issue last summer where the DI was throwing out some codes (FLASHING CEL!) but nothing like that now.

I'm thinking possible vacuum or fuel problem, but where do I start to look and how do I go about diagnosing - I don't want to buy a DI "just-in-case".

Anyone out there seen this before?
 

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If it helps I'll ask the following questions to stir some thoughts up
for you.
1) What fuel are you using?
2) Have you replaced your fuel filter?
3) Have you checked your vacuum lines yet?
4) Is your car stumbling at idle, on take off, or both?

Flashing CEL's generally point to the O2 sensor checking your engine
for running rich or running lean.

Some checks to do:
1) Check your spark plugs to see how each plug is firing.
2) Check for leaks on your vacuum lines, particularly if your car is a mid 90's car. I found 2 cracked vacuum lines on mine.
3) Check to see if your DI Cassette is properly firing.
4) Check to see that your oil is properly topped off.

There are similar dialogs here on your situation.

hope this helps stir up your thoughts a little,
good luck....
 

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Discussion Starter · #3 ·
DC_SAAB said:
If it helps I'll ask the following questions to stir some thoughts up
for you.
1) What fuel are you using?
Always premium 92-94 octane (usually 93) based on availability - name-brand only - usually Marathon, other times Shell, BP, Sunoco
DC_SAAB said:
2) Have you replaced your fuel filter?
Not yet - I just bought one yesterday ($43 - YIKES!) and it's raining today ($43 - YIKES!)
DC_SAAB said:
3) Have you checked your vacuum lines yet?
Yes, I looked at all the lines, replaced the PCV fitting, its bushing and the line going to the check-valve - tested the check valve and it's working fine (blew through in one direction, couldn't blow through in the other
DC_SAAB said:
4) Is your car stumbling at idle, on take off, or both?
All of the above - stumbling on idle and under accelleration - not too much when just driving steadilly, though.

Additionally, it only stumbles when warm - first thing in the morning it runs just fine - after it warms up it starts to stumble.
DC_SAAB said:
Flashing CEL's generally point to the O2 sensor checking your engine
for running rich or running lean.

Some checks to do:
1) Check your spark plugs to see how each plug is firing.
Pulled the DI and all the plugs and wire-brushed and re-gapped them. They all looked about the same - whitish-gray residue on the tips of the anode and the diode (correct terminology?) some black residue around the base - dremel took care of all of the above.
DC_SAAB said:
2) Check for leaks on your vacuum lines, particularly if your car is a mid 90's car. I found 2 cracked vacuum lines on mine.
I did inspect the vacuum lines I could see - is there a diagram anywhere showing them all, in cased I missed some? The vacuum line under the cover, coming out of the TB has been renewed.
DC_SAAB said:
3) Check to see if your DI Cassette is properly firing.
How do I do this? With traditional wires I know you can hold a wire up to the plug and see if you get an arc - is there anything that can be done with the DI?
DC_SAAB said:
4) Check to see that your oil is properly topped off.
Just had an oil-change 2 weeks ago - haven't put more than 50 miles on the car since then.
DC_SAAB said:
There are similar dialogs here on your situation.

hope this helps stir up your thoughts a little,
good luck....
Oh, I'm stirred all right! :? :? :?

Thanks for the info - I pulled out the front O2 sensor last night and cleaned all the gunk off of it - lots of carbon residue ('97 turbo - 75K miles) - and the threads on the sensor and the standoff it goes into, so that's making good contact now (I hope) but I can't seem to get the rear sensor off to check it - just can't get a good angle on it to appy enough torque to loosen it up. Even if I did, I probably couldn't get to the threads on the pipe itself, just the sensor.

I'd go out there again today, but it's raining so this will have to wait a day or two yet.

Thanks for all the advice, though, I do appreciate it.
 

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HNNLIC
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Definately check your DI cassette. A way to check it is to remove it from the engine, and pull the fuse for the fuel pump. With it out of the engine(but still plugged up), plug in a spark plug to the DI, and have someone try and start the car. You can either use four plugs in each DI hole, or rotate the spark plug each time. You should get a spark from each hole. If not...then your DI cassette is shot.
 

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Haven't been here in a while...sorry about that.

I'm thinking DI Cassette, and I have a spare if your interested in purchasing one. Because a flashing CEL light would tend to indicate misfiring or stumbling which would be the result of a rich fuel mixture to the 02 sensors.
Then you said your plugs were grey, when I'm thinking a light tanish color.

The fuel pumps seldom go on these things, especially at the mileage you indicated....so after replacing the fuel filter....I'm going to point to a DI Cassette causing the miss-firing, and the more common to fail.

The dealership on an engine analyzer is all that's left.
 
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