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Is this Opti-Spark? @adallak

Have you determined if the transmission torque converter is going into lock up?  That may not set a code.  I know that the P0741 code will cause a hit to the gas mileage in the 4T80E

Will the O2 sensors set a code if they are slow?   I find it odd that you have never had a code.

It is possible that the knock sensor is either shorted or open causing a retarded ignition.   Can you get into real time data through the DIC?   Does it feel like a pig, or sluggish?

Tuned up recently?, AC DELCO plugs?, GAP?, ignition wires checked?, good spark/coil?, cracks or carbon tracking?

Have you put a vacuum gage on the engine to see what it reads?

The fuel trim numbers would be revealing.

Have you checked fuel pressure?   Again, you should check to see if you have a restriction in the exhaust, you can purchase a gauge for that that screws into the O2 sensor port. 

I have a 94 FSM, Ill skim through it, not sure if it covers your Fleetwood though.

Are you still in Mass?


Pre-1995 - DTC codes OBD1  >> http://z-cut.de/US/dtcobd1.html

1996 and newer - DTC codes OBD2 >> http://carprogrammer.com/Z28/PCM/OBD2/On-BoardDiagnosticTroubleCodes(OBD-II).mht

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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16 minutes ago, BodybyFisher said:

Is this Opti-Spark? @adallak

Have you determined if the transmission torque converter is going into lock up?  That may not set a code.  I know that the P0741 code will cause a hit to the gas mileage in the 4T80E

Will the O2 sensors set a code if they are slow?   I find it odd that you have never had a code.

It is possible that the knock sensor is either shorted or open causing a retarded ignition.   Can you get into real time data through the DIC?   Does it feel like a pig, or sluggish?

Tuned up recently?, AC DELCO plugs?, GAP?, ignition wires checked?, good spark/coil?, cracks or carbon tracking?

Have you put a vacuum gage on the engine to see what it reads?

The fuel trim numbers would be revealing.

Have you checked fuel pressure?   Again, you should check to see if you have a restriction in the exhaust, you can purchase a gauge for that that screws into the O2 sensor port. 

I have a 94 FSM, Ill skim through it, not sure if it covers your Fleetwood though.

Are you still in Mass?

Mike, ALL the subjects you brought up were addressed except for exhaust restriction. Most of replaced parts are ACDelco.  As I said, this car never had a code. Climate control shows any trouble code if you know how to get them, so I check everything now and then. No check engine light ever. I also know that a sensor can be bad and it will take a while to show a code, so I have replaced a lot of things "just in case".  I have the FSM, of course. The vacuum is around 20" Hg depending on a location. It is a bit low, but that's all I have got. Optispark is vented and it works perfectly. Coil, wires, plugs are new and fine.

Fuel trims would be probably helpful, but I am tired spending more $$$ on this old girl. I am trying to find a success story from someone fixing the problem just like this thread shows.


The saddest thing in life is wasted talent

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1 hour ago, adallak said:

Mike, ALL the subjects you brought up were addressed except for exhaust restriction. Most of replaced parts are ACDelco.  As I said, this car never had a code. Climate control shows any trouble code if you know how to get them, so I check everything now and then. No check engine light ever. I also know that a sensor can be bad and it will take a while to show a code, so I have replaced a lot of things "just in case".  I have the FSM, of course. The vacuum is around 20" Hg depending on a location. It is a bit low, but that's all I have got. Optispark is vented and it works perfectly. Coil, wires, plugs are new and fine.

Fuel trims would be probably helpful, but I am tired spending more $$$ on this old girl. I am trying to find a success story from someone fixing the problem just like this thread shows.

See this thread, leaky injector? Do you smell fuel at the exhaust?, black smoke?  Can you lift the rail on that engine and look for leaks?

https://www.cadillacforums.com/forums/rwd-19xx-1984-deville-fleetwood-1985/279157-1995-cadillac-fleetwood-bad-iddle-gas.html

 


Pre-1995 - DTC codes OBD1  >> http://z-cut.de/US/dtcobd1.html

1996 and newer - DTC codes OBD2 >> http://carprogrammer.com/Z28/PCM/OBD2/On-BoardDiagnosticTroubleCodes(OBD-II).mht

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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Funny, the reply in that thread comes from me (HUF). I do not think I have any leaky injectors, otherwise the fuel pressure would not hold for some 30 minutes when I prime the system. Right? No black smoke, no fuel smell in exhaust either. 


The saddest thing in life is wasted talent

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1 hour ago, adallak said:

Funny, the reply in that thread comes from me (HUF). I do not think I have any leaky injectors, otherwise the fuel pressure would not hold for some 30 minutes when I prime the system. Right? No black smoke, no fuel smell in exhaust either. 

I tried, it seems you thought of everything, I am rehashing, I guess there is no cause 


Pre-1995 - DTC codes OBD1  >> http://z-cut.de/US/dtcobd1.html

1996 and newer - DTC codes OBD2 >> http://carprogrammer.com/Z28/PCM/OBD2/On-BoardDiagnosticTroubleCodes(OBD-II).mht

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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4 minutes ago, BodybyFisher said:

I tried, it seems you thought of everything, I am rehashing, I guess there is no cause 

Yes, Mike... I am sure I have covered almost everything... well, some day the cause will expose itself, I hope so anyway. Thanks for trying to help me!


The saddest thing in life is wasted talent

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9 hours ago, adallak said:

Yes, Mike... I am sure I have covered almost everything... well, some day the cause will expose itself, I hope so anyway. Thanks for trying to help me!

That is a shame, I planned to send you an OBD1 real-time analyzer to diagnose deeper than just sitting around waiting for a code to show up, it seems the problem has eluded and defeated you.  That never happens to me, I bird dog it till I find the problem, I tried here but you seem to think everything is  OK even though you are 7 MPG down.  You didn't tell me if you are still in Mass.   I am sure the problem will call you on your cell phone one day and give up, LOL...  Let me know how you want to proceed, I was researching Opti-spark, etc.

 


Pre-1995 - DTC codes OBD1  >> http://z-cut.de/US/dtcobd1.html

1996 and newer - DTC codes OBD2 >> http://carprogrammer.com/Z28/PCM/OBD2/On-BoardDiagnosticTroubleCodes(OBD-II).mht

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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56 minutes ago, BodybyFisher said:

That is a shame, I planned to send you an OBD1 real-time analyzer to diagnose deeper than just sitting around waiting for a code to show up, it seems the problem has eluded and defeated you.  That never happens to me, I bird dog it till I find the problem, I tried here but you seem to think everything is  OK even though you are 7 MPG down.  You didn't tell me if you are still in Mass.   I am sure the problem will call you on your cell phone one day and give up, LOL...  Let me know how you want to proceed, I was researching Opti-spark, etc.

 

Thank you , Mike. I sent you a message. I know you will not let me sit and wait till  things get better by themselves! LOL


The saddest thing in life is wasted talent

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3 hours ago, adallak said:

Thank you , Mike. I sent you a message. I know you will not let me sit and wait till  things get better by themselves! LOL

No I won't,  LOL.....

Ok good, I see you are in PA, I am in NY on your way home to MA, how about we plan a get together, and I hook up a Tech 2 (with OBD1 cable adapter) I recently purchased from @OldCadTech (thank you John, I hope to get even with you one day :grouphug: ) and we see what is going on with your car?   We can game plan in advance as to what we need to investigate, i.e. fuel trim long and short term, knock sensor, timing, etc.

Let me know what you think, we can put our heads together on this and see what we can find out.

I am on Long Island, I have two ferries here, Orient Point to New London, CT and Port Jefferson to Bridgeport, CT, you can choose which is best for you. 

The ferry ride is fun and a nice way to relax instead of driving through and around NYC which can be brutal. 

What do you think?  Mike


Pre-1995 - DTC codes OBD1  >> http://z-cut.de/US/dtcobd1.html

1996 and newer - DTC codes OBD2 >> http://carprogrammer.com/Z28/PCM/OBD2/On-BoardDiagnosticTroubleCodes(OBD-II).mht

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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Thank you, Mike. Sure, two heads are better than one, especially when the second head is yours! :)  I sent you a message.

 


The saddest thing in life is wasted talent

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Well I don't know about that, but I tend to not let go until the problem is solved.  

I think "inverted cone" = V thinking usually leads to the solution, eliminating each possible problem until the cause is found works.  

I can't believe that with such a drop in fuel economy that the cause hides itself so well.  I think that a Tech1/2 should disclose the issue.  

My 94 FSM does not cover the Fleetwood, check your FW FSM to see if there is a diagnostic tree for poor fuel economy where the Tech1/2 would be helpful.

Where are you on Penn?


Pre-1995 - DTC codes OBD1  >> http://z-cut.de/US/dtcobd1.html

1996 and newer - DTC codes OBD2 >> http://carprogrammer.com/Z28/PCM/OBD2/On-BoardDiagnosticTroubleCodes(OBD-II).mht

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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I see you have been around HUF, I am finding you in my research.  Someone on an LT1 site mentioned that the O2 sensors can be slow and not set a code killing fuel economy. I need to check my autotap to see is it will link up to an OBD1, if it does I can send it to you and you can check real time data to the norms from the FSM.

http://www.cadillacforums.com/forums/cadillac-forum/t-190529.html


Pre-1995 - DTC codes OBD1  >> http://z-cut.de/US/dtcobd1.html

1996 and newer - DTC codes OBD2 >> http://carprogrammer.com/Z28/PCM/OBD2/On-BoardDiagnosticTroubleCodes(OBD-II).mht

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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Ok my Autotap only works with OBD2

https://www.allpar.com/reviews/other/autotap.html

 


Pre-1995 - DTC codes OBD1  >> http://z-cut.de/US/dtcobd1.html

1996 and newer - DTC codes OBD2 >> http://carprogrammer.com/Z28/PCM/OBD2/On-BoardDiagnosticTroubleCodes(OBD-II).mht

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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How did the plugs look when you changed them.  Was the burn good (light tan/crème color); if they were grey, dark grey or blackened that should have given you an idea as to combustion (lean or rich).  Just a thought; ignore, if answered and I missed it.


Chuck

'17 XT5, '04 Bravada........but still lusting for that '69 Z-28

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20 hours ago, BodybyFisher said:

I see you have been around HUF, I am finding you in my research.  Someone on an LT1 site mentioned that the O2 sensors can be slow and not set a code killing fuel economy. I need to check my autotap to see is it will link up to an OBD1, if it does I can send it to you and you can check real time data to the norms from the FSM.

http://www.cadillacforums.com/forums/cadillac-forum/t-190529.html

Yes, cracked exhaust manifold is a possibility, but you will not know until you actually take it off... Another PITA job, just like removing oxygen sensors was. And chances are it will do nothing ,just like replacing oxygen sensors did. 


The saddest thing in life is wasted talent

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20 hours ago, cdgrinci said:

How did the plugs look when you changed them.  Was the burn good (light tan/crème color); if they were grey, dark grey or blackened that should have given you an idea as to combustion (lean or rich).  Just a thought; ignore, if answered and I missed it.

Yes I have replaced (perfectly good) plugs. And I check them often. They look good. Spark wires are new as well. 


The saddest thing in life is wasted talent

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