BodybyFisher Posted February 4, 2011 Report Share Posted February 4, 2011 Keep doing this, I can run a regression analysis in Excel and see if in fact, temp has on your fuel efficiency. It gets too head jamming if to look at without putting it into a chart. When I get a chance I'll start building it. Have you considered that you are driving UPHILL in one of the directions?, say there is a 10 mile incline? One more thing, I want you to do a few runs where you check the on-board estimate against real world testing where you test the Average Miles per Gallon yourself by dividing the trip mileage by the gallons used. Each time use the same filling technique to fill the tank as that can make a difference. Have you cleaned your MAF with MAF cleaner? I don't think a dirty MAF would reduce your MPG that much, and it usually causes ping when its dirty, but its a thought Anybody who has any ideas, please chimb in. What are we seeing and why? Is this temp related? Why would temp make a difference anyway? Pre-1995 - DTC codes OBD1 >> 1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm 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 Link to comment Share on other sites More sharing options...
Texas Jim Posted February 4, 2011 Report Share Posted February 4, 2011 Looking back over some of the numbers... it sure "DOES" look to be temp related. That is very strange... but that's what the numbers show. Mike...is there anything that could cause it to stay in OPEN LOOP when it is that cold? If it did, in fact, stay in OPEN LOOP.. it would obviously be running a little bit richer and thus burning more fuel and that would account for difference in MPG. I have never driven mine in BELOW ZERO weather to see what it would do. Link to comment Share on other sites More sharing options...
BodybyFisher Posted February 4, 2011 Report Share Posted February 4, 2011 Interesting Jim, That is the reason I brought up the TB pre-heat circuit that is part of the purge line, it is there to stop icing, and if it has been defeated or bypassed or clogged the air entering the TB would be colder. I am too lazy to pull out my FSM, but I did a search and found this, the Intake Air Temp (IAT) sensor is part of the MAP. It would make sense to put a Tech 2 or Autotap on the engine to see what temp the IAT is reporting. However, I would think that if the IAT temp differs from the coolant temp sensor by a substantial amount, that a code would be set, but maybe that test is not done by the diagnostic. A visit to the FSM is in order to see what will set off a DTC. These codes can be set by the IAT P0110 - Intake Air Temperature (IAT) Sensor Circuit P0111 - Intake Air Temperature (IAT) Sensor Performance P0112 - Intake Air Temperature (IAT) Sensor Circuit Low Voltage P0113 - Intake Air Temperature (IAT) Sensor Circuit High Voltage P0114 - Intake Air Temperature Circuit Intermittent See this link for more detail it covers the subject nicely http://www.cadillacf...discussion.html Pre-1995 - DTC codes OBD1 >> 1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm 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 Link to comment Share on other sites More sharing options...
Texas Jim Posted February 4, 2011 Report Share Posted February 4, 2011 I went back and looked at some of the numbers. There is a possibility that the thermostat is stuck partly "OPEN". I have the same problem on my 2006 Chevy van. At temps above 45 or so...it warms up enough...but... In REALLY COLD weather it never gets quite up to normal temp... and eventually it turns on the MIL. I plan on changing it as soon as it gets warm outside. When I pull the codes...it says engine not at operating temp. But on the older cars...maybe that would "NOT" turn on a service light... I don't know. But...if it "IS" running just a few degrees too cold... it would stay in OPEN LOOP and be running rich... which would explain the difference in mileage when the temps are below zero. Link to comment Share on other sites More sharing options...
93SixtySpecial Posted February 5, 2011 Author Report Share Posted February 5, 2011 I went back and looked at some of the numbers. There is a possibility that the thermostat is stuck partly "OPEN". I have the same problem on my 2006 Chevy van. At temps above 45 or so...it warms up enough...but... In REALLY COLD weather it never gets quite up to normal temp... and eventually it turns on the MIL. I plan on changing it as soon as it gets warm outside. When I pull the codes...it says engine not at operating temp. But on the older cars...maybe that would "NOT" turn on a service light... I don't know. But...if it "IS" running just a few degrees too cold... it would stay in OPEN LOOP and be running rich... which would explain the difference in mileage when the temps are below zero. I was thinking along those lines as well, but I would think that the air temperature in the cap would be colder. But maybe I just don't notice it. Maybe the cooling system works TOO well in these things. But the thermostat should still be able to keep out the cold. I've kind of always thought in the back of my mind that it's something not letting it go into closed loop. I got ambitious tonight because it was near 40 and I did a few things to the car. 1. I replaced the fuel filter. 2. Cleaned the MAF 3. Cleaned the IAC and the well where it sits. 4. Cleaned the connector for the IAT sensor. Just in case it was dirty and giving me a distorted reading. I restarted the car and I didn't get any check engine lights, so that's always a good sign! Mike, I will continue to post my results. I go out of town 2 times a week, so I'll post each time. I really appreciate you building a table for me. Any help I can get is really great. It's North Dakota so no hills to really speak of in most of the state. The further west you go, the more there is, but I head east each week. The days I go south, there are quite a bit of hills. I'll make sure to state which way I go each time. Thanks everyone! -Dusty- 2006 Cadillac DTS Glacier Gold Tri-Coat with 175,000 miles 1993 Cadillac Sixty Special Gold Mist with 185,000 miles Link to comment Share on other sites More sharing options...
BodybyFisher Posted February 5, 2011 Report Share Posted February 5, 2011 My manual states that closed loop operation should begin when the oxygen sensor becomes active, engine coolant reaches 41 degrees F for more than 30 seconds and the PCM has seen RPM of 1200 for greater than 10 seconds. If the car does not go into closed loop you would see a code I believe. The IAT shows the temp of the intake manifold air from -40 degrees to 419 degrees My memory was correct, the PCM looks at input from both the IAT and ETC for a comparison, depending upon whether or not the IAT is lower or higher than the ECT it will set a code. Anotherwords, the IAT and ETC should more or less mirror each other, when there is a deviation, a code will set. So my opinion is that the IAT is OK.. interesting.. We are sure there are no codes correct? I was also thinking that both the ECT and IAT could be both wrong, and will look into that idea, but I am sure the ECT will set a code based on it not reaching operating temp within a certain time and the temp gage would be off. The IAC is a thermister. OK what else can be affected by cold ambient temps? Pre-1995 - DTC codes OBD1 >> 1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm 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 Link to comment Share on other sites More sharing options...
93SixtySpecial Posted February 13, 2011 Author Report Share Posted February 13, 2011 I'm thinking it's something mechanically that is failing (failed) since there are no codes being thrown. I know for a fact the thermostat hasn't been changed ever. Code the spring on the thermostat be weak and it never does shut and when it's cold outside it lets too much coolant through make the combustion not as efficient? Just a thought. There are no codes, I double checked them again. I took a little trip yesterday and went quite a bit faster than usual. 60 miles east. 74 MPH Wind WSW at 15-20 MPH 37-40 degrees F RPM around 2150 RPM Avg Mph 57.2 MPH (I drove about 5 miles in-town) Avg MPG 23.9 60 Miles West 73 MPH Wind SW at 13 MPH 35-40 Degrees F RPM around 2250 RPM Avg MPH 72.3 MPH Avg MPG 19.8MPG It seems that temp is really helping. I went 73 against the wind and got better then some days I went 62 with the wind (on a cold day) Something else appeared when I drove that fast though. I got a check coolant message in the DIC when I pulled into town. When I got out of the car I smelled coolant. I am starting another topic to continue this discussion. -Dusty- 2006 Cadillac DTS Glacier Gold Tri-Coat with 175,000 miles 1993 Cadillac Sixty Special Gold Mist with 185,000 miles Link to comment Share on other sites More sharing options...
93SixtySpecial Posted February 17, 2011 Author Report Share Posted February 17, 2011 Ok, just got back from my 240 mile run today. Here are my results: Going East: Ambient temp - 34-26 F Wind - NNE at 10 MPH RPM - Around 1900 Speed - 64 MPH Avg Speed - 64.1 MPH Avg MPG - 24.2 Going West: Ambient temp - 36 F Wind - ENE at 13 MPH changing to E at 16 MPH RPM - Around 1925 Speed - 64 MPH Avg Speed - 62.8 Avg MPG - 28.2 Overall average MPG - 26.2 This was after I replaced the thermostat. Pretty good results. I had a little help fromt the wind going west, but that's still a good number. -Dusty- 2006 Cadillac DTS Glacier Gold Tri-Coat with 175,000 miles 1993 Cadillac Sixty Special Gold Mist with 185,000 miles Link to comment Share on other sites More sharing options...
Texas Jim Posted February 17, 2011 Report Share Posted February 17, 2011 One of these days... I am going to drive my car slow for a couple of hundred miles when I am on a trip, just to see if it gets much better mileage. Just did a 250 miles trip Monday and then 250 back home yesterday... But I was running a little faster than that. :) Link to comment Share on other sites More sharing options...
93SixtySpecial Posted February 17, 2011 Author Report Share Posted February 17, 2011 One of these days... I am going to drive my car slow for a couple of hundred miles when I am on a trip, just to see if it gets much better mileage. Just did a 250 miles trip Monday and then 250 back home yesterday... But I was running a little faster than that. :) Sometimes it pains me to watch Fords and Toyotas pass me, but I know I'm saving money driving that slow. What did you get for an average on your trips? How fast were you going? -Dusty- 2006 Cadillac DTS Glacier Gold Tri-Coat with 175,000 miles 1993 Cadillac Sixty Special Gold Mist with 185,000 miles Link to comment Share on other sites More sharing options...
BodybyFisher Posted February 17, 2011 Report Share Posted February 17, 2011 Ok, just got back from my 240 mile run today. Here are my results: Going East: Ambient temp - 34-26 F Wind - NNE at 10 MPH RPM - Around 1900 Speed - 64 MPH Avg Speed - 64.1 MPH Avg MPG - 24.2 Going West: Ambient temp - 36 F Wind - ENE at 13 MPH changing to E at 16 MPH RPM - Around 1925 Speed - 64 MPH Avg Speed - 62.8 Avg MPG - 28.2 Overall average MPG - 26.2 This was after I replaced the thermostat. Pretty good results. I had a little help fromt the wind going west, but that's still a good number. I dont understand the difference here the temps are not that different now, I have not looked back but is the average mpg always lower going east? Where are you located again? Pre-1995 - DTC codes OBD1 >> 1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm 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 Link to comment Share on other sites More sharing options...
Texas Jim Posted February 17, 2011 Report Share Posted February 17, 2011 One of these days... I am going to drive my car slow for a couple of hundred miles when I am on a trip, just to see if it gets much better mileage. Just did a 250 miles trip Monday and then 250 back home yesterday... But I was running a little faster than that. :) Sometimes it pains me to watch Fords and Toyotas pass me, but I know I'm saving money driving that slow. What did you get for an average on your trips? How fast were you going? Going down there... most of the time I was running 85 to 95. Couple of stretches was 100+ for 10 to 15 miles each time. Per the DIC... 21.5 Coming back it was mostly 80 to 85. Per the DIC...21.2 I actually ran a good bit FASTER going down there than I did coming back. My Mom had to go to the Emergency Room with a possible stroke... so I was in kinda of a hurry. Thank God... she is OK. No sign of a stroke. So... I didn't get in as big of a hurry coming back...but did have quite a bit of wind. Link to comment Share on other sites More sharing options...
93SixtySpecial Posted February 17, 2011 Author Report Share Posted February 17, 2011 One of these days... I am going to drive my car slow for a couple of hundred miles when I am on a trip, just to see if it gets much better mileage. Just did a 250 miles trip Monday and then 250 back home yesterday... But I was running a little faster than that. :) Sometimes it pains me to watch Fords and Toyotas pass me, but I know I'm saving money driving that slow. What did you get for an average on your trips? How fast were you going? Going down there... most of the time I was running 85 to 95. Couple of stretches was 100+ for 10 to 15 miles each time. Per the DIC... 21.5 Coming back it was mostly 80 to 85. Per the DIC...21.2 I actually ran a good bit FASTER going down there than I did coming back. My Mom had to go to the Emergency Room with a possible stroke... so I was in kinda of a hurry. Thank God... she is OK. No sign of a stroke. So... I didn't get in as big of a hurry coming back...but did have quite a bit of wind. I'm glad your mom is okay, that kind of stuff can be scary. I think everyone in my family is on medication for high blood pressure and I know for a fact I do. I had a little scare last year and didn't know what was going on. I got double vision and it wouldn't go away. Found out from my doc that it was a "mini-stroke." Not sure what that is, but sure didn't want to hear it. Needless to say, I have tried to cut out a lot of my salt. Mike, It seems the thermostat helped my MPG a bit. Could be a fluke, but who knows. I don't usually get any different going either way, but there has been quite a bit of wind lately. If you look at the time before last, I got better going east. I'm in Minot, ND traveling back and forth to Devils Lake, ND. It's a pretty much flat road. Central to eastern ND is very flat due to the glacier that was once here. West is very hilly. If you ever come to ND, don't go to the eastern portion, it's very boring. Well...I guess the whole state is, but east is worse. -Dusty- 2006 Cadillac DTS Glacier Gold Tri-Coat with 175,000 miles 1993 Cadillac Sixty Special Gold Mist with 185,000 miles Link to comment Share on other sites More sharing options...
bobbnsueb@sbcglobal.net Posted February 20, 2011 Report Share Posted February 20, 2011 Hi all, My Cad is a 91 STS 4.9 for reference. With the possibility being discussed about not being in closed loop, I wanted to mention that when mine is in diagnostic mode there is one of the indicators that tells if it is in closed or not. And I can drive it and occasionally monitor the light. Bob B Link to comment Share on other sites More sharing options...
BodybyFisher Posted February 20, 2011 Report Share Posted February 20, 2011 Yes, OBD1 was a terrific system, very open, loved my 91 Seville Pre-1995 - DTC codes OBD1 >> 1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm 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 Link to comment Share on other sites More sharing options...
93SixtySpecial Posted July 27, 2011 Author Report Share Posted July 27, 2011 Update: I am 95% I know what my mileage problem is. Earlier this year I was on my way home and I was starting to accelerate back up to speed after slowing down going through a town. When I started getting up to speed I felt the dreadful shudder/surge/fish-on-a-hook feel and then it threw a light and immediately stopped surging. It ended up being the P0741 code. It came on now and then in the colder months and it was always when I could feel the surging. Now that it has gotten warmer, it surges a lot more, but it doesn't seems to be throwing the code as easily. I was climbing a hill in town going around 35 and it was surging pretty bad and it threw the light and it stopped right away. My guess is it is a mechanical failure in my torque converter allowing it to slip when locked up, causing the shudder/surge or however you would like to describe it. And then when it gets bad enough, the computer throws the code. Does that make sense? -Dusty- 2006 Cadillac DTS Glacier Gold Tri-Coat with 175,000 miles 1993 Cadillac Sixty Special Gold Mist with 185,000 miles Link to comment Share on other sites More sharing options...
KHE Posted July 27, 2011 Report Share Posted July 27, 2011 The 741 code is caused by excessive slip of the converter clutch. There is also the possibility the converter is not locking up due to worn seals causing fluid to bypass the lockup circuit. Either way, the transaxle needs to be removed from the car. $1200 job at a transmission shop. Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
93SixtySpecial Posted July 28, 2011 Author Report Share Posted July 28, 2011 Yeah...I got a couple of quotes a while ago. One place was $3500 for a tranny overhaul and the other was $4500 or $2500 for a used tranny. I asked for an overhaul price because I figured it's got 260,000 miles and it's going to be out anyway. What do you guys think I should do? Drive it til it can't be driven anymore? Fix up the tranny and hope everything else lasts? The engine shows no sign of being tired and the body/interior is in fantastic shape. The only other thing wrong with it is I have a weird creak near the driver's side wheel when pushed down on and I have some front end clunks (sounds like something is loose when you go over bumps). And I'm the second owner on the car. I have have all records from day one. The trouble is, if I repair it, that is almost what it books for. What if something else major goes wrong? Then I'm over book on a car with almost 300k on it. Not sure what to do. -Dusty- 2006 Cadillac DTS Glacier Gold Tri-Coat with 175,000 miles 1993 Cadillac Sixty Special Gold Mist with 185,000 miles Link to comment Share on other sites More sharing options...
Texas Jim Posted July 28, 2011 Report Share Posted July 28, 2011 Aren't you looking for a later model DTS Performance Sedan? May be time to speed up the search a little bit... I don't know... I would be really hesitant to put much money in a car with that many miles on it... But that's just me and my opinion... Link to comment Share on other sites More sharing options...
KHE Posted July 28, 2011 Report Share Posted July 28, 2011 $4500 for a used transmission???! If the car drives OK, I probably wouldn't bother fixing the transmission. Usually, the 741 code only eats up 1-2 MPG. Maybe something else is going on? Are you sure the torque converter is locking up? The shutter/fishbite symptom is usually indicitave of a worn seal(s) in the torque converter apply circuit. The worn seal causes fluid to leak internally and the result is inconsistent or no lockup of the torque converter. At any rate, a transmission shop should only charge around $1200 to repair the problem and that includes a reman. torque converter and TCC apply solenoid. There is not much else that seems to go in these transmissions but at 260,000 miles, you never know. $4500 for a used trans. is an gouge job. The clunking going over bumps is most likely front stabilizer bar bushings - a very inexpensive and easy repair. NADA lists your car for $3170 clean retail and $1245 clean trade so it is probably worth around $2500. I surely wouldn't spend $4500 on a $2500 car. Figure the payback on the trans rebuild vs. the extra fuel you're using and you'll find that even using more fuel, the break even point will be several years down the road and wouldn't be worth it in my opinion. In your case - 500 miles per week = 26,000 miles per year. At 27 mpg, that is 963 gallons of fuel. At 21 mpg, you have 1238 gallons of fuel - so you're using an extra 275 gallons of fuel per year. At $3.80 per gallon, that is an extra $1045 per year in fuel costs. You're looking at almost 3-1/2 years to break even on the fuel vs. trans rebuild cost and by that time, you will have an extra 87,000 miles on the car so repairing it really doesn't make sense to me. On the other hand, if you could find a reasonable trans. shop that would repair it for $1200, you'd break even in a little more than a year which might make sense to repair the trans. Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
93SixtySpecial Posted July 28, 2011 Author Report Share Posted July 28, 2011 No, no. I guess I worded that a little strange. $4500 was for a complete rebuild and the $2500 was for putting a used transmission (out the door). The trouble is around here that we have an extremely solid economy. Our town is FULL of oil workers getting paid a lot of money to work on the rigs and also people with oil on their land with lots of money. So all in all, little guys like me who don't have oil end up getting screwed if we don't do the work ourselves. Apartments are going for $2500 per month for a 1 bedroom. It's tough living if you don't have money out here. My experience with the P0741 code (when it's the solenoid malfunction, not a mechanical failure) is that it seems to have more of an affect in our winters up here. The colder it is, the worse the mileage loss. I was getting 26-27 MPG with my 97 STS in the summer and 23-25 mpg with my 02 STS (had the P0741). When winter came, I went to about 24-25 with the 97 and about 19-20 with my 02. Both were driven the same. I notice in my Silverado on the trans temp guage that in the summer it runs a little below 150 degrees and in the winter it doesn't even touch 100. Maybe it has something to do with the cold fluid, I'm not sure. However, I have noticed the same trend with my 99 with the the TC issue. I get horrible in the winter ~20 mpg and now I'm getting 25-26 mpg. Really? I was thinking it might be stabilizer bar bushings, but haven't really put much time into it. Do you just replace them or is there another fix for it? I suppose what I'll end up doing is just leaving it, drive it for a little while longer and end up getting a newer Seville or Deville next year (hopefully). The only thing is, the surge/shudder can get very annoying. It has been progressively getting worse. I now feel it on the highway when pulling hills. You can definitely tell the TC is locking up. You can watch the RPM and tap the brake. And when it's surging going up a hill, sometimes the TC will kick out causing the RPMs to go up and the surge to quit. Jim - Yeah, I was looking, but I ran into some financial difficulties (boss cut my salary by about $700/month) so I had to call it off. -Dusty- 2006 Cadillac DTS Glacier Gold Tri-Coat with 175,000 miles 1993 Cadillac Sixty Special Gold Mist with 185,000 miles Link to comment Share on other sites More sharing options...
Texas Jim Posted July 28, 2011 Report Share Posted July 28, 2011 Salary cuts SUCK.. especially one that big... :( Link to comment Share on other sites More sharing options...
KHE Posted July 28, 2011 Report Share Posted July 28, 2011 I was thinking it might be stabilizer bar bushings, but haven't really put much time into it. Do you just replace them or is there another fix for it? I suppose what I'll end up doing is just leaving it, drive it for a little while longer and end up getting a newer Seville or Deville next year (hopefully). The only thing is, the surge/shudder can get very annoying. It has been progressively getting worse. I now feel it on the highway when pulling hills. You can definitely tell the TC is locking up. You can watch the RPM and tap the brake. And when it's surging going up a hill, sometimes the TC will kick out causing the RPMs to go up and the surge to quit. Jim - Yeah, I was looking, but I ran into some financial difficulties (boss cut my salary by about $700/month) so I had to call it off. The rubber in the bushings takes a compression set over the years. Replace them - any auto parts store will have ones for a decent price. You will need to measure the diameter of your stabilizer bar and then get a bushings that is slightly smaller. Very easy to install them and the popping noise over bumps will go away. Before I replaced them on my STS, I could see a gap when a pry bar was used to move the bar slightly. You might want to have a trans. shop hook up their Tech-2 unit and drive the car to check it out to see if the torque converter is locking up. Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
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