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Overdrive


kens96

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Last week we had some colder then normal weather here. I had a random miss problem noticable at idle in drive. After cleaning the TB and checking for vacuum leaks the fix was to add some dry gas and fill the tank. I had excessive condensation coming through the fuel system. Now I've noticed that at around 80MPH climbing a hill the overdrive drops out and the more gas I give it seems to make the engine lean over in the power band.

My questions are:

Do I have a transmision issue?

Because I cleaned the TB does the car need to relearn TPS positions by disconnectiong the battery?

Is it because the fuel still has water and drygass in it and at high speeds its getting too lean?

Point me in the right direction

Thanks

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What probably happens when you are climbing a hill at 80 mph is that the torque converter clutch (TCC) drops out, which is normal. When that happens, you are still in 4th and when you use less throttle the TCC will engage again. Depending on how much throttle you give it, the next thing to happen is for the transmission to downshift from overdrive to 3rd gear; you might have to floor it to get that downshift. 80 mph is about where it shifts out of 2nd gear at full throttle so it won't downshift past 3rd gear at 80 mph or faster.

It's not likely that you are running lean because the Northstar uses a closed-loop digital fuel injection that maintains the gas-air mixture essentially perfectly, and if there is a problem that causes it to go lean anyway (such as a vacuum leak) it will throw an OBD II code and the Check Engine light will come on. I would run out the current tank of gas with drygas in it, fill up with your usual gas or even top-tier 92 octane and run out a quarter tank of that before I worried about fine-tuning the TPS. The car is always learning at some rate; this is how it adjusts to changes in altitude and changes in gasoline when you fill up. If you have run out the tank with drygas in it and have run a quarter tank of normal gasoline, everything should be stable and you can decide if anything needs to be done.

Top-tier 92 octane gas has sufficient additives in it to keep normal condensation levels from causing an accumulation in the tank, and keep your injectors clean. If you normally run 87 octane or 89 octane you might try running a tank or two o f92 octane through it.

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-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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No codes Ken?

If you had a TCC code, I could understand that...

By the way my sister is moving to Jacksonville, one of these days we will have a coffee when I come down to see her!

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

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By the way, if I labor up a hill, my tranny notices the laboring and drops me down, I have always been impressed by that. I suspect it has to do with vacuum, once it drops below a certain level and the PCM senses laboring it drops the tranny down to raise RPMs to stop the labor

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

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And yes once you clean the TB and IAC you MUST do a relearn, as you now have optimum air and the throttle angle has changed. Disconnect the battery

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

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Will disconnect the battery when I get home tonight.

What about the engine "leaning over" at the higher RPM? Is that a symptom of the TPS needing and education? :D

BBF - the coffee is on me !

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Will disconnect the battery when I get home tonight.

What about the engine "leaning over" at the higher RPM? Is that a symptom of the TPS needing and education? :D

BBF - the coffee is on me !

Ken, how can you tell you are leaning out? The TPS tells the PCM your throttle position. The IAC compensates for carbon buildup in the TB by introducing more air, if you clean the TB you now have too much air, the system will figure this out over time and compensate pretty quickly, but if you force a relearn that might help.

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

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Maybe I'm using the wrong term when I say leaning over, what happens is as you give it more gas at the higher speeds when the overdrive drops out the engine rpms go up and then start dropping off not movng the car as it has in the past. Need to back off the gas to get it to go.

I will try the removing the battery cable for a reset. Do I have to do anything else or let the car do it itself?

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Before you disconnect the battery you should read the codes. Here's how"

Take down the codes and post them here. They will be of the form

XXX Xnnnn [History | Current]

The XXX is the module that threw the code, Xnnnn is a letter followed by four numbers (the most important part), and the code will be flagged as History, or Current if the condition that made the module throw the code is currently being detected.

CTS-V_LateralGs_6-2018_tiny.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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Ken check your fuel pump pressure, it sounds like its not keeping up with demand

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

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Mike,

Low Fuel Pressure is exactly what it feels like !!!!! I'm going to reset and drive the next few days. To see if it was just water in the gas. Have a new gas filter on the shelf that I can try before diving into changing a fuel pump. The FPR was changed out when I was chasing that lean condition last year.

Jim - Currently have no codes. Only got a few when I was cleaning the TB. They were all history and I cleared them then. Nothing has come back.

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As stated, it is very doubtful that you have any moisture in your fuel, ethanol would stop that right away. I'd say change your fuel filter(s), even if it might be in the gas tank itself, if it has never been changed before.

Which leaves me with only one question.

Where did you find a hill in Jacksonville?

Never underestimate the amount of a persons greed.

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Ran better on the way home. Didn't drop out this time. Added another 7 gallons of BP92. Have been using only Shell92 up until we had the problem last week. Could be the station got a bad batch.

Our hills have names .....The Dames Point and Buckmann Bridges :D

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Okay we have more informition. Problem didn't show up yesterday. Today driving to work it started acting up. Paid closer attention to it. Between 70 and 80 MPH the transmission is dropping out and the engine is taching to above 3K. Let off the gas and the transmission engages. Will pop in and out of gear OD and 3rd. I think it is in 2nd but it is hard to say. Tried a WOT and it feels like it engaged. Under 60 MPH I have no issues. It breaks up a highway speeds above 60 and jerks the car around between 70 and 80.

During the cold snap last week I heard the pump in the tranny whine just before a shift until it warmed up. Didn't push it. Had it rebuilt 41K ago and serviced in December wit a filter drain and refill by the rebuilder. My guess is solenoids, transmission line pressure, torque convertor. Or is the engine telling it to do this? There are no codes.

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Okay we have more informition. Problem didn't show up yesterday. Today driving to work it started acting up. Paid closer attention to it. Between 70 and 80 MPH the transmission is dropping out and the engine is taching to above 3K. Let off the gas and the transmission engages. Will pop in and out of gear OD and 3rd. I think it is in 2nd but it is hard to say. Tried a WOT and it feels like it engaged. Under 60 MPH I have no issues. It breaks up a highway speeds above 60 and jerks the car around between 70 and 80.

During the cold snap last week I heard the pump in the tranny whine just before a shift until it warmed up. Didn't push it. Had it rebuilt 41K ago and serviced in December wit a filter drain and refill by the rebuilder. My guess is solenoids, transmission line pressure, torque convertor. Or is the engine telling it to do this? There are no codes.

This is different than the engine seeming to run out of gas at 80. Since your engine RPM is rising, it certainly is sounding like a tranny problem, smell your fluid to see if its burning. We had a member have a similar problem I recall and it was his tranny. It sounds like you are slipping. Try taking that hill in third gear and see how it holds, you seem to be just loosing OD, but the question is, is it slipping. Is your RPM rising because its dropping out of OD or because its slipping is the question.

I am still surprised you are not getting a TCC code, if you are dropping out

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

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I'm thinking the same thing. Wish it would throw a code. Unless it is purely a hydraulic issue and not electric. But my knowledge of trannys is limited. I'm going to drop it off tomorrow. The guy we use is great. Will let you know what he says.

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The 4th gear servo piston seal could be cut/damaged. If that is the case, the trans will pop out of overdrive. This will not set a code. The cover is a round 4" diameter cover near the frame rail. The seal can be replaced without removing the trans from the car but it is somewhat difficult due to to the proximity to the frame and fighting the spring on the piston.

Kevin
'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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The 4th gear servo piston seal could be cut/damaged. If that is the case, the trans will pop out of overdrive. This will not set a code. The cover is a round 4" diameter cover near the frame rail. The seal can be replaced without removing the trans from the car but it is somewhat difficult due to to the proximity to the frame and fighting the spring on the piston.

I recall when you replaced your cover seal, I posted a photo of it for you. Were you dropping out of OD or was your problem a leak?

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

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Well the good new is I can create the issue.

Try to maintain 70 MPH or above after about 20 minutes of highway driving and the car flutters out of overdrive then drops 4th gear and goes to 3rd.

Let off the gas and drop down to 60MPH and and it recovers and it drives fine.

Accelerate to past 80MPH and it does fine.

Try to maintain 70 MPH or above and the car flutters out of overdrive then drops 4th gear.

Stay at 60MPH and it seems to maintain fine.

Put it in 3rd gear and it stays solid to 3500+RPM. Did not get to keep it up there long enough to see if it would drop out since I reached my exit.

NO CODES !!! I'm at a loss but the flutter would lead me to guess that maybe a solenoid is not holding, a solenoid coil is flakey, or line pressure at that speed can't be maintained.

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I think KHE might have your problem nailed, do you have a service manual? Look up 4th servo piston, it could be that at 70, its leaking too fast past the chromium ring on the servo, but at 60 its ok? You did say you heard a pump or hydraulic noise no?

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

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The pump noise was when it was in the 20's here last week. The pump would whine at the top end of each gear just before a shift until the car warmed up. I'm not hearing it now, but we are in the 50's to 70's now. Unfortunately I don't have an FSM for this car.

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The pump noise was when it was in the 20's here last week. The pump would whine at the top end of each gear just before a shift until the car warmed up. I'm not hearing it now, but we are in the 50's to 70's now. Unfortunately I don't have an FSM for this car.

I have one for 96, Ill post you a photo of the fourth servo.

MAYBE just maybe your pump is not putting out spec, with a leak in the 4th servo, it drops out. When your pump was or IS putting out you stay in gear? Just thinking here

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

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The 4th gear servo piston seal could be cut/damaged. If that is the case, the trans will pop out of overdrive. This will not set a code. The cover is a round 4" diameter cover near the frame rail. The seal can be replaced without removing the trans from the car but it is somewhat difficult due to to the proximity to the frame and fighting the spring on the piston.

I recall when you replaced your cover seal, I posted a photo of it for you. Were you dropping out of OD or was your problem a leak?

I had a leak at the servo cover seal. I replaced the cover seal, and in the process, damaged the servo piston seal. The next day, I lost overdrive after 25 miles as the servo piston seal was damaged.

I pulled it back apart, replaced the piston seal and a new cover seal and it has been fine ever since.

Three things will prevent the trans from shifting into overdrive: 1) bad 4th gear servo piston seal, 2) bad shift solenoid, 3) burned band.

Kevin
'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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