I have lost my over drive but only when warm FIXED!!!!!!!! - Page 5 - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


1992-1999 Series I L27 (1992-1994 SE,SLE, SSE) & Series II L36 (1995-1999 SE, SSE, SLE) and common problems for the Series I and II L67 (all supercharged models 92-99) Including Olds 88's, Olds LSS's and Buick Lesabres Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

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Old 07-24-2004, 01:14 AM   #41
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okay, I am way off here. Right, 94, 95 the years techs want to forget!!! They never existed....they never existed...
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Old 07-24-2004, 01:01 PM   #42
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Does what the tranny shop say make sense (the gear ratio difference between the Buick and the Bonn.)? The Buick has 15-inch tires and the Bonn has 16-inch tires could that be why there would be a gear difference? I know that you can only interchange a 1994 parts with 1994. I was told the Buick and Bonn. were a direct swap do you know if this is true?

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Old 07-24-2004, 08:41 PM   #43
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Agreed, lets not start looking too deep into gear ratios and stuff until we have ruled out some simple things first (ie is the PCM telling the TCC to engage)
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Old 07-24-2004, 11:39 PM   #44
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Thanks for the input everyone.

I have been a little slow and did not read all the new posts.
Yes, both the engine and transmission are from a 1994 Buick La Saber it was in an accident and it only had 47000 miles on it. When I got the 1994 Bonn. it had a bad transmission and being the Bonn had 148000 miles, I just swapped the entire driveline out of the Buick into the Bonn. Now I did have to change the engine wiring harness, engine sensors (Buick had idiot lights the Bonn. has gauges) and the oil pan. (Bonn has an oil level sensor the Buick did not). The car acts like this.
If you drive normally up to 50-60 and allow transmission to shift into DO and lock up the converter all is fine but if you then coast down to 35-40 and load the engine like driving up a hill it will give a slight shudder and will no longer shift into OD. I did this at least a dozen times to confirm it. I also tried it in 3rd and same thing happens. If you can stay above 50 mph, it works fine. I can disengage the torque converter by lightly taping the breaks and as long as you are going fast enough it will relock the torque converter just fine. Does the fluid pressure change with speed and if it does is the slipping, (if that is what is happing) caused by low fluid pressure? I did put Mobil 1 ATF in the transmission when I did the swap could that be causing the slipping? This has been a long and frustrating project. What I thought was going to be a weekend project is truing out to be several months of frustration.
The people on this forum have helped a lot and have kept me going thank everyone.
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Old 07-25-2004, 10:24 AM   #45
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It almost sounds like when you slow down to 40 and then load the engine in OD (you said it shutters and no longer will go into OD) you get slippage which is sensed by the PCM and it no longer allows the use of OD. You really need to get this car hooked up to a scanner and get some real time data on the slippage when this problem occurs (exact point). Without that we are shooting in the dark.
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Old 07-26-2004, 05:24 PM   #46
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I came in to this thread late and I am far from an expert here but wanted to comment. It seems like people are looking too deep here.

There is a OD lockout that keeps the tranny from going into OD or TCC lockup until the engine heats up into what is called "closed loop". The closed loop is an emission control function, and is directly controlled by the o2 sensor, the water temp sensor, EGR valve and some others i just forgot. I think the MAF sensor is part of this system too.

It seems like your system is incorrectly starting in a "closed loop" and when it gets hot, switches to lockout OD and TCC. I would strongly suggest checking the O2 sensor first, that is the main one. Then check the water temp sensor and the MAF sensor, to make sure they are the correct ones, and that they are installed correctly and not wired backwards. Do you have the correct O2 sensor?

Also check out the EGR valve, that could be causing this too, as it redirects hot air into the intake when the engine is cold, and it switches when in closed loop. If that EGR is bad or wired incorrect, then that will mess with things. Here is an article on EGR'* that I just saw. http://www.wellsmfgcorp.com/counterp...erpoint3_4.pdf

If I think of something else along these lines, I will add some more.

Cheers,

Andrew
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Old 07-26-2004, 11:01 PM   #47
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That was my thinking also in the beginning, but after I realized you could reset OD by shutting the car off and then restarting it, (I figured because at this point it is warm and it will work fine till you slowdown where it will drop OD again) it must be torque converter related. I have found if I can keep it from locking the torque converter when I slow down ( ether by keeping one foot on the break or constantly accelerating and then decelerating never just holding the accelerator steady) It wont lose OD.

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Old 07-26-2004, 11:09 PM   #48
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The vehicle being in "Closed Loop" has to do with the fuel control system and is controlled by "feedback" via the O2 sensor while in closed loop. While in "Open Loop", the PCM ignores the oxygen sensor voltage and bases the amount of fuel to be delivered on TPS, coolant temperature, and MAF sensor inputs only. "Closed Loop" operation should begine when the O2 sensor becomes active (hot enough), coolant temperature exceeds about 120 degrees F, for more than 30 seconds and the PCM has seen RPM of 1200 or greater for 10 seconds or so.

As far as the car not being able to enter OD while still in "Open Loop", I am certain that is possible. Start your car and cruise out directly on the highway first thing in the morning and it will go into OD before the coolant temp reaches 120 degrees F and it enters "Closed Loop".

Now, at extremely high temps or towing a trailer, it is possible for the PCM to remain in "Open Loop" operation in order to control converter temperatures. If the TCC does not lock up, OD will not work.

I have never heard of the EGR valve opening during warming up. That would be injecting exhaust gas directly into a cold idling engine, thereby stalling it. The EGR will only open when certain permissives are met ie. certain engine temperature, certain engine and vehicle speeds and of course "Closed Loop" operation. It is designed to cool down combustion temps because of the oxides of nitrogen that are produced (smog) when fossil fuels are burned at too high of temps.

I have a hunch that it is temp related because my drive in the morning starts highway and OD works fine. Way home...All city first, stop and go, the tranny gets hot then OD doesn't work by the time I get to the highway. I need a scan tool myself here to check out my hunches!!
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Old 07-27-2004, 12:29 PM   #49
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You are right about the EGR, I guess I got it backwards. Thanks for clearing that up.

Here is a document on EGR operation. It is Toyota related, but it is good at explaining how it works. http://www.autoshop101.com/forms/h61.pdf

Also, that site, mainly Toyota related, is pretty good and may help others here understand some basic principals. http://www.autoshop101.com

Regarding the OD lockout until warmup, I will research that more. I remember seeing that on a GM related site or bulletin or something. I'll try and find it.

Maybe one of the Mods can give their input on the Bonneville warmup process and what happens while in Open and Closed loop.

Cheers,

Andrew
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Old 07-27-2004, 12:57 PM   #50
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Jr, you are right. My 92 SSE will not go into TCC until it is warm. However, my 97SSEi can be coaxed into TCC when it is still pretty cold.

However, when I start my 97 stone cold, get onto the highway immediately, it wont go into TCC immediately, takes about a mile before it will slip into TCC. So maybe that is what is supposed to happen, or maybe its my tranny not behaving properly. I dont know.

So JR, this thread'* original question if for a 1994. What will that do while warming up? Do you know?
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