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-   -   Transmission upshifts prematurely (http://www.bimmerfest.com/forums/showthread.php?t=586227)

IEbimmerguy 12-07-2011 02:24 PM

Transmission upshifts prematurely
 
Hello,

I have an 86 E23 (735i) which had sat with very little use for ten years. The owner died, and her older son startred it and drove it once in a while) It's a one owner car with 73,000 miles. I was told BMW recalled the car to replace the transmission at 30,000 miles, so effectively the 4hp22 EH transmission only has 43,000 miles.

I changed all the fluids,valve adjustment, belts and hoses, fuel pumps, and cooling system. I drove it and noticed the tranny shifting early on the 1-2 shift. I had the TPS adjusted which stopped it for a while, and now its back.
This is what it does: While taking off from a stop, it will change from 1-2 prematurely. Rarely it will do this 2-3 gears. I have changed the fluid 3 times and dropped the pan and did the filter too. The pan was spotless, maybe a little material on the two magnets. I cleaned the 8 pin connector, as it was a LITTLE moist with fluid.
I drive it to the store, and it has perfect shifting. I drive it on the freeway, and its great, goes into overdrive on time, downshifts great, the Sport and economy switch works. WTF?!?!
Does it sound like I have a sticking valve in the valve body? I have heard that a sticky valve will cause these issues, but thought three fluid changed would remedy this.

I took the car back to the shop I use on certain repairs and told him it was shifting weird again. He kept the car 2 days, and never did it act up with him. It had solid, firm shifts with no premature shifts!! He said that if the TPS needed adjustment again we would know by erratic shifts and rough idle.
I had previously posted the trans was slipping in error. Its shifting early....
HELP I'm stumped!!

catso 12-07-2011 06:22 PM

I think your model (the EH) is the electronically controlled trans. There's a computer or controller module that determines when it shifts. There's probably a variety of factors; vacuum, temp, speed sensors, etc. My guess is that may be the cause. Many older BMW's always seem to suffer from some electrical problems. I would carefully check all the connections, wiring, ground points, etc. and all the vacuum lines, coolant sensors, basically anything that signals the controller.

IEbimmerguy 12-07-2011 07:03 PM

Thank you for replying! Yes my transmission is the electronic one. I understand that the throttle position sensor determines when to shift, but the fact that this is intermittent in nature is what baffles me. Doesn't the TPS either work or not? Not in between?
I don't have vacuum leaks, I had it smoked tested. I cleaned and tightened the grounds I have found.
As far as the transmission module, I was told they don't go out, so I haven't replaced it. Maybe I should....

catso 12-07-2011 07:35 PM

The 8 pin connector you mentioned might be the problem, especially since you found some fluid that could affect the connections. Try cleaning it real well. Old rubber vacuum lines and boots can have intermittent leaks. Examine all of them carefully and replace anything suspect.

IEbimmerguy 01-01-2012 08:53 AM

Update: I cleaned the connector and it still shifts early.
What's so damn frustrating is that I will have 1-8 days of perfect shifting. Then one day it decides to shift early seems confused on shifts!
I don't get it?!
Would the throttle position sensor that controls shifting cause this?

catso 01-01-2012 09:29 AM

Quote:

Originally Posted by IEbimmerguy (Post 6534858)
Update: I cleaned the connector and it still shifts early.
What's so damn frustrating is that I will have 1-8 days of perfect shifting. Then one day it decides to shift early seems confused on shifts!
I don't get it?!
Would the throttle position sensor that controls shifting cause this?

It could be the TPS or possibly any of the other sensors that are connected to the transmission control unit. Intermittent problems are always the most difficult to solve.

IEbimmerguy 01-01-2012 09:39 AM

To be more specific, what sensors? I assume the TPS, the shift selector switch? Maybe the Econ,sport, and 123 switch?
I haven't tried to adjust or play with the TPS, it seems too sensitive.
I took the driver side kick panel off and looked at the trans control box. Looks perfect with no moisture or corrosion.
This issue is so frustrating because it's intermittent and my Indy that worked on this issue says, "the engine runs good and it's intermittent so it's the trans" Stumped....
My Indy seems to be done with it.

catso 01-01-2012 09:46 AM

Quote:

Originally Posted by IEbimmerguy (Post 6534904)
To be more specific, what sensors? I assume the TPS, the shift selector switch? Maybe the Econ,sport, and 123 switch?
I haven't tried to adjust or play with the TPS, it seems too sensitive.
I took the driver side kick panel off and looked at the trans control box. Looks perfect with no moisture or corrosion.
This issue is so frustrating because it's intermittent and my Indy that worked on this issue says, "the engine runs good and it's intermittent so it's the trans" Stumped....
My Indy seems to be done with it.

It may even be an electrical issue. :dunno: Check the condition of the battery, battery terminals, grounds, fuses, wiring, etc. I would even check the voltage output on the alternator, especially when the shift problem is occuring. You need to rule out as much as possible to narrow down the focus.

IEbimmerguy 01-01-2012 09:50 AM

I'll look at that the next few days I'm off. Thank you for your replies.
Do you have a similar car with the M30 engine?

catso 01-01-2012 11:26 AM

Quote:

Originally Posted by IEbimmerguy (Post 6534914)
I'll look at that the next few days I'm off. Thank you for your replies.
Do you have a similar car with the M30 engine?

No, my 528E has the M20 and the regular 4HP22 auto trans. These older BMW's all seem to suffer some electrical problems, so I usually figure that's a good place to start.

IEbimmerguy 01-04-2012 07:09 PM

Update: I figured it out!! The "angle sensor" next to the TPS is sending inconsistent signals of when to shift.
I sprayed some contact cleaner on it, and it shifts GREAT! I also ordered a new one, because I don't want these issues again.
CATSO- thank you for your help and responding to my post!!

catso 01-04-2012 08:41 PM

Quote:

Originally Posted by IEbimmerguy (Post 6541833)
Update: I figured it out!! The "angle sensor" next to the TPS is sending inconsistent signals of when to shift.
I sprayed some contact cleaner on it, and it shifts GREAT! I also ordered a new one, because I don't want these issues again.
CATSO- thank you for your help and responding to my post!!

:thumbup:

Diagnosing these kinds of problems is usually the most difficult part of owning an older BMW. The wrenching and cost of the parts is generally minimal.


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