tailgatefisher

I removed my trottlebody off my 91 I6 today inorder to clean out the back of the throat. cleaned up nicely, installed back on using a new gasket and reconnected the tps & iac sensors, vacuum lines which I labeled before removing. Problem now is it seems to have less performance than before.

I ran a code check and came up with a 634? I am thinking that maybe it is because i didnt remove the iac nor the tps while spaying it down. If I remove the trottle body again and spray some throttle cleaner in the ports of the sensors will this maybe correct the code 634 or is this related to something else. I also used alittle deepcreek seafoam spray on the trottle plates hinges not thinking of what can I had at hand.

Kattumaram

I assume the tranny is an E40D, the only tran in a '91 that will throw a 634 error code, MLP sensor giving wrong signal.

The MLP sensor tells the PCM which gear is engaged. If the sensor sends a bad signal to the PCM the transmission will start doing strange things.

There is a fix that might clear up the cause of the error code, but I'd suggest you get a new MLP sensor and install it very carefully ascertaining correct alignment when the column shift lever, tran shift lever and MLP sensor are all set to neutral.

I can't think of anything you did with the cleaning operation of the throttle body that would cause a loss in performance.

Just call me Sean

iTrader: (1)

Just to clarify a bit more, the MLP sensor isn't on anything you took apart, it's on the transmission where the shifter hooks up to it.

tailgatefisher

Its gonna be one of those fix one thing, something else goes. I ran codes before working on the cleaning and there were 1's across the board. One hour later theres my 634. This is how come i figured I did something wrong.

I also put about 2/3 can of seafoam into the tank along with 10 gallons of gas. I cant see how that would cause anything.

tailgatefisher

Im gonna check it all out today. Erase codes and drive afew miles to see if it comes back up. Not a part you can clean off, only can be replaced?

Kattumaram

You can try what I did to get the MLP sensor on my LTC to behave:
Shift the tranny to neutral and wiggle the shift lever to get neutral normalized.
Disconnect the negative battery terminal.
Remove the sensor from the tranny, disconnect the connector and
clean up the connector and contacts.
Clean up the sensor body and run a few drops of 3-in-1 oil into the seam
between the body and the rotating center piece.
Rotate briskly the center piece several times from stop-to-stop; this
helps clean up the internal contacts.
Align the neutral marks between the center piece and the sensor body.
Using a majic-marker draw a line across the outside of the sensor body
and the center piece; this helps to ascertain the final setting.
Carefully slide the sensor back onto the shifter shaft without disturbing
the setting. Use the marker line to make sure it hasn't changed.
Install and torque the mounting bolts.
Reconnect the connector and the battery; give her a try.

tailgatefisher

Yes indeed. Ill give this a try. My gear shifter may not have been completely in the gear setting and through the sensor off. It runs across all gears fine but doesnt have much of a inner stop as to hold. Thought about checking it out but never have. Never really tends to give problems.

tailgatefisher

Never had a chance to look into fixing the code 634 today. I removed the neg. cable from the battery to reset the codes and drove it today. Rechecked the codes once I got home and now have a 628. How correct are these codes. Seems odd that I never done anything except reset the codes and my 634 went away and a now 628 appears. I had the 628 code about a month ago and a code for the VSS sensor which I changed the vss sensor and both the codes went away. Does the 634 MLP have anything to do with the 628 code?
I would love to keep triple three's across the board.

Just call me Sean

iTrader: (1)

628= converter clutch error, another tranny code. They can be related, if the tranny doesn't know which gear the truck is in then it won't lock up the torque converter.

tailgatefisher

How can you tell when the torque converter isnt locking?

Seems to still shift well through all gears except the kick down when peddle is pushed down to engage. Unless Im not knowing what to look for.

Im gonna reset the codes again tomarrow and see what comes up on the way to work and home. If it comes up with the 634 & the 628 again, I will figure that I may have to replace the MLP than I will.

Ill post back with my new findings; hopefully nothing but will see.