This Sucks.....

[foreman72]

I just finished the top end on the Lumina (3.1L) and now that it started, it has some gremlins....Check engine light came on and it had 2 codes--Coolant temp. sensor, and TPS.. I changed both and the coolant temp gauge still doesn't move, and it sometimes starts at high idle(2.5K) and it takes a while, to come down, sometimes not at all....All this, and now the tranny is acting funny. It shifts fine at lower rpm's, but give it 1/3 pedal and it won't shift into 2nd unless i take my foot off the gas. And, it wont downshift (when depressing the gas pedal all the way), it stays in whatever gear you are in.......I really need to know if this thing is worth putting any more money into......I really don't want to buy a tranny.........Anyone have any ideas?

[blazes9395]

Both of these sensors are important in the proper fuction of the car. The TPS is important, as the PCM uses this to determine shift points for the tranny, and it is a big issue for your idle. Check and make sure your connections are proper and tight to both these sensors. If that checks out, you'll have to back trace these wires and make sure they are not torn, kinked, damaged.

[foreman72]

The connector itself in fine, and i tested the voltage as it says in the manual, and it checks out. I can say this, it looks like the car was worked on before. There is one green wire coming off the rear head that goes to nothing....it has a small round female connection that doesn't terminate. And there is a part of the harness where it looks like a wire was cut and either removed, or spliced in to something else....it's my first Lumina, so i don't have a good reference as to how it should be or may have been.

[foreman72]

One more interesting thing, the cooling fans run all the time, they never shut off......

[richtazz]

Depending on the year of your Lumina, there may be a separate sensor for the guage located in the rear cylinder head. It will have a 8" long green wire with a black connector at the end. The TPs will affect the trans shift, because at full throttle, the shift is delayed. If the TPS is off, the computer thinks you're on the throttle mroe than you are, and won't shift until you let off. Also check for vacuum leaks. If your trans has a vacuum controlled modulator, a leak will cause low vacuum and delay the shift. A vaccum leak would also cause a high idle.

[foreman72]

Richtazz, that describes the wire coming out of the head, however, there is nothing for it to plug into--anywhere. I spent quite a while looking for it when it was apart and going back together. I may just go to the junk yard and take some pics and snag whatever it plugs into and as far back into the harness as it goes.....I'm also going to do a "spray" test with it running to see if it has a vacuum leak. I'll post my findings later, i just hope the tranny's not beat.....Thats more money than i want to put into this i think.....

[blazes9395]

Originally Posted by foreman72

One more interesting thing, the cooling fans run all the time, they never shut off......

Thats because the coolant sensor is not working, the PCM, by default, will turn on the fans to run all the time, as it doesn't know how warm the engine is(no sensor reading), all it knows is its running.

[foreman72]

You are right sir!. Actually, i'm making progress today. I went to the junk yard and found a lumina w/that green wire, which i took. Now, here's the funny part----The green wire on the harness that is supposed to go to the sensor on the back head was spliced with the white wire coming off the TPS---i cut that wire, reconnected the green with the one on the back head, and the fans shut off, and the temp gauge works....one problem solved. However, the idle is still high, and i have no idea where the white wire from the TOS(wire "C" as the manual calls it.) Now, all i have to do is connect the white wire where ever it is supposed to go, and i'm guessing that should take care of it.....Now, to find the white wire's home..........

[blazes9395]

your half way there....

[foreman72]

Any idea where i can get a schematic for my PCM online? If i can run a wire directly from the "C" on the TPS plug to the PCM where it belongs, that way i can see if it fixes the problem....

[foreman72]

Hail Jesus! I figured it out! Turns out someone substituted the 2 wire collant tem sensor wire with a 3 wire and put in the wrong temp sensor to match...Then switched the position of the TPS and temp sensors.....All is good and it runs and shifts beautiful.....Only one more issue....Any idea why my fans don't turn on? Relay maybe? Is this a common issue?

[richtazz]

First off, congrats on figuring out the wiring mess you were faced with!

The fans shouldn't come on until coolant temp reaches 230'ish degrees. If you set the HVAC control to MAX, the fans should kick on. If not, check the two relays in the underhood relay center. You can even swap them around to see if one or the other is the issue.

[foreman72]

Well, the temp gauge goes between half and 3/4 of the gauge(i'm guessing thats pretty darn close to 230, if not highter). And then i did try the A?C to max, and no fans. Thanks for the realy suggestion, i'll try that next.