Transmission is not shifting. It has a rough idle.

[mnm0873]

I have a 1997 Ford Explorer 4.0 SOHC 4wheel drive.
I am having trouble with it having a rough idol, and the transmission not shifting. I took it to a local transmission place to have it looked at and they told me that there was two minor things wrong before they could diagnose the transmission. #1- It is miss firing, #2- The TPS is throwing a bad code. I just replaced the plugs and the TPS within the past 8 months.
What else could be the issue? I've been through this site alot tonight and have found several things it could be. I had some friends check it out and they told me it is the Mass Air Flow Sensor. Would that cause the issues with my vehicle running really badly and not shifting?
Any assistance would be greatly appreciated as I rely on this vehicle being a single parent to two children.
Thanks everyone!

 

[mnm0873]

I had a parts store check the code and my TPS was throwing off the P1120 code. So I asked them to reset the computer since the TPS is new from this summer and it has tested good. So, I drove it for awhile and it was smoother idol but the transmission was still not shifting. I parked it and it was off for about 30 minutes and I started it up and the CEL was back on and remained on. So, the next day I took it to another parts store. This time the MAF was throwing the code. He didn't tell me what the code was but he did say it was the MAF. So, my question now is, should I invest in the can of MAF cleaner first BEFORE I just change the MAF? Would the MAF cause the transmission to not shift? The guys at the transmission place said my truck is at a higher idol so my truck isn't recognizing the proper time to shift. Please help! I know I can clean the MAF and or change it if needed on my own. I'm HOPING the MAF is the cause of it running bad only and that it's not the transmission. The filter was changed that is in front of the MAF shortly after I bought my truck last year in Nov.
Thanks everyone for your assistance.

 

[EricM9104]

Dozens of sensors change how the motor runs and adjusts an automatic transmission shift points.

 

[mnm0873]

Thanks for your reply. I appreciate it. Any further information you can add?

 

[BrooklynBay]

It wouldn't hurt to clean the MAF sensor. It's less expensive than replacing it. There is a TSB on cleaning it in the technician forum section of this site. I have additional links in my list of useful threads.

 

[mnm0873]

It wouldn't hurt to clean the MAF sensor. It's less expensive than replacing it. There is a TSB on cleaning it in the technician forum section of this site. I have additional links in my list of useful threads.

Thanks BrooklynBay. I cleaned my MAF this past spring when my fuel pump went out. I'll do it again especially with all the road construction going on near my place. Will a dirty or bad MAF cause the transmission to act up also? I thought about disconnecting the MAF and see if it drives better, is it bad to drive it without the MAF connected?
Thanks again! I appreciate your response!

 

[BrooklynBay]

Driving without a MAF sensor will throw a code. A dirty MAF will cause a rough idle.

 

[mnm0873]

Thanks again. I will definitely try with the MAF cleaner first and pray for all it's worth that it solves the problem with the way it's running.

 

[mnm0873]

Update

Well, I took my MAF off, it was clean. I disconnected the MAF also and the truck ran alot worse when it was disconnected so it's not the issue.I had bought the MAF cleaner just in case I needed it and also the Throttle body cleaner. So since the MAF was clean, I didn't clean it, took off the IAC, oh my goodness it was filthy with carbon build up. Cleaned it out with the cleaner. Opened up the throttle and it had tons of carbon build up also. Made sure to clean the throttle plate really well. Reconnected the IAC and started my truck up and it died when I pressed the gas pedal. Restarted it again this time I let it idol out on it's own and then I was able to rev it. The idol was smooth! Oh happy joy! I reset the computer to wipe the code. So, took it for a test drive to see if the transmision would shift for me. It did once. There was no hesitation on take off like before after the IAC and throttle body cleaned.
Appointment next Thursday with local tranmission shop to have tranmission checked. The check engine light came back on during the test drive. Had it analyzed and was told it was code P1121. TPS not consistant with MAF. Anyone have a solution to solve it? We increased the idol before cleaning the IAC. Could the idol be too high now?
Thanks everyone!

 

[BrooklynBay]

The TPS gets worn down, and could have dead spots. This will affect the shifing of the transmission. You could check the TPS with the Ohm setting on a meter, but from what you're describing, I would recommend replacing it.

 

[mnm0873]

The TPS gets worn down, and could have dead spots. This will affect the shifing of the transmission. You could check the TPS with the Ohm setting on a meter, but from what you're describing, I would recommend replacing it.

I just replaced the TPS this week. It was still under warranty from the time I bought one in May of this year. I don't know anyone who have the voltage meter that could check it for me. I know from it's idol that it is a little on the high side of idol. When I start my truck the RPM is setting about 1500 RPM and then when I put it in gear it drops down to 1000 RPM. Before my TPS was changed it was a low idol. The RPM's would be right at 500 on starting my truck and then when it was put into gear it would drop even lower. But the rough idol is definitely gone and the hesistation on take off is nearly gone. It just doesn't shift gears.

 

[Fireside3]

Have you had a resolution?

 

[mnm0873]

Have you had a resolution?

No, unfortunately I haven't resolved my transmission issue yet. I got the idol set correctly but it's throwing code P1121 now instead of P1120. I have put a brandnew checked and verified good TPS on it for the 2nd time since May. Don't know what else to do since I'm a single mom on very limited income I can't afford to take it to have any mechanics look at it. My oldest son and I have been the one's to get the idol reset on our own. It's the first time my truck has ever idoled so smooth.
Still looking for ideas about what may be the cause of the transmission not shifting.

 

[my98nnj]

Check the wiring from the TPS to the ECU. Seems the singal isn't right and that's what's throwing your tranny off. I'm pretty sure if you get the TPS error fixed, all your transmission issues will go away. It uses the signal from the TPS to determine shift points.

 

[mnm0873]

Check the wiring from the TPS to the ECU. Seems the singal isn't right and that's what's throwing your tranny off. I'm pretty sure if you get the TPS error fixed, all your transmission issues will go away. It uses the signal from the TPS to determine shift points.

Thank you for the suggestion, I'll see about how to get that done. Other than it not shifting, it's running great for the first time since I've owned it. Getting better hopes for a good running vehicle.

 

[Fireside3]

No, unfortunately I haven't resolved my transmission issue yet. I got the idol set correctly but it's throwing code P1121 now instead of P1120. I have put a brandnew checked and verified good TPS on it for the 2nd time since May. Don't know what else to do since I'm a single mom on very limited income I can't afford to take it to have any mechanics look at it. My oldest son and I have been the one's to get the idol reset on our own. It's the first time my truck has ever idoled so smooth.
Still looking for ideas about what may be the cause of the transmission not shifting.

If you checked the TPS according to the useful thread on that and it passed, then you are getting the PCM reference voltage at the TPS and I would not suspect the PCM too soon. I would look to other common problems first.