Rough Idle, motor dies while low rpm in motion. P1121

[carl beasley]

2001 ST job One, 220K miles. One day it's fine, the next it's jerky, burping at low rpm. I can floor the throttle and she runs. then dies when I let off Throttle. Error code P1121. checked the valve cover to air intake hose, popped the KN filter and shot some Electrical cleaner on the MAF, disconnected the MAF and cleaned contacts.... What else TPS?

Really don't want to take it in to a Shop. Labor running $125 an hour, Plus cheap local low bidder Auto Parts stores. Any ideas what I can do next?

Thanks.

Carl

 

[curtis james]

maybe a vacuum leak, at low idle the mixture of air to fuel can cause an engine to idle rough or die, higher revs more fuel is not as noticeable. that is the cheaper, easy fix. if your engine is cold you can spray some carb cleaner around hoses and see if she revs up and track down the area. there is pressure gauges but a can of cleaner or starting fluid has worked for me. it stinks and can dry out hoses but it's cheap and quick, the plus side is you might get lucky and you will have a clean area.

 

[carl beasley]

I'll try that tomorrow morning. thanks.

 

[Todd Z]

Job 1's were known for intake manifold gaskets leaking.... also 1121 is a TPS code..... Replace the TPS.... It can be a bit crappy due to locktight on the screws and aluminum TB on the job 1. ALSO there is a rotation difference from job 1 -2.... Get the right TPS..... use the 2000 Explorer if you have to look it up. good luck.

 

[Phil Frady]

You check the elbows that go from the intake manifold to the PCV, they usually deteriorate.

 

[carl beasley]

Didn't have any Carb cleaner so I used some Electric contact Cleaner. Similar. Soaked all around the TPS and MAF, any rubber hose. Idle settled down. I'm taking a trip to store now. will get some Carb cleaner. The hose from the valve cover (pass side) to the rubber oval air intake is rather lose. I'll hunt that down.

Thanks for the help.

 

[carl beasley]

Well...that trip sucked. Got home. real rough running. I'm going to replace the MAF and TPS, . MAF looks straight forward. $20 on Amazon. Worried about the TPS. I have TPS as Ford F5RZ-9B989-BA


Diff Job 1. "J.K" did the Sign Off, Dated 06/04/01 "Louisville, KY. This is printed on the Black plastic grill cover, just forward of the radiator.
Vin # 1FMZU67E31UC73360 Some help on the part #'s, Please & Thank you.

Carl

 

[carl beasley]

I think the part is Potentiometer - Engine Throttle Part Number: F5RZ-9B989-BA Genuine Ford Throttle Position Sensor - Ford Parts Giant

 

[blert]

I think the MAF may also be different between J1 and J2. Many years ago I told the Autozone guy I needed one for an '01, he gave me what was listed in his computer. Installed it and the truck ran worse. Took it back and he checked the numbers. Told him my truck was a J2 and he had no idea what I was talking about. Had him give me the one listed for an '02. Been working fine ever since. Could be that the AZ database was just wrong though.

 

[Todd Z]

Sometimes it’s a lot easier to just order the parts for a 2000 4.0 if you have a job one. If you have a job 2 a lot of times it’s easier just to get the part for a 2002.

 

[swshawaii]

Job 1's were known for intake manifold gaskets leaking.... also 1121 is a TPS code..... Replace the TPS.... It can be a bit crappy due to locktight on the screws and aluminum TB on the job 1. ALSO there is a rotation difference from job 1 -2.... Get the right TPS..... use the 2000 Explorer if you have to look it up. good luck.

^ Bingo! Todd nails it.... again.

Not like the OHV vs SOHC TPS thread linked below, but incorrect rotation is often the problem.
https://www.explorerforum.com/forums/showthread.php?t=423226

 

[blert]

Sometimes it’s a lot easier to just order the parts for a 2000 4.0 if you have a job one. If you have a job 2 a lot of times it’s easier just to get the part for a 2002.

Yup, ever since then that is what I do. Sometimes they even look at me funny when I say "let's just call it an '02".

 

[DILLARD000]

Yep, same here.
2001~2003 ExST Job2 also seems to be near identical mechanicals as 2001~2003 RangerExtendedCab.

 

[carl beasley]

Just a followup. I bought a MOTOPOWER MP69033 Car OBD2 Scanner Code Reader $21. MOSTPLUS 74-50011 Mass Air Flow
MAF for $22 Both from Amazon Swapped it out. Runs smooth. the new scanner didn't show a P1121 prior to changing the MAF. Tossed my old Scanner. Thanks for your help.

 

[blert]

Just a followup. I bought a MOTOPOWER MP69033 Car OBD2 Scanner Code Reader $21. MOSTPLUS 74-50011 Mass Air Flow
MAF for $22 Both from Amazon Swapped it out. Runs smooth. the new scanner didn't show a P1121 prior to changing the MAF. Tossed my old Scanner. Thanks for your help.

P1121 is a manufacturer specific code. It is not standard OBD2 so it has different meanings depending on the manufacturer. If the scanner you have can read Ford specific codes your fine, if not then you need one that can.

 

[curtis james]

Carl, thank you for the follow up and info,, it helps fellow trackers out.. there has been a few that i have seen that do not do follow ups,,,, way cool ya got it done and for so much less then a shop will charge just to look at it. There are a bunch of well informed members on here.

 

[carl beasley]

P1121 is a manufacturer specific code. It is not standard OBD2 so it has different meanings depending on the manufacturer. If the scanner you have can read Ford specific codes your fine, if not then you need one that can.

Yes, before i replaced the MAF, the OBD2 scanner did show multiple "misfire cylinder xxx" codes. After install and clearing errors, truck runs smooth. Out for a 3 hour highway drive for a full check out. With Gas cost today, the check ride will cost more than the repair parts. yikes...