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What causes the engine to over rev when shifting gears?

 
groovygroveone
New User
Posts: 39
Joined: 03/12
Posted: 06/21/12 01:45 PM

When the engine is cold,everything is working fine. Planty of power.Excelarates like a charm.But once it gets at operating temperature,everything goes to pot.I've cleaned all componets and replace some. Checked all voltages and ohms.I have replaced the O2 sensors twice. I know it going to be something simple,but I have placed my finger on it yet.How about a little help PLEASE!!!!! Confused  

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waynep71222
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Posts: 96
Joined: 04/12
Posted: 06/21/12 08:58 PM

the only thing i could think of is the clutch pedal interlock switch may not be properly sending clutch pedal down signals to the ECM to let you know you are shifting gears...

is the vehicle speed sensor connected to the computer??  so the computer knows the car is moving..

in some instances the ECM holds the Idle air control valve way open to use it like a dash pot.. keeping the Engine RPMs up..

is your throttle body base idle setting at the lowest RPM possible with the IAC unplugged.. then verify the TPS voltage is within spec.. less than 1.0 volts..


if your base idle setting it too far open.. when the IAC backs out..  it can let TOO much air through...    just curious...   did you adjust the allen set screw in the center of the IAC valve.. that limits the amount of opening of the idle air bypass..  

is your idle air bypass valve on the correct direction.. so the high manifold vacuum is NOT pulling the valve open bypassing additional air..


i went off looking for more info for you....

have a look at this break out box..   i want one of these

http://oldfuelinjection.com/?p=12  

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waynep71222
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Posts: 96
Joined: 04/12
Posted: 06/22/12 07:29 PM

by the way... i have not seen a LOT of other people who are willing to share their knowledge of fuel injection theory..

do check out the old fuel injection site.. there is a lot of good info there..


i was also talking about the last item shown on that link.. that plugs in like a break out box.. but interfaces with the EEC4 system and displays all the sensors and data stream on a LAP top..

that is the way to go.. instead of doing it blind...  

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groovygroveone
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Posts: 39
Joined: 03/12
Posted: 06/23/12 02:40 PM

I took my car to a guy that was suppose to be good with 5.0s. He kept it a week or so. He claims that I had my 02 sensors hooked up wrong.So he corrected that.Yes it ran a lil better,but not perfect.Had a surge and bad idle. After it reach operating temp. it would idle up and down,sometime stalling out.He said for me to adjust the idle a lil at a time till it smooth out. Which I did,but it stills idle rough,,and still stays revved up after it is warmed up.I've checked all voltages and ohms.The TPS checked out ,1.01v on the idle side and 5.15 volts on the full throttle side. The IAC has been replaced,but still have to unplug it,to get the idling down. Q: I've replace the coolant temp sensor,can it be bad or not working right?  

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waynep71222
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Posts: 96
Joined: 04/12
Posted: 06/23/12 03:36 PM

surge....   PRINT THIS>.



Technical thread: Setting base idle for EEC-IV

Having to set the base idle on an EEC-IV equiped rig is rare because they come set from the factory and they (Ford) say not to mess with it. However, there are times that it is necessary such as when someone repaces the throttle body for whatever reason. Even the companies that manufacture throttle bodies say that they set them up for a proper base idle speed, but that does not always turn out to be true.

Prior to setting the base idle, the throttle body and the IAC must be clean and free of carbon build-up.

Once it has been established that the TB and that IAC are clean and dry, attempt to start the motor. If it will stay running on it's own, great. If not, turn the stop screw on the TB until it will run on it's own. Once you get it to where it will stay running, disconnect the IAC. If the motor dies at this point, the start the motor back up and turn up the stop screw until it will stay running. Now you want to set idle speed via the stop screw to the lowest setting possible between 650-850 rpms with IAC disconnected. It is key to use the lowest possible idle speed at this point to prevent a surgng idle once the IAC is hooked back up. Once the lowest possible idle speed is set, shut off the motor and hook up the IAC. With the key on and the engine off, check the TPS voltage. It should be between 0.80 volts and 1 volt. If the TPS reading is outside of that range, don't panic. If the TPS reading is within 0.60 volts and 1.10 volts, it's still acceptable, since no TPS failure codes will be generated, and it falls within the EEC-IV 0.50 volts to 1.19 volts operating range. However, 0.80 volts to 1 volt is the norm. Once a TPS reading hs been attained and it is determined that the value is acceptable, disconnect the battery negative cable and leave it disconnected for about 5 minutes. Then re-connect the battey and allow the motor to idle for about 5 minutes to make sure the set-up is operational. If idle speed falls too low or the motor dies, increase idle speed via the stop screw a little bit at a time. Shut the motor off and let it sit for about 1 minute the re-start the motor. Let it run for a few minutes and adjust the stop screw a little bit at a time as needed. If a desirable idle is achieved, then leave the stop screw alone and double check the TPS value. If the idle speed needs more adjustment, repeat the last few steps. If the TPS ends up out of the operational range, the it may need to be adjusted. To do that, you loosen up the fasteners that hold it in place and rotate it one way or the other depending on which direction you need to go. The mounting holes of the TPS may need to be oversized to allow for further adjustment, but this is not usually the case.

Side note: There is no need to reset the EEC-IV since the TPS minimum value used for idle control is reset automatically by the EEC-IV every time the key is cycled on-off with 20 seconds in the on position.  

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groovygroveone
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Posts: 39
Joined: 03/12
Posted: 06/27/12 03:42 PM

I printed out ,your instructins. Followed them to a tee. The TPS 1.07/5.12 . Adjusted to the lowes.Readjusted idle.Went thru the no load and the loaded with 2 min intervals. It's still surging at idle. Go out on the road.She still want to stay revved up in between gears. And surges at slowing down and stops. I've replaced just about everything I can think of.Added more grounds. You would think it would run perfect. OH, but no!! Anymore ideas!!  

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waynep71222
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Posts: 96
Joined: 04/12
Posted: 06/28/12 02:53 AM

i know that you adjusted it..

but its RIGHT at the HIGH limit... TPS 1.07/5.12      how long does it take you to adjust it down to 0.65...  

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groovygroveone
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Posts: 39
Joined: 03/12
Posted: 06/28/12 12:21 PM

I have moved the TPS,in both directions and it will not change.
I don't know what else to do? I guess I could oblong the holes on the TPS.  

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groovygroveone
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Posts: 39
Joined: 03/12
Posted: 06/28/12 04:07 PM

NOW I have a real problem! I don't know what I did. But I was check the TPS.Got it dowm to 0.75/5.12. Something snapped,now all I get is 0.06/5.12. If you slowly excelerate it does fine,but if you rev it up,it will drop back faster now but it stalls ,won't idle. Since the juice I'm testing has to coming thru the ecm,and since I can't get an accurate reading ,it much be in the computer(bad)!! Whats your take on this situation?????  

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waynep71222
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Posts: 96
Joined: 04/12
Posted: 06/29/12 05:01 AM

several things ...

is the Throttle plate so far closed that its sticking in the throttle bore?? causing a snapping noise..

that is a critical adjustment.. that the throttle stop is just a fraction of a turn of the screw farther open that what causes the throttle plate to stick and snap when you try to open it...

if you get that really LOW reading.. either the TPS broke inside.. probably do to the overtravel.. or was already failing..

there are only 3 wires...
5.0 volts reference voltage output from the ECM...
variable voltage return to the ecm
ground..

orange is usually the 5.0 volts
black is the ground  usually
green is the variable usually.  

when you unplug the TPS.. do you get 5.0 volts from the orange to the black wire??

http://bellsouthpwp.net/w/h/whishena/TSB94-26-4.pdf


this shows the TPS voltage specs for 93 to 95...  

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groovygroveone
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Posts: 39
Joined: 03/12
Posted: 06/29/12 06:21 AM

I'M WORKING ON A 95 SET-UP. THE WIRES ARE GY/R (GROUND), GY/W (LOW VOLTAGE),& BRN/W (HI-VOLTAGE). THE SNAPPING SOUND WAS WHEN I WAS CHECKING TO SEE IF THE THROTTLE WAS SEATED IN THE SENOR.aFTER i LOCK THE SENSOR DOWN,I CHECKED THE VOLTAGE ON  THE GY/W,IT WAS 0.06. IT ONLY SHOWS THAT VOLTAGE NO MATTER WHAT I DO. JUST AS IF THERE IS SOMETHING WRONG IN THE COMPUTER! I'VE ROAD TESTED THE CAR WITH THIS SET-UP,AND IT RUNS LIKE A SCAULLED DOG. THE ONLY PROBLEM IS THE DECELORATION,IT STALLS OUT.I HAVE EVEN CLEARED THE COMPUTER AND RETRIED THE SET EVERTHING AGAIN,BUT WITH NO SUCCESS!WHAT DO YOU RECOMMEND NOW!!!!!!

P.S.-IT HAS WENT FROM BETTER TO WORSE. THE KNOWLEDGE I HAVE TOOK INTO MY MINE IN THE LAST COUPLE DAYS HAS LEFT ME WITH A HEADACHE,BUT ITS WORTH,FROM WHAT I HAVE LEARNED! THANK YOU!  

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waynep71222
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Posts: 96
Joined: 04/12
Posted: 06/29/12 02:44 PM

here is some more... yes..its for the 4.6 and 5.4 but how it works and how its tested is exactly the same...  its 3 pages.....

http://easyautodiagnostics.com/ford_tps_test/ford_diagnose_tps_1.php  

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groovygroveone
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Posts: 39
Joined: 03/12
Posted: 06/30/12 02:06 PM

Thank you for all your HELP, The information you have sent to me has helped.
I could not ask for more.It was the TPS the whole time.But I wasn't smart enough to realize it until you sent me the info,I needed. I was looking at everything all wrong. Thank you for all your help. I have learnt alot in the past few months.Thank you and God bless!!!!!!  

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