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Discussion Starter #1
my 1994 bronco with the 5.0 and 131k original miles, the check engine light used to just turn on and off, now lately it stays on constant. it would idle at different rpms and the transmission would shift late but yet sometimes drive perfect, it would sometimes start up and idle rough or just turn off, it has turned off about 3 times before, now it wont start on the first turn of the key, i had to wait roughly 10 mins for it to magically start, i took it to the mechanic the day before it just shut off on me at a red light and he said the check engine light was showing the throttle position sensor bad, so would that cause my truck just to turn off at the light and not want to start up? what does a bad throttle position sensor cause?
 

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you're e4od transmission's shift points use TPS measurments, so it'll mess up shifts, usually you'll get a high or unsteady idle with a bad tps, also poor throttle response or dying when you tromp the gas pedal.

since you're CEL is on, just pull codes and you'll know instantly what the problem is.
 

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Discussion Starter #3
thanks, thats exactly all ive been getting, but would it cause my truck not to start at all? it was running with the check engine light on, shifting/idling like shit and all of a sudden it just shut off at the red light on the way to work and didnt want to start.
 

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Discussion Starter #4
the day before that finding out that the codes were showing the bad throttle position sensor and egr valve (which i have already replaced with a new egr valve from advance auto parts) the oem ford one was way more expensive, i also changed the position sensor on top of the egr valve causing the check engine light to turn on, so i put the original one back on the new egr valve and it caused the check engine light not to go on at that point in time
 

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Yes, if its sending WOT signals, the truck might not start. Definetly sounds like its faulty. Erractic idle, late/firm shifts, and not starting symptoms all are pointing towards the TPS.
 

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yo,
Get the Codes posted here soon.
Throttle Position Sensor (TPS) Function & Diagnosis TSB 94-26-4 for 93-95; DTC 121,122,123, 124, 125, OBD II Code P0122 & P0123
Source: by Ford via miesk5 at http://home.comcast.net/~miesk5/technical_service_bulletins.htm#technical_service_bulletins.htm
Take your time & read it.. esp for testing;
"...MANY VOLTMETERS WILL AUTOMATICALLY CHANGE RANGES WHEN MEASURING TPS OUTPUT FROM IDLE TO WOT. WHEN A VOLTMETER IS USED TO MEASURE TPS OUTPUT FROM IDLE TO WOT, THE METER SCALES OR CHANGES RANGES AUTOMATICALLY. THERE MAY BE AN ERRONEOUS METER DISPLAY UNTIL THE VOLTMETER HAS LOCKED TO THE APPROPRIATE VOLTAGE READING. THE ERRONEOUS METER DISPLAY DOES NOT REPRESENT A DEFECTIVE TPS.
NOTE: IT IS RECOMMENDED THAT THE "RANGE LOCK" FEATURE ON MANY METERS BE SET FOR CHECKING TPS VOLTAGE..."

CAPS Are Ford's. not mine,

B) - TROUBLESHOOTING THE TPS
The following is a list of vehicle symptoms which have been associated with the TPS, but can also be related to other vehicle components.
Check engine light
Stalls/quits
Hesitation/stumble
Fast idle
If an EEC error code has identified the TPS as suspect, perform PC/ED Manual pinpoint tests on the TPS.
To minimize the replacement of good components, be advised that the following non-EEC areas may be the issue:
Excessive blow-by
PCV malfunction
Vacuum leaks
Fuel pressure
Throttle sticking or linkage binding.
(A2) - EEC-IV DIAGNOSTIC TROUBLE CODES (DTC)

Testing the TPS in the vehicle electrical circuit.. etc...

GL
 

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AKA: Butthead
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Yes, if its sending WOT signals, the truck might not start.
Erractic idle, late/firm shifts, and not starting symptoms
all are pointing towards the TPS.
Cool. :)

Pretending it had an automatic choke made mine start better. :)

Was told to mash it to the floor and let up before hitting the starter.
Worked like a champ and as I used the '91 F150 more and more,
the better it got until I let it set a couple months again. Doing that
a few times won't hurt anything since there's no accelerator pump
or choke either one.

That works if it's just a little dirty.

---------------------------

I inherited it and it took a while after my stepfather died before it
got driven again see? ...so had lots of trouble at first, my '75 with
its original 2100 started better! LOL :)

Anyway, what you posted made me realize that was what was
going on, had suspected something along those lines before tho.

Cool thread idea, Buck. :)

Alvin in AZ
 

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Cool. :)

Pretending it had an automatic choke made mine start better. :)

Was told to mash it to the floor and let up before hitting the starter.
Worked like a champ and as I used the '91 F150 more and more,
the better it got until I let it set a couple months again. Doing that
a few times won't hurt anything since there's no accelerator pump


------------------------

Alvin in AZ
I thought that kind of stuff had no effect on fuel injection?
 

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I thought that kind of stuff had no effect on fuel injection?

from what i understand, holding the throttle all the way down gives ford fuel injection a "no fuel" code. to help with a flooded condition.

pumping the gas and other such things dont help a fuel injected vehicle start though... it only makes it harder for it to start
 

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si vis pacem, para bellum
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mine ran like shit!!!! the engine felt like ti was straining during the 3 days it took me to fix (thanks again O'rielly auto parts for the bad TPS) it threw a voltage too high code then when i replaced ti with the first replacement i got a voltage too low. you will be running either lean or rich. it also shifted like crap too untill i got it replaced
 

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It will go from open loop to closed loop when the TPS goes bad. In other words the O2 sensor is in the loop during closed loop, and out when in open loop. Runs like crap = yes.
 

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from what i understand, holding the throttle all the way down gives ford fuel injection a "no fuel" code. to help with a flooded condition.

pumping the gas and other such things dont help a fuel injected vehicle start though... it only makes it harder for it to start
this is correct. :thumbup
 

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I'll jump on da loop-da-loop ride too; some excerpts from TSB's and other stuff in my broncolinks.com site;

If vehicle is driven at Wide Open Throttle (WOT) or high loads, the fuel system normally goes open loop rich to provide maximum power. If the MAF sensor is contaminated, the fuel system will actually be lean because of under-estimated air flow. During open loop fuel operation, the vehicle applies Long Term Fuel Trim corrections that have been learned during closed loop operation. These corrections are often lean corrections learned at lower air flows. This combination of under-estimated air flow and lean fuel trim corrections can result in spark knock/detonation and lack of power concerns at WOT and high loads.

Open loop mode happens when you turn on your car and it revs at 1200rpms for the first 15-20 seconds. During this process, your ECU feeds more gas to the engine to warm up the car quickly before driving. (also known as choke on older cars). During this open loop procedure, the extra unburnt gasoline will usually cause your exhaust to smell very rich,

..."DTC P0125 Insufficient Coolant Temperature For Closed Loop Fuel Control "...Indicates the ECT or CHT sensor has not achieved the required temperature level to enter closed loop operating conditions within a specified amount of time after starting engine. Insufficient warm up time; Insufficient warm up time Low engine coolant level ..."
 

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AKA: Butthead
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pumping the gas and other such things dont help a fuel injected
vehicle start though... it only makes it harder for it to start
I can see where you would get a silly idea like that if you've never messed
with a dirty potentiometer while an ohm meter is hooked up to it. LOL :)

Your inexperience is showing. ;)

BTW, if you were to put your effort into trying to understand what's posted
rather than trying to find fault with it, your learning would be faster.

Easy for me to say tho! LOL :) ...since I'm what you would've called a nerd,
if you were old enough to have been in school with me way back when. :)

I've always liked learning new stuff and always will. :)
YMMV?

Alvin in AZ
 

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Thanks to FSB.com, miesk5, and all the other dudes, they got me through this one too. It would stay at rev when I backed off the gas, bounce around a bit (tach). Made the Bronco dangerous I think! Cost me like 60$ at the kragen, bolted it on and like magic, new again! Any mechanic would have charged me at least $150 for this easy job. This is one of the first things that has gotten me started on my 95', I have come a long way since. Am I the only one that shows up to work the next day with mechanic hands?!

MIKE31O
 

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AKA: Butthead
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Any mechanic would have charged me at least $150 for this easy job.
This is one of the first things that has gotten me started on my 95', I
have come a long way since. Am I the only one that shows up to work
the next day with mechanic hands?!
MIKE31O
Cool post! :)

"it's easy when you know how" -cowboy buddy

Us blue-collar-guys know how you feel. :)

Saw a really miserable young man in Costco today,
...setting up his -tasting booth-! Holy crap, huh? :)

The dumb ditch digger in AZ
 

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Discussion Starter #18
yup guys, it was indeed the tps sensor, but so happens the distributor went to, which caused it not to start, it now runs beautiful with the new egr valve i did a while ago, tps sensor and rebuilt tweaked distributor =)
 
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