Looking for opinions

[Big_Brown_Bronco]

I'm stumped.

Ive recently had some issues with "Frankie" repaired (new fuel pump assembly, filter, plugs and IAC) and a new problem has developed. When I'm driving on the hwy at speeds 65 or over (in 3rd gear) I cannot keep constant acceleration. She'll start start to slow down, kick into 2nd, speed up to where she was, cruise for about 30 seconds and do it all over again. The funny thing is it only happens at 65 mph or faster. I can run just fine at any lower speed. I've checked all the vacuum connections I can find (except the head gaskets) and the tranny is full of fluid and was just rebuilt about 6 mo. ago.

My thought is that I'm not getting enough vacuum at the high speeds, or the voltage to the TPS is low. Any ideas would be greatly appreciated!.

Thanks,

SB.

 

[BroncoJoe19]

Surging throttle definitely sounds like TPS!

Voltage to the TPS should be about 5 volts.

You can test it with a digital voltmeter, by backprobing its connector, with the key on. It should go from 0.5 - 1.0 volt at idle to 5.0 volts at wide open throttle. The transition should be smoothe.

WIth that being said. With a digital volt meter you will only be able to determine that it is bad, if it is really really bad! To be checked properly, one needs to use an oscilloscope.

Try pulling trouble codes, I just happen to have a tutorial here...

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SO here you go...

How to scan FORD on board Diagnostic Trouble Codes (DTCs) in your driveway

Howto Pull Codes 1983-1995 Mustang, F series Trucks, Econolines, Broncos, 302, 351 and more

 

[Big_Brown_Bronco]

OK, I checked the TPS.

From ground to the green wire I have 0.95 VDC to 5.07 VDC from closed to wide open throttle.

From ground to the red wire I have 0.98 VDC to 4.55 VDC from closed to wide open throttle.

Is that discrepancy enough to case me problems or indicate a TPS going south?

I will try to pull codes later today.

Thanks Broncojoe,

SB.

 

[miesk5]

yo BB!

As our pal, Joe advised; testing for Codes will help, even if you do not have a Check Engine Light (CEL)

Looks good... is it smooth from closed to open?

It is diff to tell... if the V is a smooth by visual; some use a scope or diggie VOM w/print-out capablity.

Testing & Operational Description & Parameters (click on Sensors)

Source: by Ryan M

Some major points in his extensive article:

Closed Throttle can be anywhere between 0.6-1.0 volts

 

[love_my_bronco]

i feel dumb but what is the tps?

 

[BroncoJoe19]

i feel dumb but what is the tps?

LOL... don't feel dumb. This time last year I could have asked the same question.

I learned a lot about EFI by reading through fordfuelinjection.com

The throttle position sensor is mounted on the end of the throttle body and tells the computer how far open or closed the throttle is. The TPS is pretty easy to understand how it work

 

[love_my_bronco]

is it only for EFI or is it used for carbs too?