1990 2.9L 2WD issue with sudden motor drop-off as I'm at speed 65mph...?

[Erikinho]

So, when I'm running along the freeway, the engine drops off in a fraction of a second but reengages!? It's a bit alarming... I spoke to my mechanic and he thinks it's the TPS module...? (I just remembered the TPS REPORTS from OFFICE SPACE film LOL!)
What's been your issues and fixes with this? Thanks!

 

[RonD]

Its possible TPS has a Dead Spot, but you should notice that at any speed when gas pedal is in that one position
TPS is a 5volt sensor on the throttle plate shaft
With throttle closed computer gets just under 1volt from the TPS
With throttle wide open(WOT) the computer gets 4.5volts
So it works the same as a volume control or light dimmer, a variable resistor

If there is a "dead spot", voltage drops to 0 or under 1 volt in that one position, so computer "thinks" you took your foot off the gas pedal, and if you didn't then an unexpected stumble
But at 30mph or 60mph, speed wouldn't matter only TPS/gas pedal position would matter

RPM stumble, spark system
Again this should occur based on RPM of the engine not speed, so if its distributor or TFI issue you would expect the stumble in 1st, 2nd, or 3rd gear when at that RPM


At 60+MPH fuel flow would be at its highest, unlike 30MPH, or say 2,500rpm in 2nd
So fuel flow issue would fit better
Change fuel filter
Check fuel pressure at idle, 30psi is expected, then REV engine to 2,500(approx.) and hold it there, watch to see if pressure is slowly dropping, should stay stable at 30psi, if its slowly dropping there is a flow issue, which would be much more noticeable with engine under a load(driving)

 

[Erikinho]

Thank you very much RonD! I will try your advice!

 

[Erikinho]

So, here's the latest... I replaced the fuel filter and the TPS module...The engine still hesitates when I depress the throttle...? I'm going to use an injector cleaner in the fuel and see what that does...? Any suggestions...? The car starts quickly, idles perfectly... But, it's the depressing of the accelerator pedal that the problem occurs...?

 

[rusty ol ranger]

Check the fuel pressure...should be at 40lbs or thereabouts.

Could also be a vacuum leak. Or possibly a MAP sensor. Try pulling codes, you might get lucky. Is your check engine on?

 

[Erikinho]

Check the fuel pressure...should be at 40lbs or thereabouts.

Could also be a vacuum leak. Or possibly a MAP sensor. Try pulling codes, you might get lucky. Is your check engine on?

How do I pull codes...?

 

[rusty ol ranger]

How do I pull codes...?

With this...

https://www.amazon.com/INNOVA-3145-Ford-Digital-Reader/dp/B000EW0KHW/ref=asc_df_B000EW0KHW/?tag=hyprod-20&linkCode=df0&hvadid=312158556601&hvpos=&hvnetw=g&hvrand=18432174415769973757&hvpone=&hvptwo=&hvqmt=&hvdev=m&hvdvcmdl=&hvlocint=&hvlocphy=9017392&hvtargid=pla-434264198620&psc=1

Or a test light...but i prefer the reader, makes it much simpler.

Theres instructions all over online how to do it and the reader comes with a pretty cut and dried book thatll explain it.

The code port is under the hood, passenger side corner by the blower motor, itll say "eec test" on the cover. Its basically just a pigtail of wires