Hi everyone how are you I need help with my 4.9 idk what it is but when i accelerate from 20 mph and up the car stumbles and when cruising it surges ive replaced everything fuel filter complete tune up from wires to spark plugs to distributor cap and rotor ive also changed the cat because it was starting to rattle nothing also changed the throttle position sensor car idle fine and runs fine except the stumble i also changed the egr valve cleaned the throttle body and nothing but last month i had the trans rebuilt and ever since then the car stumbles on acceleration the car has no vaccum leaks and i only have 2 codes coming up E98 High rpm from the isc motor from park to N to drive and an E55 closed throttle angle out of range idk if the tps misadjusted has anything to do with stumbling under acceleration and idk about the isc since it is bad if it will cause that? please please help i want my baby back to normal she only has 102,000 miles thank you!!

Bad ISC alignment could cause it but seems unlikely. You should fix it anyway, maybe it will help or maybe it won't but it's not good to neglect your baby anyways

yeah i know i try to take good care of my baby i just really wanna know what's wrong with her

Have you changed the injectors? The injectors are problematic on this engine. Replace them with the much more reliable Ford 4.6/5.0 injectors.

I have not yet changed the fuel injectors but all this happened after i got the trans fixed before i got the trans fixed the car didn't have a stumble at acceleration or any of this the car runs great just the stumble it has.

Just now i did a fuel system pressure test and a vaccum test and everything tested out great idk what the hell could make the car stumble

Fix the TPS.

Ok HUF thanks i will do that and let you know what happens

I agree with HUF, don't start guessing when the car is telling you it has problems. R&R the tps and lets us know of the results.

Ok HUF thanks i will do that and let you know what happens
There is a procedure to adjust the TPS. Do you have Factory Service Manual? If you don't , get one on eBay cheap.

The procedure as I remember it is short, so in case you don't have a manual, I'll quick type it out while my frozen pizza dinner is baking.

Start engine
Raise throttle hammer off idle to raise rpms slightly
Push in on plunger if ISC until it fully retracts.
Unplug ISC motor while fully retracted.
Release throttle hammer

The throttle hammer will now be resting on the min air screw. Adjust this screw until the engine idles at 450 rpm.

Shut engine off
Enter diagnostics pushing OFF and WARMER on the climate control panel
Navigate to the TPS angle display (can someone chime in which this is on the older pre-94+ displays?)
Adjust TPS until the display reads anywhere between -0.5 and 0.5
Tighten down TPS screws, plug in ISC motor, disconnect/reconnect battery.
Perform idle learn.

This is off the top of my head, and I don't have a great memory...If I've made an error, some please correct me.

That procedure is for the ISC motor, NOT the TPS. After you have done this,
"Start engine
Raise throttle hammer off idle to raise rpms slightly
Push in on plunger if ISC until it fully retracts.
Unplug ISC motor while fully retracted.
Release throttle hammer"
adjust the plunger to throttle gap to .060. Plug it back in and you are good to go.

That procedure is for the ISC motor, NOT the TPS. After you have done this,
"Start engine
Raise throttle hammer off idle to raise rpms slightly
Push in on plunger if ISC until it fully retracts.
Unplug ISC motor while fully retracted.
Release throttle hammer"
adjust the plunger to throttle gap to .060. Plug it back in and you are good to go.

While the ISC adjustment shares the same first steps, I believe it is correct for the tps as well... worked on all of my 4.x's anyway.

http://www.v8mr2.com/reference/adjustments_engine.pdf

View halfway down page 3

The min air screw is critical to all throttle body adjustments, it is the baseline for both the TPS and the ISC.

Remember that the 4.x's are no northstars. They still have distributors. The TPS IS adjustable and it is heavily relied for ignition and, in combination with the hall effect switch, fuel injection timing. In the N* case, with distributorless ignition, tps adjustment does not exist. On a 4.X, adjusting only the ISC and moving on will result in a poor running engine.

That procedure is for the ISC motor, NOT the TPS. After you have done this,
"Start engine
Raise throttle hammer off idle to raise rpms slightly
Push in on plunger if ISC until it fully retracts.
Unplug ISC motor while fully retracted.
Release throttle hammer"
adjust the plunger to throttle gap to .060. Plug it back in and you are good to go.

Ranger,
To adjust the TPS, Drewsdeville retracts the ISC motor plunger with hand instead of commanding with climate control buttons. He did not describe ISC motor adjustment.

Huf, I realize that he retracted the plunger by hand. That is the same way to do it on the ISC adjustment. I did not think that there was an adjustment to the TPS. I thought it was just a potentiometer. I'll have to go read up on that in the FSM one of these days. Sorry if I muddied the waters.

I finally Fixed my problem it was just the TPS needed to be adjusted right and now nomore stumble at acceleration my baby is finally back and is running great im so happy to have my baby back and running great!!!:)