Would the Map sensor on my 1991 F150 5.0 liter, cause the engine to surge at highway speeds and also when I come to a stop it surges,if I don't give it gas it stalls.I've replaced the O2 and TPS sensors.Also installed new TFI module,plugs,wires,coil and distributor cap.Also tach jumps whenever I give gas-from a previous post Winfordr mentioned tach jumping might be caused by bad pickup unit in distributor. Haven't had a chance to change it yet.I also checked fuel pressure-it was fine. 35-45psi. Not sure what to do next.

RJMACK

 

Just to be sure, do you have any trouble codes?

They can give you some clues....

1987 F150 Reg Cab, 302MFI, AOD, 3.55 Rear, K&N Filter
https://www.ford-trucks.com/user_gallery/displaythumbnail.php?&photoid=4972&.jpg

 

My dad's truck had a similar problem. Try this, start the truck, then pull the vacume hose off the map sensor, see if it smooths out a bit. (it's not going to run very good, just better) His was loping so bad it would barely run at idle, we unplugged it and it sort of smoothed out. Replaced the MAP and all is good.

 

Checked the codes today.koeo I had codes 334 and634. KOER I had codes 116,538 and 632. I put a new ECT sensor on which cleared the 116 code but still get the other codes. The 538 code-Insufficient RPM change during KOER dynamic response test. Not sure what that means.Code634-MLP(manuel lever position)sensor out of self-test range.Also not sure what that means.Code 334-EGR closed voltage higher than expected.I'll try cleaning EGR to see if that clears the 334 code.

 

Quick word of caution...could get pricey to replace sensors as they show up in a code, and you may just be chasing your tail...And not the real problem..someitmes the problem can lie outside of the sensor or the ECM controlled devices, and could be "plain old" engine stuff...Leaky intake comes to mind as well as vacuum leak. Something you may want to check for in your case.... you can save yourself a lot of headaches with a good vehicle repair manual and a meter...

That said, you can ignore code 538..you did not perform the "goose test"...the system will "prompt" you with a quick needle sweep when it wants you to give it full throttle....(although it may be a good idea to rerun and perform this goose test as it may give you more info)

Code 632 is likely that you did not press the brake pedal when it wanted ..if so another one you can ignore (same as above though, good idea to perform this to ensure that you get a clean self test).

Code 634 (O,M) Park/Neutral Position (PNP) or Clutch Pedal Position (CPP) circuit fault Electronic shift transmission - Manual Lever Position (MLP) sensor out of range in PARK - Transmissions

Also, for engine running tests (and all tests for that matter), make sure the vehicle is warmed to operating temp...

Good idea on the cleaning of the EGR..it may in fact be stuck, as a code 334 indicates EVP issue of some sort..

Keep plugging away and you will prolly find it...

1987 F150 Reg Cab, 302MFI, AOD, 3.55 Rear, K&N Filter
https://www.ford-trucks.com/user_gallery/displaythumbnail.php?&photoid=4972&.jpg