Engine Hesitates and surges

had you said something earlier about eh abs you might get a better response. the abs has the cruise control connected directly to it. as you apply the brakes it kills the cruise. so it's eiteh rgot a short in it or one of the wires are touching where they aren't supposed to an dkilling the cruise. it also connects to the trailerbrake if you have one as well as the speed sensor to the rear. if any of htosea re screwing up or the abs unit itself then your cruise isn't going to work right. nexttiem give ALL the information you can, engine/trans 4wd or not as well as a complete detail of what is going on.

This makes so much sense, I'll check this wiring. I do have trailerbrakes also. Truck is a 93 f150 with a 351w which has the upgrade to the lighting mass air flow kit from ford. Thanks for so much

He is correct. Check the wiring (especially the trailer wiring) for damage. There also is a plug at the rear of the vehicle for the wiring to the trailer. Check it for damage.

Thanks

Going for test drive Sunday.

Engine Mechanical problem
1993 Ford F150 V8 Four Wheel Drive Automatic 185,00 miles

When trying to maintain a steady speed the engine speed drops and picks up again over and over. If I accelerate the miss is not noticable. I have also noticed that sometimes the oil pressure gage will drop to zero while idleing in gear after the engine is warm. If I slightly speed up the engine or take the load off by placing the trans iout of gear the pressure gage returns to normal. Thanks

Ok first with the oil pressure we need to know what the actual oil pressure it. So it needs to be tested with an actual guage if possible. Otherwise you need to replace the sending unit and see if the pressure comes back to norm. Most fuel injected vehiles have a fuel pump shut off and if the oil pressure is low it may trigger this. So lets get a pressure reading first to see if the engine is just tired and needs some repair.

Let us know what you find.

I sure will. I have completely unhooked all the trailer brake wiring. Thanks

Thanks

Well it looks like the trailer brake controller is causing the up & down when on cruise. The wiring harness checks out fine also. Thanks for all the help.

Disconnect the controler and see if that helps.

That's what I did & it stopped the surging. Guess it's in the trailer brake controller.

Surges bucks at idle. Under load falls on its face I've changed map sincer cleaned throttle body new throttle bottle control module and sincer changed distributor and the ignition control module coil test good on the ohms please help lost all hope

That makes sense. Time for a new controller.

scan for codes and check fuel pressure with a gauge first auto parts rent gauge

I guess so, didn't think it could cause a surge problem. I could see it kicking it off totatly but didn't think it would cause a surge. Guess it did, thanks guys.

Thanks for the reply there's no codes after replacing what I did fuel checks out good also

Glad to help.

check for a vacuum leak and check vacuum from intake if 15" or below suspect a clogged exhaust. also check voltage at tps should be0.34 at idle and 4.84 wide open throttle. fuel pressure should be 30-45 psi key on only and 30-40 at idle. Using your finger is not a test to many people do that and figure it's ok

Thank you for your help. Never had it back on the computer after I put the new parts on ended up buying 3 new BAD! Parts from orileys. Once again thanks for your help

my truck surges when at idle and has very poor fuel mileage. what can help

Truck cranks and runs, When Idling, engine surges. Gets worse when you drive it down the road. Will surge & buck after 40mph. Replaced throttle position switch, coolant sensor, distributor, cap, rotor, plugs & wires. Removed upper intake, cleaned it out. new gaskets, cleaned throttle body including EGR ports, replaced MAP sensor, and replaced fuel filter. Seemed to help for about 15 minutes, then began surging & bucking again. Any suggestions as what to try next?

Have you checked for codes? fuel pressure correct? Same colde as warmed?

Fuel pressure was 49 psi. Only code that shows is MAP sensor, which I replaced, but code still comes up. & yes, runs same cold or warm

See diagram Dist look like it? if yes remove TFI have tested VERY prone to cause problems.

What diagram? & What is a TFI?

that fuel pressure is whyll the problem is happening?

at normal idle the engine surges sometimes it stalls when in drive and foot on the brake other times it will rev way up and can barely hold it with the brakes replaced map sensor throttle positioning sensor and egr any other ideas?

Check the IAC and check for vacuum leaks.

fuel pressure good 45 psi

forgot to tell you have taken care of any vaccum leaks so I will check the IAC

As far as I can tell, fuel pressure to engine is ok, it seems to get plenty of fuel. Shows 39 PSI at the post on the fuel rail. (miss typed the last one, not 49) As long as you give it gas, it runs great. has a little miss, but once you let it idle or hold at a steady speed, it surges, & bucks like a mule.

Let me know what you find.

no TFI Module on this distributor

is the IAC cleanable or repairable?

Truck is late 94 so Dist has shutter vane and ICM see diagrams locate and have ICM tested

I have seen them get carbon on the pintil which causes a leak. In that case, they are cleanable. However, if they are non functional, they are non repairable.

Had Ignition module tested, passed ( cycled 25 times )
Would the IAC cause this problem? I know it might at idle, but would it cause the problem while driving as well?

just tested IAC, it's fine. went and had codes scanned, here is what it showed:
DTC172 ( o2 sensor fault, lean)
DTC 213 (SPOUT circuit open)
DTC 332 Insufficient EGR flow (had hose off to test EGR vacuum)
DTC 538 Insufficient RPM change during KOER
DTC 632 Overdrive trans cancel switch

we pulled the short bar out of the SPOUT wire harness, checked timing. 10BTC. put short bar back in & checked timing again, still 10BTC.
Seriously stumped as what to check next...

While the engine is idling, it will surge or increase is rpm for approx 5 seconds, then stop for 10 seconds, then surge again. The surging stops when the heater control switch is turned off, just like an engine acts when it is low of freon in the AC. Turn the heater on, and the surging starts again.