1990 Ford F-150 F-150 that running a muck

DAMARCO6201

MEMBER
1990 FORD F-150
V8
2WD
AUTOMATIC
200,000 MILES

My F150 surges will it runs until it stops. When I remove the vacuum hose from my intake manifold to a connector that operates where heat comes out of the vents( floor, vent, defrost etc.) It idles up stronger and the surge is gone, When I put it in to gear it surges slightly, in stop and go traffic it will hesitate, surge and sometimes cut off. Sometimes when accelerating it will start real slow and then it will jump forward in speed and force as if I slammed my foot on the gas
please help me, my family and I need the truck to run our home based business

7 Replies

JACOBANDNICKOLAS

MECHANIC
109,747 POSTS

WHen you disconnect the hose to the HVAC do you plug the hose? Has the check engine light come on?

Was this

answer

helpful?

Yes

Monday, December 28th, 2009 AT 11:54 PM

DAMARCO6201

MEMBER
4 POSTS

No I haven't plugged it. It seems like the hose on the line is too small because as soon as I plug it to the hose (intake manifold side ) it starts to surge but it's the same hose thats been on it(its a hard vacc line it hasn't collasped). No check engine comming on either. It started it out of no where, I drove home no problem came out the next morning for work the truck would not start, nothing at all like something drained the batt. Got a new batt. And now all the problems I said plus the backfiring when I let off the gas.

SPONSORED LINKS

Was this

answer

helpful?

Yes

Tuesday, December 29th, 2009 AT 6:25 PM

JACOBANDNICKOLAS

MECHANIC
109,747 POSTS

I need you to disconnect the hose and plug the vacuum supply to the engine. I need to see if the engine begins to surge again. When you remove the vac line, you are allowing extra fresh air to the engine which leans the air fuel mixture. The fact that the vacuum hose goes to the HVAC makes no sense to me. But the fresh air changing it tells me that it could be getting too much fuel to the engine and not enough air when it is plugged in.

Let me know.

Joe

Was this

answer

helpful?

Yes

Wednesday, December 30th, 2009 AT 12:16 AM

DAMARCO6201

MEMBER
4 POSTS

I've plugged the port and it surges and then it cuts off

Was this

answer

helpful?

Yes

Wednesday, December 30th, 2009 AT 10:34 AM

JACOBANDNICKOLAS

MECHANIC
109,747 POSTS

That is what I thought would happen. Now comes the hard part. Without the check engine light, it could be many things. I would recommend having the throttle position sensor (TPS) checked first.

Let me know what you find with that.

SPONSORED LINKS

Was this

answer

helpful?

Yes

Wednesday, December 30th, 2009 AT 9:58 PM

DAMARCO6201

MEMBER
4 POSTS

I JUST CHECKED THE TPS ON THE TRUCK. I UNPLUGGED IT AND MEASURED VOLTAGE GOING TO THE TPS AND IT WAS ABOUT 4.78V - 4.83V WITH THE KEY IN THE ON POSITION. ( THE TPS PIN AND THE SIG RTN PIN )I MEASURED OHMS ON THE TPS SENOR WITHOUT OPENING THE THROTTLE IT WAS.78 OHM'S WITH THE THROTTLE WIDE OPEN IT WAS 3.24 OHM'S I WENT AND PURCHASED ANOTHER TPS AND DID THE SAME MEASUREMENTS BUT NOT ON THE CAR I MEASURED THE NEW TPS OUT OF THE BOX.61 OHM'S AND THE I TURNED THE CENTER PIECE TO SIMULATE THE THROTTLE OPENING UP AND IT MEASURED 4.33 OHM'S (ALL MEASUREMENTS WERE MADE ON THE 20K OHM SETTING) WHAT DO I DO NEXT THANKS

Was this

answer

helpful?

Yes

Monday, January 4th, 2010 AT 12:52 PM

JACOBANDNICKOLAS

MECHANIC
109,747 POSTS

If everything falls within spec, I need you to remove the EGR and check it for carbon build up and to make sure that the valve is working properly.

I realize this is a pain, but without the light, this is what happens.

Let me know what you find.
Joe

Was this

answer

helpful?

Yes

Monday, January 4th, 2010 AT 1:44 PM