Your truck has a vacuum leak that I would fix before proceeding with anything else (which can be affected by vacuum leaks).

 

Have you changed the gasket behind the throttle plate? The factory ones will come apart and suck air.

It is normal for the engine to rev way too high at start up, but 2200 is too far up there, suggesting a vacuum leak somewhere. 1500-1600 is more normal. People have been chasing the surging issue for years on these trucks. The best you can do is get it to where is is not as annoying, as I have never seen it completely cured on one of these engines with any miles at all on it.

What I have done is blocked off the egr with a plate, plugged the vacuum lines going to the egr controller. The controller on the side of the block is something that will leak vacuum, but you won't be able to hear it.

I tried using restrictors between my iac and the throttle body, which helped the high start, but would cause problems in cold weather with not fast enough response. What I finally did was splice into the iac wire and run a flip switch into the cab. When I start the truck I turn it off, and the truck will only idle up to around 1100 or less, then after a few seconds I will tap the throttle and turn the switch back on, which will let the truck idle up some as it should.

To help control the surge I keep the base idle when warm around 1000 by adjusting the throttle plate screw. When doing this you need to adjust your tps to keep the voltage just under 1 volt. I also move my timing up a few degrees, with along with the advanced tps voltage, gives me more power. My surging is managable now, but only if I keep the idle up around 1000. Any less and the dreaded surge appears after about two minutes of cold idle, but not at temp.

The ECM is just too slow to react on these early MAP engines. I have not changed my MAP sensor, and that could help. If anyone has, post back and let me know if it does.

This is kind of rigged up, but my truck is finally back to where I can enjoy driving it. I have had the truck since '91 or '92, and I have fought the surge since day one.

 

Thanks guys, I will look into all this!

Hunt, good luck on your truck too bud...maybe we'll get it figured out...

 

Had the same problem. Replaced Vac lines, tested sensors, wires from/to the computer, eventually replaced the MAP on a whim, and Boom done. Had an intermittent bad connection inside.
-Mike

 

Thanks MPC. Anything like that is highly posssible, every sensor but the TPS/IAC is original.

 

The only vacuum leak I could find was where the egr and intake come together. When I sprayed carb cleaner on that spot it would jump up a few hundred rpms. I cleaned the connecting points on the MAP, tps and iac and it did not do anything. I will clean the other connections soon.
I think my MAP might not be reading right. Before I replaced that seal underneath the hood I was going through window motors like crazy (My dad was to before I got the truck). So I am thinking that since the MAP is underneath that seal then it has taken a little to much water than it needs.

EDIT: I got the truck in 2007 and they have had it since it was new.

 

Cool bud...I haven't made any progress with mine yet, got busy...

 

And mine's back (as of yesterday). However it only does this when warmed up, and drops out of the high idle routine. I'm not sure if its just operating at higher RPM's that's stopping it or if there is a sensor that in ignored by the ECU durring that routine. ECT is good and new. Not sure if it's the same with your trucks.

My tach is out of whack at low RPM's. Check yours against a handheld dwell/tach.
The computer should baseline the TPS input at startup (according to ford fuel injection, an older article not in the main section), so adjusting the tps base rotation should not increase idle. Only changing the stop screw should. ( by moving the plates)
-Mike

 

I ran across the thread the other day. https://www.ford-trucks.com/forums/1...cyl-laggy.html

I opened up my ecm and discovered that my ecm is pretty bad inside so ordered one and it will be in tomorrow and will let you know how it goes.

Also after unplugging and plugging the ecm my extream high idle on start up has gone away???

 

Yeah, and we still haven't heard back from the OP as of yet.
What a soap opera that turned out to be.

Good for you for taking the initiative to follow the direction I've been trying to point everyone towards.

Please do let us know how it went.

Bob

 

sorry i went AWOL. so far, i've came to no conclusion on my truck. no soap opera, just trying to track down an idle issue. i need to open up my ECM, as it probably is the culprit, just been busy and my truck has just sat for the last few months since it's not my daily driver anymore. the idle issue still comes and goes...i'll update this when i finally get around to working on it again.

 

I dont know if any one else mentioned this but it might also be the throtle positioning sensor. Theyre known to go bad.

 

thanks but that's already been replaced...

 

Well, going back to last Janurary, you said:

"So far, to combat the problem, it's had 6 new injectors (not my doing), a new high pressure fuel pump (on the rail, again, not my doing), and the rear in-tank pump (you guessed it, not my doing...), new IAC (my doing...), new TPS (me again) and I've checked for vacuum leaks."

To me, it sounds like something other than the stock injectors were installed along with an adjustable fuel pressure regulator..... i.e." a new high pressure fuel pump (on the rail, again, not my doing).
I think that "high pressure fuel pump on the rail" is actually an adjustable fuel pressure regulator commonly used to reduce the fuel flow to higher rated (non-stock) injectors.

If that's the case then you're messing with the "computer" pre-programming big time.

Please do read page 4 of this thread:https://www.ford-trucks.com/forums/1...l-laggy-4.html and see what happens when you mess with fueling and what it does to the computer.

The OP in that thread has spent hundreds of dollars and huge amounts of time and effort because he was running "non-stock" 15lb. injectors.

Something for you to check out.

Bob

 

ya know, you could be right on the injectors and possibly the high pressure pump. they SHOULD have been stock, but who knows? how could i go about checking to see if they're stock injectors? i've seen no evidence of an adjustable fuel pressure regulator...the regulator is still the original, stock piece...the pump on the rail might not be an OE-style though...i'll look into all this...thanks a lot bud!