87 Ranger 2.9 IAC working too hard.

[wingzam]

I have another thread going on a running problem but hadn't mentioned a symptom because I had been told by a mechanic that it was a normal condition so I wanted to post a new thread for this.
Starting the vehicle cold the IAC does alot of correcting.The idle goes from low to high a number of times before it settles at an even 800rpm.A friend said this wasn't normal and suggested this might be a vac leak.
I've been thru the vac system and can find no leaks.Has anyone had any experience with such a problem?Any suggestions?
The running problem is rough idle and hesitation throughout the rpm range especially noticeable from 1500-3000rpm.at rpm's lower and higher than this it is not nearly as much but is still perceptible.At higher speeds it's hard to tell.
Thanks

 

[HndMeDnBroncoII]

sounds like a vaccuum leak to me put a gauge on it see how it reacts

 

[wingzam]

Cold Start the idle goes up and down trying to stablize - vac reads 21Hg and wavers eradically but not quickly between 3-5Hg.
Warm at 800 rpm vac is 18.5 and slow wavers between 18 and 19.

Operating temp vac is 19Hg with slow wavering to 19.5 and 20Hg.
Part to half throttle produces steady 23Hg
Stab the throttle - reading drops to zero and jumps to 25.

 

[IMenriched]

see if this helps. http://www.therangerstation.com/Magazine/Summer2003/VacuumLeaks.htm

 

[wingzam]

Well,as best as I can figure,the intake manifold gasket should be changed before I go any further.Its already leaking so that will take care of that.Afterward i'll have to take it to a shop that has a good OBDI diagnostic set up and see if they can find anything.

 

[wingzam]

No luck at the mechanics,although he's leaning toward a misfire - distrubutor pick up or ignition module.Last night I took an inductive timing light and put it on each cylinder wire to see if I could find any evidence of misfiring.Got consistent even pulses,but only did this for idle..if i'd been thinking just a little bit more I would have run the rpms up just a bit,but i'll do that tonight....seems like a legitimate test...

 

[Cyberbeer]

Would a leaky injector cause this? Extra full dripping out after shut off?

 

[wingzam]

Would a leaky injector cause this? Extra full dripping out after shut off?

The injectors are new.Replacing them solved a rough starting problem,but did nothing for the hesitations.

 

[wingzam]

An update for anyone that may view this thread:First of all,for anyone who is changing out their computer - a new unit must be "Flashed" by the dealership so the computer will interface with the vehicle properly.
Did a compression check,all good.Spark plugs (3 months old) all looked like new.Replaced intake manifold gasket which began leaking coolant,combustion chambers were clean as a whistle.When I removed upper plenum found a threaded plug on the underside which accessed the EGR ports-cleared this.Replaced Coolant Temperature Sensor - mainly because it was suggested by a mechanic,was cheap,and is buried to the point of being a bit of a bitch to get to.
All this only made the slightest difference.
Am going to change out the Air Charge Temperature Sensor.This too was suggested as a possible cause - and is cheap.
Prologue:Wether or not this fixes the problem i'll be buying another vehicle from a friend and getting rid of this one.This Ranger ran decent when I bought it.After doing a tune-up and changing out some basic parts it ran rough.Chasing the problem ate up money that would have gone into other maintnance and a paint job,making it a keeper.
I'm not going to add up the money I pissed away on this thing (other fixes I made were ultimately pointless).The time and effort wasted,and the frustration created - these were friggin priceless!!
I've owned a 2.0 and 2.3 liter version of this vehicle which I did real well with,but this particular version - 1987 2.9ltr - is just a monster.The complex wiring,the slow computer,the OBDI system,the architecture of the engine,and other things particular to the 87 - made it a complete mess.
If you're trying to troubleshoot one of these I wish you luck.My advice is either "Abandon all hope yee who enter here",or dump it now while you still have money in your pocket and hair on your head.Run and don't walk away from this version of Ranger.RUN!!!

 

[Cyberbeer]

Check the fuel filter canister and see if somebody put a filter in it. If they did and you have an inline filter rip the canister style out and reseal it. If it wont reseal properly get a new canister from Ford. I had similiar problems, now with a new canister and now filter in it, the truck runs a ton better.

 

[wingzam]

Check the fuel filter canister and see if somebody put a filter in it. If they did and you have an inline filter rip the canister style out and reseal it. If it wont reseal properly get a new canister from Ford. I had similiar problems, now with a new canister and now filter in it, the truck runs a ton better.

OK just for sh*ts and grins,and that I love bathing in gasoline,i'll give this a try...if it doesn't work i'll just go ahead and have my last cigarette!

 

[Cyberbeer]

There was also a service bulleten on the 89 and later IAC's, something about needing to reverse the polarity of the wires.

 

[wingzam]

There was also a service bulleten on the 89 and later IAC's, something about needing to reverse the polarity of the wires.

Oh great!After I have my last cigarette i'll get in the bathtub and reverse the polarities!.....But something else is going on - this thing is sucking a dollar bill to the exhaust pipe.It was doing this a little before but now its more frequent.
Had run a vacuum check that didn't show any indication of bad valves etc..Have adjusted the valves to Haynes recommendation of 1.5 turns down (this yielded 2 clicking lifters when previously I only had one).A mechanic told me its a quarter turn down.
Ya know,I had bought factory repair manuals for this thing and many test/check procedures had been superceded.Tried to find these supercedings and got nowhere.Talked to Ford and they couldn't help me..
...Wait a minute,Just checked the (nearly worthless) factory manual for valve adjustment - it says 4.5 turns down!!Geeze!!!...I'm going to have to run another thread and see what I can find on this - that seems like a helluva lot considering how hard they were to turn to 1.5...and the threads that were left at that point...

 

[wingzam]

There was also a service bulleten on the 89 and later IAC's, something about needing to reverse the polarity of the wires.

I'll call Ford and see if they have any bulletins I can look at.They're always so helpfull !!