I had posted this as a reply to another thread, but would appreciate any assistance.....
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I have 87 Ranger 4x4 w/2.9 that has recently been rebuilt. After replacing the MAP, EGR, IAC, EGR p/s, and the EGR vacuum switch, I have an idle that surges from 600 rpm to 1300 rpm. At the initial start up, cold, it will run well for about 10 sec at which point this surging idle starts. It tends to go away when the engine is to temp, except for when I am stopped. Here's the odd part, if I am depressing the brake pedal, it will surge up and down, even when warm. Lift my foot off the pedal and the idle smooths out. Soooo, figuring the brake booster my have a vacuum leak, I disconnected the vacuum line, plugged it up, started the engine, depressed the brake, and, this is the odd part, the idle still surges as before. Lift my foot and it smooths back out. So what would cause the idle to surge when the only connection left is the brake light switch?
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Well after checking this out in more detail, it appears to be more of a voltage issue. In fact, the idle will begin to surge even when it is put into reverse and the backup light come on. Typically, I will have the headlights on as well, but this doesn't seem to effect the idle at all. But as more lights are illuminated then the idle starts to slowly fall off, down to around 600 rpm and then it will suddenly jump up to around 1300. After that, the cycle begins again until the brake pedal is release and/or the trans is taken out of reverse.

I did pull codes and I got 63 & 32 with the KOEO, and no codes with the KOER. The only thing I can think of is that the voltage is droping enough as the different lights come on and it is enough to effect the idle.

Any all suggestion are greatly appreciated.

Bill

 

It would appear that you have a wiring problem associated with the rear lights, brake, turn, tail, backup. Either a short or a ground problem I suspect a ground problem. code 32 is egr not controlling code 63 is tps out of range. all could effect idle. Check your grounds and look for damaged wiring.

 

I have checked all of the grounds and they seemed to be making good contact. The only one I would question, and not even sure if it grounded, was the main neg battery cable that fastens to the engine block had to be replace. I use a typical Pep Boys cable, but the original one had what appeared to be just a clamp which bolted to the frame. Could this be part of the grounding system and a possible cause?

Prior to the engine rebuild, there was an issue with the alt which in turn cause some wiring to overheat and melt the insulation. All the questionalble wiring was replaced and the truck ran great.

I have recheck all of the reworked wiring and all seems to be intacted. I have check all of the other wiring to the various sensors and controls and that all seems good too.

I will check the circuits for shorts tonite, but with so many different circuits making there contribution to the problem, I would suspect a grounding issue too. That being said, what are the possibilities of it being a faulty alt or batt that just can't put out the juice?

I did pull the brake light bulbs out and though that would help determine if there was a short, but when I probed the light switch at the pedal, I got 12v on the input side of the connector and 8v on the output side of the connector. Put the bulbs back in and the output side drops to .2v. I am figuring that has something to do with the emer flasher and turn signals.

One of the things that, for my best of reasoning, that points me to the battery is the two codes that come up on the KOEO test. I thought I read in the code discription that they were caused by low output voltage? When the KOER test is performed, both codes disappear. I have replace all of the EGR and related components and still find it odd that it comes up, unless I somehow didn't clear the codes correctly.

Thanks.

 

Good grief, you've been busy on this one bh91709!!!!

Why not run this puppy by your favorite autoparts store for a "in vehicle", electrical system check up, via their portable electrical system tester.

It can properly "load test" the entire electrical system, with everything in the vehicle & will likely be able to sniff out any faulty components, like a alternator with weak, leaky, or shorted diodes, worn brushes or sliprings, shorted or weak battery cells, high resistance battery cables or connections, excessive parasitic drain, ect, ect!!!!

Let us know what you find.

 

Yup, this has been one extensive project.

Sorry for late reply, been in meetings all day Fri and Sat.

I checked the continuity throughout the truck and all checks well. So the lack of a good ground seems to be ruled out. The battery voltage read around 12.5v when at an idle and just shy of 12v when the truck if off.

That's a great idea pawpaw, I think I will do that, but it will be Fri before I can get to it. I will let you all know what they come up with.

I did confirm that I cleared the codes incorrectly and once I fixed that mix up, everything comes up as "pass".

Bill.

 

Well 12 volts on the battery when the vehicle is off & the battery is unloaded, is low!!!! That shows your battery is only at about 50% charge!!!!

A fully charged battery should read 12.6 vdc or more, with a digitial multimeter. So it sounds like the alternator isn't doing it's thing, if it's only putting out 12.5 volts, thats way low!!!!

The alternator sounds like it has problems, maybe weak, leaky, or shorted diodes, worn slip rings or brushes, or maybe a regulator problem, so that autoparts store electrical system checkup will likely turn something up.

Don't delay fixing this though, as using your battery in this discharged state, will cause unnecessary plate sulfation & shorten it's life & you'll have yet another expence!!!!

One other thing, slowly recharge the battery overnight, at say 4-6 amps with a battery charger, BEFORE you replace the alternator, should it test bad or weak.

Don't try to recharge a run down battery with a alternator, it's not a battery charger & both it & the battery can be damaged by doing so.

Just some more thoughts on the subject.

 

Here's the lastest in this "project".....

Replaced the battery with a new, freshly charge one. Voltage reads 12.62v.

Removed the alternator and had it checked and it indicated failing. Exchanged it out under warranty, installed, and guess what, not a dang thing changed.

So, with a digital meter, I check the voltage drops as each system was turned on.

engine off - 12.60~12.65 v
engine running - 14.40~14.50 v
headlights on - 14.30~14.35 v, engine running fine.
high beams on - 14.25~14.30 v, engine running fine.
fan blower on - 14.25 v, engine running fine.
brake lights on - erratic voltage drop. Starts at 14.25v drops to about 13.5 almost immediately, then fluctuate up and down, gradually losing voltage until it reaches about 12.50 v. All this time the engine idle is surging. Take the brake lights off, engine smooths right back out. Same holds true for the reverse backup lights. As soon as they come on the voltage begins to drop.

Turn off the headlights and fan blower, the brake lights or backup lights come on, the voltage drops, idle surges.

I don't know if the brake and back up light curcuits have anything in common except for the tail light housing. It just seems to me to be somehow related to the tail light area. I haven't found any shorts or chaffed wiring around the tail lights or engine compartment.

Where can I get my hands on a wiring diagram? The ford service manual I have doesn't have that information and the autoparts store don't have the Haynes manual for this year.

I haven't given up on the "in vehicle" electrical test yet. Hopefully that may show something.

 

Well seems to me some things DID change!!!!

With the new battery & alternator, the electrical system voltages came up to normal, loaded & unloaded, thats a GOOD change.

Now, did the engine cold idle change for the better, after the new alternator & battery were installed????

It seems to me you had, maybe three or more problems, a weak battery, a weak alternator with resulting low system electrical voltages, both of which you've fixed & a third problem, which seems to still be with you, the brake/backup light/engine surge problem & maybe the computer codes.

One which was a low TPS signal voltage, maybe due to the battey/alterator problem, or maybe due to excessve electrical load & resulting voltage drop when the brake lights & reverse lights come on line & the electrical system voltage drops as the system loads down.

I'd be plenty careful here, as it seems you have a sizeable electical short, or maybe a ground loop problem somewhere, as it seems to be really loading the alterntor down or maybe a wired ground loop, is messing with the engine control sytstem.

If it's a short & that electrical load remains on for too long a time, it could damage your new alternator & battery.

I'd try to figure a way to isolate things & test the rear wiring harness & wire run, without the battery & alterntor connected & the engine running, maybe like the following!!!!

I'd also pull the fuses for the computer & any other sensitive solidstate devices, while doing the following tests.

Disconnect the battery cables & alternator wire connections.

Then hook up a battery charger equipped with a circut breaker & 12 volt test lamp in series, as a load, to the battery cables & begin a systematic troubleshoot, using the circuit breaker protected battery charger, as a power source & the test light as a indicator & load limiter.

Then step on the brakes, or put it in reverse & see what happens!!!!

You should be able to use this set up, or some variation of it, to safely isolate your problem.

Something you said & questioned, about replacing the battery ground cable, with a generic one from Pep Boys & it not having a chassis or block ground, caught my eye (I'm not clear on just what you were asking), but in general, you bet it could figure in here, as the engine & chassis need all their grounds & good quality ground connections back, to the battery, or you could possibly get into some real wierd "ground loop" problems & no telling what affect it could have on your engine control electronics, with an electrical load trying to find a suitable electrical "return path of least resistance" to the battery.

So be sure the new battery cable has all the connection points the OEM one had, or fashion whats neeed & be sure the gauge of wire matches the OEM one, or heck just go get a OEM one, with all the pigtails!!!!

To see if this may be part of your problem with the brake/reverse light engine surge thing, you could run a quick test try, using a good quality jumper cable, at the in question ground point, back to the battery B- cable & see if things improve. If so, you know one more thing you have to do.

 

Good point, I did overlook the fact that the voltages came up to normal.

The cold idle still starts of at a high rpm, 1500-1600, and then drops down to 1100 rpm with only one small hiccup in the transition. There is a momentary stumble but it catches itself right away.

The computer codes cleaned right up. I was reading codes from the CM which I had not cleared correctly. Once that was done right, they were gone and no other came up except for the pass code of 11.

Let's go to the test. As I am understanding it, using a curcuit protected battery charger for a power source, connect the ground clamp the the ground cable and the positive clamp to a 12v test lamp and the 12v test lamp the the positive battery cable, correct? So, for example, as I were to step on the brakes, the test light should come on. If this is correct, I am not sure just what that means other than there is connectivity through the brake light wiring.

One thought I had was to isolate the wiring harnesses and feed voltage to the brake and back up light from an independent source. Not even sure what that would do for me other than to see if there was a short that was causing problem. In either case, I would of thought that the fuse would give way if a short was there.

Alright, the battery cable. I recall there being, what appeared to be a clamp that was midway down the grounding cable that attached to the frame before it continued down to the engine. Thinking back, it seemed that this clamp was making full contact with the copper wire. If that be the case, then it could be that I do not have a sufficient ground to the frame. I have a good set of jumpers, I will try that too.

Thanks....

 

I too, am concerned that you might not have a needed frame ground, or a good enough frame ground & it's causing some kind of crazy ground loop problem.

I've seen some nutty things happen with ground loops over the years.

Using a good quality jumper cable, as a test ground, should answer that question though.
As it's easy to set up & do, you might try it first.
If your probems clear up, you know what the root cause is & what to do to remedy it.

If a faulty or missing ground isn't the problem, then you might try the battery charger test rig.

On the battery charger I'd use one that has a built in circuit breaker, just in case you short it's leads, it'll shut itself down, so it won't get damaged.

On the battery charger powered test rig, thats how I envision the hook up, so if you have a short circuit in your rear wiring harness/bundle, the test light should be lit brightly, as the short circuit would essentially connect the lamp accross the charger.

If things are ok & you still have the tail lamps in, it should glow dimmer, as the lamp would be grounded through the resistance of the tail light lamps, if they're still in place.

You said you'd removed the lamps to check the sockets, & for other problems, so just leave them out for this test. If the test light doesn't light up when you step on the brakes, or shift into reverse, you don't likely have a short cicuit in that particular wire bundle.

If it does light up, with all the lamps removed, then you likely have a short somewhere in that circuit & will have to try & run it down.

You could begin at the nearest electrical connector for that particular wire bundle, disconnect it, then rerun your test light set up & see where the light remains off, then the problem will be between those last two points.

I had to do this on the Daughters 77 Celica once, to find a open fuel pump circuit. what a PIA that was, but I found & fixed that puppy!!!! Just hang in there, go slow, be careful & through in your testing, take it one step at a time & you'll likely solve it.

There is a piece of electrical equiptment, called a fault finder, or short finder, or short tester, that might help, if you think you need one.

Most autoparts stores carry them, some offer them on their "Loan-a-tool" program, so ask before you buy.

Keep us posted, will be interesting to hear what you find.

 

It never ceases to amaze me as to just how something as simple as a ground can cause so much trouble.

Remember that clamp on the ground cable from the battery to the motor? Well, I simply attached a grounding cable from the motor to the frame and the problem seems to be cured. If fact, even the small hiccup just after start up went away too.

Pawpaw, if you ever come out here to the left coast, send me an email, I owe you a drink of your choice. Thanks for your help, I really appreciate it.

Bill

 

Hey it's great to hear your "on the road again" Bill, good find fix & feedback.

Those simple low cost fixes are the sweetest ones aren't they, makes ya feel good to win one now & then doesn't it!!!

Allright I'll keep that offer in mind!!!! Good Truckin!!!!

 

Glad to hear it is fixed. Over the years I have seen far more ground issues with vehicles than any other wiring issues. And it still amazes me how DC voltage will find its way to ground through other components. I have had fuel pumps run when a door was opened turning on the dome light.

 

I am both amazed and humbled at this.

Drove it into the office today and she ran like a champ. But I guess that should be expected since I had replaced just about every component there was, plus one ground cable