Attempts stall, Idle Pulses 600-800 rpms, horrible MPG

[Selectron]

If that shows that the short is on the PCM side of that connector, then I don't know if it's even worth gaining access to the PCM just to unplug it, because what are the chances of six separate wires all being shorted to ground? Pretty slim, so I think it would probably be safe to assume at that point that the PCM is responsible for the short. I don't know how much effort is involved though so if it isn't too big a job then you might want to continue, just to confirm it for sure.

[searcherrr]

Yeah, I think its worth trying and I thank you highly for giving me this idea.... because I was really worried earlier today that the new injectors may have ruined from when I did the tests. Could they really melt from constant 12v? I wonder how long it would take for them to melt.

Even with the PCM disconnected from the injectors the fuel pressure still went down at a rate I thought faster than it should (see "drop rates" in a few posts above). So, I will do your idea tomorrow before I have it sent to the shop.

All this discussion really makes me want to tear it apart at the cowl before I send it to the shop too, but every time I decide to veer from the shop I end up on a week or 2 long testing spree. If the PCM is bad, the shop owes me one anyway. If I could get it tested and back together in the morning early enough before towing it, maybe I'll get to the tests that require removing the cowl.

EDIT: I posted this post when I'd seen post 270. Hadn't seen post 271 yet. Glad that would eliminate having to remove the cowl, though I'll decide if I want to do that or not after I try your post 270 suggestion. - Removing the cowl requires remove the windshield wiper arms from their motors and various layers of cowl stuff.

[Selectron]

If it's going in to the shop anyway then I wouldn't bother removing the cowl. I would do that quick C128 test though, just to see if the short is in the injectors, or in the PCM.

[wiswind]

Just off the top of my head......the injector internal circuit is a coil.....which pulls a "plunger".....the internal "valve" when energized....
A coil would have a low resistance value.....don't know if there is any resistor to limit current or not......don't know if there is a specification on resistance value....but don't be surprised by a low value......
However.....you should read a super high resistance between the injector teminals and chasis ground......as the only path to ground should be through the PCM.......momentary when the PCM calls for it.

[searcherrr]

Resistance Tests to known good Chassis Ground C128 Female & Male ends:

NEGATIVE BATTERY CABLE REMOVED.

Injector's harness (female end of C128) to ground:
Result: Zilch. No meter reaction. 0.0L

PCM Side (male end of C128) to Ground:
Results:
VPWR: 0.055 ohm (Confirmed link from VPWR to Ground with no Power on)
Inj 6: 0.9 to 1.5 ohm
Inj 5: 0.0L
Inj 4: 0.0L
Inj 3: 0.0L
Inj 2: 0.0L
Inj 1: 0.0L

New Test using PCM side male end of C128 only (no chassis ground): C128 Inj 6 lead pin to C128 VPWR pin
Result: 0.055 ohm

I'm still at a loss here as to whether this is the PCM itself (now since I've confirmed it to just 1 injector #6 crossing the VPWR lead) or just the wiring. It is a light green/orange striped wire. I'd really be surprised if it was grounded together where the harness melted, because that day the shop owner came over and repaired things I sat and picked through every single wire that was stuck to anything and we focused on repairing all those. He inspected it and so did I afterwards and we were satisfied.

I've only had 4 hours sleep so forgive this question for my clarity:
VPWR wire should always be grounded right? Even when there is no power via battery? Always hot when battery is connected right? - If so, then I am correct to observe an Ohm value from VPWR to Ground or not?

Helping me lean towards the PCM I have the OBD scan software not able to show me the OBD compliance information on the computer (which is available on all other car's I tested), and a fault was said to be present when I looked at fuel trims, and the TPS is not showing up in any % at all and does on other vehicles using the same software.

What ya'll think? I'm about to call the tow truck and I don't know whether I should tell my shop this stuff or not. I am tired of doing their work for them and my findings and thoughts affecting what they decide to do, but if I don't tell them at the same time and they miss this then they might replace the PCM without knowing about the VPWR to #6 grounding.

[Selectron]

That eliminates the injectors then - they're certainly not shorted.

The PCM circuits responsible for grounding injectors 1 to 5 are all healthy too, or at least we can say they're not shorted.

So that leaves the PCM circuit for injector 6, which should not be showing that low resistance to ground, and which is of course indicating a fault condition.

The VPWR wire should not be grounded, because that's the 12V supply, and if it really was grounded then it would be blowing fuses. That wire feeds 12V to various engine controls and components (including the PCM and injectors) via the switched contacts of the PCM Power Relay, but only when the ignition switch is at Start or Run. I shouldn't pay too much attention to the reading of 0.055 ohms from VPWR to ground - it isn't blowing fuses, so it clearly isn't shorted. You might have a charged capacitor across that supply rail, which might be skewing the resistance reading.

I recall tripletdaddy recently had a short-circuit in the PCM which was causing injector #6 to be held open when the ignition was switched on - and that's also a '95 3.8L. I think there's a thread in here but I seem to recall that the thread in Engineering and Technical drew more responses. That's here - I don't think it will tell you anything you don't already know, but it's interesting that he had the same fault on the same year and model.

Since you're aware that injector #6 is being held open, apparently by the PCM, I think that would be worth mentioning to the shop.

[searcherrr]

Fuse "S" blew when I was doing injector testing.... prior to the wiring repairs though. I would venture to say it'd blow again if Inj.6 and VPWR are left the way the are.

I told the shop explicitly what as going on. Towed earlier today. I disconnected the battery & C128 before I gave it to them. They are gonna get me new plugs to replace the ones I lost, so I'll have a backup set. The rest well.... should be their fault and on their bill.

About that 0.055 reading... prior to testing I measured my test leads cause I was using the alligator clamps and it came up 0.5 - 0.6. So the test result was really 0.555 - 0.0556 ohms when I tested VPWR and 1.4 to 2.0 ohm when I did Injector 6 color wire. I simply subtracted the difference of resistance observed in the test leads cause i thought I was supposed to. Correct?

In any case when I measured VPWR to chassis ground the meter did react that a path existed and this is with the battery unplugged for a duration of overnight. Could a capacitor still be charged overnight?

Shop says they won't get to it till tomorrow. Here we go again with the waiting of a week... 2 weeks... yada yada... we've been backed up. etc... The Owner is doing it and he'll be the only one touching it too. I will work their nerves to get it out faster.

That is interesting what happened with trippletdaddy. I wonder if we've uncovered a possible manufacturer wiring defect????? or just sketchy 95 PCM's. Oddly though, this PCM is a 3rd party bought one.

[drzoidberg]

I didn't read all 19 pages of this thread (just first and last), but just my two cents...sorry if it's redundant at this point.

Have you considered the crankshaft position sensor? If you have a new engine, perhaps it was installed incorrectly and the engine is therefore not able to control its timing? I think I remember that being the cause of others' similar symptoms occasionally.

Have you tested the rectifier/voltage regulator on the alternator?

Vacuum leak? Air filter clogged? Stuck EGR? Bank ST & LT fuel trim values might help diagnose.

Those are all completely uninformed, uneducated wild guesses, but I guess if you haven't found the problem yet, it won't hurt to mention. Also, I assume you've tried starting the car at part throttle to see if that clears up the idle?

[searcherrr]

Thanks for chiming in DrZoid.

All things you suggested are good suggestions, though I have ruled them all out except the CranKshaft Position Sensor and a clogged EGR pipe.

I do not think the EGR is clogged though as i'd expect the clog to be at the top by the DPFE sensor and recently I saw the opening there and it was clear. I don't think the little tubes that spawn off the EGR pipe were clogged either as I saw no debris in them when the vac hoses were removed.

I have considered the CKS for a long time now since its the original. Its one of few remaining items that is still original. I would think a fault would be generated if it was bad, but if its OFF that is something I wouldn't know.

Currently though we're on to something for sure with Injector #6 being grounded with the VPWR lead full time. I think its a bad PCM as I have observed this same grounding on injector's 2, 3 and 5 at one point in time before the PCM wiring harness was repaired.

I will look into how to set the CKS though, just in case my MPG issues are not fully resolved when I get the van out of the shop AGAIN.

[Selectron]

Fuse "S" blew when I was doing injector testing.... prior to the wiring repairs though. I would venture to say it'd blow again if Inj.6 and VPWR are left the way the are.

Considering that you've had power applied to the circuit plenty of times in the last few days, and the fuse didn't blow, yet upon disconnecting connector C128 you then measure a dead short between VPWR and ground, then it's very likely that you still have an intermittent short-circuit somewhere in the harness. If you were to apply battery voltage under that short-circuit condition then the current flow would be 12V divided by 0.055 ohms, which is 218 amps - a truly massive current, which your battery is capable of supplying, but which would of course blow a fuse almost instantly. So that would seem to be the first issue.

Looking more closely at the resistance between injector 6 low end and ground - 0.9 to 1.5 ohms, and so not a dead short - the significance of that would depend on whether it's located in the harness or within the PCM, which you won't know until the PCM has been unplugged and the resistance re-tested. If it's within the harness then it would cause the injector to remain constantly open but wouldn't cause a fuse to blow, since it only adds slightly to the injector's normal resistance of 14.5 ohms, so the injector would function normally, with the exception that of course it wouldn't respond to switching commands via the PCM since it already has its own continual low resistance path to ground and so would be held continuously open. Or of course it might be the resistance of the now-damaged PCM's injector switching stage for injector 6, if it is indeed damaged, which you won't know until the connector is unplugged.

The final anomaly is that you've measured 0.055 ohms from the 12V supply rail (VPWR) to the low end of injector 6, and then a further 0.055 ohms from the injector low end to ground. So if we look at the total resistance between VPWR and ground via that path, it would be 0.055 ohms plus 0.055 ohms, which is 0.11 ohms, and that would give a current flow of 12V divided by 0.11 ohms, which is a huge 109 amps, and would of course blow a fuse in no time at all. Although of course the fuse would blow anyway in response to the 0.055 ohms between VPWR and ground, causing the 218 amp current flow which was mentioned earlier.

So based on those resistance readings, it looks like you still have a faulty harness, with the possibility of a faulty PCM switching stage for injector 6, with the latter being not yet confirmed.

Finally, consider this: The 0.055 ohms from VPWR to the low end of injector 6 might have a special significance, because the current flow under those conditions massively exceeds anything which the PCM is capable of carrying. Consider the operation of the PCM injector switching stages when the vehicle is functioning normally - with a running engine, voltage will be around 14.5V, which is applied to the 14.5 ohms of the injector coil, causing one amp of current flow. The switching transistors within the PCM will be rated such that they can carry that one amp with some margin of headroom - they might be rated for two or three or more amps and so will be operating comfortably within their limits. Then suppose the wiring harness gets disturbed, and that 0.055 ohm path from VPWR to the low end of injector 6 coil suddenly appears - current will take the path of least resistance, effectively bypassing the injector coil, and so a massive 218 amps would attempt to flow to ground via the PCM's switching stage, inevitably destroying the switching semiconductor (rated at just a few amps) long before the fuse can respond, and blow, since fuses are relatively slow-responding devices. It's possible that that is how the PCM's switching stage for injector 6 came to be fried, if indeed fried it is, which you won't know until the PCM connector is unplugged and fresh resistance readings taken.

[wiswind]

PROGRESS!!!!!
If the short to ground from #6 injector.....unplug the fuel injector wire harness.......if short is still there....then it is in the injector wire harness.
If it is gone....it is from the fuel injector wire harness plug....through the PCM.
You could unplug the PCM to see if it is the PCM or inside the wire harness from the fuel injector harness plug up to the PCM plug.

You could unplug the electrical connection from fuel injector #6 and see if you hold fuel pressure with everything else connected.........

[searcherrr]

Just read the last 2 posts. Thanks guys.

Very fine analysis Selectron. I have always thought about going to school for electrical engineering to become familiar with the limits of certain electrical devices and circuitry. While my knowledge is greater than most in this area, I still don't know things like "what amperage can this or that run" and what amperage or volts would be produced by certain situations (shorts, regular setup, etc..) so its very helpful having this technical information.

Wiswind - I cannot describe how invaluable you and this forum is. In several occasions and perhaps even more than 90% of the time the responses and persistence in this forum represent humanity at its best..... caring, giving & helping with only the reward of feeling good about it. While we know an alternate purpose of this site is to run ads and make money, at the same time it does function as a place people can go to network using the best qualities of humanity. I know its all sappy n all that, but I feel this thing finally drawing to a close.... ever since February 2008 when the Jasper engine was installed. Its never run right since then and this has been why.

Thank you all for the best of your humanity.

On an another note, I had initially thought when I was reading ya'lls posts the following thought occurred to me:

Does it ever bother you all that it always seems like 1 more test, 1 more test, 1 more test, 1 more test, 1 more test, 1 more test,... etc... till you get to the bottom of whats going on?

1 more test - makes me feel so exhausted before I even lift myself up to go do the test, because I know it will lead to 1 more test. I just see it like an infinite loop in programming code. I keep believing, "IT CAN BE FIXED" and "THERE IS AN END IN SIGHT" .... but it always seems like "1 more test". I try to keep it that simple too, because if I think its gonna result in 20 more tests.... I get really discouraged. "1 more test" is kinda like a trick for my mind to keep going without losing the sanity. lol

I think the shop thinks I'm frakkin insane or maybe they cannot believe someone of my magnitude of patience, especially on what most people tend to not care about...... "AN OLD VAN". I just cannot begin to describe what having a VAN does for a person. Forgetting all the stupid stereotypes that exist about VANS, Vans allow you to do as much if not more than trucks. Mini van or regular... they accomplish a great deal.

This thing was never supposed to be a vehicle that I repaired. When I first got it, it was intended to be a weekend "get-away to the beach" vehicle that I'd sleep in to avoid hotel fees and come home (4 hours to beach and back), but shortly after I got it I started to learn the benefits of having a large capacity A/C enclosed big vehicle.

What this has turned into is far short of fixing a van. It has become almost a science project. It is probably the longest learning experience of my life and I'm much better for it now as it has broadened my understanding of what I never really knew that well, "How an automobile functions", and not just the basics..... the deepest stuff.

Well, enough tree sap. Just wanted to say a few things.

As it stands now, van has been in the shop since late Monday afternoon and I haven't heard anything yet as usual. I'm gonna call'em tomorrow and see if they've even started it.

[searcherrr]

Day 3 at the shop come and gone. Haven't even touched it yet. I guess its what I can expect since I'm asking for "special service" as in I've told the owner that I only want him working on it. Hopefully he will get to it tomorrow.

I almost freaked when I called over there cause the other owner said the main owner was out test driving and I thought he meant the van and had not begun working on it yet. That would've been bad news. lol

In any case I hate when momentum is fouled by something like this. Steams me up.

I think I will be going to visit my gf 330 miles away soon, so maybe the van will be done when I get back.

[searcherrr]

Thursday - June 11, 2009 -
Talked to the shop owner and he'd finally gotten to it on Wednesday actually and I am still out of town. Missed his call and caught him Thursday.

Well, my and you guy's efforts recently paid off. PCM it is. The shop owner ohm'ed things out for himself and as soon as he disconnected the PCM the grounding of injector 6 and VPWR went away.

He actually only confirmed injector 6 and I don't think confirmed VPWR, but I told him before he powered it all up to make sure to check the ohms on both wires. I dunno if he'll actually do that or not, but I do know I'll check it before I drive away with the van. I guess with inj 6 verified to ground in the PCM he didn't feel he needed to test the VPWR circuit due to the wiring repair job we'd done prior.

The PCM will be FREE!!!! It was put in however in 2007, but the shop owner worked the deal with the manufacturer somehow to get it in a warranty swap.

The 2nd PCM (this new one will be the 3rd) was put in when the original engine was in there. I dare say this problem existed all the way back then cause similar wiring mishaps and sensor's blowing out happened just after that 2nd PCM was installed. So its likely that someone at their shop prior to the engine replacement mis-routed the PCM wiring which caused it to melt etc...

Anyway, I get back in town to pick it up Monday or Tuesday at which time I'll test it and drive it and listen to it run etc.. and post back. I just hope now we're done chasing ghosts in the machine. If the MAF (AFM) blows this time right after the new PCM is installed I will get a shotgun out and shoot the van, cause thats exactly what happened immediately following the 2nd PCM installation as soon as I drove off the repair shop's lot. I guess I'll be hopeful again though, and hope for the best.

[tripletdaddy]

Hey! That sounds great! I thought you fell silent because you offed it and was in jail, or you took it off a cliff putting you both up in a ball of flames.......if you were so lucky. I guess not. I didn't think there are any cliffs in Louisiana or any high enough to do any harm. Sorry I've been silent as I've been snowed in with my own tail chasing.

I wanted to tell you again, but I'm pretty sure I said what you have sounds like what I had with the injector grounding out causing the injector to be open or on all the time. I think I determined that the injector was grounded only when the key was on with or without the engine on, so the PCM was doing that. If it's grounded at all times, no matter what you do or don't have connected, it will be a hard ground through the wiring harness, or the injector itself is grounding to the head. Since you had the wiring harness melt, you most likely fried your PCM as you already suspected, but it could also have been the initial grounding of the injector if not the only ground.

Another symptom of this problem besides gas leaking at the exhaust manifold and in the exhaust gas at the tailpipe, is the fuel pressure will not stay where it belongs at KOEO. The pressure will go up when first turning on the key but will go to zero because the shorted injector is open and will let the gas out. I'm pretty sure the power to the injectors, and a lot of the other sensors, etc., are powered by VPWR (red), as soon as the key is turned on. The circuit to each of those devices, like the injectors, won't be completed until the PCM provides a ground to it. I'd guess either the melted harness and/or the PCM took out your MAF as well. Seems to me the shop that misrouted your wiring harness should have to install a brand new one and anything else that was taken with it, like your PCM.

To check to see if your injector wiring is ok, you need to check to be sure the colored wire is not grounded when KOEO. If you have a hard short, you will have a short in that wire with the engine off, but I don't recall if the PCM normally grounds that and the red, power wires when turned off. You only have power at the red when KOEO and Engine ON, and it should be about one volt within BAT+. I can't remember if red (VPWR) will be grounded by the PCM or open when the key is off. To do these tests, you may be able to pull the connector to your 6 injector, but I know it's tight getting to it as that is the one I had go bad, which I find very peculiar and interesting we had the same one go bad. Hmmmmm. I think you should be able to get some meaningful measurements by piercing the wires with a pin or needle near the injector rather than strugging with disconnecting the injector or the PCM. Since I had to remove my PCM, it was easy enough to check the resistance and shorting to ground of the wiring to the injector. You could do comparative measurements with another injector wiring. The OEM injector resistance should be around 7 - 16 ohms. A circuit that should not be grounded will have at least 10,000 ohms resistance. The Ford TSM, I think you said you have covers this, albeit it took me awhile to work through it. The HD - Misfire .... pinpoint test section covers this pretty good. The pinpoint tests are what you want in the PCED, OBD Manual section. Boy, you lucked out on a new PCM. Wish I could have fallen into that, but at this point, I think you more than earned it, as you have the greatest stick-to-it-tiveness I ever heard. I still can't believe you didn't sink it in the bijou or torch it!?!

Finally, if the mechanic has the van running, which I assume he will when he says it's fixed, all of the above will be moot as it will have to be correct in order for everything to work correctly. I'd only worry about incorrect values, shorting, etc., if it isn't working correctly, you get codes, etc. Did you have any codes? I had a misfire code, but for cylinder 1 not 6. The misfire detection explanation did not explain that scenario.