hi everyone, i am new to the board but heard this was a great place for tech support.

my truck is a 1994 ranger xl, 4.0l auto 4x4 with 320,000 km's

here is my problem.

truck starts but won't idle on its own, and cylinders 1 and 5 are not firing at all.

here is what i have done so far.

new coil pack, new plugs, tested plug wires, changed out icm, found 2 SPOUTS and they tested fine, tested all wiring for shorts between the coil pack and icm. cleaned all grounds from engine to body and chassis. cleaned MAF, new fuel filter, swapped around relays, new alternator, replaced a bad vacuum line

thanks in advance for your help....

 

Welcome to FTE.

You've been busy on this puppy.
Be sure to check out the "Tech info" thread atop this forums thread listing page.
Lots of good wrench turning info there.

Did this problem come about slowly over time, or suddely after some event???

Do you have a CEL lit or blinking & if so, have you had the computer scanned for trouble codes?

Most autoparts stores will scan the computer at no cost, if the CEL is lit, then post All trouble code Numbers, as they can offer up good trouble shooting clues.
If you can't get it to the store for a scan, beg, buy, borrow, or steal a code reader, or scantool & post All of the code Numbers found.

You may have more than one problem, but seeing as how you say that you have no spark on cyl's 1 & 5 & we know they are paired together in the coilpack & share a secondary winding, lets begin there.

Did you have this no spark problem before you replaced the old coilpack???

Did the old coilpack windings ohm out bad, or did you have it bench tested for output to know it was bad????

Was the new coilpack bench tested, or continuity tested before you left the store with it, so that you knew it was likely good????

If you know the new coilpack is good, then check it's electrical connector & wiring back to the computer.

On V6 engines, the coilpack has three seperate windings, in which cyl's 1/5, 2/6 & 3/4 are paired, to each share a seperate secondary high voltage winding.

B+ 12 volts is fed to each coils primary winding at KOEO & the computer provides timed primary winding ground switching, triggered by a signal from the crank sensor, for each of the three coils to fire the two spark plugs connected to them.
One plug is being fired on it's compression/power stroke, while it's companion is being fired on it's exhaust stroke(waste spark ignition system).

So check that you have B+ to the 1/5 coils primary electrical connector contact, at KOEO & continuity on the 1/5 coils primary ground return wire, going back to the computers firewall electrical connector.

Let us know what you find.

 

hi, thanks for the quick reply. i read through the tech info on the type of ignition system i have. some really good info there.

my problem seemed to slowly happen over time. it started out only when cold it would have a slight hesitation but once it warmed up we were good to go. but this also didn't happen all the time.

then one day it died on me and i was able to limp it home. i was not getting spark on 1 and 5 so i tested the coil pack and the secondary windings on 1 and 5 were out of range so i replaced the pack. tested the new one before install and was good to go.

the truck ran great for about 2 weeks before it finally gave up the ghost. it died on me and wouldn't start at all. got it towed home and started checking it out.

first thing i did was check the coil pack primary and secondary windings and they checked out all good.

then i once again checked for spark and nothing again on 1 and 5.

i disconnected the battery to reset the computer to see if that would help. it did as now it will start but not stay running without giving it a ton of throttle, still dead on 1 and 5.

next i put in new plugs and tested the plug wires. no change.

i tested for 12 v at the coil pack with the koeo and that was good, i checked the harness from the coil pack to the icm for shorts and nothing there.

replaced the icm with a used one from a running 1995 explorer, didn't change anything,

checked all grounds for corrosion cleaned them all.

then i noticed my alternator would get really hot when i would run the engine on high throttle so i thought maybe the voltage reg was shot and it was over feeding the system messing with the electronics so i replaced it. again no change.

then i just started checking randoms like the vacuum lines and SPOUTS. i found 2 and they tested fine.

the only other thing is, i can start the truck but when it dies i need to turn the key all the way off in order to get it to start again.

also i have codes 212 and 232. i found those by using the jumper wire, cel, key on engine off method.

i really hope i answered all your questions. thank you for your time and help.

Lloyd

 

Just a guess, you understand - it may be the camshaft position sensor.

 

OK, good feedback & trouble shooting.

The trouble codes are confirming that the computer has detected a problem with the coil pack primary circuit, so you need to continue to concentrate your trouble shoot on the wiring & connections in the 1/5 coils primary circuit.

I know you said you checked for shorts to ground on it's wire back to the computer firewall connector, but did you also do an end to end continuity check on the wire, from the coilpack electrial connector, back to the computer connector, so that you know you have a good low resistance electrical connection/continuity on that lead????

Wiggle the wire on both ends when doing the continuity test & check the wires termination for a good tight crimp & it's pins/sockets for corrosion, bent or pushed back pin, or spread, or pushed back socket.

If that checks ok, test the leads continuity from the computers firewall connector, into the computer.

The trouble you have seems to suggest that lead is open circuit, or high ressitance, somewhere aong the way.

If you don't want to do all that, you could try hooking one lead of a 12 volt test light to the coilpacks connector B+ feed, the other to the 1/5 coils primary computer return connection in the plug, crank the engine & see if it blinks, as the computer switches it's ground connection on & off.

This gives a visual check of the wiring & connections all the way back to & through the computers ground driver.

From what the trouble codes are suggesting & the coilpack is saying, the test light isn't going to blink, because that circuit is open somewhere between the coilpacks electrical connector & the computers ground switching driver.

Good suspect points are electrical connectors, anywhere a wire feeds through a partition, is routed close to a high heat source, or sharp edged vibrating point, or where the wire makes a sharp bend.

As I've said, it sounds like you may also have other issues, but for now, stay focused on finding & fixing this problem, before trying to dive into another one.
Keep us posted on your trouble shoot.

 

ok, so i got back on it tonight with some help from a buddy who is pretty savy with mechanics. we did all the checks you described and found nothing out of the ordinary.

we tested for spark again, this time running the engine at high rpms and it seems 1 and 5 do spark, but only at high revs, and still very very very little spark at that.

after double checking connections and areas for bad grounds and shorts, it seems the only thing left is the PCM.....

thoughts?

 

Could be a bad driver in the pcm.

Did you do the 12 volt test light check on the 1/5 lead to the computer, to see if it would blink when the engine is canked????

 

the lead from the pcm to the icm? or the icm to the coil pack?

 

Testing at the coilpacks electrical connector 1/5 coil primary lead, that goes back to the PCM, that it's driver ground switches to fire that coil.

If the 12 volt test light is dim, then that part of the circuit is high resistance, or if it doesn't blink the circuit is open, or the resistance is so high it can't pass enough current to light the lamp & would cause low current flow through the coilpacks primary & a weak spark, or no spark if it's open circuit or the PCM driver isn't switching as it should.

To calibrate the test lamp brightness, in the connector, touch one of the other two good coil pack primary leads going to the PCM to be switched by it's driver. The test lamp should flash brightly as the engine is cranked.

I'd disable the fuel pump if you do much cranking/testing, so you don't wash the cyls down, or flood the engine, while the coilpack is disconnected & the engine is cranked.

 

oh i got ya....ok cool i will try that tomorrow....thanks again

 

i haven't had a chance to check out the power yet, but i just want to make sure i have my thinking on the right track.


to make spark basically it follows these steps correct?

sensors to the pcm, pcm to the icm, icm to the coil pack?

and the pcm is also called the ecu?

thanks

 

The crankshaft sensor sends the PCM crankshaft postion info & it uses this info to tell the ICM when to fire which coil & it's pair of spark plugs.

So the computer controls the icm with info it gets from the crank shaft sensor & tells the ICM when to fire the plugs.

The computer uses camshaft sensor input to tell the fuel injectors when to squirt & it can also use the camshaft input to tell the ICM when to fire the spark plugs, if the crank sensor fails.

It can also use the crank sensor info to tell the fuel injectors when to squirt, if the cam shaft sensor fails.

At KOEO the coilpacks are hot & have B+ to them, so their primary windings are electronicaly ground switched, to cause the correct coil in the pack, to fire the correct pair of spark plugs.

If a coils primary ground lead, or the driver that's electronically switching the ground for a particular coil, has a high resistance problem, the coil might not fire, or make a weak spark, because of high resistance in it's primary ground switched portion of the circuit, or in the B+ feed, part of the circuit.

In other words, you could measure 12 volts B+ unloaded at the coil pack, but as soon as the drivers turn the ground on, to electrically load the circuit & fire a coil, if too much resistance is in the B+ feed part, or in the ground switching wiring, or in the electronic driver, that resistance could cause a voltage drop that could result in a weak, or no spark condition.

So the B+ feed needs to be back probed while the engine is cranked, to make sure 12 volts B+ is on the coil under electrical load, when the computer grounds the 1/5 coils primary winding.

 

awesome thanks again, you definitely know your stuff....i totally appreciate all the help.....

thanks once again
Lloyd

 

ok i tested the connector with a test light as you suggested...all three pins seem to be really dim but the feeder for 1 & 5 seemed a little dimmer......

 

OK, were all three blinking when the engine was cranked????