Testing coils on a coil over plug system?
 

I need to check the coils. How should I do it?

Re: Testing coils on a coil over plug system?
 

There may be better ways.... But the best way I have found so far, is either heat/temp check on exhaust via EGT readings, or using a touchless thermometer. (bought mine at Harbor Freight for a few bucks) See if one cylinder is cooler than others.

Or if that doesnt work, then it is just brute force... replace (or if you don't have a lot of spares, rotate by putting a spare one in, and if no change, move the removed one into the next position, etc.) each one until you see a difference. No difference, no problem...

When we had problems with a coil pack, it only showed up at load, or higher rpm. At low rpm, it worked just fine.

Good luck Art!

David
The New Hemi Guy

Re: Testing coils on a coil over plug system?
 

I'm having trouble keeping it running when putting the car in gear. Have changed the converter (no help). Checked and recheck all wires and grounds. Changed the fuel filters (no help). Done a leakdown test (2% to 4%), looked at the top end, all cams and running gear look okay. Checked plug wires 27 to 29 ohms resistance, new plugs. Double checked timing.
When I drop it in gear it just gets crappy and stalls. I've data logged it and there is nothing showing that could cause this. What ever it is it seems to have gotten worse, before I could keep it running with the gas pedal but now it is almost impossible to keep running.
It seems to get worse as I work on it. Then get a bit better the next day.
There are no vacuum leaks, when I put my hand over the intake it reacts immediately.
I've played with the tune (richening it or leaning it) and it doesn't seem to change much and doesn't get better

Re: Testing coils on a coil over plug system?
 

Art, good auto parts stores carry adjustable coil checkers. Very simple. If you can't find one, Snap-On used to carry them too. Their's just cost more. Set the adjustable gap to 40,000 volts. Should have a sharp blue spark. Should hear a snap each time it fires. Sounds crude maybe, but will show up a weak coil in a heart beat. Hook it to the spark plug end of the wire, you may also find a leaky plug wire.

Re: Testing coils on a coil over plug system?
 

Art, if the engine runs when not in gear, how well does it run? does it sound normal, snappy throttle response? Though it is possible that you have an ign. problem, I'd doubt it would start at all with a bad coil, 4 cyl. engines with just 1 hole out tend to just barely run. Assuming you have headers, easiest way to check for dead hole is a spray water bottle, start engine let run a few minutes, then spray header tubes, should be instant sizzle on all. That will at least tell you if you've got a dead one without spending a dime. If you find that you do indeed have a dead cyl. as mentioned before swap coil with another cyl. if misfire follows you've got a bad coil, if not look at the control circuit for that coil. Good luck ans please let us know what you find. Joe

Re: Testing coils on a coil over plug system?
 

A leaky wire, boot or cracked plug can show up in gear and not idling in neutral. A little de-natured alcohol or soap in the water will break the surface tension so the water will cling to the plug wire, boot & plug, instead of bead up and not cover the entire surface. That will find small leaks quicker. I prefer the alky. A jumper wire, one end grounded and the other on a thin screw driver or ice pick will help find leaks too. Run the screw driver (or ice pick) along the coil's body, plug wire, boot and plug. a good digital lab 'scope is good for checking wave forms for the control circuit. If you are used to using them you can pick out a coil with an internal problem also by using the secondary clamp. I have an old Fluke 98A that still does that kind of work really well.

Re: Testing coils on a coil over plug system?
 

Ed, yes I agree putting engine under load will amplify any ign. system issues. After rereading Arts' post I noticed you said you have 27-29 ohms on the plug wires, how long are they that sure is low resistance their not by chance solid core? Other things I've seen, Engine coolant temp sensors giving incorrect temp reading causing incorrect pulse width. This one sometimes gets overlooked.What kind of fuel press. do you have? Does it put out any smoke, as in excessively rich, can you keep it running by adding fuel...ie. carb cleaner? Need to try to determine if you're dealing with an Ign. or a fuel issue. Joe

Re: Testing coils on a coil over plug system?
 

I just tried to put it in gear with the wheels off the ground. And it goes in okay the wheels turning I can give it throttle slowly and it accepts it (won't crack the throttle on the jackstands though). But when I step on the brake the engine slows down and then dies when the wheels stop, unless I work the throttle hard.
Going to try to raise and lower the fuel pressure by 5 pounds and see what happens.
Another thing I checked was the injectors and the fuel rail and switched to different manifold setups.

It is definetly a lack of power thing. But it seems to be in the lower rpm range. Once it gets up to around 4000 it runs decent.

Re: Testing coils on a coil over plug system?
 

Al, make bigger fuel pressure changes. It doesn't drop cylinders? Just dies? If it does not drop cylinders it sounds rich to me. Like Joe said, the coolant temp sensor may be out of calibration. Usually if one is too lean to idle in gear they will surge some in neutral. If you have an open in the coolant temp sensor or it's circuit the ECU will consider that -40 deg F. If that ECU has a scan function check that out. If it shows -40, take a piece of a paper clip and jumper the 2 pins in the coolant temp connector. You should then see something like 300 + deg F. If you it's the sensor. If not it is a wiring issue.

Re: Testing coils on a coil over plug system?
 

Art what kind of car are you working on? I copied part of a page from a GM service manual, not sure if this will help.
This ignition system uses individual ignition module/coil assemblies for each cylinder. The engine control module (ECM) controls the spark events by transmitting the timing pulses on the ignition control (IC) circuits to the individual ignition module/coil assemblies in firing order sequence. Each ignition module/coil has the following circuits:




•

An ignition 1 voltage circuit





•

A ground circuit





•

An IC circuit





•

A low reference circuit

Re: Testing coils on a coil over plug system?
 

Art, maybe try decreasing your fuel injector on time ie. leaning it out. Won't hurt anything at low RPMs. If that doesn't help try going the other way, you say you can keep it running by working the throttle... so that means it wants either more fuel or more air. By the way are you running "speed density" setup, if so maybe a MAP sensor issue? Joe

Re: Testing coils on a coil over plug system?
 

I've thought about changing the injector on time, as well as changing the fuel accell enrichment. But in the past the car ran okay the way it is setup. So I want to find out what happened.
I have a hall effect cam position sensor, and a magentic crank sensor with a 20 tooth wheel. I'm going to try to check them today. And I've got a coil on plug tester on order.
I'm running in open loop (I think thats alpha N).
I have a thought that the problem has been "caused" or made worse by the use of the two step function. When I started trying it is when this problem started.
I'm on the way out right now to get a handheld laser temp gauge to check the different cylinders ( my hearders are wrapped so I can't do the spary bottle).
I trying to get another ecu to try. The map sensors are built in to the ecu.

Re: Testing coils on a coil over plug system?
 

Coolant and inlet air temp sensors seem to be working fine. I've datalogged and they seem in sync with what they should be. I have the temp correction on off because I can pretty much control the coolant temp. It is setup to run at 150* to 160*
I've tried 2 different manifolds with different fuel rails injectors and inlet air sensors. I've put a timing light on it so I know nothing moved.

This problem started when I tried the launch control function on the ecu. At first it would just shut down when I got up around 3000 rpms.
I was able to put the car in gear with no problems. It only showed when I was on the 2 step. Since then it has degraded to not wanting to idle in gear at all.
I have turned off the launch control no change, removed the program and installed one that I used prior to trying the 2 step many times now. And it doesn't seem to matter.
I tend to believe I hurt something when trying the 2 step. And I'm trying to figure out what. The other day it got to where I couldn't even start it (I was actually happy I figured now I can find it) but the next morning it started. So I'm tending to think it's something heat related electrically.

Re: Testing coils on a coil over plug system?
 

Let us know what you find out.

Re: Testing coils on a coil over plug system?
 

Art, hows ECU are you running? Joe

Re: Testing coils on a coil over plug system?
 

When I find the problem I won't have to post it. You will hear me cheering for at least 2000 miles.

I'm using a ViPec V44 almost the same as Autronics but with a lot more options The guy that built the Autronics (Ray Hall) branched out on his own. Excellent customer support, they don't think it's in the ECU. I sent them programs and datalogs. But they are sending me another to try, if I don't get it solved in a couple of days.

Re: Testing coils on a coil over plug system?
 

Art, this is probably a dumb question, but does it still have the lock up disc in the torque converter?

Re: Testing coils on a coil over plug system?
 

No lockup in converter. And I changed the converter That was my first suspect.
The car ran fine in the past. So I don't want to get way off base with adjustments.
I've tried to raise/lower fuel pressure, raise/lower fuel injector flow, raise/lower ignition timing. All with no improvements.
Right now I'm chasing the possibility that my LS1 coils could have been installed with reverse polarity. And when I activated the 2 step function in the ECU I might have damaged them. If they are not the problem the only thing I have left is to change the crank and cam pickups.
I've leaked down checked the motor looked at the top end for cam wear etc. Gone through the fuel system. Checked timing to see if the timing belt jumped a tooth (could not have because it would have bent valves) Checked the plug wires, changed all the plugs etc.
I hope I'm barking up the right tree with the coils.
One thing that seems to improve it a little is putting a muffler on the collector. I'm hoping that putting some back pressure on it. Allows a weaker spark to burn more mixture in the chamber and make a bit more power.

Re: Testing coils on a coil over plug system?
 

Art,
Getting worse with heat and better when cool.... I still think Coil Temp affect has to be something in the electical controls.. Coils or sensors that time the electrical cycles being bad. I Still think the 2 step circuits in your computer are not working correctly. I would talk to the guy that did that and try to get it deactivated...completely. Get it running as a foot brake set up and then go back to the 2 step.

Re: Testing coils on a coil over plug system?
 

Art, the LS1 coil pinout is A= ground, B=low reference to PCM, C=coil control PCM, D=Ign power or B+ The low reference on terminal B is the PCM ground for the coil. Hope this helps. BTW you stated that this all seemed to start after using the launch funtion in the ECU, in what manner does your system limit RPM? does it do Ign. only, fuel only or a combination of these?

Re: Testing coils on a coil over plug system?
 

First I deactivated it in the ecu, then I removed the wiring from it.
I'm trying to get it back to running right without the 2 step. I ran fine before. I had it idling at 1000 rpms, drop it in gear and hold 900 rpms. When that comes back. Then I'll tackle the 2 step.

The launch control function can cut spark, fuel or timing. I was told for the N/A just to use the spark. It worked flawlessly in neutral but went ballistic when against the converter.

Re: Testing coils on a coil over plug system?
 

Art, not sure I would spend any time looking at Crank or cam triggers, as they would just make the engine quit no matter what. Did you get your spark checker if so do you have nice blue spark from all coils? I asked before about MAP sensor... what does it read? Do you have any tuning tables that use the MAP input to change fuel or timing perhaps coil on time based on MAP or fuel enrichment based on MAP sensor? Can you "see" in real time what timing and pulse width is being commanded by the ECU?Also can you view your Crank sensor count in real time, sometimes referred to as Wheel dbug counts?

Re: Testing coils on a coil over plug system?
 

The ecu is programmed to use the map sensor and the tps to change timing and fuel.
The map sensor is in the ecu. It has a calibrate function, and it matches the internal bap sensor. According to the datalogs the map reading changes seem to be right. I can hook up a seperate map sensor. I don't know is I have a wheel debug option.
I just checked the wiring for the coils and it seems to be correct But I did notice that I get 11.8 volts at the pos side of the coil (ignition on) when I get 12.5 at the battery. This is going to require more inspection. This is without the fuel pump on only the ecu and (heated) wideband O2 sensor is energized. I'm wondering why an ecu takes that much voltage when I might try to disconect the O2 sensor and see what happens.

Re: Testing coils on a coil over plug system?
 

Art, if you have 12.5 volts at battery and 11.8 volts at coil you are seeing voltage drop in that circuit, what voltage does the coil have when it's running?

Re: Testing coils on a coil over plug system?
 

The only thing on is the O2 sensor and the ECU. I'll check it with the O2 sensor unplugged
When the car starts and runs the voltage goes to 13.9

Re: Testing coils on a coil over plug system?
 

Art, yes the heater in the 02 does require a bit of amperage, so that's most likely where your voltage is going. You said you datalogged your engine while this is happening what inj. pulse are you seeing how bout coil dwell and calculated timing? you should be seeing some sort of change in these, what happens cto the 02 reading?

Re: Testing coils on a coil over plug system?
 

Joe,
What I don't understand is he is getting lean 02's even when he is going rich on the settings. I keep thinking it is something to do with the coils not having good enough output (or a signal) to fire the plugs and he has more 02 in the pipe because the engine is an air pump when the plug doesn't fire... ???
Sensors don't read raw fuel, but they read raw air...right? Any ideas?

Re: Testing coils on a coil over plug system?
 

Adger, you are correct if a cyl. misfires it is "read" by the 02 as lean. There are a few thigs that can cause an unwanted lean condition, obviously a miss as we discussed, fuel pressure, low injector pulsewidth, a radical timing change I believe could also induce this issue as would a vacuum leak. For this engine to quit it has to be losing...1 the correct amount of fuel...2 the correct amount of spark as well as at the correct time. Now thaty being said, Art has indicated that he's put a timing lite on it and all looks good, what the timing is doing just proir to stall may be unknown, say forsome strange reason the ECU decides to drastically retard the timing.... what happens, or say the ECU decides to decrease the coil dwell time what happens? The same can be said for the injector control if for some reason it decreases the pulsewidth what happens? Any of these things can cause the symptom he's got. As a starting point I would log injector pulse width... coil dwell time... ECU calculated Ign. timing, also the crank trigger wheel counts as well as the cam sync trigger if available. Another handy tool I use quite often is an inline spark checker as well as a "noid" lite. While carefully observing these during the event it can be apparent that the coil quits... then the engine stalls or you see the noid lite quit flashing then the engine stalls, this happens very quickly but with an engine that repeats the failure quite often it's easy to pick out. Have a problematic car now from another shop that just quits at times, by using my lab scope I noticed that at times the 18X crank signal gets erratic, gonna replace that and see if it's fixed. Wish I were close enough to go help ART first hand however I belkieve he's got the smarts to locate this issue.

Re: Testing coils on a coil over plug system?
 

If it is better with a muffler, it makes me wonder, is it in closed loop? First, that is not what you want. Second, if you insist on closed loop make sure you have the minimum closed loop RPM to something like 4000 RPM. You DO NOT want the ECU making fuel corrections at lower RPM with open collectors. Pulling oxygen back in the collector during the overlap cycle with big race cams. It will make false corrections due to the O2 "seeing" thar oxygen and returning a false lean indication to the ECU, causing a very rich mixture.
Are the spark plugs black after an extended idle?

Re: Testing coils on a coil over plug system?
 

Open loop. Only using the O2 sensor for dataloging and manual quick tune. The O2 sensor is in the collector so it does not read acurately at any thing below 3500. I have put a 2 foot curved extension on the collector to get the idle settings close.
The plugs look dark but not sooty or wet. They look like they have always looked.

Re: Testing coils on a coil over plug system?
 

Hey Art.....I personally have had cam and crank sensor failures that caused a loss of power and the engine did not want to run unless the rpms were up.....they can fail and send a false trigger signal to the ECU......


D L Rambo....

Re: Testing coils on a coil over plug system?
 

That sounds like my problem. I'll check them out in this order. Because the only way I know of the check the pickups is to replace them.
I'm going to wire a direct hot line to the ECU (bypassing switch panel). Then I'll check out the coils. If they are good I'm going to replace the ECU (They sent me a spare) If that isn't it I'll replace the pickups. Then If it isn't fixed I'll have thrown all the parts at it I can think of.
Today I started it up and was able to get it in gear with out to much trouble. I let it warm up fully then shut it down It got to late to start it up again (hot). I'll try it tomorrow If it gets worse when it's hot. I'm thinking coils.

Re: Testing coils on a coil over plug system?
 

The correct way to diagnose those is checking the sensor wave forms with a good lab scope. Not by just throwing parts at it. You may find a poor ground or reference voltage issue instead of the sensor.

Re: Testing coils on a coil over plug system?
 

Most modern Engine Management system only use the cam sensor @ start up to synchronize the fuel and Ign. events... most systems will continue to run correctly even if you unplug the cam sync. Now the crank sensor is a different story, yes they can be intermittent, and after reading back thru the posts I see Art's running a VR ( Variable Reluctance) sensor, this type of sensor is very sensitive to 2 things.... air gap and RFI. He could try making the gap slightly less or more and see if it effects the running. Most VR sensors run best @ .050 gap, check the resistance of the sensor, you can also hook up a DVOM set to AC volts with sensor unhooked crank engine sensor should produce about 1 volt AC while cranking.

Re: Testing coils on a coil over plug system?
 

Thanks Ed but I don't have a scope. And by the time I load up the car and take it to someone that does and knows how to use it. It would be much cheaper to just throw the parts at it.


I'll check the air gap on the crank sensor and try to check the sensor. Can I just hook up the wires to my volt meter (AC mode). And then crank the motor over with the starter?
I did move some wires around when I changed intakes and converters, I'll take a look to make sure nothing is running close and parallel.

Re: Testing coils on a coil over plug system?
 

Art, yes hook up your meter and check the resistance, then switch meter to AC volts and crank the engine, you should see Approx. 1 volt AC give or take it depends on the cranking speed the faster it turns the higher the voltage. You said you moved some wires around... anything near the crank sensor or it's wiring? As I said these type sensors are quite sensitive to interference. By the way is this sensor shielded? Also as Ed stated there's no real replacement for proper diagnsis, I realize not everyone has a scope on hand... however by simply replacing a part you could be missing many things, poor connections broken wires ect. that's why that strategy sometimes back fires on people. We see alot of vehicles from other shops that have had large amounts of parts hung only to find simple wiring issues as the source of the problem. We have alot of customers balk at our charge to diag. their veh. however with a proper diagnosis a sucessful repair is almost guaranteed.

Re: Testing coils on a coil over plug system?
 

Nothing in the front of the motor was touched. But the cam sensor (hall effect) wires were moved a bit whe I put new trans in, then moved again when I changed intakes.
I called msd a while back, and asked how to check the cam sensor. They said if the light is on it's fine, that there is no other way to check it other than replace it.

Re: Testing coils on a coil over plug system?
 

So you're running an MSD Ign. and a seperate controller for fuel? And yes they are partially right... if it has a cam sync LED that blinks it is seeing the signal however a hall sensor is easily checked, you could even use a DVOM if it has a fast enough sample rate, most switch from 0 to 5 volts. Adger had stated that you are seeing the engine go lean during the event is this the case and if so what reading are you getting?

Re: Testing coils on a coil over plug system?
 

No mds ignition, only a hall effect sensor on my intake cam. The wires from it are in the back of the motor (drivers side in my case). And my battery and wires are also in close proximity. When changing the trans all these wires were moved a bit to get at the bolts etc. Again as always I got "excellent" customer service from msd. They said there was no way to check the sensor. I would have checked it way back on my list if I knew it could be done.
I was going lean during the 2 step operation. Which I believe is normal. During the stalls it doesn't seems to indicate anything but slowing to a stop.

Re: Testing coils on a coil over plug system?
 

Art, as I stated before, and this is just my opinion from nearly 30 years of driveabilty diagnosis. A crank or cam sensor issue will 99% of the time result in an immediate stall, not slowly quit running. Basically if this engine runs normally in nuetral and you place it in gear you are really only doing 1 thing, increasing the load. The sensor responsible for measuring engine load is the MAP sensor. You said it seems to read normally, what BAR sensor are you using, after quickly scanning some of your systems operating capabilities I saw that you can use MAP or Throttle pos. as your load measurement. From my perspective the engine needs 2 things to happen when it's loaded 1 the fuel needs to increase and 2 the spark instant needs to increase. From what you're saying the engine just seems to slow down to the point of quitting which to me at least indicates it is lacking in proper amount of fuel or spark lead to maintain it's desired idle speed. If I understand correctly you have an indicator lite for Cam sync input? Perhaps on the ECU, if so does this lite quit blinking just prior to stall. Sorry for all the questions but I'm really baffled by this situation and trying to determine what's Not causing it.