When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
To my question: does anyone know a way to test ignition coils as fitted the to AJ26? Mine are the ones with 2 pins rather than the later 4 pinned, diagnosable ones... I'm having misfires when cold (fires into the exhaust). Before I order 8 new coils, I wanted to see if I can check and find a faulty one...
They work fine (mostly) when warm/hot/up to temperature. But when cold I can't tell what one misses and the car will not produce a fault code.
I don't have info for testing coils but it doesn't sound like coils are your problem. I would first start with a good cleaning of the MAF and throttle body with the appropriate cleaners. I would also check the gap and clean the plugs.
If they have a lot of miles I would just replace the plugs. If you are getting misfires when cold and not setting code I would look for other causes.
Normally I wouldn't think warming the engine would make the coils work better.
The TB is brand new. The MAF works perfectly and the plugs are all only 15k km old... Not even half their lives yet. All well gapped. Lambda sonds are new. Compression is fine. Temperature sensors and knock sensors are all working properly.
When the engine is warm, it works perfectly. Untill then, it doesn't fire properly.
Are you getting a misfire code? If so and it's specific to a cylinder or more you could try moving the coil pack to another cylinder to see if the code follows. I'm not sure if the old technique of measuring resistance across the terminals and output would work for these, but I would take a few out and check to see if they have similar resistance, if the ohms are way out of spec on one that might be an indication of a failing coil.
If you took off your ignition coil covers before starting the engine, you could either disconnect one coil at a time with it running or while the 2 pin coil wire is connected, carefully lift up the coil and listen to see if it has a consistent spark or an intermittent spark. A consistently firing coil means it's good. This may take a few cold starts to find the one at fault. After thinking about it some more, I'd just recommend the lift while coil wire is connected method.
Last edited by Addicted2boost; Dec 27, 2016 at 05:56 PM.
What does make you think it is the coils?
You did not mention, but I remember you run LPG right?
I guess you start up on gasoline though (if I remember right, u mentioned before u got these problems).
It sounds more timing or mixture or ECU related, although I have no idea how the systems interconnect, and how the LPG system integrates with the original stuff.
Food for thoughts?
Last edited by ericjansen; Dec 28, 2016 at 05:07 AM.
I don't see all 8 going bad as plausible. Indeed, if they used to work then 2 going bad is unlikely, so at most buy 2 and swap until you find the bad one(s).
Though it doesn't sound much like a coil fault at all.
if I remember right, didn't you happen to have an IDS? When I was browsing through mine I saw sth called "misfire monitor". Did you already try this? Or doesn't it work with the 2pin coils? Just a thought.
What does make you think it is the coils?
You did not mention, but I remember you run LPG right?
I guess you start up on gasoline though (if I remember right, u mentioned before u got these problems).
It sounds more timing or mixture or ECU related, although I have no idea how the systems interconnect, and how the LPG system integrates with the original stuff.
Food for thoughts?
The LPG runs on the engine ECU timing and adapts the opening duration of the LPG injectors accordingly.
Cold and warm starts are always on petrol (I won't write gas as my car runs on gas when switched over).
I had some slightly instabilities before I had the LPG system installed. But they were only at lower speed where the revs were a little eratic...
Originally Posted by JagV8
You could use a COP tester.
I don't see all 8 going bad as plausible. Indeed, if they used to work then 2 going bad is unlikely, so at most buy 2 and swap until you find the bad one(s).
Though it doesn't sound much like a coil fault at all.
The thing is, the ignition system is the only part of my car which won't set a code...
Originally Posted by xjr2014_de
Hi Daim,
if I remember right, didn't you happen to have an IDS? When I was browsing through mine I saw sth called "misfire monitor". Did you already try this? Or doesn't it work with the 2pin coils? Just a thought.
Doesn't work on AJ26 engines due to the lack of diagnosable coils. Mine are 2 pin rather than the diagnostical 4 pin coils ...
The thing is though, they all fire... That is the mystery. Just some seem delayed...
What about checking the ignition control modules? Since you got the AJ26 engine, you should have one per bank, right? I don't have my Jaguar documents on hand right now, but I can check tomorrow if I can find any pinpoint tests concerning the module.
Best regards, Alexander
Daim, not sure if this helps, as mine are 4 pin coils. but not long ago I kept getting a reduced performance code along with misfire codes. searched over and over, the the other night I pulled off the "beautification panels" to check if I may have a possible leak from one of the hoses on the purge valve, load and behold, the plug somehome came off the purge valve. but not sure if your set up uses the purge valve. Oh, and mine ran rough at start up
While reading your thread one thought occurred to me: if your Engine Coolant Temperature Sensor (ECTS) is shorted or stuck at a low resistance, the ECM will interpret the resulting low voltage to mean the coolant is hot and will not apply cold-start fuel enrichment, leading to lean running and the possibility of misfires until the engine warms up. You can easily test the ECTS with an ohmmeter or voltmeter and this chart from the Engine Management Systems manual:
I just searched the DTC Summaries manual for fault codes related to the ECTS, and while there are some related to high ECTS resistance or a disconnected ECTS, I don't see any that indicate low ECTS resistance or a shorted wire harness (though I may have missed one if it's there).
While reading your thread one thought occurred to me: if your Engine Coolant Temperature Sensor (ECTS) is shorted or stuck at a low resistance, the ECM will interpret the resulting low voltage to mean the coolant is hot and will not apply cold-start fuel enrichment, leading to lean running and the possibility of misfires until the engine warms up. You can easily test the ECTS with an ohmmeter or voltmeter and this chart from the Engine Management Systems manual:
I just searched the DTC Summaries manual for fault codes related to the ECTS, and while there are some related to high ECTS resistance or a disconnected ECTS, I don't see any that indicate low ECTS resistance or a shorted wire harness (though I may have missed one if it's there).
Please keep us informed.
Cheers,
Don
Hey Don,
cheers for your input.
I changed the sensor before for a brand new one. No change.
On a side note: wouldn't the temperature gauge inside the car also display a "warm" engine instead of cold? Mine shows cold and it warms up normally (on gauge)...!?
If it is backfiring (is that what you mean by "firing into the exhaust?"), it sounds like it has jumped a tooth and is mis-timed. It has been, what, a year since you renewed the tensioners?
Any way to test ignition coils?
