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BOBBYSS
BOBBYSS, Master Technician
Category: Chevy
Satisfied Customers: 17326
Experience:  ASE MASTER CERTIFIED, AA DEGREE AUTO/DIESEL TECH
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My 1995 chevy k2500 is burning up ignition coils. When they

Customer Question

My 1995 chevy k2500 is burning up ignition coils. When they fail, anytime I try to go past 3/4 throttle, the engine has no spark, and at cruising rpm in overdrive my engine has a slight miss. My grounds are all connected and clean, I've changed multiple ignition control modules and primary coils. And my plug wires are all performance wires that are new and in good shape. New distributor cap and rotor also.
Submitted: 1 year ago.
Category: Chevy
Customer: replied 1 year ago.
Also, when I change the coil, sometimes when I change the module, I can take the truck down the road and it works fine, but the first time I try to really get on it it permanently kills one or the other.
Expert:  BOBBYSS replied 1 year ago.

Hello, my name is***** for the question. The most common cause of failure to cause this is poor wiring from the coil to the module. I would replace this first. The second most common is power still being applied after the vehicle is turned off. This is typically caused by a relay of ignition switch failing. I hope this helps. If you need more help let me know.

Customer: replied 1 year ago.
Okay. Will check both tomorrow. Should an ohms check of the 2 wires from the coil to the module be enough to see the problem, or do I need to run two new wires?
Expert:  BOBBYSS replied 1 year ago.

These wires can show good during an ohm test and fail intermittently during operation. If they are OE then I would personally replace them.

Customer: replied 1 year ago.
Well I put in a new relay, and I tried the wires from the coil to the module from a friend's truck with the same setup, went down the road and same story as before. I did notice that there's an extra flat blade connector at the coil, but it looks like it was deliberately taped up and out of the way. It's just a short white wireally and the single blade pin.
Expert:  BOBBYSS replied 1 year ago.

That connector is there is you need a spot to hook up a tach input. Did you happen to check and see if you continue to have power at the coil? When the coil fails what does it actually do?

Customer: replied 1 year ago.
What wires should I be checking for power at the coil? The ones coming from the module or the other set? And they should not have power at either wire with the ignition off?
Expert:  BOBBYSS replied 1 year ago.

With the ignition off none of the wires should have power.

Customer: replied 1 year ago.
No power at either of those wires with the ignition off.
When it fails, I have a very even miss when at cruising rpm in od, but in 3 it runs better. Not great but better.
Then any time if I'm cruising alone, tps at ~20% and try to Rev up like in a passing situation, the engine dies, rpms drop, and might have a stray detonation or two, then everything will catch and Rev up like it's supposed to.
Also, I hooked up my tts data logger today and watched it while I was on my way to work. I didn't see anything too out of the ordinary, tps and o2 showing about normal, coolant temp seemed spot on.
It's not counting any knocks when the issues are showing themselves, but I did notice that my charcoal cylinder readding on the data logger was showing either 100 or 0, no in-between.
Customer: replied 1 year ago.
Oh. Other issue is it only falls on its face on drive. I can hammer the throttle with the truck in park just fine, it'll Rev up and down no problem. But If I put it in drive it kills it with any sudden accelerator movement.
Expert:  BOBBYSS replied 1 year ago.

Thanks. Sorry for all of the questions, but does changing the coil fix it every time?

Customer: replied 1 year ago.
No, it does not fix it every time. Last time I put a coil and module in I saw no change. And I tested them out immediately after install
Expert:  BOBBYSS replied 1 year ago.

It sounds more like a fuel pressure issue to me. Like a lean condition. Did you happen to record fuel trim. Readings when the problem occurred?

Customer: replied 1 year ago.
when it fails it'll jump to 14 or 15.
Expert:  BOBBYSS replied 1 year ago.

That sounds like it is lacking in fuel pressure when this occurs. Do you have a fuel pressure gauge to watch the pressure while driving?

Customer: replied 1 year ago.
No, I don't have a pressure gauge that I can watch while driving. I had put the fuel trim to fuel not being ignited in the cylinders, then to o2 sensor picking up the rich state. I don't know if the 14/15 is coming from a rich or lean condition, but I can smell a little gas at idle, I had thought it was a rich condition.
Customer: replied 1 year ago.
But I would love to find that it's a fuel problem instead of chasing my tail on ignition.
Expert:  BOBBYSS replied 1 year ago.

Usually if it reads like that it means that the computer is commanding more fuel. The best way I know of is with a long hose on a pressure gauge to see what it does while driving. I would check the pressure how it is first and see if it is high or near the bottom. It needs to be over 55 psi.

Customer: replied 1 year ago.
I thought a tbi setup needs about 12-16psi, and the later fuel injected units need the higher pressure?
And please correct me if I'm wrong, but wouldn't the fuel problem also show up in a parking gear rev?
Expert:  BOBBYSS replied 1 year ago.

Sorry. I missed that detail in your description. My assumption was late model 1995. Yes, that is what the pressure should be, and no, most fuel pressure issues don't show up until it is under load.

Customer: replied 1 year ago.
Okay, I'll get a gauge to run it with tomorrow. Thanks!
Expert:  BOBBYSS replied 1 year ago.

Sounds good. I will await your response then. Thanks and have a great night.

Customer: replied 1 year ago.
Fuel pressure held steado at about 15, put in a new filter just because. Still didn't see any improvement.
Expert:  BOBBYSS replied 1 year ago.

On the intake manifold there is a MAP sensor. Do me a favor and while the engine is warmed up tap on the sensor fairly hard with the handle of a screw driver. See if the idle changes when you do that. If it does then replace the sensor.

Customer: replied 1 year ago.
I've already put in two map sensors as well. Even tried hooking it to a different vacuum port on the throttle body.lol
Expert:  BOBBYSS replied 1 year ago.

Thank you. We need to check and see for sure if the engine is lacking fuel or spark or both when it stalls out. WHen it does this see if you can see fuel coming from the injectors while cranking the engine. Then see if you have spark. We need to know so that we can determine for sure which direction to go in.

Customer: replied 1 year ago.
The wire that leads off the coil to hook up a tach, could I hook up a timing gun or multimeter to it and see my spark there? And then I could monitor it while driving down the road at the coil?
Expert:  BOBBYSS replied 1 year ago.

You would have to install a tach to it.

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