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Thread: Anyone with Northstar V8 Experience? Random Misfire Reply to Thread
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Topic Review (Newest First)
04-06-2014 11:27 PM
shepherdmom Just an update, changing out the spark plugs seems to have fixed the problem.
04-05-2014 04:52 PM
shepherdmom
Quote:
Originally Posted by Lucy Dog View Post
A bad catalytic converter is fine to drive with. It's really no big deal... it's basically just a filter attached to your exhaust for pollution/emissions. You're just never going to pass emissions testing without one.

You'll get a check engine light sooner or later for a bad cat if you've already killed it.
Oh doesn't matter then... No emissions testing here. We are too far out in the boonies.

Its a 2006 Buick Lucerne.
04-05-2014 03:27 PM
Lucy Dog
Quote:
Originally Posted by shepherdmom View Post
Thanks everyone, I will show these posts to him.

Lucy Dog, I've probably already killed that converter thing you were talking about. Its been doing this for several months now and I've been driving the dang thing. I don't have a choice.
A bad catalytic converter is fine to drive with. It's really no big deal... it's basically just a filter attached to your exhaust for pollution/emissions. You're just never going to pass emissions testing without one.

You'll get a check engine light sooner or later for a bad cat if you've already killed it.
04-05-2014 01:57 PM
Nigel
Quote:
Originally Posted by shepherdmom View Post
Thanks everyone, I will show these posts to him.

Lucy Dog, I've probably already killed that converter thing you were talking about. Its been doing this for several months now and I've been driving the dang thing. I don't have a choice.
Yes, Lucy dog is correct, excessive misfires will kill your catalytic converter if allowed to go on. You can check the temp (laser pyrometer) on the inlet side of the cat and compare to the outlet side, the outlet should be hotter, something like 350 deg in and 450 out, can't remember the exact % of difference. If the temp is similar in/out its probably dead.

What year is the engine/vehicle?
04-05-2014 01:27 PM
shepherdmom Thanks everyone, I will show these posts to him.

Lucy Dog, I've probably already killed that converter thing you were talking about. Its been doing this for several months now and I've been driving the dang thing. I don't have a choice.
04-05-2014 11:35 AM
Lucy Dog
Quote:
Originally Posted by shepherdmom View Post
We have a code reader. It is not throwing codes. When it first started happening it was random misfire cylinder 8... Husband moved the coil to 6 and the next code it threw was 6 so he replaced that coil. The coil worked for about 2 weeks then went bad. You could really feel that. Code stayed on so he returned and replaced coil. Then it started moving around to 4 then back to 6 so he replaced the other 3 coils. It hasn't thrown a code since but you can still feel the intermittent misfire, especially when sitting at a stop sign and sometimes going uphill. This has been going on for a while now and it's making me crazy. Hubby says he will replace plugs this weekend and if that doesn't fix it, I'm going to have to take it to a dealer. Grrr.. Did I mention I HATE cars.
I don't think I've ever heard of a car actually misfire and not throw a code. Does your scanner show pending codes too? I've had cars that have misfired without the CEL coming on. I'll connect my scanner and there will be pending codes.

Typically, misfires are caused by a few things unless you're getting other codes: spark plugs, coils, injectors, electrical wiring, or ECU. That's pretty much it.

Smart moving the coil around from 8 to 6 to test it. That was going to be the first thing I recommend you doing, but he already did that. It's very obvious when a coil is completely bad because you lose a lot of power. It typically isn't a quick misfire and back to normal.

When was the last time he did the spark plugs? How many miles and years.

Fuel injectors are also a possibility, but it's pretty rare for them to fail. For all three to fail in a small time frame is a very low possibility.

If all of these things don't fix the problem, it's most likely something electrical. Wiring from the ECU to the coils can and do go bad. There could be a short somewhere in the wiring on cylinder 8 causing electrical issues to jump from 8 to 6 to 4. That's a real possibility. The ECU itself can also have a short somewhere and may need to be replaced. When you get into electrical stuff like this, you really need to know what you're doing and can get expensive.

Regardless what the problem is, be careful driving the car if it keeps misfiring. When a car misfires, unless the injectors aren't spraying fuel and that's causing the misfire, fuel is going to leak into your catalytic converters and eventually kill that too. Depending on the car, each cat installed usually runs about $400-$500 each at least. Enough misfires and it's going to kill your cat.
04-05-2014 09:23 AM
sehrgutcsg If you've already replaced the coils and it is no longer throwing codes and the misfire is intermittent I would be looking at spark plug wires I hope this information helps you out.
04-05-2014 03:34 AM
shepherdmom
Quote:
Originally Posted by Lucy Dog View Post
That's impossible. If there's an actual misfire, there's an immediate code. A car won't misfire without throwing a code - it happens simultaneously. Your check engine light might not come on immediately, but if you hook up a scanner, there will be a pending misfire code at the very least.
We have a code reader. It is not throwing codes. When it first started happening it was random misfire cylinder 8... Husband moved the coil to 6 and the next code it threw was 6 so he replaced that coil. The coil worked for about 2 weeks then went bad. You could really feel that. Code stayed on so he returned and replaced coil. Then it started moving around to 4 then back to 6 so he replaced the other 3 coils. It hasn't thrown a code since but you can still feel the intermittent misfire, especially when sitting at a stop sign and sometimes going uphill. This has been going on for a while now and it's making me crazy. Hubby says he will replace plugs this weekend and if that doesn't fix it, I'm going to have to take it to a dealer. Grrr.. Did I mention I HATE cars.
04-05-2014 02:41 AM
Lucy Dog
Quote:
Originally Posted by shepherdmom View Post
Just misfire... But it is misfiring a lot more often than it is throwing codes.
That's impossible. If there's an actual misfire, there's an immediate code. A car won't misfire without throwing a code - it happens simultaneously. Your check engine light might not come on immediately, but if you hook up a scanner, there will be a pending misfire code at the very least.
04-05-2014 02:33 AM
Lucy Dog You actually feel the car misfire? Are all three cylinders misfiring at once or is it one at a time? Is it a quick misfire then back to normal or is it continuous while the cars running?

The only way to really diagnose the problem is with exact codes. You can go to any autoparts store and they'll scan the codes for free.
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