blinking check engine light Misfiring/Knocking at Idle only - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


1992-1999 Series I L27 (1992-1994 SE,SLE, SSE) & Series II L36 (1995-1999 SE, SSE, SLE) and common problems for the Series I and II L67 (all supercharged models 92-99) Including Olds 88's, Olds LSS's and Buick Lesabres Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

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Old 02-01-2008, 10:29 AM   #1
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Default blinking check engine light Misfiring/Knocking at Idle only

Hi Guys this is my first time posting on this site. I have a blinking check engine light and a constant misfire at idle that sounds like it'* knocking. Just from idle to 2500rpm they're constant misfires, but once you get past that is runs great (way faster than it was). Before we did anything to the car is was running fine, but the check engine light was on and the codes said that it was faulty plugs and wires or coils. So me and my dad started the tune up. So we changed the coils and the car sounded a little better. So we decided to check the wires. As I was check the wire on Spark Plug 1 the wire handle was sliding back, but the wire was still on the spark plug. So I replaced it with an wire in a box in the garage from my gtp (which was stupid on my part). So when I started it up the was a constant misfire on idle and the check engine light was blinking. So then I took the wire off and I saw a piece of metal still on the spark plug from the broken wire. So then I just replaced just the front with 3 double platnum Autolite spark plugs with the old wires. Started up did the same thing as it was at first. So I bought some new ignition (spark plug) wires from Autozone. Started up still misfiring at idle. So we drove it around the block to see if we blew a valve or cylinder. As we drove it I noticed a better performance change in the car. Although I don't know what to do about the misfiring/knocking problem . Please help I just bought the car about a month ago and I really like it. I am going to try to change the back 3 today and see what happens.
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Old 02-01-2008, 12:34 PM   #2
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Lose the plantinum plugs. They are not suggested for supercharged cars.

Use an ohm-meter to check the resistance of all 6 wires and report them back here.

Use Techinfo to check all 3 coils and report the numbers back here.

Use a scantool to determine exactly what cylinder is misfiring if possible, and report any codes back here.

Inspect all 6 spark plugs and take a closeup pic and post the pic back here for us to help you read your plugs. Keep them in order and mark them for what cylinder they came from.
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Old 02-01-2008, 11:46 PM   #3
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Default More problems

Now I just changed the spark plugs in the back of the engine with new wires and went to start it up and wouldn't start. It sound like it about to turn over, but it just squeals and stops. I think the battery is causing the problem, because when I went to Autozone for a code check and it said I had low voltage to the front spark plugs which I think was causing the misfire. I also just found out that the firing order was wrong could that cause a Misfire. Please help!! :(
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Old 02-01-2008, 11:57 PM   #4
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Yes, firing order can cause a misfire. Get it corrected. Facing the engine, 135 in the front left to right. 246 in the rear left to right.

Don't ever let autozone test anything for you. Please do the checks I listed above or we can't help you.
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Old 02-01-2008, 11:57 PM   #5
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Wellwren I just did everything you told me to do except for the scan tool. I checked the coils and they were all good. I check all 6 wires and were also good. One thing I found was that on the cylinder #3 spark plug was black and had a bad gas smell (this plug was brand new)and the front middle spark plug was clean, but had a bad gas smell. Also while removing the rear spark plugs the middle one had a bad gas smell too. But then I found out that the firing order of #2 and #3 were mixed up and also #5 and #2 was mixed up could this be the problem
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Old 02-02-2008, 01:19 AM   #6
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The front middle plug IS the #3. So what was the other one?

You didn't post any of the numbers. How do you know the wires were good? What resistance did you record?

Where are the pics of the plugs? This is important. Also explain how you have the wires hooked up. Have you mixed up your coil order?
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Old 02-02-2008, 10:41 AM   #7
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Here is how the wires, coils, and plugs are connected:

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Make sure they are connected as shown. Ignition wires are fragile. When you remove the wire boot from the plug or the coil, twist, then pull on the boot; be careful not to pull on the wire. That can cause the conductor that carries the current inside the wire to break without you being able to see it. That is one reason why you need to use a little silicone dielectric grease on the inside of the boots - to make removal of the boot a little easier. This happens a lot on the back wires where it is more difficult to get your hand on the boots. It sometimes helps to lie down on the engine so you can reach those back boots more easily. A broken internal conductor will cause a miss, sometimes intermittent. The routing of the rear wires is also pretty important. Keep the wires away from the oxygen sensor wiring and don't let the #6 wire rub against the bracket with the fuel lines. This can also cause a miss.

So, even though your wires are new, you may have broken one taking it on and off, and sometimes it is possible to get a bad wire right out of the box. That'* why willwren is asking you to test the resistance of each wire. To test whether you have a broken internal conductor, connect an ohm-meter to each end of the wire, then pull on the wire and wiggle the ends around and make sure you do not lose continuity.

I used to re-use ignition wires routinely, but in recent years, I have become more careful about re-installing wires. Some newer, radio suppressing ignition wires use carbon fiber conductors that are surprisingly brittle and easy to break internally. When exposed to heat over time, the wire components can deteriorate and are even more likely to break. The breakage usually occurs when the wire is being removed. That is one reason that it is a good idea to change wires when you change plugs. If you get the wire routing right the first time, and have never removed a new wire, you can be pretty confident that the conductors are OK. But, if you have had problems and had to remove and re-install them several times, the likelihood of breakage is increased.
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Old 02-02-2008, 11:21 AM   #8
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Thanks so much you guys I had it all wrong I though the firing order was 1-2-3 in front and the back was 4-5-6 was that what was causing the costant misfire? Could it had damaged anything. Also I am going to send pic or spark plug and wires soon. Once again thanks
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Old 02-02-2008, 01:33 PM   #9
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Quote:
Originally Posted by blackssei96
Thanks so much you guys I had it all wrong I though the firing order was 1-2-3 in front and the back was 4-5-6 was that what was causing the costant misfire? Could it had damaged anything. Also I am going to send pic or spark plug and wires soon. Once again thanks
Just to clarify: Firing order is the order in which the cylinders fire and for this engine is 165432. Because our engines have no distributor, knowing the firing order offers little help in properly connecting the ignition wires between the coils and the spark plugs. Cylinder numbering follows different conventions depending on the manufacturer. For many engines cylinder #1 is the cylinder closest to the front of the engine. The front of cross-mounted engines is the end where the belts run. Some manufacturers of V6 engines number one bank odd and the other even; other manufacturers number them as you guessed: 123 on one bank, 456 on the other. When working with different engines, you need to check to be sure how your cylinders are numbered. So, what you had confused was cylinder numbering and consequently wire routing.

This is why it many recommend to change out one plug and wire at a time. That way, if the car was running properly before, it will be running properly after you change out the plugs and wires.
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Old 02-02-2008, 02:34 PM   #10
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Default Found the Problem

I found the problem. You guys were right the firing order was way off and the constant msifire at idle is gone, but it is still a small misfire at idle, and it is still a little sluggish. I think that spark plug wire on #2 is bad because the boot was disconnect from the handle, Ignition coil 3 (3 and 6) is bad (the primary was .04 and the secondary was 5.43), and

I also smelled gas in the oil what could cause that. I think it happened when I flooded the engine or when it was misfiring. [
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