mazdanash626

Cylinder 3 Misfire

19 posts in this topic

Hello fellow 626 owners. I could use some help if any of you have the time. I was recently given a 2000 626 LX-V6 auto. It has 134,000 miles on it. When it was given to me, it had the check engine light on. I ran a code scanner on it, and it indicated "P1131 - Lack of HO2S 1/1 SW, Indicates Lean." I replaced the downstream O2 sensor. The upstream one was recently replaced. Codes were cleared and the light stayed off about 6 miles. Then it came back on. It started to run rougher.

I replaced the spark plugs and ran some fuel system cleaner. Didn't help the issue. So I took it to the dealer. They came back and told me I had the wrong brand of spark plugs (Autolite). They advised I needed NGK. They wanted to charge me $300 for parts and labor for 6 new plugs. I told them to keep it and give me my car back. It was a BS diagnosis. Tonight, I replaced the spark plugs (6) with NGK platinum tips. I also fixed a valve cover oil leak. Issue still persists.

I ran the code scanner tonight and the following are present:

P0133 - O2 sensor ckt slow

P1131 - Lack of HO2S 1/1 SW, indicates lean

P0303 - Cylinder 3 misfire

P0171 - System to lean bank 1

The ignition coil has been replace within the past 2 months.

Any ideas before I call the dealer tomorrow and tell them they were wrong and to give me back my 1 hour diagnostic fee?

Thank you in advance for your help.

MazdaNash626

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The DTC's P0133, P0171 and P1131 all do with the front RH 02 sensor (in the exhaust pipe/manifold firewall side). Check for any vacuum leaks especially between the MAF and intake. The misfire could be a bad plug wire...switch the wire with another cylinders and see if the code follows the wire.

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The DTC's P0133, P0171 and P1131 all do with the front RH 02 sensor (in the exhaust pipe/manifold firewall side). Check for any vacuum leaks especially between the MAF and intake. The misfire could be a bad plug wire...switch the wire with another cylinders and see if the code follows the wire.

Thanks for the info. I'll look into that today.

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So this is what I've done so far. I replaced the fuel filter yesterday. Problem persisted. I then swapped the 3 and 5 cylinder plug wires. Check engine light came back on, but with only one code - multiple cylinder misfire. So I went ahead and replaced the ignition coil today. Turned the car on and it still idled rough. No CEL. I drove it for about a mile and it came back on. Checked the code and it's P0171 - system to lean bank 1.

I can't tell if there are any vacuum leaks. I don't hear anything abnormal under the hood. I guess by abnormal, I don't hear air leaking. I've looked around and some folks are pointing to the MAF sensor, ECM or fuel injectors.

Car was a hand me down. I've already put in about $500 into it. Debating to just put it up for sale and recoup some money. I've read spraying brake cleaner on the MAF to clean it out. Maybe I'll try that tomorrow.

Any other ideas?

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Before trying to diagnos further I'd replace the wires! You go from a cylinder 3 misfire to a multiple misfire tells you something!!

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If misfire DTC's were displayed with the P0171 it COULD be a sign of fuel injector failure.

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u can use carb cleaner spray to check for vacuum leaks

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u can use carb cleaner spray to check for vacuum leaks

Ive used carb cleaner on many occasions to find vacume leaks. Spray along the vac. line and when it hits a leak, your engine will rev up.

Works wonders. Just be careful around electrical. Highly flamable.

Another trick ive used to find a bad plug wire...a spray bottle with water. mist over the plug wire in low light and if its bad youll see the arc.

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So here is an update to this beloved car. After replacing the last O2 sensor and it still not running right, I took it to a mechanic here in town. He was highly recommended by a co-worker. He advised that the camshaft position sensor needed to be replaced. While he was there, he replaced the timing belt tensior and some other gaskets that were leaking. The next day I go to pick it up and it was worse. The car would randomly cut off. He kept it overnight to do more troubleshooting. He finally got it to the way it was when I took it in. Misfire on cylinder 3. He advised me to replace the plug wires (3rd time), ignition coil (3rd time), and the O2 sensor (near firewall) that I just replaced with factory parts. And if that didn't work, EGR valve.

This is getting to be more of a headache that what it was worth. I got the car from my father because it belonged to my sister and she got a new car. Rather than trading it in, he gave it to me. I figured I would put a few hundred dollars into it and be good to go. Wrong. $1,600 later and no resolution.

Just to recap, here's what I've replaced:

Spark plugs (3 times - 1 set with Autolite, other 2 sets with NGK)

Plug wires (2 times - 1 set with Duralast plugs, 1 set with O'Reilly's parts brand)

Ignition coil (2 times - both with aftermarket brands)

O2 sensors (2 upstream, 1 downstream - all bosch branded direct fit)

Battery

The problem with the car is that it has a rough idle and misfires under load. The shop did a compression test and it was good. He also checked for vacuum leaks and there were none.

Any ideas would be greatly appreciated.

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So here is an update to this beloved car. After replacing the last O2 sensor and it still not running right, I took it to a mechanic here in town. He was highly recommended by a co-worker. He advised that the camshaft position sensor needed to be replaced. While he was there, he replaced the timing belt tensior and some other gaskets that were leaking. The next day I go to pick it up and it was worse. The car would randomly cut off. He kept it overnight to do more troubleshooting. He finally got it to the way it was when I took it in. Misfire on cylinder 3. He advised me to replace the plug wires (3rd time), ignition coil (3rd time), and the O2 sensor (near firewall) that I just replaced with factory parts. And if that didn't work, EGR valve.

This is getting to be more of a headache that what it was worth. I got the car from my father because it belonged to my sister and she got a new car. Rather than trading it in, he gave it to me. I figured I would put a few hundred dollars into it and be good to go. Wrong. $1,600 later and no resolution.

Just to recap, here's what I've replaced:

Spark plugs (3 times - 1 set with Autolite, other 2 sets with NGK)

Plug wires (2 times - 1 set with Duralast plugs, 1 set with O'Reilly's parts brand)

Ignition coil (2 times - both with aftermarket brands)

O2 sensors (2 upstream, 1 downstream - all bosch branded direct fit)

Battery

The problem with the car is that it has a rough idle and misfires under load. The shop did a compression test and it was good. He also checked for vacuum leaks and there were none.

Any ideas would be greatly appreciated.

Well bro, since I posted a reply on here, my '99 626 2.5 started missing like crazy. I turn the ac on and it is rough, man, especially at a redlight. Bro, Ive learned over the years to start with the cheapest thing first so I changed the fuel filter (like you, no change) checked my plugs...they are bad so Im going to change them this weekend. But, here is the main question I have. Did the car sit for an extended period before you got it? The reason Im asking is mine sat for about 3 months before all this started. I got to thinking that maybe while it was sitting there with less than a quarter tank of gas, it may have built up condensation in the tank putting a higher amount of water in the gas. I bought some gumout fuel system cleaner (also removes water) and the thing is running alot better. gonna put another bottle in this week and see if it improves more. Hey it is a possibility and cheaper than $70 an hour to a mechanic that cant fix it, lol. One other thing, did you double check the gap on your plugs when you replaced them? That can cause a misfire and also make sure the boots are seated on the plugs correctly. They should "snap" on. Maybe we can put our heads together and figure em both out, lmao!!

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just thought id stop by.

it seems you've done all things electrical, but not fuel.

maybe the fuel pump is going bad or already is?

running lean and misfiring might mean low fuel pressure.

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So here is an update to this beloved car. After replacing the last O2 sensor and it still not running right, I took it to a mechanic here in town. He was highly recommended by a co-worker. He advised that the camshaft position sensor needed to be replaced. While he was there, he replaced the timing belt tensior and some other gaskets that were leaking. The next day I go to pick it up and it was worse. The car would randomly cut off. He kept it overnight to do more troubleshooting. He finally got it to the way it was when I took it in. Misfire on cylinder 3. He advised me to replace the plug wires (3rd time), ignition coil (3rd time), and the O2 sensor (near firewall) that I just replaced with factory parts. And if that didn't work, EGR valve.

This is getting to be more of a headache that what it was worth. I got the car from my father because it belonged to my sister and she got a new car. Rather than trading it in, he gave it to me. I figured I would put a few hundred dollars into it and be good to go. Wrong. $1,600 later and no resolution.

Just to recap, here's what I've replaced:

Spark plugs (3 times - 1 set with Autolite, other 2 sets with NGK)

Plug wires (2 times - 1 set with Duralast plugs, 1 set with O'Reilly's parts brand)

Ignition coil (2 times - both with aftermarket brands)

O2 sensors (2 upstream, 1 downstream - all bosch branded direct fit)

Battery

The problem with the car is that it has a rough idle and misfires under load. The shop did a compression test and it was good. He also checked for vacuum leaks and there were none.

Any ideas would be greatly appreciated.

Well bro, since I posted a reply on here, my '99 626 2.5 started missing like crazy. I turn the ac on and it is rough, man, especially at a redlight. Bro, Ive learned over the years to start with the cheapest thing first so I changed the fuel filter (like you, no change) checked my plugs...they are bad so Im going to change them this weekend. But, here is the main question I have. Did the car sit for an extended period before you got it? The reason Im asking is mine sat for about 3 months before all this started. I got to thinking that maybe while it was sitting there with less than a quarter tank of gas, it may have built up condensation in the tank putting a higher amount of water in the gas. I bought some gumout fuel system cleaner (also removes water) and the thing is running alot better. gonna put another bottle in this week and see if it improves more. Hey it is a possibility and cheaper than $70 an hour to a mechanic that cant fix it, lol. One other thing, did you double check the gap on your plugs when you replaced them? That can cause a misfire and also make sure the boots are seated on the plugs correctly. They should "snap" on. Maybe we can put our heads together and figure em both out, lmao!!

That describes a lot of what's going on with my 626. I ran fuel system cleaner in it twice. No change. It probably sat for a 2-3 weeks with a quarter tank of gas. When I first got it from my dad, it had a check engine light on that was stating it was running lean on one of the O2 sensor banks. I replaced the downstream O2 sensor and it seemed to work fine until the next day when the light came back on. I drove it some more for about a week until it started idling rough and started to run bad under load. That's when I started throwing parts at it. I replaced the spark plugs. The original plugs were Autolite. They worked fine the previous 5 years my sister owned it. No change. Changed the fuel filter. No change. Took it to the dealer. Spent $90 for them to tell me I had the wrong brand of plugs. BS. But I changed it anyway to NGK. No change. Then I changed the wires. No change. Then the ignition coil. No change. Even replaced the battery (needed it anyway). No change. Somewhere in between there I ran the fuel system cleaner.

The shop I took it took to told me I had to replace the plugs. I said What?!?..they're brand new. He told me 3 of them were and 3 were old. The 3 "old" ones look like it had rust on them or something. Don't know how it got there, so he replaced them with NGKs again. That's when he diagnosed the camshaft position sensor. My dad replaced the camshaft and crankshaft position sensors back in November 2009.

Fuel delivery is the only route I haven't gone. The reason why I haven't is because it's always consistent to cylinder 3 misfiring. Even when my dad had it, he said cylinder 3 was misfiring. If is was fuel delivery, wouldn't it be random misfires?

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The reason why I haven't is because it's always consistent to cylinder 3 misfiring. Even when my dad had it, he said cylinder 3 was misfiring. If is was fuel delivery, wouldn't it be random misfires?

hmm your right...

but did you mention sluggish feel and the likes as well? or only a #3 miss?

the only other world that would cause issues would be internal...

hair crack on #3 chamber or valve not sealing all the way...ect ect

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The reason why I haven't is because it's always consistent to cylinder 3 misfiring. Even when my dad had it, he said cylinder 3 was misfiring. If is was fuel delivery, wouldn't it be random misfires?

hmm your right...

but did you mention sluggish feel and the likes as well? or only a #3 miss?

the only other world that would cause issues would be internal...

hair crack on #3 chamber or valve not sealing all the way...ect ect

It did feel sluggish at one point. I would depress the throttle and it wouldn't respond like a normal car would. After changed the coil pack and plug wires, it seemed fine. I don't know anymore. This shop and the one my dad took it too when my sister had it are doing almost the exact same things. Perhaps no one knows what it is. Maybe it could be a wire that's frayed or who knows.

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Have you checked the fuel injector for cylinder 3? You said earlier in the thread that some people were pointing you toward the injectors, yet it appears that you haven't checked them. I think it would be worth your time to switch the injector from cylinder 3 with another cylinder. You can then see if the other cylinder starts misfiring. The cost of doing this is FREE.

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Well here's the good news. After giving up for a couple of months, I decided to take the advice I was first given from a friend. I changed the fuel injector for cylinder 3. After taking out the fuel rail, the #3 injector was gummed up. It had lots of carbon deposits around the nozzles. Ther other two injectors were much cleaner. After replacing it, the car ran PERFECTLY! Smooth idle, smooth shifts, everything.

I put on about 51 miles and the CEL came back on! Awesome right? I took it by the parts store and the same codes came up again - P1130 and P0135 (O2 sensors). Crazy thing is that I've replaced all 4 sensors. I would love to drive it as it is, but I need to get it through emissions or else I can't get tags for it.

Any ideas?\

Thanks!

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Both codes point to the Front Right Hand (firewall side) O2 Sensor. The P0135 could be causing the P1130. Probably a defective harness. Use the attached testing procedures to troubleshoot.

DTC-P0135.pdf

DTC-P0135.pdf

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