David Elliott

Flashing Check Engine Light

28 posts in this topic

Our 2001 Mazda 626 has about 158,000 miles... last night my wife was driving it and about 3 miles from home, the check engine light started flashing and the car was running rough.

I changed oil (which was about due) and the oil level looked really low before I changed it. I also changed the plugs, but there is no change in the engine. The engine is shaking a bit as well.

I'm not sure what to check next. I'm afraid to get it over to Pep Boys to run a diagnostic... any input is appreciated!

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welcome to the forums, sorry to hear about your problem. as a start point are there any other symptoms? smoke? does it idle fine? any funny smells/noises? and any fluids dripping out of the bottom of it?

i'm afraid an engine running rough could be caused by so many things we might be stabbing in the dark for a while... i'll get back to you with a way to pull your own codes from the engine...

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Thanks,

I do know the check engine light comes on (steady) for a few days and shuts off for a few days. Other than the engine running rough, nothing else is amiss! The engine vibrates and shakes... and no fluid leaks

I may be brave and bring it to Pep Boys...

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since you changed the plugs and just did an oil change look to see if you bumped a Vacuum line off just in case it is that simple of a fix..

Welcome to the boards .

Dan

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Alucard, since you have an 2002 do you know if it's possible to jumper pins with an OBD-II car. Do you have the same diagnostic box near the fuse box that the 93-95's have where you can jumper it and use the check engine light?

Vibration is associated with rough running. Two go hand in hand. What's different is really bad almost violent shaking of the engine or interior dash. Had that happen to me. Can you get some video or audio so we can see/hear the vibration. The longer the video or audio the better.

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Dan, I will check the hoses, but the rough running was the reason I changed the oil (overdue, actually) and the plugs. I will have to get a video as soon as I can...

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another item item to look for is the FPR (Fuel Pressure Regulator) mine was running funny this time last year and it was the FPR leaking thou the Vacuum hose..

Dan

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That caused vibration? I would have thought it would stall. If it's borderline stalling yeah that will certainly cause a heavy vibration but it should have an erratic idle, it shouldn't run that rough all the time. Weird. I'll have to remember that one.

David, something else you could try is taking out the spark wires one at a time and see if the engine runs worse each time (which it should). Are you sure it's just running rough and not misfiring? If it doesn't then you've found a bad ignition wire. Don't overlook rough running issues because of bad spark. Visually inspect each wire for rubbing, fraying, or arcing to the block. It's possible spark is lost through the boot itself so inspect the inside of the boots the best you can for carbon tracks.

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once in a wile yes.. but it took me a month to finally figure it out..and I was surprised to find it was the FPR as I have never had to change a Mazda one before.. not only that this is my Daily Driver and working 7 days a week does not give me a whole lot of time to play\fix the cars..

Dan

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David, do you have a 2.0 I4 or the 2.5 v6? The blinking CEL means that it is detecting an ongoing problem, in your case likely a misfire detected. My next guess would be the spark plug wires.

Many of the local parts stores can loan you a code reader and that may help to narrow the chase.

btw I had a v6 that often had trouble with a random misfire, but it certainly wasn't a cheap fix. I'll have to check exactly what that was.

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It is a 4 cyl... I changed the plug wires within the last year, so I doubt it's those, although anythings possible.

I will check all hoses... I do know there is a large one from the air filter that takes in fresh air (it appears) that was all cracked up... as a quick fix I wrapped it pretty good with electrical tape. However, if that one was as bad as that, there may be others that are needing to be replaced, too...

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All right... here is a video I just took. The vacuum lines all seem ok... I put a new PCV valve in about 8 month ago. My wife thinks it is a motor mount, but I don't think it's that (so I need input). There is an ozone smell coming from the exhaust, too... so I'm not knowing if a catalytic converter problem would do something like this.

djdevon... we have an AutoZone nearby but I have tried to get a free code scan from them in the past and was turned away... maybe that's changed.

VIDEO

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I wanted to check the distributor, but it is a distributorless system. My Haynes book says to replace if the module is cracked, but the cracks I see are by two of the mounting holes (on the edges) and not in the module itself.

There are two weird looking hoses in the back of the engine... they are woven and very lightweight. One looks like it is unweaving apart, but I don't know what these hoses are for and I don't want to mess with them, as they are hard to get to...

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Thanks for the video. That helps. Can you take some video or a good clear picture of the cracks in the module? It's possible that cracks in the module could be creating the problem.

Looks like you've got some serious vibration going on there. I have seen engines lose spark on a cylinder (for whatever reason) and shake like that. They won't shake that bad when the engine is running properly so it's not a bad engine mount. Your wife made a good guess but your engine won't vibrate that hard only due to a bad mount. The engine is shaking for other reasons. Basically, one of your cylinders isn't running correctly. It could be a simple no spark issue or something more serious like compression loss.

You have an OBD-II car. Is it possible for you to invest in an OBD-II code scanner yourself? I believe most AutoZone's do offer free code scans. At least they do in my area and for just about everyone else I've met on these forums. After doing some research it seems that AutoZone and other retailers stopped providing free scans a couple years ago in California. Whether they started back up or not I don't know. So I would call first just to make sure either way. That is providing you're comfortable making the trip there and back. If not, invest in a cheap code scanner and do it yourself from the comfort of your own driveway. Doesn't have to be anything special with bells and whistles. Just enough to give you a readout of your codes.

Once you get the codes and check for good spark on each cylinder, report back with results and we can go from there. We can help you get it diagnosed one step at a time but you have to do the legwork.

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Ok... here's some more pictures... the cracks I see are on three of the corners. I don't think this would affect the ignition module, but who knows?

I also added pictures of two of the plug wires where they plug into the module. Again, I changed these less than a year ago, but they look a little corroded (just slightly).

Something my wife reminded me of... for a while the number one wire would come loose from the plug, so I was running on 3 cylinders until I plugged it back on. It's been fine for about six or seven months, but when I changed the plugs a few days ago, the wire was REALLY sung on there. I'm not sure what bearing that would have on anything, but I figure I should mention that, too...

img-325517-1-626a.jpg

img-325517-2-626b.jpg

img-325517-3-626c.jpg

img-325517-4-626d.jpg

img-325517-5-626plugwire.jpg

img-325517-6-626plugwire2.jpg

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Looks like stress cracks on all the mounting bolts. I don't think that's normal either. It's possible they were over tightened and any amount of engine vibration could lead to that. The wire and module terminals look in good condition. If there was any arcing going on it would look out of the ordinary and probably show up as a carbon tracked line maybe even a few little burn spots on the rubber boots. Nothing jumps out as looking bad. Actually I don't see the corrosion your talking about. The terminals are a nice shiny silver and that's all you need for good contact. If you see any places that do have corrosion use a wire brush to clean it up the best you can. Use some dielectric grease in the boots to prevent arcing to the boot.

The cracks look more like a symptom of engine vibration not a cause.

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One other thing I just noticed as I was getting the ignition pack back in... What sensor is this that I have circled? The insulation for the wires is cracked, but don't know if the wires themselves are damaged. The wires seem intact and they are not stripped so that bare wires are touching.

I am still checking on the diagnostic tool...

img-325520-1-sensor.jpg

img-325520-2-sensor2.jpg

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djdevon.. thanks! I thought as much on the pack, but being a VW airhead I'm not too familiar with more modern cars like this ;-)

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the thing you have circled is your oxygen sensor, part of the emmision control system, is possible for a bad one to cause rough idle but not for it to knock out one cylinder...

and dj, it appears that while america got obd2 in their 5th generation 626's the european ones still run obd1... to my knowledge all obd2 sockets should be dl16, ie 16 pins a bit like the old serial port connector, i still have the old self diagnosing jumper wires...

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Thanks... I don't know if it has knocked out a cylinder or not... I think we are just assuming that? It doesn't feel like it, at least...

So yes, my question is if the wires on the 02 sensor are cracked, will that cause rough idle and a flashing CEL?

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Bad O2 can cause rough idle and some cases misfire on one or more cylinders. If you have other issues such as a vacuum leak, it will throw the air/fuel mixture even more out of range. There comes a point when the car won't be able to compensate for the variables it cannot account for. Bad O2 sensor and vacuum leaks would certainly make the car run rough. Since the car doesn't use the O2 data until the car warms up it should theoretically run best for the few seconds after the car is started. When it warms up that's when it should be at it's worst. This is all just best guess though. You have to get in there and take some readings via backprobing and get a code scan to be in a better situation.

O2 sensors are measured between 0 and 1 volt. If you have a multimeter you can probe the wires and check the reading yourself to see how it's performing. Good sensors will regularly switch from between .2 to .7 voltage on a constant pattern. If it is switching irregularly replace the sensor.

This is an excellent video on O2 sensor diagnostics. He uses an oscilliscope which of course the majority of us don't have. This will give you a visual learning pattern into how an O2 sensor reports data.

Then use what you've learned there you can use a multimeter to see if it's switching properly as seen here.

I don't have a manual for the 98-02's and I'm not going to speculate which wires should be probed

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I think I know enough... Yes, the car seems fine for the first few seconds and after it warms up is when it runs rough and the CEL starts blinking. I just may invest in a new sensor anyway, as the one in there has been in there for 160,000 miles or so.

The vacuum hoses I see are associated with the PCV and those are not cracked at all. I don't know if there are other vacuum hoses, though.

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There are vacuum hoses all over the place. I'd check your throttle body gasket as those tend to break down more than any other gasket in the car. If you have a vacuum leak that would be a prime suspect. Check your intake tubing for obvious tears. If it's big enough it will make a hissing sound.

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