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Old 10-17-2013, 01:14 PM   #1
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Default Sudden intermittent high AFRs. Car responds to higher VE #s

Alternate Topic Title: My car is being a F#&king Punk.

The past several days I have been having this intermittent problem.

I will be driving down the road and at some point the car starts running REALLY rough. My AFRs spike to max and I limp it to the side of the road. The first couple times I tried disconnecting and reconnecting plugs (FPR I think?, IDLE, EGR) and miraculously it started running fine. Because I couldn't see the laptop from where I was standing I didn't know which plug fixed it.

So today I was driving to work when all of a sudden it happened again. I pulled off the road and pulled the EGR plug and left it disconnected. I saw that my AFRs were back to normal so I started driving. This was no big deal because I had been contemplating removing the EGR entirely anyhow. A couple miles down the road, the AFRs spiked again. Now I am really concerned.

There has to be one of a couple things going on. Either I have not enough fuel, or too much air. I think I was able to bypass the too much air thing by unplugging the EGR coil, but I am not sure how that works exactly. Either way, I don't think that the small amount of hot air going into my intake manifold would be enough to spike the AFRs this badly.

So, I think I have a fuel problem. I created a limp map to get me to work this morning that consisted of multiplying my standard and idle VE map by 1.25. Even then, it ran like crap. The AFRs stayed in the 10-15 range though so I at least felt safe driving on very light loads the last two or three miles.

Looking at the log I have steady MAP, RPM, PW, MAT, everything leading up to the sudden spike. Total Corrections are not spiking either.

Additionally, I have noticed that my AFRs have been moving quite a bit on a steady load. By quite a bit I mean almost a full point at steady temp, throttle, load, etc. Under boost I have been having problems where I will go rich enough but I occasionally have spikes of lean (by about a point) for a split second. This sounds like useful information to me.

What do you think is the problem? What is more likely based on my symptoms? Injectors, FPR, Fuel Pump? Other?

Car is MS3, sequential fuel and wasted spark. Log will be a attached shortly.

I don't feel safe driving it even with the limp map more than a mile or two and I work about 35 miles from home. I am hoping I can get it at least close enough for my towing service not to cost me out of pocket.
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File Type: msl 2013-10-17_10_modified.msl (692.0 KB, 74 views)
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Old 10-17-2013, 01:23 PM   #2
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I think you're mis-interpreting this. You probably have a basic misfire going on. When you misfire -- for any reason -- you end up with oxygen in the exhaust that gives a lean reading. It does not mean you are actually lean.

You probably have an ignition issue -- maybe a crank sensor going out.
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Old 10-17-2013, 01:27 PM   #3
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Ahh, I should probably do a trigger log or whatever it's called next time it happens.

It definitely feels like a miss. Any other ideas?

As dumb as it sounds, could it be my harmonic balancer being loose? I will go yank on it when I have a few minutes free.
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Old 10-17-2013, 01:33 PM   #4
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I wouldn't think a harmonic balance would correct itself.
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Old 10-17-2013, 01:47 PM   #5
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Thinking out loud... If I was having an ignition issue would I be able to get indicated AFRs in the normal range by upping my fuel like I am doing?
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Old 10-17-2013, 03:43 PM   #6
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What I saw from your write-up is that this is an intermittent issue and you haven't been able to isolate the cause. You also mentioned that you multiplied the entire VE table by 1.25 (note to self . . . Req. Fuel might have been easier) and the car still "ran like crap."

BTW, I don't know that it's an ignition issue. Could be fuel. I just didn't want you thinking that a lean reading means lean fuel when you're misfiring, because it may not mean that at all.
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Old 10-17-2013, 04:25 PM   #7
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Good point on the Req fuel. I didn't think of that.

I have heard horror stories of catalytic converters catching fire due to so much fuel in them...

It does indeed FEEL like a misfire, but then what does it feel when you go really lean? My knock sensor isn't picking up any more noise than normal. Maybe that swings the needle back to the ignition? Maybe I should pull a plug wire and see if it gets worse or doesn't matter at all.
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Old 10-17-2013, 04:27 PM   #8
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Change your plugs? I fouled mine, it ran like crap after it started, but after 15 mins of highway driving it ran (almost) just fine.
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Old 10-17-2013, 04:34 PM   #9
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A plug inspection would be a great first step no matter what.
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Old 10-18-2013, 10:12 AM   #10
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I will be picking up a coil today unless I can find one to borrow. The more I think about it the more the coil makes sense. I half want to create two maps that disable two of the injectors so I can just run it on two cylinders to limp it off the road should it happen again.

Even if it isn't the coil causing the problem, it is a good idea to keep a spare coil around from what I hear.
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Old 10-18-2013, 10:18 AM   #11
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Coils are easy to test. Idle the car and remove plug wires 1 at a time until you find the one that doesn't change anything. If all 4 have an effect on the idle it's not coils.
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Old 10-18-2013, 10:50 AM   #12
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The problem is that I drove it home last night with only a few hiccups of no more than 3 seconds each. It's kinda hard to troubleshoot when it's running fine.

My thought is I will pull the plugs and see which of the plugs looks like it has had been though abnormal conditions (black, sooty?) and replace that coil and drive it. If it still has problems, switch coils on the side of the road. Drive it some more...
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Old 10-18-2013, 11:25 PM   #13
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Swapped coils. Took a short drive , and I am sitting on the side of the road as we speak. High AFRs... Update when I get home.

UPDATE:

Home safe. Car ran better after upping required fuel number but still felt like a miss. I pulled plug wires for cylinders 1 and 3 and they both sparked.

At this point I am thinking maybe I have an intermittent injector? Any other ideas?

Last edited by Chiburbian; 10-19-2013 at 12:20 AM.
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Old 10-20-2013, 05:39 PM   #14
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Today I replaced the stock "high-pressure" fuel filter that is just outside of the tank. Immediately after replacing the filter I did a pressure test on the outlet of the filter and got 58psi, both while static and while running.

The crud that drained out of my old filter looked like tea with milk.

I then hooked up the fuel line to the outlet of the filter, buttoned it all up and started the car again.

I started the car, my AFRs were looking fine. I did a small drive but by the time I got out of my driveway the AFRs were sky high again.

Now that I had a malfunctioning car I figured I might get a little further with troubleshooting. I placed the pressure tester between the fuel supply and damper #1 in the engine bay. I started the pump via the diagnostic port and did not read a single PSI on the gauge. I started the car, high AFRs and again, not a single PSI indicated. With engine off, I removed the tester from the "T" and let the pump run for a minute via diagnostic port. I then (with a rag to catch the leakage) pressed in on the schraeder valve to see how much came out. It was barely a dribble. If there truly was any meaningful pressure in the line I imagine it would be quite a shot out of the valve.

So, I am thinking that it might be a pressure regulator that is sticking open, returning nearly all of the fuel to the tank.

Any thoughts? Am I testing it wrong?
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Old 10-20-2013, 07:12 PM   #15
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Based upon the condition of the fuel from the filter, I suspect you've contaminated the fuel system and your fuel pump may be toast. Maybe flow test the fuel pump first.

If fuel pump is bad, replace but also flush the system and clean the injectors.
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Old 10-20-2013, 07:20 PM   #16
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I idled the car for about an hour and every time I started to go lean I revved the engine which got it to get back to the correct AFRs.

I still wasn't showing any fuel pressure so I must have had it connected wrong?

Anyhow, I took the tester off the fuel line and hooked it all back up. Once again, AFRs stuck high. When I took off "t" it sprayed fuel everywhere like I had expected it to do earlier. This is right after the car had been running fin and even after I pulled the fuel pump relay and run the car till it stopped running.

I am letting it cool down to ambient to see if anything changes.

I wonder If either I am the subject of vandalism or perhaps I got some bad fuel at some point in the past. I am really afraid that I may have to end my year with pulling the tank and having it steam cleaned.
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Old 10-20-2013, 09:13 PM   #17
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That would really suck if someone put sugar in your tank.
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Old 10-21-2013, 12:06 AM   #18
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Ok, after some deliberation here is my plan:

Siphon fuel from Miata to my winter beater.
Put about a gallon of the best 93 octane I can find in it.
Throw a fuel system cleaner in, and an additional four gallons of good stuff.
Drive it around my neighborhood, try and slosh it around as much as possible. Anytime the AFRs go high, park it. After about two hours of collective driving, no matter how long it takes around my neighborhood, siphon the rest into my winter beater.
Throw two gallons of good stuff in the tank, see if I can go more than 3 minutes without having a lean spike.

If that works, go ahead and leave my neighborhood.

Otherwise, order fuel pump. Depending on what the tank looks like when I pull the pump, I will decide wither or not to pull the tank for a full steam clean.

Or, is injector cleaner a waste of money and I should just do the fuel pump?
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Old 10-22-2013, 10:57 PM   #19
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Change of plans.

I swapped the cam sensor per Savington's recommendation and that didn't fix it so I started wiggling wires in the engine bay, especially stuff like injector harness etc. Sure enough, when I wiggled the injector harness towards the back of the block the pitch of the engine changed. I squeezed wiggled the harness and sure enough the engine died - as did my megasquirt. Luckily it was just the 30A injector fuse.

Looking at the wiring diagram, 12v is supplied to the injectors, fuel pump, and ECU via the INJ fuse. Somewhere down the line that 12v is being shorted either directly to the block or perhaps to grounds that might also be in that bundle.

This may not actually be my problem but it makes sense. I have heard stories of insulation breaking down especially when subject to vibration and heat. I am going to pull the upper manifold tomorrow and see about removing the injector harness.

We will have to see if the wires are salvagable or if I will have to do some splicing. Also I need to figure out what is causing this wear. I wonder if I might have forgotten to fasten down the bundle at some point and the vibration in addition to the heat might be degrading the wires quicker than normal.

Tonight was one of those situations where something failed but it made me smile because that failure pointed me in a direction of something that is consistent with my problem.
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Old 10-23-2013, 11:42 AM   #20
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Yay! Progress.

I've had one ocassion where insulation rubbed through due to harness contact with the intake manifold. Luckily, in my case it was just a water temperature sender wire. Anyway, fixed the wire and added Adel clamps (padded clamps) and tie wraps to avoid a repeat. It happened at the firewall side of the intake manifold. You'll find that the harness makes a lot of turns back there and can easily come in contact with the IM. Injector harness runs through that area too IIRC.
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