Got Smoke

snip: I don't think having spark would make any difference with all that fuel.

My god, how much fuel can you be talking about that, having a spark wouldn't make a difference? That seems totally nonsensical to me. I mean, your injector is squirting fuel in there every time the plug is supposed to fire. If it doesn't fire, there will surely be gas buildup which, correct me if I'm wrong, one spark can pretty much take care of just about ANY amount of gas real quick. Sounds to me like a coilpack problem or a worthless plug wire. Did you try switching plug wires (careful)?

Chris

Put in a new set of wires and coil pack. Didn't do the trick, unfortunately.

Ken

Chris D'Agnolo wrote:

Could it be a totally defunct lifter or something along those lines? How many miles does your engine have on it?

As far as the injector, your thinking it might be spraying a steady stream all the time instead of properly pulsing?

Chris

I wouldn't rule out anything right now. It's got 182K but has always been well maintained.

That's the thought. That's why I am looking at the procedure in the shop manual that checks for that very condition.

Thanks,

Ken

I'll try to keep this short and invite comments. Sad to say: it appears to have "fixed itself".

I did the injector test. Wired the injectors to the fuel rail, disconnected their plugs and pulled them free from the engine; jumpered the F/P to GND connections in the diagnostic connector and had an assistant turn the key.

You could see the tension on the assembly as the fuel pump kicked in. But nary a drop of petrol was to be seen on any of the four injectors.

Looking at the wiring diagram revealed something that probably everyone in the Miata community except me already knew. We all know that each spark plug fires twice, during the power cycle and the exhaust cycle. If I recall correctly, Mazda did this to ensure proper burning of the exhaust gases. What I didn't know, but it makes sense, is that fuel is injected for both "top of the cylinder" events (power and exhaust).

How do I know this? Because the wiring diagram clearly shows the fuel injectors for the #1 and #3 cylinders wired in parallel. The #2 and #4 cylinders are similarly wired.

And that brings me to the bit of investigation that I missed. I pulled the #1 plug and it looked pretty much OK. I then pulled the #2 plug and it was soaked with gasoline. Then (and this is the mistake part)I stopped pulling spark plugs. Had I continued, there is a good chance that I may have found plug #4 to have been similarly affected.

I realized this once the injectors passed their leak test. I pulled the #4 plug, it looked like it had a bunch of carbon on it, but no gas. Of course, the car had not run for over a day, so the gas may have evaporated. I then put everything back together to see what would happen next. Had the rough running and dumping of fuel through the system continued, I could have pulled all four plugs to see what's what.

But, of course, the car started and ran fine.

I don't know all that much about fuel injectors. Can they be commanded "on" all the time? If so: I am thinking it may be a problem with the ECU. Why? Because it comes and goes. I could imagine an injector that sometimes fails to inject. How about an injector that sometimes always injects. Does that make sense?

So if someone would like to suggest something other than the ECU, I am all ears. I haven't seen anything written about a problem like this, but perhaps someone else had a similar experience.

Thanks!

Ken

KWS wrote:

It wouldn't hurt to clean all of the chassis ground points until the metal is shiny. You can search miata.net for their locations. Flaky grounds can make the ECU wonky. (The usual early sign of grounding problems is a jumpy tach, but who knows?)

Thanks, Lanny. Can't hurt. I did search and didn't find much. Can you suggest a search term? I tried "ground", "grounding", "electrical ground". I even tried "shiny". Zip.

I recall seeing this written at one time or another, but it isn't showing up.

Ken

Lanny Chambers wrote:

I had what may have been a similar problem on my '93 ( now 186k and rolling).

It would occasionally load up with gas and run very rough. It would generally only happen after it had been running a short while, was stopped for a few minutes, then restarted. It would be flooded when trying to restart, then would take a while to burn the cylinders clean.

I also thought that I had leaking fuel injectors, so had my local garage run a fuel system cleaner through. This was not a can of additive that is put in the gas. This was a closed type system that is probably the same cleaner that is used by the injector cleaner/rebuild services, but is done on/in car.

That may have helped things, but the problem would still occur. I manually read the error codes, and half the electronic system had errors. So I think Lanny's note about cleaning grounds is appropriate. I checked and cleaned all engine compartment grounds and ... I used good quality electrical cleaner, and heavily cleaned all connectors between the CAS and the coil packs. Also cleaned the connectors on the ECU itself.

That did the trick.

Now if it gets a little rough, I spay down the coil packs and connectors, and have not had the problem since.

The primary circuits (trigger) to the coil packs are near the bottom of the packs, and partially exposed. It is a good place for oil, dirt, and grease to accumulate. Add a little moisture, and strange firing can be expected. Spray heavily with the electrical cleaner to get the junk off, and ensure that the connections are clean.

Note, there are a few types of electrical cleaner. Some have lubricant in them and are designed for switches and rheostats. Do NOT use this type. Also make sure that the cleaner is safe for plastics and rubber. No reason to create more problems.

Good luck.

Thank you, Sir. Nothing speaks louder than results. I'll definitely give it a shot.

Ken

Stephen Toth wrote:

I have found this corroded ground connection point to be at fault of many ground problems.

My 91 had ground gremlins that would shut off the fuel pump. I'm not sure cleaning the grounds will cure things in this case, but it is a very cheap and quick preventive maintenance that might very well save some grief in the future. Many have moved the ground cluster that I have pictured, to a higher spot on the firewall to keep it out of the slop that tends to collect in that area.

Good luck and keep us informed

Thanks, Mike

Here is the latest:

I have been driving the car all week without incident. The more I think about it, the more I am convinced that the problem was a stuck fuel injector. I suspect that my messing around with them freed up what was probably a stuck armature.

So if it occurs again, the first course of action is to do a little percussion on the fuel injector at the #2 cylinder. I strongly suspect that will fix the problem. I will probably not wait and swap out the injector.

I will look into the grounds. I found a few others that I cleaned and re-attached.

Ken

Mike wrote:

I have the same problem. I have a 90 miata with 177K miles. I have lots of white smoke and unburned fuel come out of the tailpipe and on the header as well. I posted my problem on the miata.net.

I was told I have a blown head gasket by couple of mechanics. However, my car never overheat or lose any coolant. Oil and coolant are ok. No oil in the coolant and no coolant in the oil which is the symptons of a blown head gasket. I checked all my spark plugs, 3 out of 4 are ok but on # 3 cylinder, the spark plug is covered by unburned fuel. I disconnected the wire off the fuel injector on the # 3 cylinder which left me to run on only 3 cylinder. Leaving the wire unplugged on the fuel injector on # 3 cylinder, I ran the engine no more white smoke. Turned engine off and plugged the wire back on the # 3 cylinder and ran the engine again, white smoke came back. I think I have bad/stuck fuel injector. The fuel injector keeps spraying fuel all the time. I don't know how to fix a stuck fuel injector other than replace it. you got your fuel injector unstuck, how did you do that?

Sam

KWS wrote:

Hi Sam,

Sorry this response is taking so long; I haven't monitored this newsgroup for several days.

When I pulled the fuel rail to check the injectors, the injectors were OK. They remained OK when I re-installed them and are so to this day. So the problem, unfortunately, "cured itself".

The big question: is the problem caused by a sticking fuel injector armature or is the ECU commanding the injector "on" all the time? When you pulled the plug (which was a very good diagnostic technique), the problem went away and returned when you reconnected it. That means that the injector remained closed when you had the plug disconnected; suggesting the ECU is the source of the problem.

In your Miata, however, the #3 and #1 injectors are activated at the same time. Therefore, an ECU failure such as that described would affect both injectors, not just one.

So it does not look like an ECU problem. Thanks, by the way, for doing this.

There might be some sort of friction in the injector that keeps the armature from returning to closure between fuel impulses. Once you remove the drive, however, the spring eventually brings the armature to the unactivated position and the valve is closed.

My next step, when the problem occurs again, would be to perform a little percussion on the injector to see if it becomes "unstuck". That means I would tap it or, depending on how you measure force, beat on it a little.

I bought some used injectors off of eBay and am awaiting their arrival. What I will probably do is chicken out and replace the #2 (in my case) injector with one of them and see what happens.

Depending on how the injector is constructed, I may do a failure analysis on the suspect part. I am actually in the business of doing FA, so it might be fun.

Good luck with your problem. Keep us posted. I promise to read more often.

Ken

sam snipped-for-privacy@yahoo.com wrote:

case)injectorwith one of them and see what happens.

Hi Ken,

I got my fuel injector unstuck and the car is running normal again. I used a 12mm wrench and gently tapped on the bad injector and that did the trick. No more white smoke and fuel consumption is normal again. With all the unburned fuel going thru the oxygen sensor and catalyst converter, i think they might have been damaged. How are your oxygen sensor and catalyst converter working after the stuck fuel injector started to work again?

Also, I found some companies that we can send our fuel injectors in to be clean/rebuilt. It sounds better than buying brand new which can cost up to $100 each injector. Here's a video from youtube that shows how they clean fuel injector.

case)injectorwith one of them and see what happens.

Hi Sam,

Thanks for doing the test that I planned to do when the injector hangs up again. You clearly identified the problem as being with the injector. And, you saved me some work.

I also have a concern about the catalytic converter. The O2 sensor didn't appear to be bothered by this; the car runs great. I'll know more about the converter when emission testing rolls around again.

I suppose that cleaning the injectors makes sense. The reason yours (and mine) hung up is probably due to sludge of some sort from the fuel. So they probably force something other than gasoline through them that cleans them up. Ultrasonic cleaning is certainly effective.

You can probably do something similar by putting them into an appropriate solvent and exercising the coil. The action of the armature going back and forth will likely agitate the solvent internally and break the crap free. One way to tell would probably be to put the injector into a clean beaker of solvent, pulse the coil and see if anything disgusting comes out the ends. Whatever doesn't get cleaned out by this method will likely be gone when fuel starts through again.

I bought four used injectors off of eBay. I paid like $35 for the injectors and shipping. One course of action is to send them to the place you noted, pay the $80 and then swap out the ones currently in the car after they come back. Another is to do it myself. Thanks also for doing this research.

All the best,

Ken

case)injectorwith one of them and see what happens.

a clean beaker of solvent, pulse the coil and see if

Hi Ken,

I made this short video when my miata had the stuck fuel injector.

Were those your symptons as well?

I did tried to bid on ebay for some used fuel injectors. I didn't win. I don't have time to stay up with the bid.

Sam

case)injectorwith one of them and see what happens.

a clean beaker of solvent, pulse the coil and see if

That looks like it, Sam. When you rev the engine, big clouds of white smoke came out, right? I also had the puddle of gas that you see on the ground below the tailpipe.

Yep...that looks like it.

Ken

case)injectorwith one of them and see what happens.

theinjectorinto a clean beaker of solvent, pulse the coil and see if

Yep lots of white smoke when I rev the engine. It was hard to believe that is fuel coming out of the tailpipe until I saw it with my own eyes, 2 gallons gone on idle just under 10 minutes. I wonder why my car didn't caught fire.

sam

case)injectorwith one of them and see what happens.

theinjectorinto a clean beaker of solvent, pulse the coil and see if

The interesting part of this is that nobody else has talked about the same experience. Considering the huge number of Miatas and the fact that they easily go 200K miles, I know that there are more stories like ours. But, perhaps, somebody reading this will save themselves the grief that you and I went through to diagnose this. Of course, it's been a little fun and a learning experience.

Perhaps I'll do a writeup for Miata net.

All the best,

Ken