DivinDriver

iTrader: (15)

Take this as intended, Whisper... but you kinda are making me glad I'm carburetted.

Whisper

Well, carbs have their own problems, though, don't they. It's not like fuel injection is the carb's evil twin. I have other fuel injected cars and they run smooth as butter.

I have a feeling that if I were to slap a carb on this one, it wouldn't fix anything.

jinxed4dub

iTrader: (7)

hows the voltage at the fuel pump, and have you checked fuel pressure/volume , kinked lines, TPS?

Whisper

Don't know, yes/no, yes, and yes.

Whisper

Ok, I've nothing else left to check so I took it to Lee Johnson Mazda - they have a guy there who's experienced with the old 7s. Had them run the compression test, vac leak check, mixture check, and all that diagnostic stuff. Overall everything checks out, so I guess that's about it. All things considered I suppose this is as good as it's gonna get, I'm just gonna drive it to a grand and see if it smoothes out.

Meh.

Kentetsu

A couple of years ago we installed a used 12a in my car, and got the wrong flywheel on it. The result was a vibration at idle, but seemed to go away with higher rpms. It was just bad enough that I knew something was not right. I would try to find out exactly what flywheel was installed.

I assume you have verified that:

a. Your spark plug wires are routed correctly (don't laugh, it happens)
b. Your leading ignitor is actually controlling your leading plugs

I was also going to suggest running a can of Seafoam through the gas tank, in case you had a minor clog in an injector, or a sticking apex seal. But you seem to have covered both of those using other methods.

Good luck...








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DriveFast7

iTrader: (1)

I watched the video and the vibrations don't look bad. I'd like the compression to be higher with a rebuild. If Rob didn't say the irons were lapped then assume they weren't and that could be where compression is uneven or low. You said the rotor housings are new Are the apex seals also new?

Could be bad spark plug wires.

Kentetsu

Basing things on just this one post, it sounds like cross-talk between the plug wires. Random misfire...

Whisper

I spoke with Rob and he said to wait until it's somewhat broken in, at least 500 miles or so, before trying to pass judgement on this. According to him even with new housings and seals instant smoothness is not guaranteed, since Mazda seals and housings aren't always perfect.

I'm just gonna put on miles and see.

Kentetsu

I had forgotten that I had posted this earlier. I still think I'm right. If you think about it, the only possible causes for what is happening (based on the OPs description and DDs video) is either inconsistent apex seal action, or an ignition event occuring at the wrong moment (yes, of course it could be fuel related, but I don't speak SE so we won't go there in my post!).

Now, if it is an inconsistent apex seal action, there's nothing we can do about it right now. So lets move right along to the other possibility, which we might actually be able to address. (btw, it's Friday night and I'm ever so slightly drunk, but this is when I do my best thinking.)

So, what can make the spark happen at the wrong time? I'm sure I won't get them all, but I'll give it a shot (feel free to chime in with anything I might miss):

• Spark plug wire cross-talk (caused by either bad wires, bad plugs, or bad grounding)
• Bad grounding (yes, I know I already mentioned it, but it really deserves its own mention), either at the motor, or the chassis, or battery
• Distributor malfunction? (I have not experienced this, but it seems entirely possible, there are a lot of electrical type thingamajigs in there and you can't trust even one of them, little bastards!)
• Coil malfunction? (This one I actually doubt is a likely suspect, but would be easy to check for sparking after dark)
• A burr in the housing, probably by the spark plug hole, causing the fuel to ignite early.
• moisture in the distributor cap
• Worn cap and/or rotor
• Unignited fuel exiting the motor, then igniting randomly in the exhuast system
• Any sort of loose connection anywhere in the system (ignitor, dizzy, coil and all of the wiring in between)
• A bad coil that isn't capable of holding a charge (firing early) or is too capable (firing late)... Is this one possible?
• Well, I've been sitting here thinking for a couple minutes now and can't think of anything else (but I'm sure I've missed a bit)

Anyway, that's my honest and slightly drunken opinion. Now all the sober guys can critique it for me... The wife wants me to come outside and play with my boys, and I think that sounds like a great idea (maybe a little full contact football, eh?) so I'll see you all later. Hope I've done more good than harm. lol

Whisper

That's a good list, and over the course of the last few months I've gone through pretty much all of the items you listed and none of it made much difference.

Actually after Mazda fiddled with mixture and TPS setting yesterday, it idles a bit smoother, and today I drove it some more and it wasn't too bad.

David Dale

was this problem ever fixed? i have a misfire similar to what is in the video but i have a s5 :O