I also realized that I did not install the charcoal canister, which I did not mention previously. I just bypassed it.
Also, the connector circled in the picture below is not connected to anything. Would that normally be for something in the emissions system?
NermalSnert said: FYI, On my stock '97, the idle air must be metered. Ran like you're describing when I put a small air filter on the IACV. Ran fine when I plumbed it back into the intake track.
So I should clean my IACV?
Sorry. I don't know the answer to that. My issue was something I changed that didn't work so I put it back.
Have to look under the hood of a like vintage miata to see what that wire is.
But do you have the o2 sensor hooked up? If you do, disconnect it, and try it again.
I have seen wiring issues that makes the O2 sensor send back the wrong information, which will overwhelm the feedback control, making the engine run really badly. And in that vintage, detection of that error is poor, as is the reaction to that failure. It should react reasonably well for a disconnected sensor- unless the fault is crossing the wrong wires on the engine/body side of the harness.
See what happens, and then it will either eliminate or find that as a source of the problem.
Looks like charcoal canister stuff on my 94.
Looks like the fuel filter I need is in stock at the Local Auto Zone. Not convinced it is the issue, but at <$10 its easy enough to eliminate the possibility of. My other thought is to also hook up my fuel pressure tester and see if it could be the fuel pump. I could potentially see it not having an issue until it's warmed up....
Will try the O2 sensor idea too. The O2 sensor IS plugged in, and it is fairly new because I replaced it when it was in my 97 only a couple months before pulling the engine. (Appears that an O2 sensor for a 97 is the same as for a 94, so that should be fine.
Honestly half of me is thinking just get a MSPNP so I can delete half of this garbage. BUT... That's till probably more money and effort than finishing diagnosing at this point.
AWSX1686 said:Looks like the fuel filter I need is in stock at the Local Auto Zone. Not convinced it is the issue, but at <$10 its easy enough to eliminate the possibility of. My other thought is to also hook up my fuel pressure tester and see if it could be the fuel pump. I could potentially see it not having an issue until it's warmed up....
Will try the O2 sensor idea too. The O2 sensor IS plugged in, and it is fairly new because I replaced it when it was in my 97 only a couple months before pulling the engine. (Appears that an O2 sensor for a 97 is the same as for a 94, so that should be fine.
Unplug it. the failure reaction is to just ignore the feedback and use the MAF sensor. If that "fixes" it, the problems in the wiring.
Bad ignition cables can cause similar issues. They're cheap enough, and only seem to last about 40k miles. Change them.
AWSX1686 said:I also realized that I did not install the charcoal canister, which I did not mention previously. I just bypassed it.
Also, the connector circled in the picture below is not connected to anything. Would that normally be for something in the emissions system?
Pretty sure on a 1990 car that connector is just sitting there like that. I dont have the car with me but can check tomorrow if no one corroborates.
Fuel Filter
Spark plugs
Spark plugs wires
No change.
Issue/behavior is the same with or without the O2 sensor plugged in.
Starting to think I'm just missing something with the MAF wiring. It seems straight forward, but there's gotta be something deeper. Honestly thinking about dropping it off at one of the shops nearby that is crazy good with electrical issues....
Do you guys think a sucky battery could cause these issues?
I've been putting off replacing the battery for too long, so I wonder if replacing it would some some issues... As in, right now I jump start it every time...
Might see if one of the local placed has one available tonight.
In reply to AWSX1686 :
Worth a try... it's possible that the electrical load to just run the engine is so high that even the alternator can't keep up.
Can you get a voltmeter on it?
I had my alternator go out last summer on our NA, and didn't realize it until it killed the battery. I got it jump started and drove it home. I had my laptop, so I pulled up TunerStudio and watched the voltage steadily drop on the way home. It was ~ 8 volts when I pulled in the driveway. It never exhibited any symptoms like you've described... Honestly, I couldn't believe it was still running!
I'm running on Megasquirt, so it is possible the stock ECU could require more juice...??
Sorry I'm late to the party. Maybe I missed it but has anyone suggested a dirty air filter? My E12 had a K&N cone that was packed with dirt but "looked" OK. Car laid flat at about 2000 rpm. By chance my neighbor said "start it without the air filter" and Boom Pow Surprise that was it.
AngryCorvair said:Sorry I'm late to the party. Maybe I missed it but has anyone suggested a dirty air filter? My E12 had a K&N cone that was packed with dirt but "looked" OK. Car laid flat at about 2000 rpm. By chance my neighbor said "start it without the air filter" and Boom Pow Surprise that was it.
That's worth a shot! I did look at it and it seemed ok, but it's easy enough to try and I'm willing to try just about anything at this point.
New battery made no difference, besides the fact that I didn't need to jump start it.
I put the DMM on the battery and was getting 14.5 volts when running, and no change in volts when I had someone rev it to cause the issue. Seems like the battery and alternator are fine. Unless there's somewhere else I should test volts from?
If you're getting 14.5 while it's running, the alternator is most likely fine. It's regulated, so revving shouldn't matter. Mine puts out a steady 14.x volts when running.
AWSX1686 said:AngryCorvair said:Sorry I'm late to the party. Maybe I missed it but has anyone suggested a dirty air filter? My E12 had a K&N cone that was packed with dirt but "looked" OK. Car laid flat at about 2000 rpm. By chance my neighbor said "start it without the air filter" and Boom Pow Surprise that was it.
That's worth a shot! I did look at it and it seemed ok, but it's easy enough to try and I'm willing to try just about anything at this point.
Years ago I had a similar issue caused by a fuel filter. Let it sit and it would run just fine. After running a bit wouldn't rev but would idle. Figured restricted enough to prevent fuel flow adequate for higher rpm but allowed enough to idle.
wlkelley3 said:AWSX1686 said:AngryCorvair said:Sorry I'm late to the party. Maybe I missed it but has anyone suggested a dirty air filter? My E12 had a K&N cone that was packed with dirt but "looked" OK. Car laid flat at about 2000 rpm. By chance my neighbor said "start it without the air filter" and Boom Pow Surprise that was it.
That's worth a shot! I did look at it and it seemed ok, but it's easy enough to try and I'm willing to try just about anything at this point.
Years ago I had a similar issue caused by a fuel filter. Let it sit and it would run just fine. After running a bit wouldn't rev but would idle. Figured restricted enough to prevent fuel flow adequate for higher rpm but allowed enough to idle.
I replaced the fuel filter. I suppose it could potentially be the fuel pump though.
Well, I sent if off to the shop so that they could hunt down the electrical gremlin causing the issue, and hunt it they did! I picked up the car last night, and it is running very well! It's so nice to have a miata again. Now I am just waiting on new clutch hydraulic parts before I drive it too much further.
The culprit?
Water had seeped into the ECU. They were able to take it apart, clean it, verify all the solder connections were good and now it's running great. They did say they don't know how long it will last, so I will probably order another ECU to have on hand, but still.
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