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FIX  IT MAN
FIX IT MAN, Master Technician
Category: Mazda
Satisfied Customers: 17143
Experience:  Automotive Technician Trainer
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I have a 1990 Mazda Miata with a rough idle and excess smoke

Customer Question

I have a 1990 Mazda Miata with a rough idle and excess smoke out the tailpipe I have replaced the iAC and the TPS and the air valve I have check the fuel pressure its 40 pounds do you have any insight the plugs and wires seem to be okay .it comes and goes
on an idol.
Submitted: 1 year ago.
Category: Mazda
Expert:  FIX IT MAN replied 1 year ago.
Hello, my name is Bobby. Thank you for the question. Can you tell me what color the smoke is that is coming from the tail pipe?
Customer: replied 1 year ago.
Blk I can tell it's to rich
Expert:  FIX IT MAN replied 1 year ago.
Thank you. You need to do a compression test on the engine. It sounds like you may have worn out piston rings or valve stem seals that are leaking.
Customer: replied 1 year ago.
it's not a oill smell is a fuel smell and it comes and goes sometimes the motor smooth out then it messes around again like 1 of the sensors. It seems to do worse after it warms up
Expert:  FIX IT MAN replied 1 year ago.
Can you tell me if you have looked at the spark plugs and if so how did they all look?
Customer: replied 1 year ago.
I will ck that out tomorrow and let you know thanks
Expert:  FIX IT MAN replied 1 year ago.
Please let me know as that will give me an idea of where to start.
Customer: replied 1 year ago.
Just did a compression test all were 180.the plugs are blk like excess fuel.I put in new plugs didn't help.like I said earlier the exhaust smells like a rich smell like its getting too much fuel in the motor. While running I pulled the spark plug wires off on each one to see if it change the motor which it did so its not a electronic problem I don't believe.
Customer: replied 1 year ago.
When you go out and drive it when you're going through the gears it does pretty good to you slow down and hold a steady speed in that time comes and goes doesn't quite have the best pick up and go when you first take off like its got too much feel what regulates that I'm assuming the fuel regulator
Expert:  FIX IT MAN replied 1 year ago.
Thank you. It sounds like it may be the fuel pressure regulator on the fuel rail or it might be a bad O2 sensor or a bad coolant temperature sensor. Either one of these will cause the computer to put in too much fuel into the engine.
Customer: replied 1 year ago.
I'll check with the coolant temperature sensor first being that tends to start acting up when it starts warming up I'll let you know thanks
Expert:  FIX IT MAN replied 1 year ago.
Let me know what happens. Thank you.
Customer: replied 1 year ago.
Had to order the temp sensor should get it tomorrow and hopefully have an answer
Expert:  FIX IT MAN replied 1 year ago.
Let me know when you have a chance to get to it.
Customer: replied 1 year ago.
I just put a new fuel regular on and that didn't help.coolant temp next than 02 senser.?
Expert:  FIX IT MAN replied 1 year ago.
I hate just putting parts on like that without using a scan tool to verify their operation.
Customer: replied 1 year ago.
Just put a temp sensor on that didn't help I just adjusted the timing a little bit that didn't help where do I go to next...
Customer: replied 1 year ago.
It's still running rich I can tell it out the exhaust pipe
Expert:  FIX IT MAN replied 1 year ago.
Were all of the spark plugs the same color.
Customer: replied 1 year ago.
Yes. The only thing left is the o2 sensor and the catalytic converter
Expert:  FIX IT MAN replied 1 year ago.
Do you haven vacuum gauge?
Customer: replied 1 year ago.
No.but I did spray starting fluid all around long time ago to ck for vacum leaks nothing changes. Should I put a Gage on it if so what should it read
Expert:  FIX IT MAN replied 1 year ago.
Yes. I would like to know what it reads at idle and when you hold the rpms steady at 2500.
Customer: replied 1 year ago.
17@ an idel and 19@ 2500
Expert:  FIX IT MAN replied 1 year ago.
And does that 19 hold for a long period of time or is it higher and then it drops to there?
Customer: replied 1 year ago.
It holds.
Customer: replied 1 year ago.
No ck engine lt but anyways I disconnected the battery just to reset the computer. Maybe that might help that didn't do it either could it possibly be a injector partially plugged or something like that the motor goes up and down it will smooth out for a little bit then back and forth and raw exhaust out the back I pulled the o2 sensor out and it's pretty black I popped a new one and that didn't help either.the pcv is OK also.I dumped some sea foam in the tank also ..so far nothing I've done has helped.. Getting frustrated...
Expert:  FIX IT MAN replied 1 year ago.
At this point I would pull the fuel rail with the injectors attached and pressurize the fuel pump and see if you get fuel leaking from any of the injectors. Besides the computer itself possibly being faulty it may be a leaking injector.
Customer: replied 1 year ago.
I'll give that a try I'm leaving out of town tomorrow for a week be back next Tuesday I'll tear into it then and let you know thanks for the help here so far..
Expert:  FIX IT MAN replied 1 year ago.
Thank you for the update. Please let me know when you can.

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