idling issue.

[noisy_cricket94]

Hey guys, just bought a 92 mx3 v6 5spd. When sitting with the car running in neutral, the idling becomes erratic and jumps between 900 - 1300 rpms. Anybody have an idea what that could be? I'm thinking maybe a bad vacuum line or IACV?? Anybody agree or disagree? I tried searching, but couldn't find anything. Thank u in advance.

[noisy_cricket94]

A previous owner installed a spectre cone air filter at the end of the factory intake tube. He also threw away the factory air filter box. And the car spits and hesitates throughout the entire rpm range in every gear. Checking condition of plugs and wires today. Hoping my problems will go away with a proper air filter and new plugs and wires. Also I hope its just a matter of the girlfriend filling the tank with 87 octane.

[davmac]

87 octane will not effect idle.

Vacuum leak is a definite possibility. Do a visual inspection of the intake tubing - it is common for the accordian section to develop cracks and leak. Check vacuum lines also for obvious bad lines - there are many vacuum lines on this engine. If you find nothing obvious then move on to making sure all the basics are in good working order. Plugs and ignition wires are a good idea. Follow up with tune up settings:
- Set TPS - use this link and the next page from the manual to set TPS close throttle position
- Set the idle speed (engine warmed up then jumper TEN & GND in diagnostic box) and follow instructions here and in following pages
- Set ignition timing - see above

Report back if you're still having problems.

[noisy_cricket94]

Just got done jumping the two terminals in the diagnostic plug under the hood. Pulled codes 15, 17, and 23. The site I went to says codes 15 and 23 are my two oxygen sensors. Code 17 was listed as "feedback system. Or closed loop system - left hand side". What the hell does that mean?

[davmac]

W/o oxygen sensor input the ECU has no feedback to go into closed loop control. So all codes are related to O2 sensors.

Replace the O2 sensors and check that the wireing is good. You might save some money and use the universal Denso O2 #2344209. Just splice it into the connectors you have.

[noisy_cricket94]

2 bad o2 sensors would make my car run like its not firing on all cylinders (spitting, sputtering and horrible hesitation)????

[davmac]

O2 sensors not likely source for spitting, etc.

More likely:
- vacuum leak or unmetered air coming in through cracked air intake tube
- bad spark due to bad plugs or wires
- bad injector

Bad O2 will have the ECU running the engine rich and would give poor economy, some hesitation and rough idle. I'd be surprised if it was so bad you think it is actually misfiring.

[noisy_cricket94]

Yeah, it runs really rough. But no matter how fast I'm going, when I let off the accelerator, everything smooths out and sounds like it should. Until I have to accelerate again.

[davmac]

Runs smooth at idle?

I know you're chasing the EGR issue, but really need to get the basics set - adjust TPS, idle and timing as best as you can.
I guess you think the EGR is stuck open. For now just block it to eliminate the EGR effects. EGR is tough to get to, but if you can remove the exhaust pipe input you might just block the pipe there with a coin or something and see if your idle becomes smoother. If the EGR is already off the engine then fashion a plate and use the EGR mounting screws to hold the plate and block the EGR.

[noisy_cricket94]

Called autozone today and picking up 2 universal o2 sensors tomorrow. Followed by new plugs, wires, cap, rotor, and air/fuel/oil filters and oil change next week. I'm not really chasing any specific issue, i just dont know how to check timing, or adjust the idle. It doesnt idle smooth, it just smooths out when i let off the gas and slow down while the car is still in gear. everyone I talked to kept telling me the same thing you told me: change the o2 sensors. If both are completely shot, the motor will run like crap. They also told me to follow that up with a complete tune up.

[davmac]

Use the link I provided in post 3. Set TPS first - you'll need feeler gauges and digital multimeter to read ohms (or continuity). Rather than write out the procedure try to use the link (kinda hard to see that there is a link embedded on the word "link" and "here"). Idle is then set using the screw on the TB. Again follow the manual at the link and be sure the TEN and GND are jumpered when you set idle.

Great plans for lots of new parts, but O2 sensors, plugs, wires, cap and rotor will cover the bases for ignition problems (if you have any). Filters and oil nice to have but not immediately necessary. Good luck.

BTW timing is adjusted last and the car will run pretty good with the distributor just set in the middle of the adjustment range. Besides no point in adjusting timing unless idle set to spec. You'll need a timing light to check and set.

[Mazda_Powered]

The K8/KLs are very picky when you're trying to tune them...davmac definitely has some great advise, especially with the o2 sensors.

Generally I find most K8/KL missfires come from the internal coil system, o2 sensors, or have issues with a vac leak at the EGR system.

Don't forget to ALWAYS ALWAYS put the car into diagnostics mode before you make ANY adjustments on the KL...or it will backfire lol. Also disconnecting the battery while servicing the car always helps.

I'd start with checking the resistance on the internal coil & ignition wires, then checking out the TPS setting, then ignition base timing.

[edgar7654]

its that little thing on ur throttle body idk what its called its round and is right where the hole for the intake goes its not the tps this thing i had the same problem except mine jumped between 1000 and 1500

http://images.wrenchead.com/smartpages/partinfo_resize/DUS/217-1829.jpg

[Mazda_Powered]

That's the IAC (Idle air control) which controls your cold/warm idle speed. Unplugging it would diagnose if it's acting up or not, so give that a shot while you're in there.

the TPS sits facing you on the throttle body (when looking from the front of the car) and is attached to the throttle wheel/plate on the throttle body as well. You have to use a volt/multimeter to check and adjust the TPS settings...once again do this in Diagnostics mode so the ECU will get proper input.

To check the resistance of the coil and ignition wires use an ohm/multimeter and probe both ends of the wires and write down your numbers. IIRC it should be less than 50omh/ft, so depending on the length of the wire the numbers will vary. Also I cannot recall the specific wires to probe the internal coil to get it's resistance numbers, but a quick search should solve that.