Rough idle

Lack of acceleration,chugging,hesitating,bogging,misfiring etc. could be caused by one of the following below:

Start here inspect and test all the items below and comeback with some results.

Oxygen sensor.
Catalytic converter.
Fuel injectors dirty/sticking.
Mass airflow sensor/Airflow meter.
Throttle position sensor.
Crankshaft position sensor
Knock sensor
Manifold absolute pressure sensor.
EGR Valve
Fuel pressure regulator leaking or defective fuel pump.
False air leakage.
Fuel contamination.
Foul/defective spark plugs.
Open spark plug wires.
Ignition coil/Coil packs defective.
Incorrect ignition timing.
Cap and rotor.

Note:If it doesn't apply disregard it.

97 mazda 626 with 120k. 2.0 liter. Whenever i floor the gas either the car wont respond or it will start strong and then between 3 and 4 thousand rpm's it will start to stutter hard. Also, when i come to a complete stop and then try to keep going the car will either shut off or move very very slow. I recently adjusted the idle, cleaned the egr, and changed distributor cap and rotor, plugs, and fuel filter. Do i need to adjust the idle or is it something bigger?

Try checking the actual fuel pressure, if ok- check the throttle position and mass airflow sensor

Well althougth there is a screw to adjust the idle.....it is not to be touched!

try taking a spray bottle with water and misting the distributor and wires.

also if you have any brake cleaner, spray it around the intake (near the head) if it runs rough with either of these sudgestions let me know

Cosmo...Mazda TEch

What should i do since i've adjusted the idle screw? Should i spray the distributor and wires even though i just replaced the distributor cap and rotor??

Just had the timing belt change. Its in time now but it idles extremely rough at low rpm. Rides smooth when accelerating but jerks after reaching 4100 rpms down to 3100 rpms and does not have the same power it had before the change. I cant set the cruise control, speed drops if I remove my foot from the accelerator. We have changed the plugs, cap and rotor. Any ideas?

Inspect and test all the following listed below:

Oxygen sensor.
Catalytic converter.
Fuel injectors dirty/sticking.
Mass airflow sensor/Airflow meter.
Throttle position sensor.
Manifold absolute pressure sensor.
EGR Valve
Fuel pressure regulator leaking,fuel filter or defective fuel pump.
False air leakage.
Fuel contamination.
Foul/defective spark plugs.
Open spark plug wires.
Ignition coil/Coil packs defective.
Incorrect ignition timing.
Cap and rotor.

Note:If it doesn't apply disregard.

could it be the egr valve?

Engine running rough or misfiring can be cause by the following:

1.Defective spark plugs
2.Inadequate spark/coil,defective spark plug wire.
3.Lack of compression
4.False air leakage.
5.Faulty fuel injectors.
6.Insufficient fuel pressure.
7.Contaminated fuel.
8.EGR valve that is leaking.
9.Oxygen sensors.
10.Throttle position sensor.
11.Manifold absolute pressure sensor
12.Mass Airflow Sensor
13.Idle air control valve

Note: If it doesn't apply disregard it-

https://www.2carpros.com/articles/engine-misfires-or-runs-rough

My 1995 Mazda 626 idles roughly in neutral. The normal idle speed in neutral is supposed to be 700-750 rpms. The rpms are at about 700 but drop down frequently to about 550 and bounce up and down between 550 and 700. I noticed that there is a air duct hose that has a crack in it. Could this be the problem? Also, what does the air duct hose do? Thank you!

A lot of sensors and emission system use vacuum created by the engine to operate properly. If you have air leak or vacuum leak, the engine will not work properly as shown by the air duct leak. Your description of air duct, to me that is the air intake hose. If that is what you mean, you have another vacuum leak.

1995 Mazda 626 mileage: 102,000. I recently replaced the upper radiator hose, spark plugs and wires. When I started the car, it idled rough and would jerk upon acceleration. I rechecked the spark plugs for proper gap, checked the wires for connection and the firing order. All was correct. My muffler has a couple of small holes in it and someone said it might be the catalytic converter clogging up. I think I knocked off a vacuum line. What do you think? Thank You.

We do not think the muffler or the catalytic converter is your problem. You mentioned knocking off a vacuum line. If it is still off or incorrectly reinstalled that would definitely cause your problem.

Make & Model: Mazada 626 LX 1998; 4 cylinder 2 liter
Mileage: 96,000

Background info: I've had the timing belt replaced, I've replaced the IAC, vacuum hoses, new plugs & plug wires, cleaned EGR valve, had alternator tested - it tested good, replaced a/c & heater control unit. Local mechincal adjusted base idle.

The problem starts when anything puts a load on the motor - the a/c is the greatest drain. The RPM's dropped drastically when a/c is turned on. When alternator was tested I did notice a 19 amp drain on the charging system when the a/c was cut on. It went from 69 to 50 amps. Is this normal? I've pulled out the relay for the compressor and it still pulls down the motor with the a/c on. I've taken the compressor belt off and it still does it. I've jumped out the high and low pressure switches on the a/c system and it still does it. I've looked for a short in the wiring and can't find one. I don't have any check engine lights or codes. If my PCM is failing shouldn't I get a code? I have not had the a/c system checked yet. Any help would be GREATLY appreciated.

So with the a/c relay out of the car, it still draws down when turned on? I take it the comp isnt engaging? It wont if you have the correct relay. Be sure of this and get back to me.Otherwise you have some strange electrical things going on

Yes. Correct the comp isn't engaging. I'm sure I have the right relay. I've even unplugged the comp clutch. And I've removed the a/c belt off the clutch, ran the car, turned on the a/c it still pulls down.

Are you turning on the blower fan or just the A/C?

The a/c will not come on unless the blower fan switch is in position (1).There are five switch positions. (0-4) 0 positon is off and 4 is high. I have disconnected the blowers main plug, which completely takes the blower out of the system and when I turn the a/c on it still pulls the motor down. I think the blower is OK.

Sounds like it is time to tear into it and see why it pulls the engine down when nothing is on. Go to link at bottom of main forum page for repair manuals, will have all wiring diagrams so you can see what you are doing

I Have the Haynes Repair Manual for my car. I been through the heating and air conditioning system wiring diagram and I did find one thing. If I pull out the 10 amp a/c fuse the problem goes away but, this also disables the controls for the a/c. The a/c fuse supplies power to the air intake actuator (part of the blower unit), swing louver (oscillating vents in middle of dash) and to the heater/ a/c control unit. (Which I have already replaced) I have also unplugged the louvers and the blower unit and the proble is still there. I wish I had a diagram of the control unit so I could see where the power from the a/c fuse go after the a/c switch is in the on position. Do you know of a place I can get this electrial diagram? Its not in the Haynes Manual.

Try the link I told you. That is professional software, not the book you buy at Autozone

My car had a tps problem since I have had it, and it finally gave up to me a few days ago. It was changed today and the idling was a little high, but it was smoother than I have ever remembered it. As I was driving it throughout the day, the idling got more rough than before, dropped between 300-600rpm and would stall. any ideas to what it can be?

Do you have any codes?Have you checked for any yet?

I got a code for the catalyst converter which needs a gasket. Other than that, I have no other codes.

I would check for a vacuum leak.

Also i would see if cleaning the idle air control valve helps any.

I would also see if cleaning the idle air control valve helps any.

Thanks, I'm going to check on all of that in the morning and will definitely keep you posted

1996 Mazda 626 LX mileage: 70,000. When cold, no problems are apparent. Once at normal operating temperature, it idles erratically and stumbles during normal acceleration, the stumbling is similar to water in the gas or misfiring. It operates well at a constant speed (say highway speed). The "check engine light" has come on. Reviewing the Haynes repair manual, it appears that the problem might be with part of the emissions control systems (oxygen sensor). Haynes has a description of how to get the codes from the OBD by using a jumper wire (between terminals STI and GND) and watching the light to get the number of flashes (i.e. the engine's Morse code). It appears from the diagram of the OBD connector that my car has the OBD-1 system (a group of 25 or so terminals in a compartment under the hood (not an under dash model that seems to be the OBD-II. The directions that they give do not work. Furthermore, in another part of the book they present another example of this same OBD-I connector and give the same terminal (STI) a different name (TEN) that matches the terminal name and position as shown in my car. I am guessing that they have mixed up the diagrams and terminal names. Can you give any information on how to get the codes from the OBD system as a help? I have been told by an auto service provider that the problem with my car is that the oil seals around the spark plugs (o-rings) are shot on the front three cylinders, and that the head cover gasket needs to be replaced, the plugs need to be replaced, and that the special spark plug wires need to be replaced. However, they could not get the codes. I cannot trust them to make the right call if they can't even access the codes (they say they don't have the computer hook-up) and we do not live near a dealer. Your assistance would be greatly appreciated as a second opinion.

You car requires an OBDII scanner. This should tell you if there are any fault codes in the computer. In addition, check the rubber boot cracks between the airflow box and the intake manifold.

Alright keep us posted.

Hi guys, I went and found out I didn't plug in a sensor. Other than that the car runs smoother. It still vibrates a little when on idle. I'm not sure if that is still a vacuum problem.

If its running smooth engine wise then you could have some bad engine mounts.

rough idle and bad gas smell on a 94 mazada 626 4 cylender

May just be a tune related problem, faulty leads or plugs, get a scan done and do the basic tune items first, start here.

mark (mhpautos)