my 2004 mazda 3 won't idle all the time. sometimes it idles fine. when driving the car it's fine but when i stop at a light and have my foot on the brake and the car is in drive it starts surging from 200 to 1200 rpm's and sometimes shuts off. The car will restart right away and if you keep your foot on the gas it is fine. But it doesn't do this all the time. Any ideas on what is going on?
Country: CanadaMake: MazdaModel: 3Year: 2004Engine: 2.0
nothing but i had to put a new alternator on the car a week ago and that is the second alternator in one year but i don't think that is related to this problem.
Hi and welcome to Just Answer, my name is XXX XXX I will attempt to help you with your problem.
Before we move on I have a few questions to ask you.
First, do you have an engine light on?
When you are back online please respond and I will get back to you as soon as possible. Thank you and I look forward to helping you solve this problem.
no right now the engine light is not on but up until a week ago when i changed the alternator it had been on. I think when i took the positive post off the battery to change the alternator it reset.
Removing the battery does reset the engine light.
The problem sounds like it could be with an idle air control valve but it would be good to know why the engine light was on because a surging idle could be due to a vacuum leak which would cause a lean code.
If possible, if you drive the vehicle enough the engine light would turn back on and that could help you diagnose the problem.
Most auto parts stores will scan why the engine light is on, so if possible get the codes scanned if you can get the engine light back on. In this case for diagnostic reasons it would actually help in solving the issue.
In the meantime, you should check for vacuum leaks.
To do this when the engine is at a surging idle, get some carb cleaner or starting fluid and spray down the intake area, vacuum line and see if the idle "responds" to the external fuel.
Does this make sense?
where is the intake area? And if it responds then what?
The intake area is basically the top part of the engine itself
If the engine does respond to spraying fuel it means that a gasket or vacuum line is bad allowing some outside air to enter the engine.
when this happens the extra air can cause the engine to surge as you are describing.
Usually extra air entering in the engine will cause an engine light. Because the air to fuel ratio in the engine is too lean it will cause a lean code.
This is just a possibility and it's actually very common.
So if the engine does respond the the external fuel, you know there is either a vacuum line broken somewhere or an engine gasket leaking.
ok tks i will give this a try.
Awesome, try this first. If possible get the codes read, as I mentioned some auto parts will scan for free, just make sure the engine light is on before getting the codes scanned otherwise it's basically pointless.
At any time, if you find anything or not please let me know how it goes so I can advise you further.
If I am offline, still respond, I will get back with you as soon as I am available.
Good luck and thank you.
Hi Tim, sorry for taking so long to get back to you but my friend at work has a code reader and we used it on my car for the past few days. The code that keeps coming up is manifold pressure low. We clear the code but it comes back on again. My friend said it reads just under 14psi which he said is low. So we think there may be a problem with the manifold pressure sensor but heres the thing my car has been running great for the past 3 days even though the code keeps coming up. But the weather has been a lot warmer lately which may be the reason the car has been running ok. Any thoughts on what you thing the issue is would be great and after i will hit the accept button so that you can get paid. Tks
Well the code p0107 is either cause by a MAP sensor issue or a wiring problem or computer failure. If you have a DVOM I can guide you through the testing of the MAP sensor.
Also, I would recommend having a good look at the throttle body and make sure the throttle is clean as well.
Do you know how to do this?
How does it look?
The code is actually a p0106 code. My friend and i took off the barometric sensor and cleaned it and also the mass airflow sensor and cleaned it. The throttle body was pretty dirty and we sprayed some carb cleaner in there to clean it as well. I drove the car to work again tonight and he had the code reader hooked up and the pressure went up to 100 which he said was what it was supposed to be. No codes came up and the car is running great. Haven't had the problem for 4 or 5 days now with the car. However even when the p0106 code was coming up the car still ran fine yesterday and the same the day before that. Any ideas on what might be causing this code? However as i said it did not come on since we cleaned those sensors and the throttle body so maybe that was the problem.
There is a service bulletin on the code, and it's possible that was causing the error number. However, if all is good, I wouldn't jump to get anything looked at. If the engine light does come back on, you should contact the dealer about this TSB. click here to see the tsb
tks very much for your help.
ASE certified Service Manager