Question about 1999 Mazda 626

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Engine revs when brake applied

I used to just have problems with the car sputtering at idle...replaced the IAC and that fixed things for a few months...now idle loping and sputtering as bad or worse than ever, but when I step on the brakes now, the car revs to 4000+ RPM, so can't even get it out of the driveway without a tow. Wondering if just the whole computer could be shot. I'm not made of money so wondering what the possibilities are before I start sinking dough into it.
Any help would be soooooo appreciated.

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  • 329 Answers

Your brake booster needs to be replaced.

Posted on Oct 12, 2008

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My 2001 monte carlo starts but revs up and bogs down while still scared to drive to auto store


A few different thing's could cause that , IAC - idle air control valve , vacuum leak , engine electronics , (sensor's) Would need to do testing to say for sure ! Know how to do basic engine testing ? Your best bet would be to take it to a qualified repair shop that has the diagnostic tools to find an fix this problem ! Wouldn't trust part's store's , they just want to sell you parts !

Sep 10, 2016 | 2001 Chevrolet Monte Carlo

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What does it sound like to u when the car starts up (picky sometimes) Revs good (sounds strong) rough idle with foot on gas at lower rpms and dies without applying gas?


i'd try a fuel addative to clear through fuel,cylinder/valves and the cat converter may have a carbon/sludge build up ,cheaper than getting iac and the idle may be the blockage symptom give it a go nothing to loose,must have quite a few miles on it

Apr 28, 2014 | Hyundai Motor 1995 Accent

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Why should the truck shut down at a low idle or when u apply the brake to it the idle slows down an it cuts off on a 1992 ford f150


In some cases, the throttle body is dirty or the iac valve is faulty.
I would start with those two things.

Oct 11, 2012 | 1992 Ford F150 SuperCab

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Vehicle stalling at traffic stop like im about to run out of gas


Start with the simple and replace your fuel filter and clean your throttle body, When cleaning your throttle body pay attention to your IAC (Idle Air Control) valve passage way with is located on the back side to your throttle body air intake barrel.
Just follow the instructions on the spray can of throttle body cleaner and be safe. This should address your stalling issues from a dirty IAC valve.
Thank you for suing Fixya and be safe.

Apr 18, 2010 | 1996 Chevrolet Blazer

1 Answer

When my 1991 geo storm warms up the idle skips around.... it doesnt stall out it just sputters and gos from high to low idle


Sounds like your idle air control, or IAC valve. Take it off and clean it out with some brake cleaner. Carbon deposits and gunk can build up and prevent the IAC valve from operating properly, by causing it to stick. If cleaning it doesn't work, you may have to just replace it. It happened to me on my Sentra, tripping my check engine light, sputtering hard, idled crazy, no power, etc. But once I cleaned it off, it ran so smooth. You'll need to get a replacement gasket, though, or make your own out of gasket paper.

Feb 04, 2010 | 1991 Geo Storm

1 Answer

I have a 1997 gmc serria 1500 4x4 5.7l i replaced the iac motor and it still reves up high could it be the tps


When replacing the IAC it is a self learning item the computer will teach. You need to do this to fix this problem first since you DID replace it. Have the engine good and cold (not hot) let set three hours if warm. Now we are ready. Place the parking brake on. Start the engine. Put your foot firmly on the brake. Put the car in drive. You will not go anywhere for the next proceedure. I do hope you have a tachometer. You will need to rev the engine in gear between 1100 & 1299 RPM's and hold it there for 5 minutes. This is the proceedure to have the self learning codes from the switch to the vehicles computer stored. When your done this truck should idle at 800 rpm's

Jan 20, 2010 | 1997 GMC Sierra

1 Answer

Revs up and down at low revs


you need to clean or replace your idle air control valve(IAC). The IAC allows your engine to idle smoothly by opening and closing a valve that allows air flow to the engine that is monitored by the computer. The IAC get dirty causing it to stick and move slower than it should which causes the up and down idle

Oct 29, 2009 | 1998 Ford Escort

1 Answer

Engine wont idle on my vitara jlx 1993


Check your air idle control valve, check for the wires to be fretted or broke, and also check the vacuum lines to it. 
The air idle control valve mey be dirty and a good cleaning with throttle body clean through the throttle body may help clean the carbon build up. 
If there is a Auto Zone, have the Vitara scanned for a DTC code. 
Here is a few things you can do. 
Checking  the IAC (it's called the ISC on Single Point TBI)
It is screwed to the throttle body, and has a 2 pin electrical connector) with an Ohmmeter - the solenoid should be 11 to 14 ohm.  If not, replace.  


To test the IAC / ISC
Use a Duty Meter, and adjust the air adjust screw to get 50%.  If the revs are not right at that point, adjust some more to try to get them correct, but if the duty goes below 28%, a vacuum leak is highly likely.

Air Adjust screw for TBI / Single point   look on the Throttle Body, just below the fuel line and maybe an inch to the left of the Fuel Pressure Regulator - it looks like a cross head screw into the TB.

The 8v (Single Point / TBI) uses a throttle opener device to open the throttle extra during starting.  When the engine starts to run, a vacuum line is applied to the device through a vacuum servo valve, controlled by the ECM. The vacuum closes the throttle opener, to bring the revs down to normal.  The ECM will operate the VSV after about 10 sec from engine start (less if the coolant is warm).

Try these things for now and keep me posted. good luck.

Jun 01, 2009 | 1999 Suzuki Vitara

1 Answer

Car sputters or dies when idling, but starts fine.


I suspect you have an idle circuit issue. When the thottle is closed, the throttle valve is almost closed (like 95%). The linkage on the throttle body is against the hard stop.
SO, when idling you need a way to let enough air into the engine to maintain an idle speed. The IAC, Idle Air Control valve is the way you do that and the engine computer controls the rate of air flow.
Sometimes it gets plugged up so you can clean it with a little carb cleaner. Might have to take it apart.
Also, you have a MAF, Mass Air Flow sensor that tells the computer how much air is flowing through the air cleaner intake at any time. The sensor gets coated with varnish and vies a false reading. Clean it gently with carb cleaner and a toothbrush.
Other than that, I would go to an auto parts store that can run a computer scan for free to see if you have any fault codes stored. They will tell you next stpes.

I assume you 2.0L SPI engine & not Zetec.


Idle Air Control (IAC) Valve —2.0L SPI Removal
  1. Disconnect the idle air control (IAC) valve electrical connector (air cleaner outlet tube removed for clarity).
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  1. Remove the IAC valve.
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  1. Remove and discard the IAC valve gasket.
cdecc8a.gif Mass Air Flow (MAF) Sensor Removal
  1. Remove the air cleaner outlet pipe.
  1. Disconnect the mass air flow (MAF) sensor electrical connector.
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  1. Remove the MAF sensor.
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clean element inside carefully


PS. A good running engine makes for a better running transmission

Mar 02, 2009 | 2003 Ford Focus

1 Answer

I am currently experiencing engine idle problems, i have recently purchased the vehicle and the engine has been fine until now. When i stop at junctions and the engine is idleing it seems to now and again...


You need to replace your IAC (idle air control valve). The IAC, like it sounds, control the idle of your car. When they go bad they will cause the low idle and stalling. The IAC is located on the throttle body and is usually held on with a couple of screws. It is an easy relatively cheap fix that you can take care of by yourself. Let me know if you have any more questions. Thanks for rating my response and for using FixYa!

Aug 04, 2008 | 2001 BMW Z3

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