Mazda protege 2000 auto 120000miles no codes 1.6L

My car at start will REV to 5000 rpms then back to 2000 then back and forth between 2000-3000.
Some back ground. The car stated to rev high and brakes got weak. I wrongly assumed it was the vacuum line going to power brake booster. Someone repaired it so I replaced it. Not the problem so I thought it must be the power brake booster it self. Replaced it still does the same thing. Took off the TPS checked it with voltmeter oms in normal limit and 5 volts going to it. I used carb cleaner to try to find vacuum leak and could not find one. Any thoughts of next step. I assume the reason the rpms go up and down is the computer trying to adjust it. Throttle plate moves with my finger and accelerator cable.

 

Neil;

before you throw any more parts at this problem I suggest to do some deep cleaning. Use MAF sensor cleaner for the MAF sensor, use Throttle Body Cleaner for everything else. I like CRC products.

Clean: throttle body, EGR valve and orifices (if your car has EGR), Clean the MAF sensor, IAT sensor, Idle Control Motor.
Take off the air intake hose and bend it to see if it has cracks in particular at the ribbed section. Use duct tape to seal off cracks, you can replace the cracked hose later.

Report back.


I doubt that your brakes got weak. The engine was (is) pushing while you brake because it does not go down to idle as you let go of the accelerator.
While you are under hood look for anything that might have been left disconnected. I am thinking electrical harnesses and hoses.

 

Don't like that video. I have a real good 3 minute video. Pushing on a throttle butterfly plate may throw your ECU out of whack. Please watch this video: Rough Idling Issues |*MotorWeek
Another way is to disconnect the negative terminal of battery, followed by a depression of the brake pedal. Now clean whatever. When done, re-connect battery and let idle for 10-15 minutes before driving. Let it re-learn for 50 miles or so before complaining.
Your ECU may need to be re-set try the battery trick. Otherwise re-programming @ dealer.

CRC FTMFW!

 

Noggin makes a good point here, in particular if you have an electronic accelerator. but you mention the cable so you have a cable operated accelerator.
To eliminate the pedal/cable as a possible cause you could disconnect the cable at the throttle body and start the engine. If you have normal idle then look what keeps the cable from returning. (clean, inspect, lube). IF there is no change in idle the pedal/cable assembly are o.k.

 

Thanks for replies. The idle goes up and down with the throttle cable disconnected. My brakes did get weak had to put car in neutral and turn off at stop lights to get the car home. Pushing the throttle plate after the fact I doubt would cause the ECM out of wack. Airhose is good.

Im taking the throttle apart and cleaning today I'm report any chhanges after I put it back together.

3 Things that got me stumped.

No Codes

Computer must be controlling idle. 5000 start up then drops to 2000 then goes up and 3000 and down to 2000.

Brakes weak.

 

On bottom the throttle body there is two hose connections, they where plugged so after a box of pipe cleaners and can of carb cleaner I got it clear. Brakes came back too.
Thanks again for the replies.

 

Maybe (I am not sure though) these are vacuum lines to the advance and retard ports as shown in this diagram:


I am glad you got it fixed.

 

Mine is doing the high rev and low rev and when I let off the gas it dies, Do you think cleaning those hoses would help me, too?