Idle extremely low under braking???

M

mxjosh82

Member
:
03.5 MAZDASPEED Protege
Alright guys just about 2 days ago, my idle has been acting up. While I am slowing down and the clutch is depressed my idle drops down to about 200rpm until I come to a complete a stop. When I stop the idle goes back up to 800, drops down to 500, and then holds steady back at a normal 800rpm. It has been doing it almost every time I am coming to a stop now....any suggestions?

Thanks guys
 
my car idles a little low when coming to a stop sometimes. I just figured it was part of owning a protege..lol. It never really bothered me though
 
It's done it here and there before, but never this bad, the cars just vibrates and feels like it wants to die then come up to normal.
 
If I had a vacuum leak wouldn't the idle stay low and not go back to normal when I come to a complete stop?
 
I'm going to clean the EGR and IACV soon, since I found some other people having a similar issue and it helping them. I'll post up if it helps at all or not. Thanks for the suggestions so far.
 
mxjosh82 said:
If I had a vacuum leak wouldn't the idle stay low and not go back to normal when I come to a complete stop?
Click to expand...

No, The brake booster operates off of Vac.. Which would amplify the problem.

You most certainly have a Vac Issue..
 
BRIAN_MP5T said:
No, The brake booster operates off of Vac.. Which would amplify the problem.

You most certainly have a Vac Issue..
Click to expand...

I found out that it is not necessarily only on brake when this happens, if the clutch pedal is pressed in and the car is just slowing down off brake, the same issue is there, but I will also check to vacuum leaks while I am cleaning things.
 
Well I cleaned the IACV, cleaned the throttle body since it was off anyway, topped off the coolant and replaced a vacuum house I noticed was cracked towards the tip and still having the same issue. I ran out of time to do other things, so this weekend I will check for other vacuum leaks, check my plugs, check PVC and maybe clean EGR valve....the mounting bolts for it look like a kick in the dick as far as where they are located.
 
mxjosh82 said:
Well I cleaned the IACV, cleaned the throttle body since it was off anyway, topped off the coolant and replaced a vacuum house I noticed was cracked towards the tip and still having the same issue. I ran out of time to do other things, so this weekend I will check for other vacuum leaks, check my plugs, check PVC and maybe clean EGR valve....the mounting bolts for it look like a kick in the dick as far as where they are located.
Click to expand...

I wouldn't even waste your time attempting to remove the EGR. Does your boost guage read in the minus 20-22 range at idle? If so, so much for a vacuum leak. Do you even know how old your plugs are? Just go ahead a pick up 4 NGK V powers for less than $10 and throw them in after gapping 0.028-0.031. And pick up a Purolator PV 1047 and stick that in too. Don't forget the can of Seafoam and do two treatments back to back and put the remaining 1/3 in your gas tank.
 
I replaced the plugs a little less than a year ago, yes boost gauge is reading between 20-22....I've heard both good and bad about seafoam, so I am hesitant to do that.
 
I've done countless Seafoam treatments in my MSP and everything that I own with an engine. You have to be pretty stupid and or fail to heed the directions to have a problem. Bet the people that had problems won't admit to either. Bought mine brand new, It currently has over 96,000 miles. Never cleaned my EGR/IAC or ThrottleBody plate. Never have had an idle dip. Good luck solving your issue.
 
Mine does this too. I wrote the original EGR fix thread but this is different. It happens when the rpm drops quickly and it is most certainly a vac leak. My boost gauge reads 9-10mmHg at idle! Has for awhile now.

Pretty sure it is a plastic intercooler issue, so an FMIC is coming next.
 
BOOSTR said:
I've done countless Seafoam treatments in my MSP and everything that I own with an engine. You have to be pretty stupid and or fail to heed the directions to have a problem. Bet the people that had problems won't admit to either. Bought mine brand new, It currently has over 96,000 miles. Never cleaned my EGR/IAC or ThrottleBody plate. Never have had an idle dip. Good luck solving your issue.
Click to expand...


I'll look into it more. Today the idle this morning was fine as it was sitting after it warmed up and vacuum was reading perfectly fine. By the time I got to work (an hour later) the idle was fluctuating between 200-800 for a good 15 seconds (never has done it that long before) and the vacuum was dipping below normal. I really can't work on it at all anymore until this weekend. I will post updates then. Thanks for the help!
 
122 Vega said:
Mine does this too. I wrote the original EGR fix thread but this is different. It happens when the rpm drops quickly and it is most certainly a vac leak. My boost gauge reads 9-10mmHg at idle! Has for awhile now.

Pretty sure it is a plastic intercooler issue, so an FMIC is coming next.
Click to expand...

My vacuum is no where near that at idle, and I have a FMIC and hardpiping.
 
20VAC is where it should be
but it its irrelevant because if the FMIC is cracked the VAC will still be good, but the correct volume of air won't be measured and the car will run like ass
 
BRIAN_MP5T said:
20VAC is where it should be
but it its irrelevant because if the FMIC is cracked the VAC will still be good, but the correct volume of air won't be measured and the car will run like ass
Click to expand...

This is where it sits while idling after I have started it and let it warm up for about 10-15 minutes before driving it...where it should...
guage.jpg


Now when I got to work, it was dipping slightly below that as it was fluctuating (20-25)
 
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