Rough Idle

[dannyboy17]

Yeah, another issue with the car.
When Im a light holding down the brake, car seems to idle at 1500rpms if I let go off the clutch, if I press the clutch down slightly it goes back to normal (800rpms). Also if I put the hand brake on and I let go off the brake pedal, the rpms go a little up too around 1200rpms. This is driving me crazy, how can the brake and clutch have anything to do with the idle?

Argh, this car never stops to frustrate me lol
love it one day, hate it the other...

 

[downtube]

There was a thread somewhere about a bad clutch switch screwing up idle.

 

[neox.286]

could you elaborate on that?

 

[downtube]

When I bought my '00 protege, it had a rough idle. I searched all the mazda forums I could find, and ran across a thread identifying the clutch switch as possible cause. I don't recall which forum; I don't see the thread here.
The guy had been fighting an idle problem for long time, replaced many parts, and finally the dealer identified it as a bad clutch switch. Don't recall which clutch switch (there are two, one engages with the clutch up, one with the clutch down).
My problem, it turned out, was caused by a cracked intake boot.

 

[downtube]

Found it
http://www.mazdas247.com/forum/showthread.php?t=123637185
and it's here so I don't get in trouble for posting a link to another forum

 

[neox.286]

hmm, doesnt seem to relate to my problem

what about your issue, what were your symptoms?

 

[dannyboy17]

thanks, but doesnt seem like my problem tho

Mine is the opposite, if I let the car sit and I dont push the clutch in, the idle will get messed up, for example if I turn on the car and I get out, idle will be messed up till I go back and press the clutch a little bit in, then it will be normal again.

Ive gotten a few CELs, well see what happens though.
P0507 Idle Control System RPM Higher Than Expected
P0172 System Too Rich (Bank 1)
P0850 Park/Neutral Position (PNP) Switch Circuit

I can notice the car is running pig rich, but I still cant figure out whats wrong with it.

Could a cracked exhaust manifold cause this? Cracks are small, but Im not sure if its leaking thru there or not.

 

[Velocifero]

maybe exhaust mani, maybe vacuum leak have you checked your vac lines, are they still the stock rubber? another issue, maybe look at the MAF. I had a cracked MAF housing that was causing the car to run odd. maybe spray some MAF cleaner on it to check that too.

edit: add: not too sure about that neutral circuit though, first I have seen that.

 

[dannyboy17]

i checked and rechecked all the vac lines, found a small leak that was making me hit fuel cut and fixed that problem. But the rought idle is still there, tried to clean the IAC valve, also the EGR.

It also has a diff MAF now, still the same.

Its funny tho for the neutral circuit, both my MSP's have been thru an engine swap by different shops, and once they are done they keep throwing that code. I dunno what it can be, but it doesnt make a difference on how the car runs tho.

Im gonna seafoam later on to see how much smoke comes out of the manifold, if its more than normal I guess Ill have to swap it.

 

[downtube]

Mine would idle too low, to the point of almost stalling. Occasionally the PCU would overcorrect causing RPMs to shoot up. Cause turned out to be a crack in the air intake boot.
Sounds different from yours.

 

[Velocifero]

long shot, but check the plugs on the back side of the tranny and make sure they are looking ok.

 

[dannyboy17]

long shot, but check the plugs on the back side of the tranny and make sure they are looking ok.

hmmm, would you mind telling me how to do that? which plugs?
like taking out the battery, battery tray, and looking over there behind the tranny?

 

[Velocifero]

hmmm, would you mind telling me how to do that? which plugs?
like taking out the battery, battery tray, and looking over there behind the tranny?

pretty much yeah. there are two plugs, one is reverse sensor and the other I am not sure about, you can probably get to them from under the car as well, just find them and try to follow the best you can make sure the one I don;t know isn't unplugged or disconnected in some way, maybe bare and grounded out who knows, I am just trying to see why that nuetral circuit code is there