Idle Issue

T

Tw1g007

Member
:
2002 Mazda Protege5
Hey guys, I know this subject has probably been discussed to death but I need a little help.

So, my car has had a minor idle issue for a little while now. I haven't really had a chance to check it out, however it's starting to get worse. It's only when my car is at a stop. The idle speed is supposed to be at 750 rpm, but currently it's been at 500 rpm and yesterday it dropped to about 350 rpm. I know this is really bad for the engine, so I was just looking to see all of the possibilities as far as what it is.

I was going to look into cleaning the Idle Air Control, maybe replacing the injectors, fuel filter, and maybe the fuel pump (I need to test it to see if it works).

The other problem I have is that my car has been sucking down gas like crazy. I was averaging 400 miles a tank about 6 months ago, but it's been declining since then. About 3 months ago I swapped out the transmission (which needed to be replaced) with one from a 626. I assumed the taller gear ratio in 5th gear would increase my mileage a little bit, but it hasn't made a difference. So basically I would like to know if you guys have any ideas as to why my car is guzzling gas so badly.

Thanks
 
I would check the air cleaner first and if that is OK see if there are any small pipes off round the inlet manifold. You can spray WD40 around that area and if the engine speeds up you can home in on the leak. Do not spray WD40 on the exhaust!
 
I think you should start with half a can of seafoam in the gas and half up the brake booster vacuum line.

It could be just dirty (injectors) and you may be able to clean it internally without taking anything apart.

It's cheap and easy and could save you lots of time, effort and money.

If not,.. here's the big list of potential causes...





 
Last edited:
cartracer12 said:
Vacuum leaks between the throttle plate and MAF sensor. Vacuum leaks that are after the throttle plate would cause a high idle rather than a low idle.

Sent from my XT1032 using Tapatalk
Click to expand...

Only on speed density systems, on a MAF engine any vacuum leak will cause strange idle behavior.
 
MrGiggles said:
Only on speed density systems, on a MAF engine any vacuum leak will cause strange idle behavior.
Click to expand...
A large enough leak past the throttle plate cannot be choked out by the IAC and will cause high idle.

Sent from my XT1032 using Tapatalk
 
cartracer12 said:
A large enough leak past the throttle plate cannot be choked out by the IAC and will cause high idle.

Sent from my XT1032 using Tapatalk
Click to expand...

When I had a pretty good vacuum leak from my injector seals, it resulted in an idle oscillation from 0-700 rpm, and an occasional PO171 code. The idle speed was not abnormally high.
 
Interesting. How many kms did your car have when the injector seals went?

Sent from my XT1032 using Tapatalk
 
So I should check for;

Vacuum leaks
Clean the MAF
Clean Injectors/fuel system
Possibly injector seals?

Did I miss anything?
 
The_big_dill said:
Start with:

- clean air filter
- clean MAF sensor
- clean IAC
- clean EGR
Click to expand...

Okay, I'm actually looking to put the stock system back in because the original owner put a makeshift "short ram" system in which is terrible. He also never maintained the air filter so it's in need of replacement anyway.
 
Btw, I know where the EGR is, but where is the IAC (and will I be able to clean it with Carburetor cleaner?)
 
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