HELP! Rough Idle at stop light, already cleaned EGR and IAC, replaced mounts
 

Help, I'm at my wit's end with my 97 LX protege 1.5L.

It's that common rough idle problem with the protege.

Right now, my car idles very rough, interior vibrates like crazy when I pull to a stop sign or stop light, with the brakes pressed, and in drive. The RPM surges up and down to close to 1-1.5k? It gets a bit worse with A/C and defogger on. If I switch to neutral, vibration goes away.

I have cleaned out EGR, cleaned out throttle body, replaced PCV, changed air filter, replaced breather tube, changed fuel filter, replaced timing belt, ac/power steering belt, water pump, mounts, spark plugs.

Yes the mechanic has run me to the ground replacing belts, and mounts, fuel filter I cleaned the EGR, and throttle body myself. I also cleaned the IAC valve too.

Most recently, the mechanic said that the TB gasket was on backwards - a bunch of BS....so he put it back on and put sealant all around it.

Since then, the car still idles rough almost a bit worse. I bought a used MAF, which actually increased the acceleration/power response for the car a bit. I also replaced the battery, and cleaned up terminals and ground connections. However, the idling is still poor.

Recently, the check engine light came on, then went away. The code was P0505. I have since bought a used throttle body with IAC valve. I already tried cleaning the exisitng one, but could the IAC just be bad? Should I replace it with a used one? Are there any other sensors that could be bad?

The car was meticulously serviced and has 98000 miles on it. I'm at the point where I may want to get rid of it if I can not solve this idling problem.

Do you have any other suggestions? Or anybody in SF Bay area want to buy a 97 Protege - with rough idle - lol! It has new front brakes, and relatively new tires! Already replaced timing belt and water pump! It just vibrates at stop signs that's all!


Thanks for your help

Phil
ppcchi@hotmail.com

Hello, Phil, and welcome. Since this place is not very active, I would suggest you ask your further questions at www.clubprotege.com . As far your problem goes, you are not the only, and there are many people who are trying to figure out just what the hell is wrong with our cars sometimes. However, to help you out a bit, P0505:

DETECTION CONDITION

- PCM detects no continuity of idle air control valve curcuit
- Actual engine speed is excesseively higher or lower than target speed preset in PCM for more than 14 sec.

POSSIBLE CAUSE

- Idle air control valve malfunction
- Leakage in intake-air system
- Open or short circuit in wiring from idle air control valve terminal A to PCM terminal 4G
- Open or short circuit in wiring from idle air control valve terminal B to PCM terminal 4H

I hope this helps a bit.

Hi, my Protege has almost the same problem too and consumes much more gas than it suppose to be, about 20mpg. I don't think it is normal, can anybody tell me what't wrong? I just replace the air in-take hose, which cost me 78$. Thanks a lot.

Poor gas mileage can be a result of many thigns. Really, and I mean REALLY, dirty air filter, or MAF has gone bad, etc. Replacing your intake hose probably could solve a bad idling problem, but that should not have affected your mileage. Are there any other syptoms, check engine light, etc?

The engine light is fine. When the car run in high speed, it is very smooth and powerful. Thanks.

check your charging system, see if your battery or alternator is having a problem, I think its 20 bucks for the diagnose at mazda.

A friends protege was doing the same thing , found out his Battery was toast, and bring the engine to its knees with a super low and ruff idle

Hi, thanks, somebody inspect the car and told me one of the valve pressure is lower than others, what did this mean?