When I was given this car the check engine light was on and the motor idled very low, rough, and erratic. I was told by the previous owner that the check engine light was for the EGR Valve. I replaced the fuel filter one day and after that the car would not idle after reaching operating temperature. Once you push the clutch in, the RPM’s drop straight to 0. I changed the fuel filter with a different one and the problem did not go away.
I then pulled the TB off of the intake, and the intake off of the engine. I cleaned all of the air passages in the intake (the EGR passages were completely clogged). After that I installed a new EGR valve and gasket, intake gasket, and TB gasket. I pulled the battery to clear any codes. After all of this, the motor still will not idle. Sometimes it will almost die and then kick up to 1,200 then drop down again.

Does anyone have any idea what could be causing this problem?
Does anyone know what the OHM specs are for the Throttle Position Sensor?

Thanks

ccannon222

 

I have a 00 Protege and have been having the similar problems. I used seafoam to clean the intake, throttle body & fuel system and I thought for a day or two the problem was gone. Then the engine all but stalled and the Check Engine light came back on. I hillbillied it and adjust the idle control to keep the RPM's up a little higher but even then it occasionaly wants to drop lower but it doesn't stall for me any more. Any one have any "real" solutions?

 

Does the 1.5L 4cyl in my 98 have adjustable idle? If so, where is it located. I glanced at the TB last night and did not see any adjustment screws.
Please forgive my ignorance, I am used to working on toyota's which have an adjustment screw on top of the TB

Thanks

ccannon222

 

Ok, first, I think you have a 1998 1.5l.
Second, Is it still throwing the code? If so that will tell you where to start. and what was the code when it was throwing it.

The idle is controlled by the PCM through the Idle air control valve. DO NOT ATTEMPT TO ADJUST!!!!!

Throttle position sensors do not tend to be a problem on these unless it has been shorted. Resistance between the outside terminals should be 4-6 Kilo-Ohm.

Number one job, get the code...

 

There is no code currently in the computer. Once I pulled the battery the check engine light when off. I have since borrowed a friends OBD II tool to double check.
As for the previous code, I do not know the exact code. The previous owner said that it was an EGR code. Having been told about the problems with the EGR passages in the intake getting clogged, I decided to pull it and clean everything out. Since I had the intake off I thought it would be a good idea to replace the fuel filter as well.
I would have checked the code before pulling the battery but I did not have the tool at the time and I was in a hurry trying to get this car fixed for my wife.
I have checked for vacuum leaks and haven’t found any. I will be borrowing a fuel pressure testing tool this weekend.
I will admit I know very little about Mazda’s EFI system. The IAC valve and TPS are very common problem on older Toyota 4cyl’s that I am familiar with.

Thanks for the ideas, please keep them coming.

ccannon222

 

cannon, if it was an egr code, it was probably P0400. I just had that and you did the right thing, especially if you got the 2 directly behing the TB. However, you likely didn't need the new EGR valve if the ports were plugged as the code sets because vacuum differential (and thus, EGR flow) is not what it should be due to the clogged passages.

Once the code (or a code i should say) comes back, check it right away to help with diagnosis. Other than that. like Mazda ES said, do not adjust the idle, you have to set "minimum air" with the IAC disconnected, ie non-regulated idle, and then the computer uses the IAC to set proper idle from the base airflow. If the base (minimum) airflow is screwed up, the car will run like crap. So that is one potential cause, but with the sudden appearance it sounds like possibly fuel related.

Others could be:

- remove and clean the IAC
- test fuel pressure....if memory serves, it should be in the 34-38 range and in the 40's primed but engine off. if out of these specs, then pump or regulator could be the culprit. A quick check for the regulator is to remove the vacuum line....the idle should change and there sshould be no fuel coming out the hose or smell.

Hope this helps.

 

My '00 DX had a low/rough idle when I purchased, and it went away after these changes:
- Replaced plugs (they were pretty bad)
- Replaced air filter (filthy)
- Replaced plug wires
- Cleaned EGR valve
- Unclogged EGR valve port
- Cleaned MAF sensor with electrical cleaner
- Replaced the air intake boot (was cracked where the crankcase vacuum line connected)
I think the last three were what made the difference. Hope this helps.

 

Update,

A mechanic friend of mine told me that sometimes when you fix a problem on these cars, then pull the battery that the car will not run right right away. He said to start the car up, let the car idle up to operating tempature. Then try driving it. If I still get the stall problem, repeat the warm up then drive. This sounded weired to me.I tried it, and the car now runs fine. The idle is a tad low and rough but no big deal. I then drove the car to work and the CEL came back on. Pulled the code and it is a P0400. I pulled the vacum hose that comes off of the EGR valve and goes to some sort of module. I now have vacum at this module where I did not before the cleaning. Could this module be bad? If so, is there a way to verify this?

Thanks

ccannon222

 

I think you are talking about the EGR Boost sensor, which is connected to a solenoid, which is on the same rack, bolted to thefirewall.Go to the junkyard and get another one. 1.8l, 1.5l and 626 all have the same setup. The junkyard won't charge you alot for it, most won't even know what or where it is. Bring WD40 and tools, especially a sharp knife, Mazda used an aluminum nut screwed onto a steel stud, and they are a bugger to get off. There is a rubber isolation stud between the bracket and the firewall. One option is to cut through the rubber to get it off the junkyard car, then let it sit in the WD40 for a couple of hours back at your shop to free it. Do the same with the car you are installing it on.