UPDATE ***
Replaced the "new" IAC with a genuine Mazda IAC (part #FSN5-20-660B) and the car now idles just as it is supposed to in all phases. No more racing to 3000 rpm! Car now runs great! Just goes to show you that some aftermarket parts, though they say they are OEM replacements (and even claim the same FSN5-20-660B part number), are not really true OEM replacements. For more details, go to my third post below.
Unfortunately, this was not the end of the problem for very long. There was more waiting around the corner... And at the end of the day, I found that I had unknowingly caused the high idle. Here's the discussion about that.
**************
Hello Everyone,
Long time lurker, first time poster...
My daughter's 2003 Protege5 starts and revs immediately to 3000 rpm and holds there for about 15 seconds, and then gradually drops to normal idle (700-800 RPM). It only occurs on a cold start. If there's any heat on the engine, it starts and idles normally. Road performance is fine. The IAC is brand new, I find no vacuum leaks, and the computer has been reset properly. No codes or CEL's. But this is just the latest in a series of issues that I've addressed. And I'm about ready to pull my hair out...
The Saga Begins
We bought this P5 used from a dealer many miles from us. On the drive home, she started having engine cut-out and stumbling with a CEL code P0300 (random misfire). After some fits and starts (and reading a lot of posts here on this forum), I realized that it was probably a bad coil and replaced them both. Problem solved. But as part of this process, I bought an EGR valve to install (since that might have also been a contributor), and since I had it, I decided to install it, as well as change the oil and filter, flush the radiator, tranny fluid, replace the thermostat, radiator cap, and other odds and ends that need to be replaced on an 11 year old car with 80,000 miles so that it is a reliable machine for my daughter to drive.
Coincidentally, while reading through different topics on this forum, I stumbled across the VICS butterfly valve failure issue on 2003 Protege5's. Since I have some experience repairing cars (though not a professional mechanic), pulling the manifold and checking the valves seemed pretty straight forward (again, using info from this forum), so I figured I'd pull it, inspect the VICS and VTCS valves, replace the gaskets in the intake system, replace the EGR, and everything would be lovely. I was wrong...
Removing the manifold was more of a PITA than I thought it would be, but I got it apart and found the resonance chamber filled with oil sludge from an PCV failure in a prior ownership. (The VICS and VTCS valves were in good shape, albeit covered with oily sludge.) So, we cleaned that up, put new gaskets on everything, installed the EGR (with new gasket), sealed it all back up, and started it.
Now a new problem arose. The idle was erratic. It would fluctuate and drop to 500, hold there for a few seconds, vibrate the hell out of everything, and then come up to normal. I reset the computer according to the manual, but the problem remained. It would do this "drop and rattle" frequently before and after warm-up, such that every time you came to a stop while on the road, it would idle so low that you hoped it wouldn't die. But after a few shaky moments on the edge, it would come back up. Otherwise, road performance was fine. So, more research here on this forum indicated that it might be a bad/dirty IAC. So, I bought an aftermarket IAC (and gasket) and a MAF (since I was there anyway) and installed them. (Those IAC screws are a bear...)
Now, I had a screaming new problem - On start, the engine raced to 3000 rpm, holds there for about 15 seconds, and then drops into normal cold idle limits. It only does this on a dead cold start. If there's any heat on the engine, it starts and idles normally. Yes, I've checked for vacuum leaks and reset the computer according to the shop manual, and all other parameters are normal - and no codes or CELs. Everything works like it's supposed to except for that screaming start!
I can't find anyone else with this kind of issue or any posts addressing such an extreme high idle on cold start. After studying how this particular IAC gets control pulses from the PCM at start up (rather than relying on a thermowax bead), I'm beginning to believe that my new aftermarket IAC may in fact be bad. I ruled out coolant temp sensor since I can't imagine a temperature situation - even an erroneous one - where the PCM would tell the IAC to idle the engine at 3000 rpm. (BTW - our ambient temperatures have been around 70 on cold starts.) And if it was a bad PCM, I would think that it would have other issues other than a high cold start idle. But, before I buy another IAC, I wanted to throw this out to you guys to see if you had an idea of what it could be.
Please help while I still have some hair left.
Melsman
Replaced the "new" IAC with a genuine Mazda IAC (part #FSN5-20-660B) and the car now idles just as it is supposed to in all phases. No more racing to 3000 rpm! Car now runs great! Just goes to show you that some aftermarket parts, though they say they are OEM replacements (and even claim the same FSN5-20-660B part number), are not really true OEM replacements. For more details, go to my third post below.
Unfortunately, this was not the end of the problem for very long. There was more waiting around the corner... And at the end of the day, I found that I had unknowingly caused the high idle. Here's the discussion about that.
**************
Hello Everyone,
Long time lurker, first time poster...
My daughter's 2003 Protege5 starts and revs immediately to 3000 rpm and holds there for about 15 seconds, and then gradually drops to normal idle (700-800 RPM). It only occurs on a cold start. If there's any heat on the engine, it starts and idles normally. Road performance is fine. The IAC is brand new, I find no vacuum leaks, and the computer has been reset properly. No codes or CEL's. But this is just the latest in a series of issues that I've addressed. And I'm about ready to pull my hair out...
The Saga Begins
We bought this P5 used from a dealer many miles from us. On the drive home, she started having engine cut-out and stumbling with a CEL code P0300 (random misfire). After some fits and starts (and reading a lot of posts here on this forum), I realized that it was probably a bad coil and replaced them both. Problem solved. But as part of this process, I bought an EGR valve to install (since that might have also been a contributor), and since I had it, I decided to install it, as well as change the oil and filter, flush the radiator, tranny fluid, replace the thermostat, radiator cap, and other odds and ends that need to be replaced on an 11 year old car with 80,000 miles so that it is a reliable machine for my daughter to drive.
Coincidentally, while reading through different topics on this forum, I stumbled across the VICS butterfly valve failure issue on 2003 Protege5's. Since I have some experience repairing cars (though not a professional mechanic), pulling the manifold and checking the valves seemed pretty straight forward (again, using info from this forum), so I figured I'd pull it, inspect the VICS and VTCS valves, replace the gaskets in the intake system, replace the EGR, and everything would be lovely. I was wrong...
Removing the manifold was more of a PITA than I thought it would be, but I got it apart and found the resonance chamber filled with oil sludge from an PCV failure in a prior ownership. (The VICS and VTCS valves were in good shape, albeit covered with oily sludge.) So, we cleaned that up, put new gaskets on everything, installed the EGR (with new gasket), sealed it all back up, and started it.
Now a new problem arose. The idle was erratic. It would fluctuate and drop to 500, hold there for a few seconds, vibrate the hell out of everything, and then come up to normal. I reset the computer according to the manual, but the problem remained. It would do this "drop and rattle" frequently before and after warm-up, such that every time you came to a stop while on the road, it would idle so low that you hoped it wouldn't die. But after a few shaky moments on the edge, it would come back up. Otherwise, road performance was fine. So, more research here on this forum indicated that it might be a bad/dirty IAC. So, I bought an aftermarket IAC (and gasket) and a MAF (since I was there anyway) and installed them. (Those IAC screws are a bear...)
Now, I had a screaming new problem - On start, the engine raced to 3000 rpm, holds there for about 15 seconds, and then drops into normal cold idle limits. It only does this on a dead cold start. If there's any heat on the engine, it starts and idles normally. Yes, I've checked for vacuum leaks and reset the computer according to the shop manual, and all other parameters are normal - and no codes or CELs. Everything works like it's supposed to except for that screaming start!
I can't find anyone else with this kind of issue or any posts addressing such an extreme high idle on cold start. After studying how this particular IAC gets control pulses from the PCM at start up (rather than relying on a thermowax bead), I'm beginning to believe that my new aftermarket IAC may in fact be bad. I ruled out coolant temp sensor since I can't imagine a temperature situation - even an erroneous one - where the PCM would tell the IAC to idle the engine at 3000 rpm. (BTW - our ambient temperatures have been around 70 on cold starts.) And if it was a bad PCM, I would think that it would have other issues other than a high cold start idle. But, before I buy another IAC, I wanted to throw this out to you guys to see if you had an idea of what it could be.
Please help while I still have some hair left.
Melsman
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