AntleredRuin
New member
1999 LTD V6, 2wd, non-Cali emissions
OK, so I have some weird backstory; not sure if it's all related, but every detail helps, right?
I'd been getting a P0505 code for my IAC off and on for about a year. It would come on, then go away within a few minutes, and stay off for months at a time. More and more often, the 4Runner would stall when sitting still like in traffic, maybe once every other week. Started back up just fine though.
Then the IAC code stuck and didn't go away, and I got another code, the P0171 lean code, and the 4Runner started getting hard to start when hot. If it was on, and I turned it off and right back on again, it would work, but if I waited maybe 15-20 minutes, it would crank and stumble its way to life, and run rough for about 30 seconds to a minutes during which I had to give it gas or it might stall. If I cut it off and tried to start it again, it wouldn't start at all. If I waited 45 minutes or so, it'd start up just fine.
I'd cleaned the IAC when I first bought the 4runner over 3 years ago, and had read that often when you have an IAC CEL, cleaning it sometimes only temporarily fixes the problem; you'll need a new one soon.
So I figured I'd get a new one, cause why not? I found one on Amazon. It was NOT OEM Denso, but had nearly 5 stars for over 50 reviews, so at $40, I figured it was worth a shot.
I installed the new IAC, cleaned my MAF with MAF cleaner (I clean it a few times a year), cleaned the TB out (it was pretty black), and installed a new air filter.
Cranked it up, and it started fine, but the idle was never right. It was always too high, even when warmed up. It'd sit around 800RPM when in Drive, and over 1500RPM when in Park. I adjusted the linkages for the TB, reset the EFI relay, pulled the battery, etc. Nothing fixed it.
The new IAC made the P0505 code go away, but the P0171 came back, and I also got a P0125 (insufficient coolant temp). The coolant amount is fine, and I read that the MAF can throw that sometimes while it's relearning, so I pulled the battery to reset the codes, but they came back again. Also, the hard starts were still there.
After a few days of this (to see if the ECM would relearn), around 150 miles, I decided to reinstall the old IAC (after a thorough cleaning). I also replaced the large air inlet hose connecting the air baffle to the TB because it was pretty cracked (Duct tape had held it together for years, but it was time)
The idle returned to normal, the P0505 code stayed away, and the P0171 came back. I've driven it for a week like this, and yesterday, the P0125 came on for one drive, but turned back off the next. The P0125 code is currently off.
The hard starts are still happening, but seem better. Now it can start when warm, multiple times in a row, but it sputters a bit while doing so, but once on it idles smooth.
So I'm kinda stumped, but I have some ideas. I almost don't care about the P0171, but the hard starts can be potentially dangerous and stranding. The most obvious ones are the MAF and the O2 sensors. The MAF is not new, but I've traded in a non-OEM spare that's currently working fine in my wife's 2003 Rav4 (same part number), and the issues remain, so I put my original one back in. So MAF could still be the issue, but I don't think so. I'd have to buy a brand new one to be sure.
I've read that the upstream O2 sensor could cause a P0171 code and a P0125 code so I'm leaning that direction, as mine has almost 200k on it. Really needs to be done anyways. Could a bad O2 sensor 'overheat' and cause hard starts until it cools down?
I'm just mostly confused about the warm hard starts. Research shows these are usually mostly fuel pressure related, but the timing with my other codes seems to indicate otherwise. It cranks fine, so not a battery or starter issue. It just stumbles like it doesn't have the proper fuel mixture, but only when warm.
I read somewhere that someone's fuel injector cracked internally and was releasing fuel pressure. I also read that the Jeep guys used to wrap their injectors with reflective insulation to prevent heat-soak and vapor-lock.
Any ideas?
Edit: No gas smells at all, and it drives great once started. I had a bad FPR a few years ago, and the symptoms were different.
OK, so I have some weird backstory; not sure if it's all related, but every detail helps, right?
I'd been getting a P0505 code for my IAC off and on for about a year. It would come on, then go away within a few minutes, and stay off for months at a time. More and more often, the 4Runner would stall when sitting still like in traffic, maybe once every other week. Started back up just fine though.
Then the IAC code stuck and didn't go away, and I got another code, the P0171 lean code, and the 4Runner started getting hard to start when hot. If it was on, and I turned it off and right back on again, it would work, but if I waited maybe 15-20 minutes, it would crank and stumble its way to life, and run rough for about 30 seconds to a minutes during which I had to give it gas or it might stall. If I cut it off and tried to start it again, it wouldn't start at all. If I waited 45 minutes or so, it'd start up just fine.
I'd cleaned the IAC when I first bought the 4runner over 3 years ago, and had read that often when you have an IAC CEL, cleaning it sometimes only temporarily fixes the problem; you'll need a new one soon.
So I figured I'd get a new one, cause why not? I found one on Amazon. It was NOT OEM Denso, but had nearly 5 stars for over 50 reviews, so at $40, I figured it was worth a shot.
I installed the new IAC, cleaned my MAF with MAF cleaner (I clean it a few times a year), cleaned the TB out (it was pretty black), and installed a new air filter.
Cranked it up, and it started fine, but the idle was never right. It was always too high, even when warmed up. It'd sit around 800RPM when in Drive, and over 1500RPM when in Park. I adjusted the linkages for the TB, reset the EFI relay, pulled the battery, etc. Nothing fixed it.
The new IAC made the P0505 code go away, but the P0171 came back, and I also got a P0125 (insufficient coolant temp). The coolant amount is fine, and I read that the MAF can throw that sometimes while it's relearning, so I pulled the battery to reset the codes, but they came back again. Also, the hard starts were still there.
After a few days of this (to see if the ECM would relearn), around 150 miles, I decided to reinstall the old IAC (after a thorough cleaning). I also replaced the large air inlet hose connecting the air baffle to the TB because it was pretty cracked (Duct tape had held it together for years, but it was time)
The idle returned to normal, the P0505 code stayed away, and the P0171 came back. I've driven it for a week like this, and yesterday, the P0125 came on for one drive, but turned back off the next. The P0125 code is currently off.
The hard starts are still happening, but seem better. Now it can start when warm, multiple times in a row, but it sputters a bit while doing so, but once on it idles smooth.
So I'm kinda stumped, but I have some ideas. I almost don't care about the P0171, but the hard starts can be potentially dangerous and stranding. The most obvious ones are the MAF and the O2 sensors. The MAF is not new, but I've traded in a non-OEM spare that's currently working fine in my wife's 2003 Rav4 (same part number), and the issues remain, so I put my original one back in. So MAF could still be the issue, but I don't think so. I'd have to buy a brand new one to be sure.
I've read that the upstream O2 sensor could cause a P0171 code and a P0125 code so I'm leaning that direction, as mine has almost 200k on it. Really needs to be done anyways. Could a bad O2 sensor 'overheat' and cause hard starts until it cools down?
I'm just mostly confused about the warm hard starts. Research shows these are usually mostly fuel pressure related, but the timing with my other codes seems to indicate otherwise. It cranks fine, so not a battery or starter issue. It just stumbles like it doesn't have the proper fuel mixture, but only when warm.
I read somewhere that someone's fuel injector cracked internally and was releasing fuel pressure. I also read that the Jeep guys used to wrap their injectors with reflective insulation to prevent heat-soak and vapor-lock.
Any ideas?
Edit: No gas smells at all, and it drives great once started. I had a bad FPR a few years ago, and the symptoms were different.
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