One-way check valve on IAC and methanol injection don't mix
by SirThomas88 » Sat Sep 10, 2011 12:51 am
Intro
If you have a TRD supercharger on your 1MZ-FE you should probably read through this.
My car has been experiencing four pronounced problems and I think I found the culprit. Important things to know about my car is that my Camry is a 2000 v6 Supercharged, 5-speed manual, and methanol injected about 6" before the throttle body.
Problem 1: Poor Idle / Stalling
For roughly year or more now, my car has been occasionally idling poorly and sometimes stalling after coming off the highway and to a stop (especially after hard boosting). I had removed and cleaned out the IAC last summer with TB cleaner and it improved slightly for a very short amount of time. This summer, I have been avoiding turning on my A/C because when I do the RPM's would drop to around 500 and the car felt horrible and even stalled once or twice.
Problem 2: Occasional Lean Condition at Idle
Sometimes, and often after engine breaking, my car will idle low, rough, and my Air Fuel Ratio (AFR) gauge reads lean, often above 18:1 (gauge cannot read higher than that). It will often stay like this for moments or minutes, until finally slowly readjusting to the correct 14.8:1 ratio. Usually, stepping on the throttle for a bit helps to return it to normal.
Problem 3: Boost Leak
As winter was ending, I noticed that my boost gauge was reading that I wasn't making full boost. I've got a 5.5PSI pulley, and I was only reading 4 - 4.5lbs peak boost, and it would gradually rise as I got to redline. It also was somewhat inconsistent, sometimes the leak was 1 PSI, sometimes only 0.5 PSI. I checked my boost gauge for leaks and such, couldn't find a solution.
Problem 4: Consistent stalling at idle.
This started occurring about a week ago. Every time upon coming to a stop after getting off the highway my car would immediately stall. If I was cruising on the highway and depressed the clutch pedal, the RPMs would drop right to 0 and the car would shut off. Sometimes it would hover around 100 or 200 before dying. The first time this happened, it stopped after half a day and worked for the rest of the evening until I got back on the highway and drove home. After that, it had been happening consistently once my car was warmed up. I would have to apply gas at stop signs to keep the car around 1k RPM.
Soluton 1, 3, & 4: Sticky/Rusted/Broken One-Way Check Valve on IAC
Since I have a supercharger, I had installed a plastic one-way check valve on the vacuum line running off of the Idle Air Control (IAC). The purpose of this is to prevent boost from leaking back through the IAC vacuum line and into the throttle body.
Upon dissasembling my intake to inspect and clean my IAC, I tested the check valve by blowing into it (and stupidly sucking air through it which resulted in copious amounts of rust on my tongue :facepalm:). I also noticed that air was passing through both directions, and not very well either. This valve is the same sort as the one used in the break booster. Pictures of check valve at bottom
I replaced the check valve and hose with new vacuum hose w/o a check valve. But upon testing it, the car had not improved and was still stalling instantly at idle if I wasn't on the gas. Took me three days before I tried blowing through a hose into the bottom of the IAC to find out that the IAC was stuck as well. It is my belief that rust and debris from the broken/rusty IAC valve spring had gotten lodged into the IAC and was preventing it from moving. Since when I first blew into the IAC, I could feel it come loose.
Solution 2: Exhaust Leak?
My car still sometimes goes lean at idle, but I think it's because the gasket for my rear header to the y-pipe is leaking (I know it's leaking). It's my belief that after heavy boosting or engine breaking, it sucks in fresh air from outside, causing my rear O2 sensors (and my AFR gauge sensor) to read very lean, causing a rich condition which causes the car to idle poorly. This is just a theory. I'll be replacing the gasket soon. If anyone has any better idea (failing pump, O2 sensors, injectors) do tell!
Conclusion and Thoughts
Today I installed all new IAC vacuum hose and took it for a drive. The car is idling around 800 - 900 RPM when warm, and around 700 RPM with the A/C on. I've only driven the car for about 45 mins, but considering the problem would occur immediately after the car warmed up, it seems to have been fixed. The car's idle feels smooth and consistent.
It seems likely to me that the methanol which I inject directly before the throttle body probably rusted out the spring mechanism in the one way check valve, resulting in it becoming increasingly stuck over time. It probably was stuck half open, half closed, which is why I was both loosing boost, and at the same time not idling properly. Likely, over the past year the stopper inside the valve probably would move around and get stuck in different positions of open and closed, resulting in inconsistent symptoms. This would make sense why the symptoms would occur most after doing heavy boosting on the highway and coming to a stop. The boost pressure from the S/C probably would force the check valve to get stuck closed. Eventually, it either got stuck entirely closed, and/or debris from it got stuck in the IAC, causing a consistent and instant stall at idle.
If you have a TRD supercharger on your 1MZ-FE you should probably read through this.
My car has been experiencing four pronounced problems and I think I found the culprit. Important things to know about my car is that my Camry is a 2000 v6 Supercharged, 5-speed manual, and methanol injected about 6" before the throttle body.
Problem 1: Poor Idle / Stalling
For roughly year or more now, my car has been occasionally idling poorly and sometimes stalling after coming off the highway and to a stop (especially after hard boosting). I had removed and cleaned out the IAC last summer with TB cleaner and it improved slightly for a very short amount of time. This summer, I have been avoiding turning on my A/C because when I do the RPM's would drop to around 500 and the car felt horrible and even stalled once or twice.
Problem 2: Occasional Lean Condition at Idle
Sometimes, and often after engine breaking, my car will idle low, rough, and my Air Fuel Ratio (AFR) gauge reads lean, often above 18:1 (gauge cannot read higher than that). It will often stay like this for moments or minutes, until finally slowly readjusting to the correct 14.8:1 ratio. Usually, stepping on the throttle for a bit helps to return it to normal.
Problem 3: Boost Leak
As winter was ending, I noticed that my boost gauge was reading that I wasn't making full boost. I've got a 5.5PSI pulley, and I was only reading 4 - 4.5lbs peak boost, and it would gradually rise as I got to redline. It also was somewhat inconsistent, sometimes the leak was 1 PSI, sometimes only 0.5 PSI. I checked my boost gauge for leaks and such, couldn't find a solution.
Problem 4: Consistent stalling at idle.
This started occurring about a week ago. Every time upon coming to a stop after getting off the highway my car would immediately stall. If I was cruising on the highway and depressed the clutch pedal, the RPMs would drop right to 0 and the car would shut off. Sometimes it would hover around 100 or 200 before dying. The first time this happened, it stopped after half a day and worked for the rest of the evening until I got back on the highway and drove home. After that, it had been happening consistently once my car was warmed up. I would have to apply gas at stop signs to keep the car around 1k RPM.
Soluton 1, 3, & 4: Sticky/Rusted/Broken One-Way Check Valve on IAC
Since I have a supercharger, I had installed a plastic one-way check valve on the vacuum line running off of the Idle Air Control (IAC). The purpose of this is to prevent boost from leaking back through the IAC vacuum line and into the throttle body.
Upon dissasembling my intake to inspect and clean my IAC, I tested the check valve by blowing into it (and stupidly sucking air through it which resulted in copious amounts of rust on my tongue :facepalm:). I also noticed that air was passing through both directions, and not very well either. This valve is the same sort as the one used in the break booster. Pictures of check valve at bottom
I replaced the check valve and hose with new vacuum hose w/o a check valve. But upon testing it, the car had not improved and was still stalling instantly at idle if I wasn't on the gas. Took me three days before I tried blowing through a hose into the bottom of the IAC to find out that the IAC was stuck as well. It is my belief that rust and debris from the broken/rusty IAC valve spring had gotten lodged into the IAC and was preventing it from moving. Since when I first blew into the IAC, I could feel it come loose.
Solution 2: Exhaust Leak?
My car still sometimes goes lean at idle, but I think it's because the gasket for my rear header to the y-pipe is leaking (I know it's leaking). It's my belief that after heavy boosting or engine breaking, it sucks in fresh air from outside, causing my rear O2 sensors (and my AFR gauge sensor) to read very lean, causing a rich condition which causes the car to idle poorly. This is just a theory. I'll be replacing the gasket soon. If anyone has any better idea (failing pump, O2 sensors, injectors) do tell!
Conclusion and Thoughts
Today I installed all new IAC vacuum hose and took it for a drive. The car is idling around 800 - 900 RPM when warm, and around 700 RPM with the A/C on. I've only driven the car for about 45 mins, but considering the problem would occur immediately after the car warmed up, it seems to have been fixed. The car's idle feels smooth and consistent.
It seems likely to me that the methanol which I inject directly before the throttle body probably rusted out the spring mechanism in the one way check valve, resulting in it becoming increasingly stuck over time. It probably was stuck half open, half closed, which is why I was both loosing boost, and at the same time not idling properly. Likely, over the past year the stopper inside the valve probably would move around and get stuck in different positions of open and closed, resulting in inconsistent symptoms. This would make sense why the symptoms would occur most after doing heavy boosting on the highway and coming to a stop. The boost pressure from the S/C probably would force the check valve to get stuck closed. Eventually, it either got stuck entirely closed, and/or debris from it got stuck in the IAC, causing a consistent and instant stall at idle.
14.11s 101mph quarter mile. 5 Speed v6 Supercharged @ 5.5psi
- SirThomas88
- SolaraGuy Driver
- Posts: 471
- Joined: Mon Dec 07, 2009 9:37 pm
- Location: Baltimore
I took it to the dealership and they said "we cant seem to find the prob. Wait till it gets worse so it throws another code" ...hmm thats strange wtf are they ASE certified for if they cant find the problem??
That happened 3 1/2 years ago and its been fine since
