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After all the searching I could do and all the fixes I have tried I can not figure this one out.
The problem is that the car dies at idle and when it does idle it's very rough and does some surging through the lower RPMS, but not in a consistent way. If I punch the gas in neutral and let the rpms come down it will catch itself at 1375 rpm and then it drops to where it wants to "Idle" and dies. It also displays the code P0171 System too lean.
Now at first this looks like it is an easy thing to trouble shoot but let me tell you what I've done and if I've missed anything.
The car is a 2004 Manual Trans. The engine is relatively new and has about 20k on it. It is Catless, has a CAI, BHR ignition kit, pulleys, airpump delete. Those are all the relevant mods I can think of.
I have:
-Changed the spark plugs
-Changed the MAF
-Changed all ignition coils (BHR Coils)
-Done smoke test for vacuum leaks
-Checked fuel pump idle resistor
-Tried idle with and without intake (in front of MAF)
-Changed the neutral switch on the transmission
-Cleaned ESS (And reset with 20 brake stomp)
-Reset ECU
-Cleaned Throttle body
Notes:
-Fuel pump was changed under recent recall.
-Power steering goes out even though I've cleaned all the plugs and happened around the same time (Could be related if electrical issue?)
-Car had 0 issues with all the mods and this engine.
-Car has NO ISSUE starting even when hot. It starts like a champ right away.
Let me know if you guys can think of anything it may be.
Can you hook up and OBD reader and check the short term and long term fuel trims, and airflow if you can get it to warm up for any period of time. Airflow at warm idle rpm and no throttle should be around 5 g/sec. Report back with as much data as you can.
There aren't too many things that cause system too lean, very often it's a vacuum leak. Some locations for vacuum leaks can be hard to seem Which CAI is it? Those can cause problems also.
Still pretty new at trying to figure out what I'm looking at when it comes to PIDs. I took pictures of what is displayed at idle. It shows that my throttle is at like 25% when I'm not touching it. I'm assuming that's probably the idle percentage.
Can you hook up and OBD reader and check the short term and long term fuel trims, and airflow if you can get it to warm up for any period of time. Airflow at warm idle rpm and no throttle should be around 5 g/sec. Report back with as much data as you can.
There aren't too many things that cause system too lean, very often it's a vacuum leak. Some locations for vacuum leaks can be hard to seem Which CAI is it? Those can cause problems also.
Also the CAI is custom. I've had it on with no problems for a few years now. I even took it off to see if that was an issue, but it didn't change anything.
Your measured airflow is 4.3g/sec, that's low for a warm idle. You have a decent size vacuum leak somewhere. Start looking
One commonly overlooked one is the VFAD nipple under the throttle body.
I missed that due to not doing the unit conversion, but he claims it was smoke tested and an open nipple would seem obvious. I always prefer the carb spray method myself. Custom CAI can throw that off some too depending on how close the MAF end is to center, flow distribution, etc.
Yeah, a vacuum leak sounds like it would be the answer, but like I said it was smoke tested. I tripple checked the vfad and I also used starter fluid to spray around and look for vacuum leaks. I've done it so much that I've nearly used an entire can.
It seems like a clogged fuel injector could be the issue I suppose. It does make sense and sometimes I will get a cut at like 2-3k in first gear and the car will cut then lunge forward. As if it got little fuel then it just dumped fuel.
Unless I can find something else that makes sense then I may just remove the entire upper intake manifold and replace the injectors while I'm there.
Also, I really do appreciate your guys' help. Thank you
Can you illustrate your custom CAI? Team has another good point, your MAF could just be reading crazy because it's not a smooth airflow. Do you have mesh screens before it?
Can you illustrate your custom CAI? Team has another good point, your MAF could just be reading crazy because it's not a smooth airflow. Do you have mesh screens before it?
Well I've been using this same CAI for years prior to this with no issue. I also removed the CAI to make sure it wasn't the issue and it was still doing the same things. It doesn't have a screen in it but I can add one. Also the MAF is mounted in the stock place, so everything from the maf back is stock.
I will remove it once again to see if it makes any difference, but I'm not sure why it would cause these abrupt issues years later.
I suggested it could throw the reading off some. I’ve been running numerous custom CAIs for many, many years that didn’t read exactly 5 g/s at idle, but ran within 1% STFT. That’s not going to be the cause a 25% STFT and dying idle issue. My only point was being off that much is not much of a concern given all the other factors imo. There’s something else going on.
So I was very skeptical about it being the CAI because I have used it without issue for a long time even as my daily driver. Well since many of you brought it up again and Loki pointed out that my airflow was low I decided to completely dismantle it again, reset the ECU, and try my luck.
I removed everything past the MAF (AGAIN.....) and it was idling steady and when I checked the air flow rate again it was much higher than the .58 that it originally was idling at. I guess I'm in the market for a new intake.
I want to thank you guys for giving me your suggestions. I don't normally post a lot, but I was stumped since I had already troubleshot that and didn't give it much more thought since it had been working for years. Then again, the rx8 is kind of a picky girl lol.
Hi,Since you seem to have eliminated several possibilities,the first thing that come to mind was a vacuum leak (somewhere).I recently found one on my UIM where a vacuum plug fell off.Usually you can hear a vac leak but not alwaysAlso check your air flow screen of screens.Happy hunting!
12-13-2017, 03:37 PM
Stalling at Idle and P0171
