Hard starts, running lean and performance issues.

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pdiggity

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Feb 13, 2011
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raleigh
Hoping someone with a higher level of technical mkiii knowledge can help me out. I'll start with my issues and then post a list of my engine setup.

This is a problem that seems to be getting worse. A month ago, my a/f gauge said I was running rich under throttle, now it's the opposite. I'm seeing idle a/f ratios of 15 to 16, a/f ratio of 14 is common now under any load - I was scared to let boost kick in or drive more daring than a granny because I know running this lean can get dangerous quickly ( I should be running about 11.5 a/f under boost). I'm having hard starts that's getting worse, sometimes taking 6 to 7 cranks to get it running. I get a good idle but have had to add +25% fuel at lo throttle with my super AFC to keep it that way -- this is weird because I know that the mk3 ecu is under full control until over 69% throttle. Performance is suffering some too, I've been having to re-tweak my fuel curve to keep from shuddering under throttle in second and third gear. I don't know what it could be because most of my components have low hours on them.

My specs,

Lexus afm upgrade with matching 550 RC injectors
Stage 1 turbo, downpipe, no cats
Walbro fuel pump
Full tuneup, plugs, fuel filters
AEM wideband
Apexi S-AFC
Hallman manual boost controller at 12 pounds
Jspec engine, new harness rewired w/ no issues
No engine codes except I'm missing the egr system.
 
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pdiggity

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Feb 13, 2011
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raleigh
Agreed, intake leak makes sense. I have the original intake and inter cooler piping, I'm sure it's had better days. I presume anything that would bypass the afm, I.e. air leak, could/would cause this lean a/f rough running issue?
I guess it's due time for hard piping in everything for the sure fix, been wanting to do it for a while. Recommendations on bang for the buck inter cooler/ hard pipe kit?
Would a bad intake leak cause the hard starting issues I'm having? Is there an easy way to test for said leaks?
 
airhead04

airhead04

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Aug 21, 2009
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Lima, Ohio, United States
Intake leak, take some carb cleaner or something and start the car and spray it around the intake mating points. If the car idles up, you have a leak. Also, a Boost Leak Tester. Basically you take something to plug the AFM accordian hose off, and put a fitting on so you can pressurized the system with a compressor. (Only like 15 to 20 psi) and listen. You should be able to hear some hissing. If not, use some SOAPY water, and spray around some of the piping and areas, and if its bubbling, its leaking.
 
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pdiggity

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Feb 13, 2011
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raleigh
airhead04;1843431 said:
Quite welcome.

Also, check for exhaust leaks. You should be able to hear that with the car running
Click to expand...


I have finally got around to checking leaks. I had a couple minor ones, the throttle body is from a U.S engine & I fitted it to a J-spec engine that I put in it - it always had issues sealing properly, stock gaskets wouldn't work - I permatexed it to ensure a seal. My O2 sensor had a leak because one of the bolts was on it's way to disintegrating , that has been fixed. My clamp on the air inlet hose to the turbo was bad and loose, that has been fixed as well.

I was still getting lean running and it was getting worse, barely able to start and get it to idle. I have a spare MAF sensor that I decided to try -- a few minutes of trying to stall out and it seems the ECU calibrated itself and now it's idling great and running rich again as it should (about 10.5 to 11 A/F ratio) without having to tweak anything with my Super AFC.

But, now it tries to stall out when I try to rev it up from idle -- it will throttle up if I go slow and smooth, but sudden acceleration & it immediately stalls out and drops back to idle.
?????????????????????????

Pull EFI fuse and reset ECU??? has the ECU possibly learned a horrible fuel curve from a bad AFM??
 
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pdiggity

New Member
Feb 13, 2011
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raleigh
Yes, good call. I need a good timing light anyways, lookin now on amazon as well as a good soldering set.

Following this, http://www.supra.co.nz/timing.htm

My car is a headache right now, throwing codes 24 and 31. I understand that my Apexi safc could also be the culprit for that. I need to check wiring and redo some connections, check grounds and what not. I did completely replace the engine wiring harness but haven't had issues until now.

Currently it will start with a few cranks, idles pretty good (running quite rich), but any attempt to throttle it up at all results in bogging down and trying to stall. Seems to be dumping fuel. It crazy because at the beginning of this thread I was running really lean and driving it to and from work ( more dangerous of course). Something happened and it's gotten worse in that it's not even drive able.

Update,
I've decide to also drill out the J-tube to rule out that common fuel issue because I am running 550's and Lexus AFM.
 
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pdiggity

New Member
Feb 13, 2011
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raleigh
Solved!

I finally decided to drop the fuel tank and see what was going on -- I was hearing a little more than just the whine of the Walbro. I just finished inspecting the pump and feed line from the fuel pump to the main line was completely disintegrated to the point of mush, glad I caught it before all the gunk ended up in the injectors and everywhere else. Amazing, no surprise I was running lean -- all the fuel was just spraying like a lawn sprinkler back into the tank. Mystery solved -- she's gonna be a beast once again. Maybe I need to look into some rugged fuel line for that connection?

So glad it wasn't something electrical, AFM related, CPS, etc.....
 
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