General > Turbo Tuning

Idle Issues

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powow66:
Hey guys!

New to the forums, but have been reading through lots of threads and you guys have helped me a lot with my build!
I've spoken on the phone with Brody, and first of all I'd like to say I'm very happy with the m50/s50 turbo tuning kit. The WAR chip software is an amazing platform that has extended my knowledge of cars tenfold. So far on the base tune my car pulls great at 9psi, and I've been successfully playing around with the tune to get the AFRs around 12.5 at WOT. Part throttle the car is settling nicely around 14.7 at cruising speeds.

HOWEVER here's my current issue which is related to this thread ( http://forums.millerperformancecars.com/index.php?topic=65.msg241#msg241 ):

-When I cold start the car, I need to pump the throttle right afterwards because it seems like the car has fuel starvation and wants to stall out. The car will then idle fine and start to warm up, but I notice that my AFR's slowly drop from ~14.7 all the way down to about 10.9, which is way to rich I think.

-Additionally, the idle tends to lean out intermittently and the car stalls once its warm. Doesn't matter if I drove it around or not, I need to feather the gas so that the idle will hold. From what I've been told by the admins at MP and from what I've read, I do think that the O2 sensor is overshooting the fuel corrections to bring the AFRs to 14.7, and that by changing the idle fuel values, I can minimize how much correction is needed to smooth out my idle. The AFRs once the motor is warmed up hovers at about 11. My current issue lies here, because so far I've tried changing the idle fuel values on the base tune from 100 down to 70, but once rewritten I see no change in the AFR's, it even drops a bit down to 10.8 occasionally. Turning the O2 sensor off hasn't made any noticeable affect, but I will continue playing with the fuel map and O2 sensor tab tomorrow to see if I make any progress!

Here is a list of the major components of my build:

0.120" MLS Head Gasket
ARP Head studs kit
Precision 5858 turbo
Miller WAR chip
60 lb siemens injectors
Miller MAF
CXracing intercooler
CXracing tubular T3 manifold
Tial WG and
Tial BOV (Currently open vent at idle, good/bad?)
3" plumbing
IE Oil cooler cap + oil cooler
AEM wideband O2 sensor + gauge

Replaced components:

O2 sensor
Knock sensors
Camshaft + Crankshaft position sensors
fuel pump
copper plugs (gapped to 0.025")
Ignition coils +boots
Cylinder head temp sensors
Oil pressure sensor
Both timing chain tensioners

Addionally:

-ecu scanned with no codes
-O2 sensors are about 5" from the exhaust turbine of the turbo
-cleaned ICV (strong buzz when key is in the ON position)
-inspected for boost leaks (car idles at about 22 mmHg of vacuum pressure)
-inspected FPR
-fuel pressure will be inspected, because I'm not sure how recent my fuel filter was replaced

Are there any other fuel maps I can modify to further diagnose the issue(I.e CT idle fuel maps, acceleration enrichment) and/or anything I should check mechanically? Any advice/suggestions/input would help me a lot! I'm very enthusiastic about finishing my build, and this is the final thing that needs to be resolved to get my car to the dyno! My apologies for the dense post! I appreciate all the help!

Cheers to a new year!

bulletholez:
Hey man! Glad your car is running great! I have literally this EXACT same issue that I've had 0 luck solving. Still trying to troubleshoot it to this day. I'm pulling about 20in of vacuum at idle and it loses it as it leans out, until a quick feather and back to rich idle. BOV being open as it's still metered air as it's pre-MAF shouldn't cause issue, unless it's causing turbulence. Random question, but was your car equipped with ASC from factory? This may sound weird, but my car ran GREAT when I first put it together, but I actually had my TPS plugged into the ASC "TPS" plug but obviously forever had a CEL for no TPS. Once I realized I had it in the wrong plug I corrected that, and my CEL went away, but that's when my problems started. I actually slowly started getting more lean conditions over the course of driving it. this may sound stupid but I'm out of options, I'm going to try and splice the ASC and TPS cables so the ECU sees response from "both". I'm really out of options unless my brand new MAF is bad or some other sensor that controls idle circuit that I don't know about went out... but even O2 sensors on/off still nothing. I'll check back every once in a while to see if you make any leway and if I find anything I'll post it up here. We can't be the only two with this problem! My build is very similar to yours also, could small differences that wouldn't do anything. I've changed the FPR on my car as well as flow tested my injectors to no avail.

powow66:
Thanks for your input bulletholez!

In regards to my BOV, I've tried clamping down the vacuum supply so that it would stay closed at idle just to further diagnose my issues with no luck. I do agree though that turbulence could be an issues, which is why I'm in search of a stiffer spring for it. To answer your ASC question: Yes, my car came with it from the factory, but I don't think I switched the plugs between the TPS and the ASC (since there's no check engine light whatsoever). I doubt any of the WAR chip/turbo kit hardware is faulty, but rather we have some mechanical issue we're overlooking  :-\.

Unfortunately I'm not gonna be able to further diagnose my issues until early March (my spring break from college), BUT the things that I am planning to do are:
-Replace the TPS sensor (I took resistance values and didn't get exactly a variable 1-4kohm upon opening the throttle, but more like variable 1.45-4kohm. Not sure if that's enough of a difference to need replacement, but I thought I'd do so to rule it out as being part of the issue).
-Check for Vacuum leaks (I'm gonna start by doing the old brake cleaner trick, spray around intake plumbing and observe for idle surge to find a leak)
-Unplugging the ASC (if that does anything)
-Check compression values
-Check Fuel Pressure/change fuel filter
-Trying different Crankcase vent methods (I'm not sure if I'm pulling enough of a vacuum from the crankcase, nor am I sure if that could contribute to the overall idling issue)

Regardless, I'll also stay active for any updates you may have (forgive me for delayed responses, for I am overloaded with schoolwork/work/etc.) and will post further any headway I make as well! We got this!

powow66:
Quick random thought/update: upon doing some research of the VANOS system (for my engineering research paper ;D), I realized that the vanos system retards the intake camshafts at idle. Getting to the point, I've never turned vanos ON, or set it at any of the VANOS control tab functions since I got the car running. Could selecting the "5300 (stock)" tab help with the issue or not at all? Cheers

bulletholez:
I've tried it on, off, everything. No change. Understood on the lack of time! The cold New England weather with no garage to currently use plus work and my family are slowing my wrench time. I've tried emailing and calling Miller with no response, slowly losing faith in this setup especially when a compression and boost/vacuum test both check out okay on my motor and my entire fuel system is new, injectors have been flow tested and have new filters, TPS is new, ICV is functioning properly, crank and cam sensors are new, MAF is clean and only has 1000 miles on it, the only things left are the air metering and ECU/tune. I'm actually on a silver label DME, I may bite the bullet and buy a red label to try (I hate spending money on shots in the dark), but after that this car is either getting a standalone/some other tuning setup or parted out. I'm very much over this at this point all last year it sat as I tried troubleshooting it, and have had other certified mechanic and BMW mechanic and insane gear head friends all get baffled by it still having issues. I don't want to band aid it, I want to fix it.

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