Solving Idle / Cruise Issue with Chrome on a '99 - Also Evoscan Command Questions

[Streamln1]

I am posting these questions here by Greg's request, I have a customers '99 that we tuned with the Chrome rom, fairly simple 550cc injectors and 13G turbo car dialed in for 15Psi of boost

Our WOT tune is spot on for pump gas at a conservative 10.9 AFR on the wideband and is pulling clean and car left me running great. However the customer has brought the car back to me because its idling rough when its warmed up and at low throttle cruising speeds having some issues. Car is stumbling, gurgly at idle, AFR at idle hangs out a little on the lean side of things, averaging 14.8-15.5 sometimes going all the way to 16.0-16.5, when it does occasionally stay in the 14.0 - 14.7 range its a lot happier. Car also sometimes going lean at part throttle low speeds. Car has also been throwing a P0505 Code malfunction with the IAC system.



We have been logging the car with Evoscan. Trims are staying in a normal range hanging out around +-5% and it is going into closed loop. What I have noticed in Evoscan which seems unusual is that the ISC steps are hanging out around 0-3 steps, which according to the ROM it should be 9-13 steps based on the coolant temperature once its warmed up. It just has a hard time stabilizing the idle AFR, and the car is stumbing / gurgling a lot when its acting up like this. It also seems to take a lot longer to recover from engine speed changes than my car does.

The hardest thing about this is that the problems are intermittent. My thoughts were an injector going bad, or even possibly an ignition related issue such as a coil not firing etc.

What we have tried and or replaced-

-Checked timing belt
-Boost leak test
-New Plugs and Wires (helped a bit because the wires were getting old and car needed a tune up)
-Raised idle speed in chrome to 900 RPM and reset BISS screw
-Checked IAC motor, all coils check out to be in spec and its a fairly new one, I plugged it into the harness while out of the throttle body to verify that it is at least moving and responding.
-Tried adding a bit of fuel into the low load / rpm area of the fuel map - no change
-Verified Latency settings for the injectors - RC / Lucas 550CC



Brings me to some of my questions -

-In Evoscan 2.9 I am told I can make custom request commands, I am aware of how to set SAS mode for idle speed adjustments, but I am not seeing a window I can send MUT commands to for example turn off or on individual injectors, where can I find this? There are some older threads with broken links and pics regarding this, wanting some up to date information how to do so.

-Are the readings Evoscan is giving me for the IAC steps accurate and why is there a discrepancy with the table it should be going off of?

-Evoscan also drops connection frequently with the Tactrix cable, would like to know if there is a specific setting to stabilize this so I can datalog more effectively?

I am sure I will have more questions but I think that covers it for now. Thanks in advance for your input!

[Greg E]

I ran into this exact same issue when I discovered my MAF had been hacked (bought the car that way). I've been able to recreate the issue too when an open air BOV is stuck open or at least is open during idle.

The ISC CEL is retarded. Basically it's telling you that the ISC doesn't have control over idle. Doesn't tell you why. In this case, you're running lean enough where the ecu can trim the low fuel trim, but your target idle vs your actual idle is way far off.

I would start by verifying the intake tubes are properly connected to the turbos. Bet you a taco those large o-ring gaskets are worn out.

[RealMcCoy]

Greg already said it, but low IAC counts, (and a corresponding code) would be a very strong indicator that it's getting air from somewhere it shouldn't. If I suspected the IAC was functional, and simply being closed by the ECU trying to slow down the idle, I'd go straight to looking for a vacuum leak.

[donniekak]

Not sure about what you can do in the newest chrome rom, but some cars react better to shutting closed loop off at idle, usually large cam setups. I have some other Roms I use that have that function.

In your case it does sound like unmetered air is getting into the system.

[Streamln1]

I agree, my first thought was a boost leak, its sealed up good though and we have a few leak tester adapters we use, aka some PVC fittings with a Schrader valve. It would make sense that the IAC is trying to close it up if that were the case. Unless its a leak that ONLY is present during vaccum, and not pressure, maybe a cracked line near the brake booster or clutch booster after the check valves. Gonna try the ol carb cleaner trick to see if I get any results from that.

[KeithMac]

Could be the actual brake or clutch booter as well, go for a SLOW drive with these two pipes disconnected and the plenum takeoffs sealed up?.

Have you tried adding any fuel in at the problem area, maybe 5% to 10% extra?, this way it will default slightly rich and then the O2 trim will pull it back to stoich.

If it's only in closed loop, are you suffering from a lazy O2 sensor?.

[Streamln1]

Turned out to be an injector problem, went back to stock 360cc and reflashed to stock rom and it idles perfect, no bogging or lean pop. Going to switch him out for some DSM 460cc's now. Even when I had closed loop turned off and AFR right at 14.5 ish it was still kind of stumbling and popping. Good ol RC / Lucas 550's. I had a feeling that was causing it. And yes latency table was corrected incase anybody asks.

[Streamln1]

So I never really got an answer with evoscan. I hear about a place to enter in mut commands..which would be useful. But where is this supposed command line?

[Greg E]

So I never really got an answer with evoscan. I hear about a place to enter in mut commands..which would be useful. But where is this supposed command line?

Post 8

http://www.3sgto.org/tuning-engine-electronics-ecu-discussions/10775-how-tune-your-3-s-using-chrome-flash-ecu.html#post236779

[Smokey45]

[/QUOTE]
-In Evoscan 2.9 I am told I can make custom request commands, I am aware of how to set SAS mode for idle speed adjustments, but I am not seeing a window I can send MUT commands to for example turn off or on individual injectors, where can I find this? There are some older threads with broken links and pics regarding this, wanting some up to date information how to do so.

-Evoscan also drops connection frequently with the Tactrix cable, would like to know if there is a specific setting to stabilize this so I can datalog more effectively?

[/QUOTE]

To the OP.. Did you ever get the answers to these? I'm using Evoscan for the first time to set the idle but I can't find the custom request command box. Hope maybe you figured it out before I contact Evoscan.

[Smokey45]

Nevermind... Had to go backwards and use EVOScan V2.9.0023. For some reason in the newest version the Custom request fields are missing