tuners come on in..

**0rion** · 03-23-2007, 01:10 AM

I'm trying to diagnose a problem on a buddies c-5. He has a TR230 cam, home ported heads, headers, stalled a4, blah blah. Those are the important ones.
Up until the end of last year the car ran fine. At the end of last summer the idle got rough and now it plain sucks. Open loop idle hasn't changed but towards the end of open loop it starts surging real bad and will surge until it finally dies. It's pig rich. I did a short log for him last night to see if I could tell what's going on. It looks like the car isn't making it to closed loop. It seems like when it should go to closed loop that's when the car dies. If he puts it in gear it will idle all day. Would an ECT sensor richen a car up enough to cause this? That's one thing I noticed while watching it is that the temp started out abnormally low and wasn't really coming up very fast. I'm also thinking his O2's are shot but that could be a result and not a symptom. His plugs looked like ass so we changed those out. I'm having him buy O2's because I'm sure his are fouled beyond belief if they look anything like his plugs ( I guess he's started it up a bunch of times trying to figure out what's going on and that's why his plugs fouled so bad). I'm gonna have him buy an ECT sensor while he's at it because something tells me that's the root cause. Example, the car has sat all winter in the garage but last night it was probably 50 degrees outside. His coolant temp was showing 26 degrees. I realize the car has been sitting all winter and is probably nice and cold but doesn't that seem really low since it's been 40's and 50's here for a while? After running for ~10-15 minutes the temp reached 30 degrees.
Anything else I might be missing and does anyone know where the ECT sensor is on the vettes? Is it on the radiator? I'd like to be able to tell him where it is and I'm not real familiar with the vettes. Any opinions are welcomed.

edit
What parameters need to be met before it'll switch to closed loop? I know the ECT has to meet something like 92 degrees but what else has to be met? If it were simply not switching to closed loop then why would it richen up so much and not just idle in open loop? That's what puzzles me.

**mrr23** · 03-23-2007, 06:49 AM

yeah, it sounds like the ECT sensor has gunk built up around it, or is slowing starting to die. the ECT should beon the driver's head just above the #1 spark plug, just like on the f-bodies. the one on the radiator is for the coolant level.

how the computer gets the engine to operating temps is #1 keep the fans off #2 make the a/f rich to heat the cylinders up faster.

**0rion** · 03-23-2007, 08:14 AM

Thanks. I don't know why I was confusing the level sensor with the ect. Duh. That definitely sounds like the culprit then because that temp should rise rather quickly. He said he idled the car for almost 30 minutes trying to do an idle relearn and the temp was showing 113 degrees. I told him not to even start the car until I had a chance to figure this out. Sounds like that ect is a pretty safe bet.

**tblu92** · 03-23-2007, 10:08 PM

Hello---here are a few tables that are used in switching from open to closed loop--- the numbers in the tables may not match yours but I wanted to show you a typical LS1-
b3802 LTFT learning enable temp --set at 100*
b4202 COLD open to closed loop timer set at 90 seconds
b4203 NORMAL open to closed loop temp enable set at 131*
b4204 NORMAL open to closed loop timer set at 20 seconds
b4205 open to clsed loop temp enable using IAT temps set at 100*
b4201 COLD open to closed loop temp enable set at 14*

Also this table really helps with idle issues especially on cammed cars b4307
"desired airflow @ Idle ( adding some % here helps ,start with +10 %

b3605 is the "open loop commanded fueling" with a cam typically you need to idle the engine much faster say about 1000 for example--the factory idle is 550---so you need to put the commanded fuelling from 550(stock idle) and move it to your new idle speed (cammed) this table is in MAP so you will have to convert the RPM to an approx. MAP---Also can be used to set the base open loop AFR if you can figure out if it wants more or less fuel

Hope this helps some--It still may just be your ECT sensor----

**0rion** · 03-23-2007, 10:34 PM

Thanks for the info. Before all of this his car idled pretty decent. OL idle needed a small amount of work done to it but for the most part it worked. I'm gonna spend some time on it this spring and get it ironed out hopefully.