basic questions
Hey guys, new to the forum and new to Fitech. Not exactly used to forums either, so bear with me. I'm in my second week after the install of my gostreet 400. Its on an 86 454 in a Chevy K30 with a turbo 400. Other than an Edelbrock performer intake, motor's all stock. I have a few questions/issues. More than likely basic dumb questions but I overthink things.
1. Warm idle is set for 800, and when warmed up, idle RPMs fluctuate slightly. The reading will go as low as 770 to as high as 815. The reading on the handheld jumps quickly but you can hear the occasional drop in RPMs. I can't find a vac leak but it seems like my AFR is trying to compensate for something.
2. When I'm at a steady cruise speed and ease off for a curve or to take a turn and get back into the throttle, there is a hesitation. I've increased my DFCO fuel to 80.0 but it's still there. Should I go higher?
3. If I'm cruising at a steady throttle and get off the gas to slow down for a light, RPMs seem to drop almost to the point of stalling then they come back up and rest. Normal or would that also be the DFCO?
4. My coolant temp is always resting at 156-159 degrees- never higher. I can't remember if I put a 160 stat in or not. Could've sworn it was a 180. Since I'm not reaching the 170 mark, could that be causing some of the idle issues? Moving the temp sensor to the cylinder head and checking the stat this weekend.
overall the truck starts and runs great but I think I'm missing out on a couple key things here and want to get the most out of it. Only changes I've made so far is the DFCO return setting. IAC steps are 2-3 when attempting is at 159 degrees. AFR is at the default setting (I believe 13.6) and base timing is 12 degrees BTDC. sorry for the long winded post, and not sure if I left anything out. Thanks in advance.
1. idle will hunt around a bit, this is true for any motor. Should get better like only 30 rpm change.
2. won't hurt to try higher, you can always go back
4. they have not fixed the temp sensor thing yet! Yes it needs to get to 170. But if the sensor is lying (defective) the computer won't know it.
Also bring the IAC up. Find out what the motor likes not just some number. 10 to 30 is a more sensible range.
Thanks Doug, I will not worry so much about the idle at this point. Like I said, I'm going to put a new temp sensor in the cylinder head this weekend and verify the thermostat that's in there. All I had to go on was the initial startup guide in which it tells you to set the IAC steps between 3-10. I know the unit is continuously learning but how long does it usually continue to learn?
Don't make anymore tuning changes until you replace the temp sensor. Get a delco version. Just about any V8 chevy had the same sensor in the 90s and late 80s. The computer must see at minimum 170 before it does it's magic.
Austin, thanks for the feedback. I actually just picked one up from the auto parts store on my way home but probably won't get it in till Thursday night. I will definitely try that and Share the results.
Thanks again!
Ok, got the correct temp sensor in and now she's coming up to temp. 180-185 fully warmed up. This did seem to make a difference, like I said It wasn't really running badly but just didn't know how well changes would respond if not to temp. Now with that said, I still experience a couple quirks. Idle is stable at 800 RPM, starts good when cold after sitting for a couple days in 20 degree temps.
1. When driving either slow in town or fast on a major highway, I come up to a stop and with foot off of the gas and braking like normal, RPMs drop but seem to drop low (dipping down to around 600) briefly and then back up for a second around 950, then settling back down to the 800 RPM setpoint. While this is happening, the AFR will also go very lean for a second- around 19-20, but then back down to around 13.6 Almost seems like for a second that as im coming to a stop its going to stall out on me but it never does. Is this normal behavior?
2. Im still experiencing some issues while under normal throttle, when I let off the gas for a curve or a car in front of me turning, get back into the throttle (normal acceleration) and there's a little hesitation or dead spot. I know the DFCO fuel cut should be adjusted but should I increase the number or decrease? I would think that increasing it would increase the fuel cut but maybe im looking at it wrong. I have tried increasing it from the default 65 all the way to 85 and didn't really notice a difference. I have also increased my accel pump setting for 170 degrees normal acceleration by 10. Is there something else I should be adjusting along with this? Any insight would be helpful.
Thanks in advance.