So I've had a bunch of help tuning my car with the EBL setup and the new cam I put in thanks to Fast355.

I'm now trying to get a little finer tuning in on the car and the surging idle is what's bothering me most.

I've looked over a lot of forums and tried a bunch of different things but none seemed to make a difference. My car is surging about 100-150 rpm at idle. It does it pretty regularly, but not 100 percent of the time. It seems to do it in closed loop and open loop (according to the WUB with the EBL and when I enabled the open loop bit in tuner pro).

I tried decreasing the proportional gain tables by 50, then 75 percent, and it didn't seem to do too much. At 75 percent, it seemed to make a small impact, but the car exhaust sounded different and I didn't know what impact that would have on the entire tune, so I changed them back.

I also flattened out the Low speed VE tables around the idle range, then decreased my idle SA from 30 down to 22 (in increments of 2 each time.) Apart from that, I flattened out the SA in the idle range also (but I did have the bit checked to keep the SA set at idle anyways)

Doing all the above, the idle still seemed to surge pretty much the same.



One odd thing is when I turn the AC on, the surging dramatically reduces or stops altogether. It is set now that the idle speed is 100rpm higher with AC, but it doesn't surge much at all at the speed its supposed to. I set my initial idle at 700, and with AC on it idles pretty well at 800. When I set my idle to 800, the AC on would idle around 875, with little to no surging.

Any extra insight on what I may have missed or help would be greatly appreciated. I'm still kinda dumb when it comes to tuning so it could be something small.

 

It sounds like that cam has enough duration and/or smaller LSA that the engine needs to idle at a higher RPM.

RBob.

 

210/215 @ .050 on a 110° LSA

 

That cam should idle OK in the 750 RPM area. Since it also surges in open loop it isn't the proportional gains. They are only used in closed loop.

Run it for open loop idle and get a data log. Likely find a lean area that is causing the surge.

RBob.

 

Thanks for the help! I definitely will do that.

Weirdly enough, after driving back and forth to school yesterday evening, the surging didn't happen nearly as much. It definitely happens more frequently when cold, but even after warmed up yesterday before school (in my driveway testing and getting the coolant temps up), it was surging consistently. After driving on the highway for a while, it settled down a lot until I got back near my house.

I'm starting to think my O2 sensor may be partly to blame however. Just recently, the cars exhaust started smelling very strong when I made no changes to the tune or anything else. The smell isn't always there but it's very strong when it is. I noticed my o2 sensor (about a year old) signal wire was touching my header... the wire didn't seem damaged much, but It's probably a good idea to replace at least the wire. I think after I get a little more money (potentially today), I'm going to switch to a heated o2 sensor. (any recommendations on type or just any heated O2?)

Apart from that, I did notice my BLMS seem a little weird. At idle, they are around 128, but then surge up to 135 and back (possibly the lean condition?). However, when I was driving the other night into town on the highway, they went down to around 112-118. On the SAME road back to my house on the highway, the BLMS were at 128 the entire time...

Just a month ago with the same tune, I didn't ever catch the BLMs fluctuating really at all, so I'm thinking something besides the tune may be culprit here.

 

What are your iac counts at idle? Went through this with my own, wouldn't hold steady, had to set base idle a few times to get counts to an acceptable level. Had to open throttle blades a bit more than I expected.
It would throw the blm's off during the surge. Now idles at 775 perfect and blm's are perfect open and closed loop.
Gonna try settin idle lower now and see what happens.

 

I now have a 196/206 @ .050 cam on a 109° LSA with 1.6 rockers in my Express vans 350 Vortec. Even it is pretty lopey at 600 rpm and idles a shade rough. At 750 it idles pretty much perfectly and the throttle response is alot better.

Idle at 600 rpm and ~ 16° of timing (Marine Specs)


Idle at 750 rpm and ~22° of timing (What it seems to like)

 

Well I got super busy with my senior design project for college and didn't get a chance to do much at all with my car. Now that Christmas is over and I have a little more time, I can get back into this issue!

One thing I did get to do though that did help is adjust the idle screw on the TBI unit that adjusts the idle counts. I screwed it clockwise a bit to have it very very slightly turn the throttle blades open a little. This seemed to pretty much make the surging go away completely (rarely comes back when decelerating and almost never surges at idle now), but the idle is a little higher than what I have set in my bin (about 75-100rpm).

I still have not yet purchased a heated O2 sensor, and I think I'll need to do that and then some more VE learns once that's installed. I do want to get a WB o2 sensor, but am not sure how that is hooked up to the EBL unit so I'll have to look into how it gets wired up and what exactly I need for that setup.

On a side note, I just recently found a WC T5 from a V8 I picked up which I have been looking for for about a year now. For some reason, they were not easy to come by here in Arizona but I finally got one that appears to be in great shape. I can finally be done with the inconvenient gear ratios a NWC V6 T5 has on my car!