I need help with a persistent idle surge on a build I just did for a TGO member. 91 B4C with an ATK 350 crate engine and a T5 manual trans. Engine specs are : 220/224 @50 .528in/.536ex 110LSA cam. Pro-Filer 195cc heads, TPIS big mouth base and AS&M large tube runners, 30lb injectors.

I've done all I know to do and it still has an intermittent idle surge. Sometimes it will settle down and idle OK (I have it set at 875rpm) but then if the cooling fan kicks on, AC kicks on, or even just by itself it will start surging.

IAC counts during a smooth idle are around 50, pulsewidth at stable idle is roughly 1.2-1.4. Idles in cell 8. When it begins to surge the leading indicator on the datalogs seems to be that the pulsewidth jumps north of 2ms, then the surge begins.

To save a million questions, I've attached the .bin I've gotten to. I started with SAUJP V5, the car is WAY better than it was when I started and I was making progress, but now I just can't seem to kick the surge the rest of the way out. I know a 110 degree LSA is not helping me any, but I figured I'd be able to get this thing settled down, and I'm not having success yet.

So those of you that are experts, please take a gander at my .bin, and tell me if you see something I need to change or work on. Many of you have much more experience tuning SD with a lumpier cam than I do. I've tuned lumpy cams on MAF cars, but this is the biggest cam in an SD car I've ever worked with.

Thanks so much for any assistance any of you can provide. myself and the forum member who owns the car will thank you.

 

Without looking closely yet, one option is to idle in open loop.

Is there a WB on the car?

 

You’re using 30lb injectors. The fact that an electrical voltage drop sets off the surge makes me wonder if your Injector Bias is correct. Are you using a VAFPR for regulating fuel pressure? 50 counts for idle IAC also seems a bit high.

 

Following..

 

Yes was a wideband on the car. It should be idling in open loop, but now that you mention it I don't remember looking to actually verify that in the data stream... I may not have the .bin set up to idle in open loop like I think it is. I'm not at home on my personal laptop, but from memory I raised the min rpm for closed loop to 1000rpm, can't remember the exact name of the table.

I'm not sure that an electrical voltage drop sets off the surge. I only observed the pulsewidth nearly doubling right when the surge started happening. I have not changed the pulsewidth vs battery voltage correction table in any way yet. The car does have an adjustable vacuum referenced regulator, basically an adjustable housing with a stock diaphragm on the stock fuel rail. 50 IAC counts is a tad high, if I turn the idle screw in to open the throttle blades further the TPS voltage goes over .57 volts.

 

Fan kickin on may have a voltage drop. Puslewidth changing is fuel changing which would definitely cause a surge condition.

 

Ok, so a couple of observations. I would

1. Get the correct Inj. bias for the injectors u are using

2. How are you doing the MIN Air adjustment? TPS voltage is adjusted w engine OFF. SO once u get the IAC counts down, u shut off the motor and set TPS v
to about the .53-57v level.

3. Was the stock fuel regulator setup for 30# injectors?

 

The TPS voltage isn't critical, the ECM auto zeros it. IIRC, can go as high as .9 volts before it becomes an issue. Shoot for 20 - 25 IAC steps on a warm engine and no other loads.

Check to see if the ECM is going into single fire mode (S/F) during the surging. It is either doing that or the VE table has a really rich spot in it.

Note that as previously mentioned, getting the proper injector compensation values is important.

RBob.

 

Following...

 

This is my car so if anyone has any questions for me please let me know.

 

That is correct, I wasn't thinking about that because my other large cammed MAF cars don't do this. Is the right thing to slightly flatten out the battery volts vs pulsewidth correction table?

The injectors appear to be older Bosch style, they are new, have polished bodies, I have no idea what brand they actually are, so I'm not sure where to start on the correct injector bias. Do I start with the bias for a standard set of old school Bosch units?

I never disturbed the IAC or removed it from the TB so I did not re-set minimum air. I simply adjusted the idle screw till I had what I thought was the max allowable TPS voltage. I knew the SD TPS are non-adjustable and I knew the ECM zeroed it back out each key on, I did not know that the ECM could see a value as high as .9v.

I'll look into the injector compensation bias/value and see what I can find. I don't have the car in front of me anymore, but I will see it again in a couple weeks and can datalog it and see if its going into SF mode or not.


Thanks for the help guys.

 

Yeah, looking at your bin, you have it set to 1250 rpm.

I guess what I'm thinking it could be is that you're triggering AE Delta MAP when the fans kick on (thereby the alternator putting a load on the engine) or when the A/C compressor kicks on (again, putting a load on the engine).

And it'll only take a delta-MAP of 3.13 kPa at 0% TPS to enable the delta-MAP AE fueling (according to the table "AE MAP-MAP Change .vs. TPS% for Enable")

What I'm seeing is you have the AE Delta MAP vs %TPS multplier cranked up to a factor of 2.5. Which means when the AE delta-MAP kicks in, you're amplifying it quite a bit which is dumping in even more fuel. If you're using Tunercat to make the changes, that table is backward. Smaller number = more fuel (I learned that the hard way a while ago). Your .41 in Tunercat = 2.5 in Tunerpro.

I'll bet with that cam, the idle is already pretty choppy and any disturbance like a sudden change in load is likely to generate a delta-MAP large enough to enable the AE delta-MAP.

I also agree with Tuned that the 50 steps on the IAC count is way too high. In neutral, I have zero steps. All air is going through the blades on my car. Having the idle air so dependent on the IAC and the ECM makes it more prone to idle issues on modified cars.

So what I'd do is the following:

First, you can prove my hypothesis wrong or right by

1.) Exporting the data to csv (assuming you're using the SAUJP adx file) and looking at the column entitled "In MAP AE" to see if it's engaging at idle speed

2.) If it is, then to see if it's causing the issue simply go to the table entitled "AE MAP-MAP Change .vs. TPS% for Enable" and temporarily set the value for 0% TPS to 50 kPa or something like that. It will ensure the delta MAP AE is never triggered for idle. Then start the car and see if you can get it to surge.

If it doesn't surge anymore then you know it's delta-MAP AE related, at which point I'd suggest:

1.) Change value to the stock value of 1 at 0% TPS in the table entitled "AE MAP-TPS% Multiplier".

2.) Undo the 50 kPA change I mentioned above.

3.) Open the throttle blades until you get the IAC steps to 10 or less in neutral.

Looks like you zeroed out the idle spark correction vs idle speed tables, so that's good.

If it still surges, take some tunerpro data and post it here. I'll take a look at it.

 

As Grumpy would say, the ECM is only there to help out. The motor should run well and parameters adjusted so as to minimize intervention needed from the ECM.

 

...so I crossed swords with this car over the weekend and it is still winning. Time with the car was short, so I burned a chip in advance of our meeting. In that chip I changed the AE MAP-MAP Change .vs. TPS% for Enable and set the value to 25kpa for 0% throttle. I also bumped the idle to 925 and increased the idle rpm deadband slightly to 75rpm. None of those changes did a thing. The car behaved just as it always has.

So then I started cranking open the "idle screw" until I had it idling at 0 steps at 925 rpm. For the first time it was happy. It idled perfectly and sounded awesome until the cooling fan came on and threw it into a fit. With the fan running the IAC was open 2-4 steps, and that was apparently enough to throw it into the idle surging fit. Then once the fan kicked off, it returned to 0 steps, 925 rpm idle and was happy again.

I'm out of ideas at this point unless there is a table I don't know about where I can dumb down the "attack rate" of the IAC.

 

Are you able to take some tunerpro data?

 

Fan drawing on electric system upsetting idle, might want to revisit the batt volt injector offsets?

 

I would like to add this. When I started the car for the first time in two days it was hard to start and the idle was surging and the car shut off (after about a minute). I restarted it and again it was hard to start and kept surging. Once it got upto operating temperature it ran fine.

 

Sounds like the open loop tables need to be addressed. What you're saying seems to imply the Open Loop vs MAP table is ok, but the Open Loop vs Coolant needs some work on the cold end.

Ok, so the AE Delta MAP theory doesn't appear to be the case.

How is the IAC motor itself?

 

The car started and drove fine while cold (in open loop) when I had the car in my possession. I'm not making any other changes until the idle surge is fixed, I'll only be chasing my tail.

I have not taken the IAC motor out of the throttle body. The commanded steps in the datastream and the engines behavior always shake hands, so I've not suspected its a problem. The only failure mode I've ever seen out of an IAC is that they get sticky. That would almost be a blessing in this case...

 

Also have you played with timing vs rpm error adjustments?

 

Hmmm... Steve is saying it was hard to start and surging the other day when he started it up...

Orr, when I looked at his bin, the timing vs rpm error tables were zeroed out.

It would really help to get some tunerpro data to look at, taken during the surging condition. As they say, a Tunerpro data file can be worth a thousand words sometimes... lol...

 

Yes, when I first put the car together, and I didn't have the idle screw cranked in so far the IAC was at 0 steps, the car started and drove fine when cold. I did it multiple times. The idle would surge, but it started fine and did not stall if you started it and let it idle cold.

Diagnosing this from afar is nearly impossible for me and for you guys too, I get it. I expected there to be something obvious I was missing since most of my experience is tuning MAF cars, doesn't look at this point like there is anything obvious I'm missing. I'm not sure when I'll see the car next, but I can get a datalog and post it here when that happens.

 

If thats the case i would put in values for the advance/retard allowance. Stock 8D aujp has 5 deg.

You need some when rpm swings from sudden loading like ac or fans. Now it still could be fuel related from minor voltage dips but timing i think makes the most difference. If it dips low the ecm can add some to stabilize

On my 401 and big cam using 0411 sequential i had as much as 14 deg allowance on any large rpm differences from target

 

I've always found that having values greater than 0 in those tables encouraged "hunting" at idle.

But hey, seems like anything is worth a shot at this point.

 

 

This thread should be an example of using too large an injector. The ECM can't cut off enough pulse width below 2. A 460 Ford uses a 24 lb injector and it is good to 425 HP easily. A 30 is simply to big for a 350 and will always suffer from idle issues.

 

I had 36’s in my 305, and 110’s in my 400 and did not have issues

Just need tuned right with the correct pulsewidth offsets for battery voltage and to dial in the ve table spot on so you do not have widely varying idle air fuel ratios which can upset rpm

 

 

Not necessarily. My car has never run better using 30lb injectors. And they're more than I need for my power level.

Like Orr said, just need to tune for them.

 

Are you running MAF or MAP?

Or possibly even MAF and MAP?

Are you absolutely sure there is no leakage in the intake piping?

If you have leaks in the intake (referred to as "false air"), you may have difficulty starting; and then when the O2 sensor kicks in during closed-loop, the O2 will read lean and deliver extra fuel, which could cause surging.

 

I can too do something senseless if I want to?

 

They were turbo cars that needed the fuel. I maxed out the 110’s lol. It just shows its possible to run them on 730 ecm without idle surge problems

I agree dont go to big for no reason but its not gonna kill you within reasonable ranges. There is a point where min pulsewidth is gonna be too much fuel for idle. It will be rich

 

I've always used a lot of rpm error timing in everything from old accel gen 6 dfi, 8D and $59. so I wouldn't be scared to throw some at it. also I have had great luck with the Ford green 42# the injector offsets should be around and a decent set can be found for cheap. either way, I wouldn't think 30s in working order wouldn't cause to much issues size wise.

my 1st thought was did you have the idle air count offsets to ac and fan set high enough? I seem to remember I played with that a while to get it seamless when things clicked on and off.

I don't even know if my laptop with tuner pro on it works anymore, so I haven't looked at your bin,
​​but have you tried just looking at the area of the ve that it surges too and flattening that whole area? and then if it kills the surge, work backwards from there if it causes off idle drivablilty issues.
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