AEM Questions: Enrichment, throttle response and Warm Up idle in cold weather!

[Justin311]

First off my car's base tune was performed by John Reed...and it runs nearly perfectly. Unfortunately it was hot tuned in the summer so cold start was not able to be looked at. He took his best guess and it worked fairly well, but now that its gotten really cold (0*) a few times I'm having some issues.

Problem: It takes more cranks to start the motor when its cold out than when its warm. Probably 2-3 cranks when warm, 7-8 cranks when cold. When it does catch, idle pops up to say 2k rpm for just a split second, then settles down to a much-too-low-for-warmup idle, say 900 rpm.

The idle is very weak at this RPM in cold weather, and has a great hesitation in it. Any throttle blip results in a long delay (perhaps 0.5 seconds - I can watch my boost gauge go all the way to 0 before the engine makes a peep) then a sputtery response by the engine.

So these are the symptoms I want to fix.

Solution Attempts: When I open the "Engine Start Template" it gives me the "Warm Up Enrichment Table" window. My first question is; does this enrichment factor apply until the car is completely warmed up, or does it apply only when actually starting the motor? I assumed the former, but then I second guessed myself, since its listed under the "Engine Start" pulldown, and there is no enrichment listed under "Idle".

Reed had a fairly linear curve from about 32*F to 150*, and it was slightly more aggressive from -40* to 32* Either way, I have bumped the curve up slightly, in hopes of improving the fuel atomization during that warmup period. I hope that this will improve the throttle response a tad, and help it warm up. Is this a good strategy?

Next, to fix the low idle, I went into "Idle Target Base Table". I noticed that the idle was set to 1300 rpm up to 86*, then it was a linear reduction in rpm down to 150*, at which point it was set to 1000 rpm.

Please notice I stated that my idle was around 900 rpm in warmup mode, and only dropped to about 850 rpm when warmed up. Obviously the Idle Air Controller was not responding to the ECU signal.

So I manually adjusted my idle using the screw on the throttle body - I backed it out 2 full turns. I restarted and it immediately jumped to about 1300 rpm, which is where it was supposed to be set at - so my idle adjustment must have been off. It warms up much better now, with a slight hesitation still on a throttle blip.

The two problems I still have are this:

1) Even after fully warmed up, its sitting at about 1100 rpm, although the setting is at 1000 rpm. How do I make sure the idle screw is right, and is there anything more I need to do to get the car to respond exactly to my inputs?

2) What else can I do to give it crisper throttle response when in warm up mode? Can I play with the IGN settings? There are SO many settings in idle and I'm not sure what if anything I should adjust. Is it going to be too rich (bad mpg) or slow the warm up (too MUCH fuel -> cooling effect?) giving it more fuel during enrichment as I did? What AFR do you guys see during warmup idle?? Mine seems to be right around 12:1 with my current tune.

Thanks!!

[Weasy2k]

When I open the "Engine Start Template" it gives me the "Warm Up Enrichment Table" window. My first question is; does this enrichment factor apply until the car is completely warmed up, or does it apply only when actually starting the motor? I assumed the former, but then I second guessed myself, since its listed under the "Engine Start" pulldown, and there is no enrichment listed under "Idle".

All warm up maps are until they are completed IE warmed to the set temp, there is no real way a EMS will know if this is the first start of the day or whatnot, if the temp is at a certain point the EMS should refrence this accordingly and work upward until the car is warm again (even if it means using the warmup table to increase the temp by 2 degress).

Reed had a fairly linear curve from about 32*F to 150*, and it was slightly more aggressive from -40* to 32* Either way, I have bumped the curve up slightly, in hopes of improving the fuel atomization during that warmup period. I hope that this will improve the throttle response a tad, and help it warm up. Is this a good strategy?

What doyou mean by aggressive and "bumping the curve"?
you mean adding more fuel? Changing the timing?

1) Even after fully warmed up, its sitting at about 1100 rpm, although the setting is at 1000 rpm. How do I make sure the idle screw is right, and is there anything more I need to do to get the car to respond exactly to my inputs?

Normaly how i set the idle is that i warm the car up fully and at this point I adjust the idle screw until the desired rpm is reached. If the idle is adjusted when cold then you will have a wacked out warm idle as you noticed. The cold idle control should be controled by the ecu as you mentioned there and soemthing could be messing up. Check to make sure thats all working.

2) What else can I do to give it crisper throttle response when in warm up mode? Can I play with the IGN settings? There are SO many settings in idle and I'm not sure what if anything I should adjust. Is it going to be too rich (bad mpg) or slow the warm up (too MUCH fuel -> cooling effect?) giving it more fuel during enrichment as I did? What AFR do you guys see during warmup idle?? Mine seems to be right around 12:1 with my current tune.

I have always tuned engines to pritty much follow the stock ecu's path. Have a afr that the engine likes (this varys depending on the fuel and area you are in) and use this for maybe 10-20seconds until the O2 Sensor has warmed up, at which point just use open loop and target at 14.7:1, the engine handles this fine. If you dont think thats true then why do we use heated O2 sensors The goal of the ecu is to run in open loop as much as possible and keep it around the most economical AFR hence the use of a heated O2.

Hopfully this helps

[Justin311]

Thanks for the answers

I worked with John to get it dialed in further. What I meant by "bumping" was adding fuel during enrichment....turns out it wanted to be a bit leaner, so we ended up going the opposite way.

Thanks for the tip on the warm idle set, you have a good point there. Oddly enough my idle was fine when warm but whacked when cold. I'm going to play with it somemore.

As far as your last comments about targeting 14.7....I agree, but don't you mean "closed loop" which is the only time an EMS can "target"?

[Weasy2k]

yea i keep swapping those to terms sometimes after writing alot :P

[Enthalpy]

Originally Posted by Justin311

The two problems I still have are this:

1) Even after fully warmed up, its sitting at about 1100 rpm, although the setting is at 1000 rpm. How do I make sure the idle screw is right, and is there anything more I need to do to get the car to respond exactly to my inputs?

2) What else can I do to give it crisper throttle response when in warm up mode? Can I play with the IGN settings? There are SO many settings in idle and I'm not sure what if anything I should adjust. Is it going to be too rich (bad mpg) or slow the warm up (too MUCH fuel -> cooling effect?) giving it more fuel during enrichment as I did? What AFR do you guys see during warmup idle?? Mine seems to be right around 12:1 with my current tune.

Thanks!!

It sounds like you have the cold start misfires fixed. If you don't, I can help you out.

When you change the airflow through the bleed screw with the AEM EMS, you might have to adjust the idle % vs. target table. If you want help with this, I can help you.

I set the throttle body such that the idle speed when warm with the IAC valve closed is just shy of the warm target speed. This gives the IAC valve all the airflow authority range it needs for the warmest idle and the coldest start. Some EMSes do this better than others.