TheSnail

Car is an 08 with an SOS kit

Fuel system is stock returnless with an Aeromotive 340 fuel pump and ID1000 injectors.

The car was dyno tuned to around 12:1 A/F and it holds that spot on. I took the car for a spin yesterday and and hooked up the Wideband to make sure everything was up to par. Every thing checked out, and while doing long highway pulls, it sat at 12:1 under load.

Now for the issue. I have noticed that if I drive the car for 30min+ A/Fs skyrocket to 15:1+. After driving across the state for 2hrs yesterday, a new mustang started messing with me on the highway and so I dropped it down to 4th and took off. Well maybe not took off, because it felt like the car had 150hp. I was like wtf? So I tried doing some more 4th gear pulls and it would get literally hit a soft limiter at 7.5k.

Before I thought it was heat soak that caused the drop in power, but after feeling that soft limiter, I knew it was fuel. So I reached over in the passenger seat and grabbed the wideband gauge. Plugged it in while driving and sure enough it was running lean as f***. At 4000 under load it was 14:1. By 5000rpm it was 15:1 and by 7000 rpm, it was not enough fuel for the engine to operate (18:1+). So as to not turn my pistons into a molten slurry, I did not put the engine under load for the remainder of the trip.

I think I'll call my car the Tylenol as its a time released set of issues. I can take the car for a spin this morning, and it will be at 12:1. If I continue to drive it for 30+min, the A/Fs will skyrocket. That 30+min of driving does not matter if it is city or highway or idle. Simply if the car is on for x amount of time.

Now regarding the Fuel pump. I simply dropped it in. I did not change any thing else. I did not change wire gauges, fueses or switch to a return system.

Hypothesis: Now I'm an ME not EE, but if I had to guess what was going on, it would be that some harness or wire related to the fuel pump is getting too hot, changing the resistance in relation to temperature. It may also be the pump itself is getting too hot, thus increasing the resistance. I would venture to guess that proper gauge wire or better grounds would eliminate the issue. However, I dont know wires to change gauge or how to go about it. I dont even know that is the cause, its just an assumption.

I searched fuel issues on this forum and found one from the other week who was having fuel pressure drop after driving the car around for 15min. Sounds very similar to mine.

Anywho, I was hoping you guys would have some insight of whats going on. I am too newbe in the s2k world to know if this is a common issue, so any help would be greatly appreciated.

Thanks, Voya

sohc_mshue

Hmm strange. Do you have another pump you can try? Have you monitored fuel pressure? I recommend getting a fuel pressure sensor and logging it.

cuci591

Sounds like a lazy pump.

99SH

If I read between the lines, this just happened after the tune? I would go back to your tuner and check it out. There are fuel trim (and ignition) compensations based on IAT & Water temp, so it may be set wrong.

As for the resistance theory...you can throw that out (it's very negligible)

I agree with the above poster to get a hard measurement of your fuel pressure, before you deem it bad. If you're using the flashpro do some datalog pulls of good and bad runs.

s2000Junky

This is the first thing that occurred to me as well.

If after driving for x amount of time, your AIT or coolant temp or some other factor reads at a threshold that engages these fuel trims, that were either set wrong, or never set up to begin with, it could do this. That would be the first thing I check.

TheSnail

(FULL STORY, YOU WILL UNDERSTAND EXACTLY WHAT I AM GOING THROUGH IF YOU READ THIS BIBLE OF A POST)

That is very interesting regarding the tuning of a/fs per IAT. Its all coming together and making sense now. So as some of you may recall, I went from a bone stock car to a sos kit'ed and a bunch of other crap within several weeks. My initial plan was to run SOS's 3.6" pulley so that is what I ordered. I also bought a 3.4" pulley as back up if I did not hit my target HP of 400 on the 3.6".

Anywho, I got an Jeff Evans E-tune simply to be able to drive to the local tuner to have it dyno tuned. His first map had too much timing, so he lowered it. After that it was basically optimizing the a/fs. I drove the car around for a few weeks and it seemed fine.

I took it up to Mainsteam, and had them fine tune the car for 3hrs. First pull was the E-tune on the 3.6" pulley. The tuner was waving me down to kill the pull. However, I stayed in it till redline. He said it was running way too lean, and was worried how long Ive been driving the car like that. That pull dynoed 350whp with the rev limiter set to 8500. Tuner said if I intended to hit 400 that I need to swap out to the smaller pulley before even starting, so I did.

After I installed the pulley, the car would only rev out to 8100rpm despite the hondata being set to 8500. So over the next hour the tunner tried to surpass the 8100rpms by changing ecu parameters. He changed the hondatas rev limit to 9k, that didnt do it. So he bumped it to 10k, but that still didnt do. At this point, I suggested that it was most likely ignition related at which point the tunner asked me what I gapped the plugs at. I told him it was stock gap. So I pulled the plugs and he gapped them down to .025". After which, the car reved out past 8100 and the dyno tunning continued. Eventually, the car made 390whp with a/fs set to 11.7:1.

So I went out driving the car around one of the following nights. After about 1hr of driving, I gunned it and there was alot of hesitation and it felt like the car literally had 100hp. I tried again and it again with the same results. I went home and tryed to figure it out. I concluded that it was heat soak. I figured that the slightly smaller pulley produced just more heat & energy to heat soak the engine. I then replace the coolant with nothing but DI water and watter wetter.

Car seemed fine to the short 5mile commutes to works, however, about a week later, I took it for a 1hr trip. It was mainly just coasting on the highway. I pull off the highway, and gun it from 2nd gear. It falls flat on its face as if it had 100hp. At this point I was confused, because it wasn't really a hot day, and I wasn't pushing the car on the highway. However, I was driving for about 1hr before gunning it. At this point, I was still blaming heat soak.

I started second guessing the tunner, so I pulled the plugs to check how close to .025" he set them and to my surprise, they were between .016-.019. I gapped them to .027 crank up the car which then made the car idle alot smoother. I took it for a spin and it seemed peppier. I then grabbed the laptop to do some data logs. I dataloged a 3rd gear pull, and killed the pull after I saw a/f's get to 15:1 by 7000rpm. I tryed again and again let off early as af's start increasing beyond safe as I reved it out.

So I parked the car for two weeks. I figured with me regapping the plugs to .027, the car was able to burn all the fuel thus leaning it out. So I am currently waiting on an exhaust to come in, so what I was going to do was throw that on and have the car tunned with the plugs properly gapped.

So the day befor yesterday, I thought about what the tunner was saying about not paying attention to the a/fs that hondata was recording as they were never correct and relying on the tail pipe sniffer instead. So I thought, hey, I was data logging with my laptop getting those high A/Fs from hondata. I have an actual separate wideband, so I figured I do some pulls to see what it is reading instead of hondata.

I crank up the car, jump on the highway and low and behold the A/fs sat at 12:1. So I was like: wow, guess the tunner was right about the A/F readings from the ecu. So I figured all was well. So yesterday, I took the car for a 2hr highway trip and thats when the mustang pulled up, I dropped it down to 4th and the car fell flat on its face with about 100hp.

I had the wide band still sitting in the passenger seat from day before, so I plugged it up and it now showed 15:1+ A/fs under load reaching 18-20:1 before cutting out. At this point it all made sense with fuel pressure being somehow linked to run time.

This morning, I tested out the theory again. I had to swing by the post office on the way to work so it was a 20min trip. Starting off, A/fs were holding 11.7-12:1. After the 15min mark, A/Fs climbed to 12.5:1. and right before reaching work at the 20min mark, the A/fs reached 13:1.

I quadruple checked after work driving home. The A/Fs started at 11.7:1 and 8min later were at 12.2.

That is my story, that is exactly how it played out and now I'm here.

So how do I check to see if the tunner did not adjust for ever changing IATs? That is sounding like the issue as I dont recall having this problem when Jeff Evens E-tuned it.

Also, does anyone have any recommendations for a shop around Atlanta to have the car tuned on Flashpro? As one would expect, I am now very weary of the tunner I went to. Maybe I should buy another Jeff Evans E-tune?

PS: Here is the dyno sheet of what the car was tuned to. Only difference between these two pulls is one is with the hood closed and the other is with it open.

THANK YOU ALL FOR YOUR INSIGHT, IT IS MUCH APPRECIATED!!!!

Thanks, Voya

99SH

Open you your calibration file and take a screenshot of the Air Temp and Coolant Temp Compensation and post here.

Click Calibration, and expand the Fuel drop down. The last 2 items there are the comp tables.

TheSnail

Ok, I think I print screen'ed the correct tables.

They were labled lambda low and lambda high

99SH

That's not it. See menu here:

Go to Options and select Show Advanced Parameters

TheSnail

Here is a data-log of what a 3rd gear pull looks like after about 25-30min of running. As you can see, it no longer holds 11.6:1. It just start increasing in A/f as you go through the rpms.

This is after 25-30min. After 1hr, it is 15:1 by 5000rpm etc. Just gets progressively worse.