Got my car back after months of headache and had a local shop put it together.

I have been driving my car with an ear to ear smile since I've had it back and finally got on boost on the highway. Perfectly fine AFR's starting at 14.8 tapering to 10.8 ish on a stock turbo and bolt ons. It ran like a champ for a week.

Last night, I was on the highway and on WOT it started to surge and stutter at 4k+ and I looked at the UEGO and it was 16+!

I went back to cruising and it cruises at 14.8 all day. Tried WOT and got 18! It went from driving perfect to this without any changes.

Could it be:
-Vacuum hose? (Didn't see any disconnected)
-Sparkplugs? 2k miles without issue
-Cold weather? 30 degrees ish
-Gas is 93oct as always

I really don't know much about what makes a car run lean.

Thanks for the help!

 

I looked at the UICP and it didin't pop off, but I didn't get a chance to look at the LICP. I would assume if that was the problem it would be awful afrs everywhere. It's fine under light load acceleration, just wot it does this.

 

If there is a leak in most cases you would have the opposite and run rich.

Did you check to make sure your injectors are not leaking? Maybe for some odd reason the o-ring seals might be leaking. Make sure the injectors and fuel rail are bolted on snug.

Also check the FPR vacuum line does not have any tears and is properly connected.


I had an issue where my car started running lean as well and coincidentally it started happening with the dropping temps. However, I'm running an HTA green with e85 tune. My only fix is I added a boost-a-pump which brought my a/f to exactly as I was tuned for 12-11.8 from a 14 af ratio at WOT I dont know if temps dropping would make such a huge impact.

 

LOl same thing happened to me change a new pump and the afrs went back to normal..To the o.p what are you using to check afrs??For them to be at 16 + is a bit drastic I don't think they went that high if it did you wouldn't be pretty

 

I changed the Walboro pump with a brand new one, same story. That's why I got the boost-a-pump because the double pumpers are more than I could afford spending for a while. But the BAP is working excellent.

 

Boost-a-pump send me a link for that please..My walbro pump was making a loud *** whine sounded like a cat was stuck in the tail pipe burning alive..lol..I changed it right there and then a local parts store had one and the afrs went from 12.4 to 11.2.O I pmed you once about a setup for my buschur exhaust to take away the rasp out of it but I guess you forgot.

 

Kenney Bell Boost-a-pump aka BAP


It basically increases the voltage of the pump to make it flow more. Turning the dial switch will increase voltage by a certain percent. Example a 12 volt current to the fuel pump can be increased up to 17-20 volts.

Mustang world has been doing it for a long time now, doesnt kill the pump or make its life any shorter.

Yep I remember you. If I didnt answer your question or you have more pm me I'll be glad to give you further advise.

Dfelton sorry for the off topic.

Double check what we suggested and let us know. Maybe other people can chime in as well.

 

woudnt this burnt out the fuel pump?maybe a fpr would help bump it up

 

Either your BOV popped off or you loose intercooler pipe somewhere creating a huge boost leak.

 

Did u check the uego sensor?
I had to replace my aem wideband sensor because it went bad and only showing lean at wot.
GL

 

As most have said, typically if you're running lean in boost it doesn't indicate a boost leak. If you're lean at idle it typically indicates a vac leak... rich in boost suggests boost leak. My first thoughts are... is your MAF/o2 sensor good? Is it possible that before you actually had a leak (even if it was a faulty BOV or something) and you repaired it and now you're lean? Or, as others have mentioned, maybe an injector seal issue, fuel pump, etc... Just trying to add some other ideas out there.

 

Thanks for the great response guys, good thoughts here.

-I did check the injector o rings and as far as I can tell they are not leaking.
-My UEGO WB is only three months old and brand new. I has been reading fine. The AFR's really did reach 16+ and although I didn't log yet, I'm sure its knock knock knockin on heavens door.
-The pump is an interesting idea too.

Its just strange that it just started in the middle of a long drive. did a few pulls that night with perfect AFR's

Hmmm

I'm gonna double check the FPR line and the other suggestions, thanks guys.

 

You guys are good!

It was the FPR hose that blew off! A few zip ties and some pulls on the highway and it's back in business! Thank you for all your input. Where would I be without this site?

 

No. The fuel pumps are all tested at to work higher than 12 v. Mustang guys have been doing it for a very long time. Very reliable unless the unit itself fails then kenney bell will fix it up. And it doesnt burn out the pump any faster.

In my case I did not check the sensor. Well the only way to check is by replacing it right? However when I lowered my boost from 31 psi down to 21-22 psi it did fix my a/f ratios. So if it was the sensor I dont think in my case it would show normal a/f at lower boost.

Agreed. Thats what we're here for

 

been done in dsm world since day 1. just google fuel pump rewire kit dsm

If you have to alter the pump voltage then somethings wrong imo. Evo has no need for any of that, its on a relay that switches voltages to high and low, which is also why we can keep the stock fpr on such crazy setups.

someone already mentioned it but ya, 10.8 to 16-18 = fuel pumps on its last leg.