dkersten

It would cost almost $2k to ship it there and back in a covered truck, but the thought has crossed my mind.
Last night I thought for sure the problem was the massive vacuum leak. I pulled the supercharger and disassembled it, fixed the problem, and put it all back in, then tested it with a very nice smoker for about 30 minutes. There was one tiny leak that I siliconed up after that, but I can't see it causing any major problems since it was the passenger PCV line, and it is small. I was so disappointed when I pulled out and it bogged and sputtered and popped. For the last 2 weeks, my mechanic has been driving it, datalogging every morning and evening. There is only about a 3-8 minute window where the problem occurs, then it warms up and runs fine, except for the idle dropping when coming off throttle.

The datalogging showed the Long term fuel trim going super rich when the engine is cold, but the tuner at KB told me that LTFT doesn't do anything when the engine is cold (in open loop). The AF gauge shows it is leaning out, which suggests an air leak between the MAF and the supercharger, which I did have. It is still showing lean when it sputters and bogs. However, it has thrown 2 rich codes when cold if I get on the throttle, which, once again, is NOT supposed to happen when in open loop. Between the fuel trim showing it dumping huge amounts of fuel, and the rich codes, it seems there is some kind of fuel problem. If it is misfiring, the wideband O2 would see unburnt oxygen, and the gauge would read lean even if it is fuel rich, so we ran on that premise for the last couple weeks, but haven't found anything that could cause it to add fuel. I replaced the MAF sensor with a new one from KB (90mm KB sensor), and no change. I have been confident that we will find the problem, but now my confidence is slipping. I only hope that someone else with the problem will actually find the cause and report on one of the forums what the exact problem was. I have found quite a few people with similar or identical problems, and most of them just assumed that was how it was with a supercharger. I will not settle for that.

Honestly, I have about $35k into the car and if I could sell it for $31k I would in a second. Unfortunately, in the current market, I would be lucky to see $25k, and would probably be better off returning the car to totally stock and selling all the mods. It never pays to put a $7000 supercharger on these cars..

Next week we will start over with the troubleshooting, but I know my mechanic is tired of messing with it now.. It is in the shop getting the pinion bearing replaced (brand new bearing from last gear install, that is a whole other frustration). The tuner at KB offered to try another tune, but their philosophy is one I believe in: If this tune works with this kit in thousands of identical cars, with engine and computer systems all made on the same assembly line, then my problem is not in the tune, it is something else, and tuning out a mechanical problem is a mistake. I don't want to cover up the problem, I want to fix it.

God I hope someone can find the problem and report the results here.

dkersten

[QUOTE=haproot;6384217]Sounds like idle hunting due to not enough ignition timing at idle due to the added load caused by the supercharger. Not all superchargers may create this load but some probably do.

From the Subaru world we would have to lower ignition timing @ idle when say having a lightened crank pulley or flywheel. Otherwise it hunts like that. Maybe in your cases here you need some added in the idle and low engine load areas on your map?

Also I'm not sure how a map/tune on a mustang looks like but on ours (subaru) there is a table for ignition timing compensation in relation to coolant temp. If the issue goes away when warm maybe a similar table needs to be adjusted on your tunes/maps.
QUOTE]

The only thing I am thinking different here is, the subaru starts with a super low torque, low horsepower engine where any load on the engine would need to be compensated for to prevent idle from being affected. The 4.6 3v should be able to handle a 2-3 hp strain at idle with no problem. If his problem is like mine, it "hunts" for the target idle when coming off throttle. Mine didn't do that for the first couple weeks, then started doing it and has gotten progressively worse over the last four weeks. It will drop as low as 300 rpm and jump as high as 1200 rpm before settling into the target 750 rpm. After a long steady cruise on the highway it was actually stalling when coming off throttle. I was pretty convinced this was some kind of vacuum leak problem, but now... ?

Riptide

I'm real sorry to hear that. I know it must be extremely frustrating especially after pouring so much time and money into the "project" that is the car. To be completely honest this is one of the things I am a little bit concerned about when putting a blower on mine. I don't have the know-how to fix some PITA problem like that if it comes up and would be dependent on someone else to fix it for me. Which can be a huge hassle and expense. It would be nice if we lived closer to KB or brenspeed. But we're out in the sticks.

If it were me and I eventually gave up on fixing it myself then I would probably give it a break, think it over, and decide how much I like the car. Based on that I'd either tear into it and sell everything for a loss just to get rid of the problem. Or I'd keep it, pay the money to ship it out, and have the problem fixed.

Guess we won't be seeing you this evening at the hardees.

haproot

Ok, two more things come to mind with your issues as you explain them more clearly.

1. Small exhaust leak is throwing off an o2 sensor
2. o2 sensor is going bad.

dkersten

I'm not going to let a little thing like this stop me from being there.. I will be picking up the car this afternoon and will be there. I will also be in the Fiesta show this weekend, and might even do the poker run tomorrow night. My mechanic gets my car from Monday morning to Thursday afternoon, and then it's mine again for Hardee's, and the weekend shows. Been this way for 2 weeks, looks like next week will be no different.

dkersten

Problem occurs in open loop (during cold run) when it is not monitoring the O2 sensors. haha.. I had hoped maybe an o2 was the cause, but evidence suggests otherwise. I think we are going to look at the cats next.. could be clogged from all the rich/lean running.. Also throttle position sensor could be a cause, or even EVAP control. I am also thinking maybe a bad coil.. poor connection when cold causing misfires, which dumps unburnt fuel and air into exhaust resulting in AF gauge showing "lean" due to oxygen level, but when the engine warms, the coil starts working right and problem goes away.. ? Only easy check there is to replace all coils since I don't see a particular code for misfire on a cylinder. If it is not the case, I just blew $120 on coils that don't help. *sigh*

Sorry if it seems I am jacking the thread, It is not my intention. Seems the problems the OP and I have are very very similar, if not identical, and I wanted to share the various things I have found in the troubleshooting process.

Oh, the fuel level thing is a problem with the sensor in the fuel pump, I have seen it happen occasionally too.. my fuel level all of a sudden drops in half, and eventually starts reading right later. I don't think it has anything to do with the other problems.

haproot

Definitely sounds frustrating. My next thought is yeah possibly ignition coils. I know you've played with the MAF already but it sounds the same as an issue a friend of mine had with a dirty MAF. Other things that come to mind are fuel pressure regulator, and possibly something funky with 1 or more injectors, and maybe something in the valve train, ie: sticky valve. Again good luck. I think I'm out of ideas.

Dont forget that Riptide lives close and has a working mustang with parts you guys can swap back and forth.

dkersten

Good call.. I don't think I would want to put anyone out by stealing their coils for a day, but it is a great idea. haha.

I suspected a dirty MAF, but just 2 weeks ago I put a brand new one in (housing and MAF sensor) and it made zero difference.

I think I am going to borrow the smoke machine this weekend and pull the bumper and test from the maf housing with everything in place. I can't get past the idea that it might be an air leak between the maf and supercharger. I would pull the filter and test from there but I don't know if the smoker would damage the maf sensor.

I think about the injector thing, but usually a bad injector would cause it to be hard to start too (leak fuel so pressure drops between starts, and floods engine). Also, I would think that would show up with a code too.. Not quite acting like a stuck injector..

Riptide

dkersten and OP. I have posted this picture in your honor. I think it quite relevant yes?

dkersten

Indeed.