Weird lean problem when Cruising HELP !!!

[Jay97240Sx]

Ok folks i have done my research but still no answers. I have weird lean condition at idle, when decelerating and when cruising and shifting gears. I have the JWT program with 370cc injectors, 255 lph. I bought a AEM wideband a couple weeks ago and everything ran normal.

Over the past week the car has started to idle in the 17-18 plus range where is used to be 14-15 before. On deceleration it runs rich, but at about 1800 rpm and lower it starts to lean out and goes off the scale. The part thats really weird is when cruising my AFs are usually in the 14-15 range then i will feel i very slight sutter and when i quickly glance at the gauge it will read lean off the scale (18+) for a few seconds then bounce back to 14-15.

Sometimes also while cruising if i should give the car just alittle throttle to maintain speed or gently accelerate, it runs lean off the scale then richens back up to normal (This usually occurs when im in the 2500 rpm range)

The lastest lean condition is when shifting. This hardly happens but, when i shift it runs rich because of the BOV then lean (18+) then back to normal, so the car does a double stutter.

I most also note, i have a missfire at idle and dont know if this can be apart of the problem.

HELP PLease !!!!

[LEMHEAD16]

When decelerating in gear its normal to go lean. I would be more worried about the fact that your going rich under deceleration while in gear.

I know its pretty elementary but have you check Plugs, gap, wires, cap and rotor? That's the best place to start

i would also check fuel pressure when you are experienceing htose problems. A Walbro fuel pump can push too much pressure at light loads if your FPR is out of wack.

[Jay97240Sx]

Well plugs are 2 months old and gapped properly. The rotor i checked and cleaned with a file earlier today, and will replace both by the end of the week. The walboro fuel pump i put in today, thinking that my stock fuel pump was on its way out, but no difference. The car runs 12-13 AFs when decelerating, then by the time it hits 1800 rpm and coming to a full stop it goes lean off the scale.

[NateDogg]

Without any pics or description of the setup we are shooting in the dark and just wasting time.

There are two things that come to my mind.

1) Vacuum leak.2) MAFS is too close to the turbo (vortex created by compressor blades skews MAFS reading, especially on decel).

Help us to help you. Post some pics and specs.

[Jay97240Sx]

Well i have JWT Ecu, 370cc injectors, stock maf, K&N filter, Greddy Bov, T3/T4 turbo, full 3 inch exhaust, no cats, AEM wideband.

I know if the maf is too close to the turbo it will mess with the maf readings, but this setup has been this way for almost 2 years, the aem i have for about 2 months, but this lean problem just started less than 2 weeks ago. I have changed nothing on the car.

I do have a slight vacuum leak some place around the throttle body, but i have had that leak for months. Also i have been having a ruff idle, i dont know if its related.

Im not so worried about the deceleration lean part of it, its the while cruising lean situation thats really bugs me. It happens at around 2500 is rpm in 4th or 5th gear, ill feel just a slight stutter which i can also hear from the exhaust, and when i glance at the wideband it will be lean of the scale, and if a tap the throttle it bounces back up to the regular 14-15 reading. its as if the car chokes for a second.

Whats becoming more common over the past 2 days is if i gently press the throttle say going 25-30 mph in 3rd gear, the car runs lean for a second then swoops to normal.



Note: i did make a better intake pipe a couple months ago, but everything else is the same.

[WDRacing]

Check the wiring for the stock O2 sensor and swap it out while you're looking. A cheap bosche unit works just fine.

My car won't even idle at 18:1...it would stutter and crap out. So Idle is really not a huge concern. But cruising should be 14-15, leaning out randomly makes me think O2 issue.

WD

[Jay97240Sx]

Thanx, ill look into that, i have been meaning to change it for weeks, because ive been getting o2 sensor codes

[LEMHEAD16]

Thanx, ill look into that, i have been meaning to change it for weeks, because ive been getting o2 sensor codes

That would have been a good piece of information to post.

[Jay97240Sx]

I know right but, an 02 sensor would cause the car to run sooo crazy ?? I can tell u, that sensor was dead from when the previous owner had it, and i have been driving around with it like that for months.... with bad fuel mileage ofcourse, but these problems started happening not even 2 weeks ago. The car actually bucks and hesitates alittle when it runs lean, can the o2 senser really cause that ?? and why all of a sudden now, when its been dead for a long time ???
Modified by Jay97240Sx at 9:36 AM 3/25/2009

[Jay97240Sx]

Can anyone else chime in ?? Im was just going over some of the posts, i always thought a bad o2 sensor caused the car to run rich, not lean and rich, but just rich

[WDRacing]

Here's how it works. Your car is throwing a code saying you have a bad O2. So change it...

We can't give you crap for advice until you fix the known problems. A bad O2 sensor will do all kinds of stuff because the ecu switches from closed to open loop depending on engine load and temperature.

WD

[Jay97240Sx]

Understood, im still learning this stuff, ill change the sensor asap and update on the weekend.

[WDRacing]

No worries brah. Just keep in mind that boost will always make any problem 10X worse. That's why it's important to keep the usual stuff like plugs/wires/sensors/oil all up to spec.

WD

[ss82480]

WD is such a pleasant moderator, isn't he?

[Jay97240Sx]

WD is such a pleasant moderator, isn't he?

Yes he is, and i really appreciate it. I will update on the weekend, going to the dealership tomorrow to get a new sensor, and take care of that vacuum leak.

[joenismos15]

I had the Same Problem on my setup a while ago, I got the O2 Sensor Code popping up and i replaced it, that was half my problem, My stock FPR was leaking fairly bad so i replaced that also and Viola it worked perfectly! Or at least it did till my stock engine died, i was running the original Motor with the Greddy turbo kit at the time.

[Jay97240Sx]

I had the Same Problem on my setup a while ago, I got the O2 Sensor Code popping up and i replaced it, that was half my problem, My stock FPR was leaking fairly bad so i replaced that also and Viola it worked perfectly! Or at least it did till my stock engine died, i was running the original Motor with the Greddy turbo kit at the time.

I had to order the sensor for $167 Im going to check the stock FPR. Someone also suggested to check the injectors for a broken o-ring, could cause problems too. thanx
Modified by Jay97240Sx at 6:33 PM 4/1/2009

[LEMHEAD16]

Why would you go to the dealer for an O2 sensor? Any local parts store should have one that will work just fine. For a whole lot less $$

[kouki_hmongster]

I had to order the sensor for $167 Im going to check the stock FPR. Someone also suggested to check the injectors for a broken o-ring, could cause problems too. thanx

Modified by Jay97240Sx at 6:33 PM 4/1/2009

If you have stock fpr then it would be best to go aftermarket something like aeromotive, nismo type-B, fuel lab, etc.... mine crapped out on me and caused me to go stall out. if you have upgraded fuel pump the stock fpr wont be able to handle the extra pressure and may crapp out. also you should make sure your maf is at least 12inches away from turbo, it seems to be a little close. GL

Autozone FTW O2sensor works great.

[Jay97240Sx]

Well the reason i went to the dealer is, speaking with Ben from jimwolf a couple times he said alot of people end up buying the wrong o2 sensors for their cars. And i can understand why. i have a 95 ecu running my 97, and when i ask for a 95 ecu, they pull up about 5-6 o2 sensors for the car, when i went to the dealer they only had one 02 sensor for that year car.

But please, if anyone has a setup similar to mine, with the Jimwolf and a different year ecu, please tell me what 02 sensor works for u, so i cant know better next time.

Im saving up to purchase a aeromotive Fpr, so hopefully, next week i can pick one up.

I have to fabricate a whole new intake, im looking around for a z maf, then i can start the process.