Kaveeth

Ok I'm a little bit stumped with this and I'm not sure if I should rectify this issue or just run with it. I'm about ready to give it in to a shop.

Short story: my car has started running about 1 point leaner AFR, both in open loop AND closed loop and I'm not sure if it's a real problem or not. Fixed exhaust upstream of my wideband but problem is only slightly better.

Longer story: My car previously would idle at exactly 14.7 AFR with no effort. Then I disconnected the battery because I wasn't driving it for a while. After I reconnected it I noticed that it would idle around 15.5 - 16.0. I also noticed that while cruising it would struggle to hold 14.7 and jump leaner a lot more frequently then it used to. This problem was initially only happening at idle and cruise but then it progressed to WOT and my AFRs have gone about 0.3-0.4 points leaner at WOT, so I decided I should try and fix it.

It looked like an exhaust leak issue so I took out the downpipe (my wideband is in the downpipe) and found the donut gasket in pretty bad condition. Replaced the gasket and idle started to hang around 15.1 and would jump between 15.3 and 15.1. So given that it was going to as much as 16 before I thought that the gasket made it better but may have still been leaking. I took out the DP again and sealed it with gasket cement but there was no change in the AFR's after that.

Additionally my car has developed this problem were on cold mornings when I crank it it'll sputter and the engine will hover at like 500rpm as if its being choked. Sometimes it'll jump to life after like 3 seconds, sometimes it'll die after the sputter but on the next crank it'll start instantly. Not sure if its related.

Since I've done the exhaust I'm wondering if this issue is fuel relay/wiring related or maybe leaking somewhere like throttle body. I could run with it the way it is because its not that much leaner than before, but I don't know if the problem will get worse and of course going leaner at WOT is dangerous. Anyone have any tips or insights?

ReaperX

iTrader: (5)

Do you have a tactrix cable and evoscan? Relying solely on the wb to trouble shoot this isn't going to work. You need to log your fuel trims also to rule out the front o2. But.... I am leaning towards and exhaust leak in either the head to mani..... or mani to turbo..... since you only mentioned replacing the dp gasket. I'd replace those gaskets and it will more than likely take care of your issue.

EVO GOES VROOM

how long have you had your sensor for they go out frequently depending on type of gas used etc.

Kaveeth

Yes I have evoscan and tune the car myself. Sorry forgot to mention that fuel trims are good. LTFT low and mid are both within +/- 1%.
So the car is trying to hold 15.1 at idle and not 14.7 and the fuel trims are spot on. I'm guessing that points to a leak of some sort, but wouldnt it have to be after the front O2 as fuel trims are not affected and before my wideband to show up as lean? The only gasket between those sensors is the donut gasket which i replaced so now I'm stumped.
Wideband has less than 10000k's on it and is only 6 months old, AEM UEGO. I use 98 RON

Kaveeth

Update: when I come to a stop and put the clutch in the AFR starts at 14. 7 and then creeps to low 15's.
LTFT mid used to ALWAYS hover round -1 to -2%, now its gone positive 1%.
WOT seems to be slightly richer than before I changed the gasket out, though its hard to tell as its only like 0.2-0. 3 points richer
I guess this is looking like a boost leak now?

4g63Moon

iTrader: (9)

Do a boost leak test and how long did u have the car sitting? Did u check your fuel filter?

Kaveeth

So the exhaust is all patched up new donut gasket. Just did a boost leak test and was happy to find two big leaks, one on the intercooler piping and one on the core. I though fixing those would fix the problem but not really.
WOT AFRs are ok now but the car still idles around 15.1 to 15.3
This is really getting annoying I've spent so much time hunting down this problem. Now I'm thinking maybe dirty air filter (hasn't been changed in 3 years), dirty MAF or dirty fuel filter (both the sock and filter have never been changed).

You guys have any insight? I don't want to keep thowing money at this issue, the new intercooler was a big spend that solved the boost leak but not the lean idle. How do I "check" my fuel filter? What do I look for. BTW car was only sitting for about 3 weeks.

The fact that when I come to a stop the car starts off at 14.7 but moves over to 15.3 after a few seconds, should be a clue to whats going on but I just don't know enough to figure it out.

Kaveeth

extra info: sometimes when I start my car in the morning and its cold it'll turn over and then sputter while the rpm's hover around 200-300 for about 3 seconds, even feathering the throttle won't do anything. After that it'll either jump to life and idle perfectly or die but start up instantly on the next crank.
Maybe this is another clue?