running lean, exhaust leak questions

[1Gina2G]

Okay so there has been alot of exhaust work going on that I've been doing, I wanted to do a start up to check out some things, noticed right away the wideband says it's getting 17-18 range I took it to 2-3K for a quick second just to see if anything would change, stayed the same so I cut the car off.

the wideband is in the 02 housing, 02 sensor in the bung & pluged in along with the MAF. wondering about how good the seal is on the 02 housing & downpipe, I have new gaskets but I was wondering, could an exhuast leak AFTER the wideband still cause it to read lean?

what else could I check, besides a BLT, for running lean?

 

[Paintballaa5]

Exhaust leak post wideband will not affect readings.

 

[1Gina2G]

I didn't think it would.

I just remembered, today before the start up I had to take the CAS on the head off to get clearance, Not positive on if I got the CAS back in the same postion it was originally, mostly because I know I have to adjust it with the timing light (new rebuild)

So can this be why? Should I adjust this issue first? and then check for exhaust leaks? or vise versa?

 

[n0de]

Okay so there has been alot of exhaust work going on that I've been doing, I wanted to do a start up to check out some things, noticed right away the wideband says it's getting 17-18 range I took it to 2-3K for a quick second just to see if anything would change, stayed the same so I cut the car off.

the wideband is in the 02 housing, 02 sensor in the bung & pluged in along with the MAF. wondering about how good the seal is on the 02 housing & downpipe, I have new gaskets but I was wondering, could an exhuast leak AFTER the wideband still cause it to read lean?

what else could I check, besides a BLT, for running lean?

If you are talking about a tiny leak before the WB sensor then i dont think it would cause 17-18 a/f readings, that's pretty lean. an exhaust leak after the wideband shouldn't cause it to read lean, maybe if the leak was IMMEDIATELY after the sensor but i doubt it.

Was this a recent event? What is your Fuel pressure at? (assuming you have a gauge). If you don't have a FP gauge then check your stock fp solenoid to see if the vac hoses are attached properly and nothing is T'd off of it.

 

[Paintballaa5]

So can this be why? Should I adjust this issue first? and then check for exhaust leaks? or vise versa?

I don't know anything about taking the CAS off, but if you know theres an issue, fix it. It can only add to your problem

 

[1Gina2G]

If you are talking about a tiny leak before the WB sensor then i dont think it would cause 17-18 a/f readings, that's pretty lean. an exhaust leak after the wideband shouldn't cause it to read lean, maybe if the leak was IMMEDIATELY after the sensor but i doubt it.

Was this a recent event? What is your Fuel pressure at? (assuming you have a gauge). If you don't have a FP gauge then check your stock fp solenoid to see if the vac hoses are attached properly and nothing is T'd off of it.

yes everythings recent. fuel pressure guage is at 43-44 or so as it should be. I'm really wondering about the CAS postion now, but nothing coming up about it.

Plus I think it's actually recomended that you T-off from the intake manifold line that runs to the FP solenoid for your boost guage, I'm sure thats what I did, just use rtv on the T fitting and zip tie the lines.

 

[revvrivera]

are you getting the proper fuel pressure

 

[1Gina2G]

are you getting the proper fuel pressure

fuel pressure is fine, oil pressure is fine, vaccum is fine.

 

[n0de]

yes everythings recent. fuel pressure guage is at 43-44 or so as it should be. I'm really wondering about the CAS postion now, but nothing coming up about it.

Plus I think it's actually recommended that you T-off from the intake manifold line that runs to the FP solenoid for your boost guage, I'm sure thats what I did, just use rtv on the T fitting and zip tie the lines.

Well I think I have seen ppl recommend t-ing off of that but I just try not to, if for some reason there is a vacuum leak between the intake manifold and the afpr then it could cause the it to not raise the fuel pressure while under boost which would cause a lean condition (I thought this might fit your scenario).

Back to the drawing board, ill think on this one for a bit then post if i can come up with a theory.

fuel pressure is fine, oil pressure is fine, vaccum is fine.

What is your vacuum at idle(Please include if you have aftermarket cams or not)

 

[H@xtGSX]

Which WB, and when was the last time you calibrated it? Are you running a programmable ECU, LINK? I run around 16.8 at idle, but I programmed my fueling map to do that intentionally. For the WB to pick up lean like that, you'd have to have a pre-turbo leak, if a lean idle isn't normal for your set up. The other theory would be that you are leaking air in pre-turbo, post-MAF.

 

[WES_393]

Like I posted in another wideband thread today:

Assuming the sensor is properly calibrated and fully functioning, there are only 2 reasons your wideband would display a lean reading.

1. You have an exhaust leak before the sensor which is drawing in fresh air. This is probably the most common reason for lean readings at idle/cruise. Large leaks can even throw off readings at WOT.

2. Your actually running lean. This can be caused by poor fuel supply, vacuum leaks, or even a faulty front O2 sensor.

So check for exhaust leaks and boost/vac leaks, then check fuel supply and front O2. Don't just assume you have none of those issues, check each one carefully to be certain it's not the cause. I would also let the car idle for a minute to allow the ECU to get settled into closed loop operation. Narrowband sensors are inaccurate and "lazy" when cold, which could throw off the ECU's fuel control. Even my brand new Denso front O2 takes a minute or two to start oscillating normally. So don't assume the first number you see on the gauge is the actual idle AFR.

 

[1Gina2G]

Which WB, and when was the last time you calibrated it? Are you running a programmable ECU, LINK? I run around 16.8 at idle, but I programmed my fueling map to do that intentionally. For the WB to pick up lean like that, you'd have to have a pre-turbo leak, if a lean idle isn't normal for your set up. The other theory would be that you are leaking air in pre-turbo, post-MAF.

It's a LC1 wideband, Db guage. Just the guage itself wired up, not for logging just yet...its kind of weird since I have a 95 eprom ECU but dont have the money for link, havent been lucky enough to get a link from someone for cheap. But I have evoscan and the cable for just logging. I've already seen 14-15 at idle before, then again this is before I just moved the wideband from the rear 02 spot to the 02 housing to avoid the flex section.


I'm going to do abother BLT tomorow but they say don't do a BLT on a cold engine, not to menition an engine that's not fully broken in. Last time I hear air bubling up oil in the engine since the rings arent sealed, I asked about it here I belive. no air coming out, or bubling up on the turbo at all, or anywhere on anything around the engine bay at all..I know I need to get this need warm and after a nice drive down the road for the rings..

just switched out my turbo to an evoIII16g, but running a completley stock fuel system for the most part. was told it'd be fine as long as I just didn't slap on some huge injectors without the proper tune, still have my stock 450s and rail, new filter and pump.

just a slight chance of exhaust leak since I had trouble bolting things on initally but I put new metal gaskets on with copper spray, so the exhaust was messed with, then again the entire exhaust system is new and put in by me too, doesn't sound loud at all - how else can you see? shouldn't be pretty easy to see in the cold?

 

[n0de]

It's a LC1 wideband, Db guage. Just the guage itself wired up, not for logging just yet...its kind of weird since I have a 95 eprom ECU but dont have the money for link, havent been lucky enough to get a link from someone for cheap. But I have evoscan and the cable for just logging. I've already seen 14-15 at idle before, then again this is before I just moved the wideband from the rear 02 spot to the 02 housing to avoid the flex section.


I'm going to do abother BLT tomorow but they say don't do a BLT on a cold engine, not to menition an engine that's not fully broken in. Last time I hear air bubling up oil in the engine since the rings arent sealed, I asked about it here I belive. no air coming out, or bubling up on the turbo at all, or anywhere on anything around the engine bay at all..I know I need to get this need warm and after a nice drive down the road for the rings..

just switched out my turbo to an evoIII16g, but running a completley stock fuel system for the most part. was told it'd be fine as long as I just didn't slap on some huge injectors without the proper tune, still have my stock 450s and rail, new filter and pump.

just a slight chance of exhaust leak since I had trouble bolting things on initally but I put new metal gaskets on with copper spray, so the exhaust was messed with, then again the entire exhaust system is new and put in by me too, doesn't sound loud at all - how else can you see? shouldn't be pretty easy to see in the cold?

vacuum is a tad low, 14-15 was before, what is it now.

 

[H@xtGSX]

To me, "metal gasket with copper spray" = leak.... I hate MLS gaskets regardless, but if you have even the smallest warp on the flange of the manifold (which is VERY likely), you have a leak. They aren't always loud... I have a very quiet one right now. I stripped out 2 of the exhaust manifold bolt holes and they haven't been fixed yet. I know its leaking, I can feel it pulse a little if I hold my hand right on that edge when I first start it before it gets hot. It does mess with the readings a little...

The BLT stuff you mentioned is for through the block... Just cap the intake pipe at the throttle body elbow and test from just after the turbo. An exhaust leak isn't going to show up on a BLT either, just in case you were assuming it might.

 

[1Gina2G]

I knew the BLT isn't exhaust related, is there anyway to tell for sure if I have an exhaust leak or not? Or is it best for me to just change to the composite gaskets?

trying to figure out how to test my front 02 sensor, evoscan should show right? it shows a voltage reading for it.

 

[casperfast]

the best way i find exhaust leaks and see how severe they are is by seafoaming the engine through the brake booster vac line. leaks will become wet and easily visible. a leak as far as 10in past the sensor can cause the sensor to read the outside reference air. if exhaust can go out, air can go in. if the leak is between the o2 housing and the downpipe then it will most deffinatley throw the sensor off, read lean, but actually run rich. if your factory o2 in the housing for example sees air from a manifold leak, it will see that air, richen the mixture to try and lower the ratio. this is one of the leading causes of catalytic converter meltdown/ failure.

 

[WES_393]

trying to figure out how to test my front 02 sensor, evoscan should show right? it shows a voltage reading for it.

If you can see the front O2 voltage that's all you need. The front O2 should (once warmed up) constantly fluctuate from .2 to .8 volts. If the voltage is steady or only fluctuating a small amount, the O2 sensor should be replaced. If the sensor does need to be replaced, I would check out oxygensensors.com for a quality sensor.

 

[Vander Nars]

rather sure an leak after the after the o2 sensor wont cause it to run lean.

 

[1Gina2G]

Alright well I haven't got to anything yet since my last post since I worked late today, but is there anywhere else I can use the seafoam for exhaust leak purposes? Is seafoam OK to use on new engines? seams like its made for the opposite. I'm not posituve on where the brake booster lines actually are, are why they would be exhaust leak related..

been also thinking about whether or not I can actually test the 02 sensor on the car, since its after the wideband in the 02 housing. If there's a leak, both the sensors would probably be off right? Or am I just seeing if the numbers 'jump around' like they would on a wideband?

I bet it has to be an exhaust leak, I used these really cheap gaskets I had in storage forever, thought metal was better. I can see how composite squishes down better. Since everything else is new, replaced the entire fuel system practically, new wideband and denso front 02 sensor, luckily theres composite gaskets on everything else exhaust related, just happen to use metal ones one the 02 housing to turbo & manifold to turbo. gas was burning perfect before the 16g.

 

[H@xtGSX]

WTF

Is your wideband giving the ECU the O2 sensor signal? That alone could be your problem... I have never had great results using a wideband to simulate a narrowband. They kind of suck at responding as fast as a normal narrowband... And if your narrowband is below the point it should be for normal operation, it isn't set up to work as the ECU expects it to be. Also, the wideband shouldn't be jumping around quite as much as a normal narrowband does.

I think composites are better... They compensate for irregularities better than anything else, and they are proven to be almost as durable as a properly seated MLS. The only point they are surpassed by MLS gaskets is in extremely high power situations. As an example, the 800 hp V8s used in NASCAR motors use Felpro composite gaskets... Are you pushing more head pressure than one of those motors? Doubtful... Very few of us do, and the guys who are already know this and use MLS gaskets because they have no other option.

 

[casperfast]

as far as "new " engines go, i dont see an issue, is has a chemicle reaction with carbon when combined with heat. i have used it on all of my vehicles and multiple times on my dsm(once a year). the brake booster hose is the largest vac line going to the manifold from the brake booster. its that big round thing that your brake master cylinder (thingy where brake fluid goes) is bolted to. it being a new engine, you wont really benefit from the cleaning properties, but it WILL show you where your exhaust leaks are. get the can of seafoam and read the directions on the can. i do not however recomend running it in your engine oil or gasoline as some do. and as vander said, a leak will not cause it to run lean, it can only have the opposite effect due to the false air reading the sensor is receiving.