Leaking Exhasut Manifold!

[Daboss]

Hey all me again just asking a question after a long night of reading and not finding the answer to my query. In a previous post I am having trouble with ticking/tapping noise from my engine bay, narrowed it down to lifters or exhaust manifold. I just took a look at my wideband and at idle it reads 15-16 most of the time with a jump to 14 here and there and when on wot I get readings of 13-14(way to lean for me)but, my car is basically stock with the exception that I am running an aftermarket fuel pump bosch 044 with the direct wire mod and about 9 psi of boost and from what I learned without tunning these mods should have my car running rich if anything. The rest of the mods are in the sig. My question is can a leaking exhaust manifold show a lean reading on a wideband? My sensor is placed in the decat pipe and a noticed a bolt or two missing off my exhaust manifold. So what do you guys think?

[VB-]

without knowing for sure, i wouldnt htink so. leak would let exhaust gas escape, not change its physical properties. sounds like you have a serious issue though with your A:F ratio's.

have you calibrated the sensor recently? how old is th sensor? what brand wideband?

[Daboss]

without knowing for sure, i wouldnt htink so. leak would let exhaust gas escape, not change its physical properties. sounds like you have a serious issue though with your A:F ratio's.

have you calibrated the sensor recently? how old is th sensor? what brand wideband?

Its a plx m250/300 it does not need calibration. The sensor is not more than a year old. I am wondering how when I am basically stock, stock turbo only boosted up to 9 or 10 psi, stock injectors, stock ecu, z32 afm, an un-tuned afc neo with hotwire sensor type selected 2 in and 4 out, bosch 040 fuel pump direct wire to the battery, fuel pressure 35 at idle with vacuum with it removed around 42/43 psi. I figured i should have a rich a/f ratio problem not a lean one everything seems to be in fine working order. I am confused, any other suggestions?

http://www.boostcontroller.com/index.php?item=263

That is a link to the pic and description of the exact gauge kit I have the m300.

Edited August 22, 2008 by Daboss

[The Dan]

A manifold or exhaust leak can draw in fresh air from the outside. This will give incorrect a/f ratios if not corrected.

[KiwiRS4T]

A manifold or exhaust leak can draw in fresh air from the outside. This will give incorrect a/f ratios if not corrected.

Also the location of the sensor seems less than ideal. Do they not recommend you put it closer to the manifold (did you replace your oe O2 sensor with the wideband or leave it in place?)

Your kit looks a good price though (is that US$?)

[Daboss]

Also the location of the sensor seems less than ideal. Do they not recommend you put it closer to the manifold (did you replace your oe O2 sensor with the wideband or leave it in place?)

Your kit looks a good price though (is that US$?)

No I still Have stock O2 sensor in place , and all they said was to place it downstream of the turbo no less than 24 inches away from the turbo or engine block but before the cat converter, and before you say tht they said before the cat converter and thats where I have it place they only said that so tht "IF" you have a cat converter you don't place it in that cause it will affect the reading. Also as I stated earlier I have no cat just a decat and its placed right at the front of the decat pipe. Thanks for the kudos on the kit and yea thats U.S.

[simpletool]

"stock injectors, stock ecu, z32 afm, an un-tuned afc neo "

Z32 AFM with stock computer ???? I'm no tuner or expert but to me I can't see how this is supposed to work other than giving lean AF ratios.

[R31Nismoid]

Well Z32, and no tuning... Speaks for itself.

Then you have the leaky manifold (which will also skew AFR's as stated above)...

Without a correctly working setup, could be many things. Id fix the problems, get it tuned and THEN go looking as to why things aren't right.

[**RB2530**]

Mate,

Z32 afm should never be used with stock ECU without intercepting and correcting for the difference in scaling factor ie volts/unit of airflow...Both RB25 and Z32 afm have the same output voltage range of 0 to 6V but the Z32 measures 30-50% more air...(cant remember the exact difference but I am sure some else will).

So this would be the reason your AFRs are very lean...The ECU would be thinking the engine is getting 30-50% (whatever the number is) less air than what it really is...all over the rev range...

If you've been driving the car hard or a lot I would get a compression and leakdown test done...You may have burnt valves or damaged ring lans. Dont want to alarm you but this is serious and you should check it out before you do more damage. Currently your block doesn't have any holes in it....

As far as missing nuts or studs on exhaust manifold is concerned I would fix this as soon as you can too...Missing nuts or studs can put alot of extra stress on the remaining studs..It can also cause nasty stresses in the exhaust manifold itself and also the cylinder head...