Q's for Tuners or Ford Techs

[Miles]

So my car is at Steeda.ca right now, and has had MMR STII's heads and VT STI's cams installed. They're using an XCal2 to tune the car now and are running into problems with the O2's.

Initially, they were not getting any voltage from the front O2's - they replaced them with Ford OEM O2's and we checked all the wiring.

Now the car is giving voltage, but the tuner says it's not looking right to him (voltage is way to low, next to 0 volts).

They've sent it to Ford to have it checked out, and Ford says their electrical test says everything is fine.

Any ideas? I was thinking maybe the computer is toast, but would have thought that would show in the electrical test done by Ford.

Any advice or ideas are welcome...

 

[Mike97gt]

a vacumm leak can cause voltages at or near zero. They should start by checking for any vacumm leaks, then check the MAF.. also if the tune is WAY lean or way rich at P/T you will see this happen too.

Pretty much anything that could cause the mixture to be extremely lean or rich can cause this,standard 02's have a very narrow band they can read and if you are way outside of 14.7.1 then you will have this.

 

[Miles]

Thanks svttech76, I'll pass the info along to the tuner. They had replaced the O2 sensors, but now I question if that was required.

 

[01Steeda]

wow this seems to be happening everwhere with all kinds of cam combo's lately. I got a friend here in LA with the same problem.. and I am having it also. I have patriot heads and patriot cams. Now what is intresting is what SVT said about the vacuum leak. My mechanic did say my vacuum looked low.... hmmmm.

 

[urban96]

are you throwing the CEL too?

 

[01Steeda]

well we turned my 02's off so.. i am not sure about that. I'll ask my tuner tomorrow

 

[Miles]

are you throwing the CEL too?

My car has shown the CEL since I bought it, and always figured it was due to my prochamber. It's tough to say if the problem was present before all the work was done on my car or not.

My upstreams are obviously still enabled, but the downstreams are disabled through the Xcal.

I know svttech knows his stuff - I'll keep you guys posted if that fixes the issue.

 

[urban96]

have you pulled codes? try checking the #8 or maybe it was #9 fuse under the dash. its labeld engine controll or something like that. its for the o2 sensors and egr i think, worth a shot to look i blew my fuse somehow and went crazy trying to figure out what it was

 

[Miles]

Update

I passed along the comments from this post, and the vacumm leak is probably not the cause, as the tuner said all of the data looked good re: vacumm (was his initial hunch when he got weird results).

He said that on open loop (think this means WOT and when the car initialling turns on) the car runs great, but under closed loop conditions (warmed up, idle or partial throttle) it runs like arse.

They're trying to find a spare MAF somewhere and see if that makes a difference.

It's been there for 6 weeks, what's another week, lol

 

[jstreet0204]

check for a exhaust leak. Even a tiny one. This would allow fresh air to blow across the o2 throwing off the reading. It would also explain why it runs fine in open loop.

 

[01Steeda]

SVTTech, can u explain the vacuum leak theory a bit for me. I understand what your saying just not sure why that would effect the 02's.

 

[Miles]

... would also explain why it runs fine in closed loop.

Is that because in closed loop, its reading from the table vs. the o2's? Sorry, just clarifying my understanding.

Cheers

 

[jstreet0204]

Is that because in closed loop, its reading from the table vs. the o2's? Sorry, just clarifying my understanding.

Cheers

Well I meant to say open loop, but yes, in open loop it is reading from the tables, not the o2's

 

[Miles]

Well I meant to say open loop, but yes, in open loop it is reading from the tables, not the o2's

Good, cuz I was totally confused... hahaha

 

[01Steeda]

ttt for svttech

 

[jstreet0204]

SVTTech, can u explain the vacuum leak theory a bit for me. I understand what your saying just not sure why that would effect the 02's.

Not sure when he will log back in but I'll answer for him. The o2 sensors only have a range of a/f ratios of 14:1 to 15:1 any thing that would cause a lean condition (vacuum leak) leaner than 15:1 would show voltage very close to 0 volts.

 

[01Steeda]

ahhh.. IC. ok well that doesnt apply to my condition then. thanx for the info

 

[Miles]

... so I hauled my arse up to steeda today to check out my ride, and things look good on the install. It sounds mean as hell with the new cams and heads.

They're going to clean the MAF and see if that improves things.

When the car went into closed loop, it would surge on idle and then eventually die. Very similar in issue to when I had to clean my IAC.

My new question is: would an IAC somehow impact the A/F ratio reaching the O2's, which in turn produce next to 0 volts??

 

[jstreet0204]

I the IAC wouldn't cause the o2 problem. Did they check your a/f ratio when the problem was occuring. That would be very helpful in troubleshooting the problem. If you knew that the a/f ratio was leaner than 15:1 then you would know that the problem is likely either a vacuum leak, or the MAF. If the a/f ratio was close the 14.7:1 then you would know the problem is likely either an exhaust leak, or a physical problem with the o2's or their wiring.

 

[Miles]

the tuner wasn't there, so I was talking to the shop owner. Not sure of the ratio, but it must definitely be running lean as the voltage is close to zero (less than 0.4v indicates lean condition vs greater than 0.6v which indicates rich).