Testing O2s

[95strokerPSU]

Lately my car's been a little sluggish after it warms up. I tested the IAT and ECT and they check out fine. Next up the O2s. I just put in new Bosch 13127, but I have long tubes so I guess there might be a chance they're giving a bad reading from being farther back in the exhaust. Can I disconnect them to make the computer get it's reading from other sensors? My logic being that if I disconnect them and the car isn't sluggish, then I've got a problem with O2s.

I'm under the impression that upon intial start the car is in open loop, reading off of the MAF and the ECT, but then after two minutes or so it goes into closed loop and gets it's readings from the O2s. Except at WOT, it reverts back to MAF and ECT. Is this correct?

Thanks
Dave

 

[HISSIN50]

Dave I think your good with your thinking except that (I believe) 94-95's use lamdas (just a little bit) for WOT trim. It's mostly MAF function at WOT though.

Now foxes do plain ignore lambdas at WOT.

Grady might have some ideas about the LT and lambda readings (since he runs LT's).

You are definately not alone in noticing the same symptoms in similar situations of late.

Good luck and bumpity.

 

[95strokerPSU]

lamdas = O2 readings, right?

I have an A9L puter (please don't flame me, I didn't know any better at the time). So disconnecting the O2s might be the perfect test for me, if Foxes don't use lamdas. Thoughts?

 

[95strokerPSU]

And I'm more concerned with partial throttle sluggishness. Last night after driving for about 40 minutes I had no problem breaking the tires loose by going WOT in 2nd at about 3k.

 

[HISSIN50]

I actually made a typo (I pulled an all-nighter). It's Lambdas. And yeah, that's the O2's or HEGO's.

EDIT: disregard part of this - I was thinkin and pecking while you made the post right above this one. The part throttle issue info you provided helps, but makes some of what I said useless.

Since you have the A9L conversion (no flames here - you did what works well for you), you shouldnt be using lambdas at WOT.

FWIW, when the O2's are disconnected (even permanently), the car runs in FMEM and it should run pretty darn well - I've known a few guys who ran with foxes with no O2's. A couple were stockish (GT40 top end and bolt ons) and a couple were running sick amounts of boost and the cars ran well (I read the 94+ puters run like poop with no O2 input, but since that doesnt apply to you ). That's neither here nor there.

WIth the car as is, if you hit WOT (for a fox, it's 2.7 TPS volts above your TPS baseline. Normally that's about 3.7 volts for most folks) and the car runs like a cookie flavored turd, O2's are not where I'd personally look.

But you've got some real nice power and the tune, so that can toss a wrench into the mix.

You tested the ECT, which is what I woulda done too (foxes pull timing at about 228*F as I recall, and an ECT out of calibration could cause an issue).

I dont know if you might be interested but there's now a Fox tuning sub-forum - they might have some input about what sensors could be causing an issue (Jason and the guys get to DL and see sensors wander - that's useful). Just another option.

Good luck bud.

 

[95Vert]

PSU, I just noticed this same problem. It feels heavily upon light acceleration but can lite the tires up with no problem at WOT. I was going to check my spark plugs just in case also. So, that may be my solution. I'm going to be doing the a9l swap soon. Just need the bap sensor. Do you regret getting it or what? I've got several buddies who swear by it.

 

[95Vert]

Hissin, I have the 93tb conversion. My tps read 5 volts with the key on. Is that normal? Don't mean to hijack PSU.

 

[HISSIN50]

Hissin, I have the 93tb conversion. My tps read 5 volts with the key on. Is that normal? Don't mean to hijack PSU.

I think you might have probed the VREF wire instead of the signal return. Check the other wire - it should read about 1 volts with the key on.

 

[95Vert]

I used the green and black one. I'm not sure about the brown one tho. I'll try it later today. What if it's wrogn anyways?

 

[95strokerPSU]

I used the green and black one. I'm not sure about the brown one tho. I'll try it later today. What if it's wrogn anyways?

Pretty sure the brown one is the one you want.

As far as the A9L swap I wish I hadn't done it. I still had the car SCT tuned anyway. But then again maybe it's better than if I had the stock puter SCT'ed.

My view on it is this, I did the swap and am happy with the results (up until this recent issue), but at the same time I think that I could have acheived the same level without the swap.

 

[95strokerPSU]

FWIW, when the O2's are disconnected (even permanently), the car runs in FMEM

What's FMEM stand for?

and it should run pretty darn well - I've known a few guys who ran with foxes with no O2's. A couple were stockish (GT40 top end and bolt ons) and a couple were running sick amounts of boost and the cars ran well.

That's good to know.

WIth the car as is, if you hit WOT (for a fox, it's 2.7 TPS volts above your TPS baseline. Normally that's about 3.7 volts for most folks) and the car runs like a cookie flavored turd, O2's are not where I'd personally look.

Can I check that voltage with key on engine off?

You tested the ECT, which is what I woulda done too (foxes pull timing at about 228*F as I recall, and an ECT out of calibration could cause an issue).

The ECT read 2930 ohms which translates to about 193* when I took my reading after a 45 minute drive.

What I'm thinking is since I'm having no power loss at WOT and some power loss during normal acceleration/partial throttle, that my O2s are messing things up. Tonight I'll unplug them and see what happens.

Thanks for the help
Dave

 

[HISSIN50]

What's FMEM stand for?

Failure Mode Effects Management. It's how the EEC works when one or more sensors are bad. The fox default is pretty fat.

Can I check that voltage with key on engine off?

You bet. There's nothing to really check with that. It was just letting you know that as far as the computer cares, WOT is achieved ~ 3.7 volts (you dont have to hit 4.5 volts or anything like that). Sometimes you can notice the AC clutch disengage (as the WOT relay energizes) and that's WOT, per the computer.

The ECT read 2930 ohms which translates to about 193* when I took my reading after a 45 minute drive.

That sounds like it's right-on. Now you can figure the ECT isnt telling the puter that you're at 240*F (for example) and pulling timing - that was my concern about the ECT calibration.

What I'm thinking is since I'm having no power loss at WOT and some power loss during normal acceleration/partial throttle, that my O2s are messing things up. Tonight I'll unplug them and see what happens.

I'd pull codes first if you havent had a chance yet. That's just the non-critical type of issue that can generate codes but wont illuminate the CEL.

There are a ton of things that can cause a part throttle loss of power, so I wouldnt drive myself too nuts checking the O2's (read: if they seem ok, they likely are; there are other causes).

Good luck with it Dave.

 

[mo_dingo]

The car takes a minute or 2 to go to closed loop after restart. So get your car warm. Kill it, then restart. See how it accelerates at part throttle. After a couple minutes, it will go to CL and if the O2's are the problem, the car will run bad again.

Another thing to do is reset the KAM and see if the computer can compensate because it's starting over.
Scott

 

[final5-0]

Not saying your O2's are the cause of your sluggishness (is that a word ) but I can say they most likely are not effected by running lt's if you keep things in the context of your Q.

Usually where lt's cause an issue is when at a long stop light, they can cool down a bit and the adaptive starts to compensate but they cool so much the adaptive range is exceeded and then it don't take long to arrive at hose up city.

I've seen some say that after the adaptive has helped as much as it can, the car starts to surge and shortly dies.

anyway ........

When you get moving, the heat quickly builds and that issue is gone.

You get info from various tables that rely on temp, load, time, rpm, and the like when you are in O L so yes ... the O2's are not in play during O L.

The fact you got a Fox pcm should not be an issue here IMHO.

I don't know about running without the O2's and what that might mean other than ... It ought to run OK when at WOT.

btw ... lambse/lambda is the commanded fuel ratio by the pcm. Those ratios can be seen in the fuel tables and they show up in the datalogs.

The data from the O2's will be seen by hego values.

As Scott said, you could reset the pcm but if there is a prob, it won't take that little silver box long to reach the limits of its help and you'll be right back to the same place.

You say the car is sluggish ...........
When did it start?
Was it after you changed the O2's?

If it runs no better after you put in new O2's ........
it would seem they are not suspect

Grady

 

[HISSIN50]

btw ... lambse/lambda is the commanded fuel ratio by the pcm. Those ratios can be seen in the fuel tables and they show up in the datalogs.

The data from the O2's will be seen by hego values.

Grady, I suppose I should ask, so as to nip confusion in the toosh............. For the tuning crowd, is referring to an oxygen sensor as a lambda confusing? I cut my teeth on Euro cars (Bosch engine management) and Bosch called O2's Luft sensors or Lamdas, as I recall. If these terms are not interchangable in the mainstream (or with Mustangs), I'll try to remember not to say Lambda when O2 or HEGO will suffice.

And you guys use the terms O2's and HEGO interchangably, right?

 

[95strokerPSU]

Last night after a 30 minute drive, I let it run and disconnected the ECT to get another reading. Again it was at about 2900 ohms, but when I disconnected the harness, the rpms jump up to about 2000. Is that normal?

 

[final5-0]

Grady, I suppose I should ask, so as to nip confusion in the toosh............. For the tuning crowd, is referring to an oxygen sensor as a lambda confusing? I cut my teeth on Euro cars (Bosch engine management) and Bosch called O2's Luft sensors or Lamdas, as I recall. If these terms are not interchangable in the mainstream (or with Mustangs), I'll try to remember not to say Lambda when O2 or HEGO will suffice.

And you guys use the terms O2's and HEGO interchangably, right?

As always JT, your broad knowledge background is so obvious

I have to say my input in this thread very well may be a source of confusion even though I know what I said is true

I do admit to having a vary narrow perspective of electronic tuning as I only deal with Fords and the only Fords I deal with are Stangs and then the only Stangs I've had the most expericnce with are 94-95.

When you add the fact my only self tuning experience is with the EEC Tuner/Tweecer interface, you can see how small and limited my area of experience is here

I have seen the word lambda used with the Fox Stangs in the same context as lambse is used with our Stangs and in both cases, it is all within the Tweecer environment.

When I used the word hego, I was again speaking from the Tweecer perspective since you see the output or datastream of the O2 is defined as a hego value when you look at the raw data in the logs.

Like you JT, I have seen the word lamda, lambda, or however it is spelled, used when talking about O2 sensors.

These words and acronyms can get confusing

Tweecer calls the idle speed controller a isc but others say iac

Tweecer calls the air charge temp sensor act but others say iat

I try to remember and use the more commonly used way when working in these threads but sometimes I forget

What the Hey ... I think we all are on the same page

Grady

 

[HISSIN50]

As always JT, your broad knowledge background is so obvious

I have to say my imput in this thread very well may be a source of confusion even though I know what I said is true

I do admit to having a vary narrow perspective of electronic tuning as I only deal with Fords and the only Fords I deal with are Stangs and then the only Stangs I've had the most expericnce with are 94-95.

When you add the fact my only self tuning experience is with the EEC Tuner/Tweecer interface, you can see how small and limited my area of experience is here

I have seen the word lambda used with the Fox Stangs in the same context as lambse is used with our Stangs and in both cases, it is all within the Tweecer environment.

When I used the word hego, I was again speaking from the Tweecer perspective since you see the output or datastream of the O2 is defined as a hego value when you look at the raw data in the logs.

Like you JT, I have seen the word lamda, lambda, or however it is spelled, used when talking about O2 sensors.

These words and acronyms can get confusing

Tweecer calls the idle speed controller a isc but others say iac

Tweecer calls the air charge temp sensor act but others say iat

I try to remember and use the more commonly used way when working in these threads but sometimes I forget

What the Hey ... I think we all are on the same page

Grady

Grady, I havent seen a post with that many qualifiers in a long time.

I'm gonna have to disagree with you though. Me-thinks your posts on threads like these are the helpful ones , and mine are sources of confusion and are a lack of assistance.

It sounds like almost any of the terms used are alright on a thread like this - it's in a tuning environment where one should speak more precisely (because for instance, if someone said to check the O2 value, it might be . But when you say check HEGO value, that's ).

Not even Mustangs can keep it straight with the IAT and ACT (SN95's have the former and foxes have the latter).

I thank you again for your clarification. I wont be able to remember any of what you said, so I'm sure I'll be using unTwEECerish terms again - just keep correcting me.

 

[final5-0]

I thank you again for your clarification. I wont be able to remember any of what you said, so I'm sure I'll be using unTwEECerish terms again - just keep correcting me.

IMHO ...NO correction on your part is needed my friend

I seriously doubt Tweecer speak is considered to be the definitive

be all OR end all ... of these tuning discussions.

I've just slipped into that warped way of thinking

Grady