free hit
counters
Short Term Fuel Trim - Engine/Ancilliaries - The Lotus Forums Jump to content
Pred247

Short Term Fuel Trim

Recommended Posts

Hi all,

For a while now I've had a bit of popping on the right side of my exhaust.

I've had 2 new sports CATS installed and a new centre exit exhaust added. The popping is still there and she sounds lumpy on idle because of it.

There is no problems whilst driving and she sounds lovely. Although, there is a big pop as I come off the gas at high speed! :)

I think that's normal?....... And I like the sound! lol.

I recently purchased an OBD11 reader from Gendan. Whilst the engine was running at idle, I noticed the short term fuel trim on one side was constantly up and down. But on the other side it was constantly at 0. Until I rev the engine. Once I do that, both sides go up and down.

Before I pay someone to spend hours scratching their heads hoping to get lucky. I was wondering if you guys may have an idea?

Thanks,

John

Share this post


Link to post
Share on other sites

Upgrade today to remove Google ads and support TLF.

John,

What you are experiencing looks like an O2-sensor problem. Both sides should act equal. The O2-readings should go constantly up and down - like a sine wave.

If it does not do that then the O2-sensor is suspect. -> renew it ! BTW, you should renew the O2-sensors pair-wise !!!

Cheers

Marcus

www.PUKesprit.de

Hi all,

For a while now I've had a bit of popping on the right side of my exhaust.

I've had 2 new sports CATS installed and a new centre exit exhaust added. The popping is still there and she sounds lumpy on idle because of it.

There is no problems whilst driving and she sounds lovely. Although, there is a big pop as I come off the gas at high speed! :)

I think that's normal?....... And I like the sound! lol.

I recently purchased an OBD11 reader from Gendan. Whilst the engine was running at idle, I noticed the short term fuel trim on one side was constantly up and down. But on the other side it was constantly at 0. Until I rev the engine. Once I do that, both sides go up and down.

Before I pay someone to spend hours scratching their heads hoping to get lucky. I was wondering if you guys may have an idea?

Thanks,

John

Edited by Paula&Marcus

Marcus

Share this post


Link to post
Share on other sites
John,

What you are experiencing looks like an O2-sensor problem. Both sides should act equal. The O2-readings should go constantly up and down - like a sine wave.

If it does not do that then the O2-sensor is suspect. -> renew it ! BTW, you should renew the O2-sensors pair-wise !!!

Cheers

Marcus

www.PUKesprit.de

Thanks for taking the time to reply mate.

Much to my annoyance, I had all four changed. That did not solve the problem. I really thought that was the issue my self. :realmad:

I should have been more specif on what has been changed. That's my fault. Sorry!

Ok, so far:

2 X CATS

Exhaust.

8 X Spark plugs

8 X Leads

I think that's all, I have tried so far.

John

Edited by Predator

Share this post


Link to post
Share on other sites

You could have a dogey injector on the one bank. This could cause some fuel trim activity.

Thanks for taking the time to reply mate.

Much to my annoyance, I had all four changed. That did not solve the problem. I really thought that was the issue my self. :realmad:

I should have been more specif on what has been changed. That's my fault. Sorry!

Ok, so far:

2 X CATS

Exhaust.

8 X Spark plugs

8 X Leads

I think that's all, I have tried so far.

John


1996 Esprit V8, 1998 Esprit V8 GT, 1999 Esprit S350 #002 (Esprit GT1 replica project), 1996 Esprit V8 GT1 (chassis 114-001), 1992 Lotus Omega (927E), 1999 Esprit V8SE, 1999 Esprit S350 #032, 1995 Esprit S4s, 1999 Esprit V8 GT (ex-5th Gear project), 1999 Esprit V8SE ('02 rear)

1999 S350 #002 Esprit GT1 replica

Share this post


Link to post
Share on other sites
You could have a dogey injector on the one bank. This could cause some fuel trim activity.

True and worth thinking about. Is there a way of testing this theory?

John

Share this post


Link to post
Share on other sites
True and worth thinking about. Is there a way of testing this theory?

John

Yeah, swap the injectors across the banks, if the fault moves to the other side then it is an injector issue.

Hilly


1981 S3 4.2 V8 6 speed (The Mutant)

Mutant V8 Conversion Thread

Knowledge is power .................... apparently.

 

Share this post


Link to post
Share on other sites

I would be very interested to know what you eventually find with this problem as I have the exact same popping coming off the right bank exhaust as well. Unfortunately I have not been able to get my OBDII scanner to successfully connect with the on board computer, It just keeps giving me error "unable ot connect" messages.

I too have swapped out the standard exhaust for the center exit and the high flow cats, although the popping and lumpy idle on the right bank was there prior to the change. Additionally, it also seems to be happening only at idle and not when the car is revved up or while driving.

Please post with your findings

Share this post


Link to post
Share on other sites
Yeah, swap the injectors across the banks, if the fault moves to the other side then it is an injector issue.

Hilly

Cool, I didn't think of that. How stupid am I!? Don't answer that! :realmad:

Is this a jon I can do my self. If so, what will I need and is there a guide.

Thanks so much for the response gents.

John

I would be very interested to know what you eventually find with this problem as I have the exact same popping coming off the right bank exhaust as well. Unfortunately I have not been able to get my OBDII scanner to successfully connect with the on board computer, It just keeps giving me error "unable ot connect" messages.

I too have swapped out the standard exhaust for the center exit and the high flow cats, although the popping and lumpy idle on the right bank was there prior to the change. Additionally, it also seems to be happening only at idle and not when the car is revved up or while driving.

Please post with your findings

I don't mean to be selfish, but in a stupid way I'm kind of releived someone else has the same problem No offence mate. It just assures me my car is not aone off freak never to be solved lol.

Of course I will post anything I discover for you all.

John

Share this post


Link to post
Share on other sites

John

I don't mean to be selfish, but in a stupid way I'm kind of releived someone else has the same problem No offence mate. It just assures me my car is not aone off freak never to be solved lol.

Of course I will post anything I discover for you all.

John

Share this post


Link to post
Share on other sites
John

I don't mean to be selfish, but in a stupid way I'm kind of releived someone else has the same problem No offence mate. It just assures me my car is not aone off freak never to be solved lol.

Of course I will post anything I discover for you all.

John

No offense taken :realmad:

I have only been able to find the following information about Short Term Fuel Trim;

Short FT B1 @J; Short term fuel trim for cylinder bank 1 (right hand). Primarily dependent on RH bank

oxygen sensor readings. Normal reading is 0%, but will vary (up to +20%, -30%) with operating conditions. If

a consistent deviation is required for longer than a specified period, the long term fuel trim will be amended to

allow the short term trim to return to 0%.

Any malfunction in the fuel control system usually results in either a rich or lean exhaust condition. This

is sensed, via the oxygen sensors, by the ECM which changes the fuel calculation (injector pulse width) based

on 02 sensor input. The chahge made to the fuel calculation will be indicated by a change in the fuel trim

values which can be monitored by a

Share this post


Link to post
Share on other sites

Hi John,

thats very interesting ...

Are you 100% sure that the O2-sensor connectors/wires that lead to the sensor itself are not swapped/mixed up ?

A few weeks ago we had a very similar problem with a MY97 V8. After the owner had installed the high flow cat pipes the car bisbehaved in a very similar way. After a very long inverstigation it turned out that on the right side the pre- and after cat O2-sensor-wires had been swapped by mistake.

Cheers

Marcus


Marcus

Share this post


Link to post
Share on other sites
Hi John,

thats very interesting ...

Are you 100% sure that the O2-sensor connectors/wires that lead to the sensor itself are not swapped/mixed up ?

A few weeks ago we had a very similar problem with a MY97 V8. After the owner had installed the high flow cat pipes the car bisbehaved in a very similar way. After a very long inverstigation it turned out that on the right side the pre- and after cat O2-sensor-wires had been swapped by mistake.

Cheers

Marcus

This seems very plausible to me sincein my case the previous owner did have the exhaust replaced under warranty and when I switched to high flow cats and the center exhaust I just plugged them back in the way I found them. I will have to try this simple test tomorrow as I have to go under and tighten my exhaust clamps again as they seem to have rattled loose :realmad:........Perm Locktite here I come.

Oh BTW I have uploaded a MOV of my exhaust doing its popping thing, keep in mind although you cannot tell from the video the popping is definately coming from the right bank only

http://members.shaw.ca/bkmartineau/P5303918.mov

Edited by martiy

Share this post


Link to post
Share on other sites
Hi John,

thats very interesting ...

Are you 100% sure that the O2-sensor connectors/wires that lead to the sensor itself are not swapped/mixed up ?

A few weeks ago we had a very similar problem with a MY97 V8. After the owner had installed the high flow cat pipes the car bisbehaved in a very similar way. After a very long inverstigation it turned out that on the right side the pre- and after cat O2-sensor-wires had been swapped by mistake.

Cheers

Marcus

That did flaah through my mind, but it's been doing it long before I had them taken off for any reason.

Unless it's always been there but I was not able to hear it so well with the stock CATS.

I did look at the connectors and they 'appear' to be fine. I guess the mechanic who has done work on my car and the exhaust chap would have simply put them back as they were. If there was a problem, they may not have realised it.

I can try to swap them over later if I can get under the beast ok. Are we all sure it will not cause any damage if I do? Not that I would sue lol. Just asking for an oppinion at my own risk.

John

This seems very plausible to me sincein my case the previous owner did have the exhaust replaced under warranty and when I switched to high flow cats and the center exhaust I just plugged them back in the way I found them. I will have to try this simple test tomorrow as I have to go under and tighten my exhaust clamps again as they seem to have rattled loose :lol:........Perm Locktite here I come.

Oh BTW I have uploaded a MOV of my exhaust doing its popping thing, keep in mind although you cannot tell from the video the popping is definately coming from the right bank only

http://members.shaw.ca/bkmartineau/P5303918.mov

Oh man! That is soooo weird. Not only does our cars sound the exact same, especially with the popping. But from that angle it could have been mine for all I know.

We must have the same problem!

John

Share this post


Link to post
Share on other sites

Well, I checked my O2 Sensors last night and they all seem to be in the right locations and using the right leads. Mine are still labeled from the factory RH PRE, RH POST etc so I think the theory about swapped O2 sensors isn't the problem in my case.

Anyone have any other potential areas to check.

Share this post


Link to post
Share on other sites
Well, I checked my O2 Sensors last night and they all seem to be in the right locations and using the right leads. Mine are still labeled from the factory RH PRE, RH POST etc so I think the theory about swapped O2 sensors isn't the problem in my case.

Anyone have any other potential areas to check.

You might want to check the EGR pipe for leaks. Also the EGR valve may be malfunctioning in closed loop. Not sure if this throws a specific code but it would contiribute to air/fuel problems.

Craig


2001 Esprit V8

1985 911 Carrera converted to 1974 RSR IROC race car

1967 Chevrolet Camaro SS350 convertible (goes fast and straight - limited handling!)

www.hollowayperformance.com

Share this post


Link to post
Share on other sites
You might want to check the EGR pipe for leaks. Also the EGR valve may be malfunctioning in closed loop. Not sure if this throws a specific code but it would contiribute to air/fuel problems.

Craig

No codes have been thrown on my car, just a lumpy, popping type idle from the right bank; however according to the shop manual (If I am remembering correctly) if it ever got worse it may throw a P0173 / 174 code. If it was a faulty EGR wouldn't it affect both banks and not just one side or the other?

Share this post


Link to post
Share on other sites
No codes have been thrown on my car, just a lumpy, popping type idle from the right bank; however according to the shop manual (If I am remembering correctly) if it ever got worse it may throw a P0173 / 174 code. If it was a faulty EGR wouldn't it affect both banks and not just one side or the other?

Yes, that is correct. The EGR is associated with the RH compressor duct, but the charge from both turbos has the chance to equalise immediately after the throttle bodies.

Edited by mike_sekinger

1996 Esprit V8, 1998 Esprit V8 GT, 1999 Esprit S350 #002 (Esprit GT1 replica project), 1996 Esprit V8 GT1 (chassis 114-001), 1992 Lotus Omega (927E), 1999 Esprit V8SE, 1999 Esprit S350 #032, 1995 Esprit S4s, 1999 Esprit V8 GT (ex-5th Gear project), 1999 Esprit V8SE ('02 rear)

1999 S350 #002 Esprit GT1 replica

Share this post


Link to post
Share on other sites
Yes, that is correct. The EGR is associated with the RH compressor duct, but the charge from both turbos has the chance to equalise immediately after the throttle bodies.

Sorry, to be a bit simple. Are you also suggesting it may be the EGR pipe, or that it can't be?

Thanks,

John

Share this post


Link to post
Share on other sites
Yes, that is correct. The EGR is associated with the RH compressor duct, but the charge from both turbos has the chance to equalise immediately after the throttle bodies.

I agree - just want to ensure no stone is left un-turned! Sometimes odd outcomes develop from simple problems.

Sorry, to be a bit simple. Are you also suggesting it may be the EGR pipe, or that it can't be?

Thanks,

John

In theory an EGR pipe problem would impact both banks the, causing the lumpy idle on each side. However, if one bank is running a much higher exhaust temp, it is feasible that a rich condition would only be audible on that side. The lumpy idle is probably excess fuel burning in the cat.


2001 Esprit V8

1985 911 Carrera converted to 1974 RSR IROC race car

1967 Chevrolet Camaro SS350 convertible (goes fast and straight - limited handling!)

www.hollowayperformance.com

Share this post


Link to post
Share on other sites
I agree - just want to ensure no stone is left un-turned! Sometimes odd outcomes develop from simple problems.

Thanks to all of you who have made suggestions. I'll check on that.

Ummmmmm, where is it? lol!

John

Share this post


Link to post
Share on other sites
I agree - just want to ensure no stone is left un-turned! Sometimes odd outcomes develop from simple problems.

In theory an EGR pipe problem would impact both banks the, causing the lumpy idle on each side. However, if one bank is running a much higher exhaust temp, it is feasible that a rich condition would only be audible on that side. The lumpy idle is probably excess fuel burning in the cat.

hmmm thats interesting, I have been assuming that it was a result of a lean condition rather than a rich environment. Especially when Pred mentioned that the short term fuel trim was moving up and down like normal on his left side (at idle), but the right didn't move from 0, so I assumed that since it wasnt moving up, the right side was getting less fuel thus creating a lean condition (It definately sounds like a lean "Pop"). Hehe or maybe I've had too many beers lol.

Regardless, like Pred, this little nagging idle issue is totalling annoying, not because it has affected power or drivability or anything like that, but rather because no one seems to be able to figure it out :realmad:

You know its almost like the ECM isnt adjusting the right bank short term fuel trim at idle kinda like something is slightly stuck and only when alot more fuel is introduced it begins to work.

Edited by martiy

Share this post


Link to post
Share on other sites
hmmm thats interesting, I have been assuming that it was a result of a lean condition rather than a rich environment. Especially when Pred mentioned that the short term fuel trim was moving up and down like normal on his left side (at idle), but the right didn't move from 0, so I assumed that since it wasnt moving up, the right side was getting less fuel thus creating a lean condition (It definately sounds like a lean "Pop"). Hehe or maybe I've had too many beers lol.

Regardless, like Pred, this little nagging idle issue is totalling annoying, not because it has affected power or drivability or anything like that, but rather because no one seems to be able to figure it out :realmad:

You know its almost like the ECM isnt adjusting the right bank short term fuel trim at idle kinda like something is slightly stuck and only when alot more fuel is introduced it begins to work.

I would almost say it's more like a lack of stability. For some reason it's failing to regulate the correct fuel mixture whilst idling.

I've also noticed that it will do the same thing at a steady rev higher up the range. So if you were to hold the revs at 2500rpm's it would start to make the same popping. It's more difficult to hear it though, because of the engine speed.

It's only whilst the car is accelerating everything is fine.

John

Share this post


Link to post
Share on other sites

I've often read that installing the red race ECM or high torque chip etc has smoothed out alot of cars which had previous poor idling quality, I wonder if that may smooth out this lumpy, popping idle we are experiencing/

Share this post


Link to post
Share on other sites
I've often read that installing the red race ECM or high torque chip etc has smoothed out alot of cars which had previous poor idling quality, I wonder if that may smooth out this lumpy, popping idle we are experiencing/

I can't comment on the ECM change, however my car was purchased with Johan's ECM and I have not experienced the stock unit.

It is an interesting phenomenon you are experiencing. Does it smooth out when you accelerate /under load? If it is only an idle issue, I would be less concerned (however it needs to be addressed). If it is constant through the RPM band, it needs to be solved ASAP as you don't want to burn a piston (lean) or cat (rich).

A leaky fuel injector may be involved - have you tried the bank swap suggested in a previous post?

Craig


2001 Esprit V8

1985 911 Carrera converted to 1974 RSR IROC race car

1967 Chevrolet Camaro SS350 convertible (goes fast and straight - limited handling!)

www.hollowayperformance.com

Share this post


Link to post
Share on other sites

Hi all,

I've wondered about the ECU change. Except I thought just purchasing the chip set might work?

I've not swapped the injectors yet. I'm on a course for another 5weeks so time is a problem right now. It's something will try though!

In my case, she only does it on idle.

John

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


×
×
  • Create New...