Tune resistor??
Discussion
Hi All, 94 4.0 HC 65K miles
Right - fully decatted & sleeved with lambdas & 14CUX.
It drinks like a fish, likes to shunt, stinks of fuel and revs at 1000 (adjustment screw makes absolutely no difference). Okay, I need to hold the revs on start up for a short while but that is better than looking like a t
t at the lights. I have disabled the stepper motor at 1K revs as was revving at 1300, taking about 30 seconds to come down to 1k every time = embarrasing!
I checked the tune resistor and is 39 so I am presuming UK cat tune. If I change this to 45 then will be running a decat tune? Is this correct? Will this eliminate some of the fuelling issues?
I have R Gauge but don't really understand it. Any help is much appreciated.
Right - fully decatted & sleeved with lambdas & 14CUX.
It drinks like a fish, likes to shunt, stinks of fuel and revs at 1000 (adjustment screw makes absolutely no difference). Okay, I need to hold the revs on start up for a short while but that is better than looking like a t
t at the lights. I have disabled the stepper motor at 1K revs as was revving at 1300, taking about 30 seconds to come down to 1k every time = embarrasing!I checked the tune resistor and is 39 so I am presuming UK cat tune. If I change this to 45 then will be running a decat tune? Is this correct? Will this eliminate some of the fuelling issues?
I have R Gauge but don't really understand it. Any help is much appreciated.
You need to look at the colour of the plastic sleeve on the tune resistor- white is cat tune and green non cat. . Unless you have been remapped specifically it should not be running green tune on a TVR with cats ( or had them) . If you can fire up RoverGauge and do a screen shot on a running engine at idle and post it we can check it out for you.
Edited by blitzracing on Monday 28th March 21:56
As blitzracing has said, give us something to look at and we will advise.
fwiw I had similar issues and 99% was caused by
1. 3 small/medium vacuum leaks (only detected using a smoke generator, couldn't find them using the easystart squirt around inlet joints)
2. Defective MAF airflow meter.
If you can run RoverGauge at idle on fully warmed up engine and run a RG logfile for 10 minutes,
Open RG click options - edit settings, tick data points as below
Choose
MAF Reading Type - DIRECT
Throttle reading type - ABSOLUTE
Lambda Trim Type - SHORT TERM
When the engine is warm and idling
hit "Start Log File"
Run for 10 minutes
hit "Stop Log File"
Post back here when thats done and we can take it from there.
fwiw I had similar issues and 99% was caused by
1. 3 small/medium vacuum leaks (only detected using a smoke generator, couldn't find them using the easystart squirt around inlet joints)
2. Defective MAF airflow meter.
If you can run RoverGauge at idle on fully warmed up engine and run a RG logfile for 10 minutes,
Open RG click options - edit settings, tick data points as below
Choose
MAF Reading Type - DIRECT
Throttle reading type - ABSOLUTE
Lambda Trim Type - SHORT TERM
When the engine is warm and idling
hit "Start Log File"
Run for 10 minutes
hit "Stop Log File"
Post back here when thats done and we can take it from there.
Wolvesboy said:
Hi,
Tune resistor is white wires/ yellowish see through cover (3.9 resistance)
Here is the log: a few minutes at idle. a short run then idle again. Stepper motor connected.
Any help much appreciated.
Thats great can you send me your logfile, will msg you via phTune resistor is white wires/ yellowish see through cover (3.9 resistance)
Here is the log: a few minutes at idle. a short run then idle again. Stepper motor connected.
Any help much appreciated.
and could you also post a screen shot like this ?
Edited by blaze_away on Thursday 31st March 14:54
Wolvesboy said:
Hi,
Tune resistor is white wires/ yellowish see through cover (3.9 resistance)
Here is the log: a few minutes at idle. a short run then idle again. Stepper motor connected.
Any help much appreciated.
Hey James, if you really want to put all your tune problems behind you take it to hypertune and get a modern ECU with wideband oxygen sensor installed and tuned. I will be going that way with the Cerbera at some point. They sorted out my big block F100 a few years back, and he did it quickly and effectively.Tune resistor is white wires/ yellowish see through cover (3.9 resistance)
Here is the log: a few minutes at idle. a short run then idle again. Stepper motor connected.
Any help much appreciated.
http://www.hyperdrivems.com.au/#services
blaze_away said:
Got yr log files.will analyse monday.
1st observation, idle revs are high but "idle bypass" is at zero.
Have you set the base idle to 650rpm ish , with ICV (IDLE CONTROL VALVE) hose blanked off ?
Air leak- stepper should be about 30 % open to allow enough air for the target RPM. You have a shut stepper and raised idle at the same time.1st observation, idle revs are high but "idle bypass" is at zero.
Have you set the base idle to 650rpm ish , with ICV (IDLE CONTROL VALVE) hose blanked off ?
blitzracing said:
Air leak- stepper should be about 30 % open to allow enough air for the target RPM. You have a shut stepper and raised idle at the same time.
Thanks for the information fellas.Wow I am really confused.
At present my idle is fully wound down down (totally shut) and with stepper plugged in it idles at about 1000/ 1100. If I rev up the idle takes a long time to return to 1000/1100 idle. Anything below and the engine really starts to shake/ vibrate. There is no way it would go down to 650!! It does rev faster if I unwind it though.
If I unplug the stepper, it remains the same idle but comes straight back down after revving up. Stays solid - is this because the stepper is fixed in the one position? If I then squeeze the idle pipe (leading to stepper) the engine wants to stall.
I cannot for the life of me find an air leak - I have sprayed starter spray everywhere on each connection and no change in revs, Checked the rubber hoses - all good, checked the connections as well. Also did a smoke test through the air intake and nothing. What a pita.
I had exactly the same symptoms as yours last year.
I tried the 'easystart' spray around the running engine to try finding any air leaks, that revealed nothing, no discernable change in engine revs.
This is why I then switched to a smoke tester machine.
Below is my post from last year which might help ?
I still believe you an air leak you just haven't found it yet, although clamping the stepper feed pipe does suggest otherwise.
How exactly did you do the smoke test ? (you really need a machine that generates smoke and injects it at slight positive pressure into the induction hose)
Quote from my 2021 thread
https://www.pistonheads.com/gassing/topic.asp?h=0&...
Like many on here my Chim has suffered from erratic idle,
Eg after revving it sits at 1600 ish and will not drop to 1000 rpm
At idle will sit anywhere it fancies and moves around.
Adjustment process for setting idle is difficult.
I decided to test for a vacuum leak using a smoke leak detector. Absolutely amazed at how effective it was at revealing.....
This revealed 3 leaks I had no idea I had.
1. A bent valley gasket corner
2. Small leak on stepper motor housing
3. Leaky o ring on an injector
Having fixed all these leaks my Chim now idles spot on 950rpm and revs up freely and immediately drops to idle when you come off the throttle.
All I can say is its a brilliant piece of kit that might help others suffering poor idle control
https://m.youtube.com/watch?v=URRId6fTrGo
I tried the 'easystart' spray around the running engine to try finding any air leaks, that revealed nothing, no discernable change in engine revs.
This is why I then switched to a smoke tester machine.
Below is my post from last year which might help ?
I still believe you an air leak you just haven't found it yet, although clamping the stepper feed pipe does suggest otherwise.
How exactly did you do the smoke test ? (you really need a machine that generates smoke and injects it at slight positive pressure into the induction hose)
Quote from my 2021 thread
https://www.pistonheads.com/gassing/topic.asp?h=0&...
Like many on here my Chim has suffered from erratic idle,
Eg after revving it sits at 1600 ish and will not drop to 1000 rpm
At idle will sit anywhere it fancies and moves around.
Adjustment process for setting idle is difficult.
I decided to test for a vacuum leak using a smoke leak detector. Absolutely amazed at how effective it was at revealing.....
This revealed 3 leaks I had no idea I had.
1. A bent valley gasket corner
2. Small leak on stepper motor housing
3. Leaky o ring on an injector
Having fixed all these leaks my Chim now idles spot on 950rpm and revs up freely and immediately drops to idle when you come off the throttle.
All I can say is its a brilliant piece of kit that might help others suffering poor idle control
https://m.youtube.com/watch?v=URRId6fTrGo
Edited by blaze_away on Thursday 7th April 17:51
Edited by blaze_away on Thursday 7th April 17:53
Just thinking a bit more.........maybe your air leak is either
1. An open connection on the body of the stepper motor housing ( as someone else had this on PH just a few days ago )
or
2. The gasket on the stepper motor housing
or
3. maybe the idle adjusting screw is not seating properly when its screwed fully in
1. An open connection on the body of the stepper motor housing ( as someone else had this on PH just a few days ago )
or
2. The gasket on the stepper motor housing
or
3. maybe the idle adjusting screw is not seating properly when its screwed fully in
Have now extracted the ‘idle’ run bit of the data and compared it directly with my car (which runs great at moment)
Firstly I need to say that I have assumed the following options were checked when you ran the logfiles, (MAF-Linear, Throttle-Absolute & Trim-Short Term) as these are what showed on the screen shots.
That said this is what I conclude
In the chart attached is data from Wolvesboy (W) and Blazeaway (B) engine runs at idle to help identify what is ‘normal’ vs what Wolvesboy is seeing on his Chim which has idle control issues.
The RPM, Throttle and Idle Bypass data are where significant variation is shown by RoverGauge.
These hopefully help pinpoint some areas to explore to remedy the idle control.
IMHO these are the points note.
Engine speed is circa mid point 1100rpm (W) vs 900rpm (B), with similar variability.
With that MAF’s are showing similar output
Throttle position on W is significantly lower than B. Suggest adjustment to bring the value up on W engine. I believe it should be ideally around 5% ?
Idle bypass is significantly different on W vs B which strongly supports an unmetered air leak on W.
Firstly I need to say that I have assumed the following options were checked when you ran the logfiles, (MAF-Linear, Throttle-Absolute & Trim-Short Term) as these are what showed on the screen shots.
That said this is what I conclude
In the chart attached is data from Wolvesboy (W) and Blazeaway (B) engine runs at idle to help identify what is ‘normal’ vs what Wolvesboy is seeing on his Chim which has idle control issues.
The RPM, Throttle and Idle Bypass data are where significant variation is shown by RoverGauge.
These hopefully help pinpoint some areas to explore to remedy the idle control.
IMHO these are the points note.
Engine speed is circa mid point 1100rpm (W) vs 900rpm (B), with similar variability.
With that MAF’s are showing similar output
Throttle position on W is significantly lower than B. Suggest adjustment to bring the value up on W engine. I believe it should be ideally around 5% ?
Idle bypass is significantly different on W vs B which strongly supports an unmetered air leak on W.
Just a thought ..
On your throttle linkage see if there's a gap between the cam thingy and the bracketry .. if not then it may be that your throttle is being held slightly open and not being allowed to return to the rest screw on the plenum.
Slacken the 8mm spanner size nut that's next to the bottom arrow in the piccie and just rotate the two parts of the assembly until you have a small gap a shown if none is there at the moment.
On your throttle linkage see if there's a gap between the cam thingy and the bracketry .. if not then it may be that your throttle is being held slightly open and not being allowed to return to the rest screw on the plenum.
Slacken the 8mm spanner size nut that's next to the bottom arrow in the piccie and just rotate the two parts of the assembly until you have a small gap a shown if none is there at the moment.
Hi Fellas, thanks for the replies so far.
I haven’t checked the idle return yet but will have a closer look.
I rigged up a home made smoke machine!
2 x smoke leaks. One very faint (spring location photo 1) & a detached mini hose at the back of the stepper motor housing ( photo 2).
Could both be making that much difference? The smoke from the missing hose was quite a lot! I’m hoping this is the culprit.
Photo 1
Photo 2 - rear of stepper motor housing with mini pipe not connected
What do you think?
I haven’t checked the idle return yet but will have a closer look.
I rigged up a home made smoke machine!
2 x smoke leaks. One very faint (spring location photo 1) & a detached mini hose at the back of the stepper motor housing ( photo 2).
Could both be making that much difference? The smoke from the missing hose was quite a lot! I’m hoping this is the culprit.
Photo 1
Photo 2 - rear of stepper motor housing with mini pipe not connected
What do you think?
One more thing .. do you have your vac advance plumbed direct into the plenum or into the original port on the top of the throttle body part?
Direct into the plenum sucks more advance on at closed and part throttles, this then also elevates the idle speed meaning the stepper has to run in a more closed position to bring the idle down. If there is too much base airflow that can mean the stepper is fully closed before the idle reduces fully to the target idle speed.
Direct into the plenum sucks more advance on at closed and part throttles, this then also elevates the idle speed meaning the stepper has to run in a more closed position to bring the idle down. If there is too much base airflow that can mean the stepper is fully closed before the idle reduces fully to the target idle speed.
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