Throttle disk setting Rover V8 flapper EFi
Discussion
Hi boys,
Over the last few weekends I've been struggling with a 3.5 flapper V8 in my TVR 350i
Initial symptoms, bad misfire when cold, could be cleared by persisting and warming the engine up, then problem solved, engine ran quite well...
Most if not all the problems have been traced to vacuum leaks, mainly in the injector seals and trumpet assembly, with a dodgy hose connecting the extra air valve (not the "C" shaped one) now replaced and sealed perfectly.
However, the first 2 minutes or so crom cold are still puzzling me, car fires and runs perhaps second turn of the key, but tries to tick over at 2-300 RPM even when stone cold. After the 1st 2 minutes or so engine runs fine, when fully warmed up idles nicely at 900-950 RPM, drops to 850-900 when cooling fan running. Wedging the throttle open slightly, engine will start and warm up quite cleanly.
The only thing I haven't changed, apart from a thorough clean, of the plenum chamber is the setting of the throttle disk...
At the moment I'm sure it seals completely when the throttle is closed (325 mV on the throttle pot sensor) I have several manuals on the various versions of the Rover V8 and it looks like the older ones ignore the setting of the throttle disk up so its "just" open enough for a 2 - 5 thou feeler gauge to occupy the gap, which features in the newer manuals. I've also been through Ramon's SD1 site on the net.
How critical is this setting? Can the lack of a gap produce the odd behaviour I'm experiencing? I'm 99.9% sure there are no more leaks on the vacuum side. Most of the ignition side is either brand new or been replaced in the last 12-18 months.
Regards,
Brian and a Red 350i
Over the last few weekends I've been struggling with a 3.5 flapper V8 in my TVR 350i
Initial symptoms, bad misfire when cold, could be cleared by persisting and warming the engine up, then problem solved, engine ran quite well...
Most if not all the problems have been traced to vacuum leaks, mainly in the injector seals and trumpet assembly, with a dodgy hose connecting the extra air valve (not the "C" shaped one) now replaced and sealed perfectly.
However, the first 2 minutes or so crom cold are still puzzling me, car fires and runs perhaps second turn of the key, but tries to tick over at 2-300 RPM even when stone cold. After the 1st 2 minutes or so engine runs fine, when fully warmed up idles nicely at 900-950 RPM, drops to 850-900 when cooling fan running. Wedging the throttle open slightly, engine will start and warm up quite cleanly.
The only thing I haven't changed, apart from a thorough clean, of the plenum chamber is the setting of the throttle disk...
At the moment I'm sure it seals completely when the throttle is closed (325 mV on the throttle pot sensor) I have several manuals on the various versions of the Rover V8 and it looks like the older ones ignore the setting of the throttle disk up so its "just" open enough for a 2 - 5 thou feeler gauge to occupy the gap, which features in the newer manuals. I've also been through Ramon's SD1 site on the net.
How critical is this setting? Can the lack of a gap produce the odd behaviour I'm experiencing? I'm 99.9% sure there are no more leaks on the vacuum side. Most of the ignition side is either brand new or been replaced in the last 12-18 months.
Regards,
Brian and a Red 350i
The 3.5 flapper has both a cold start injector and a cold start air valve.
The injector runs of the thermotime switch which is one of the temp sensors at the front of the inlet manifold.
The idle valve also works on time there being a heating element inside which slowly closes a ceramic disk to close off the extra air from cold.
Worth checking both of these systems.
Steve
The injector runs of the thermotime switch which is one of the temp sensors at the front of the inlet manifold.
The idle valve also works on time there being a heating element inside which slowly closes a ceramic disk to close off the extra air from cold.
Worth checking both of these systems.
Steve
Based on my own car, 1986 RRC 3.5EFi flapper.
The cold start injector serves no real purpose in UK temps & usual recommendation is just to unplug its lead. Did that just after I bought it, in 1994, & its made no discernible difference to starting.
The LR factory manual for mine gives the setting of a slight gap (0.002inch or 0.05mm) measured at the bottom of the butterfly as you mention. It does affect the idling. Clean round the bore & set the gap then see what happens. Set the throttle pot with it in that position.
The extra air valve is on the top front of the inlet manifold, is open when the engine is cold & closes as both the manifold warms up & its own heater comes into play.
Worth checking that the breather - from the tower on the offside rocker cover and its passageway in the plenum chamber are clear. Mine wasn't, the passageway in the plenum was blocked solid with crap. Result was that the engine pressurised & oil leaked out of all sorts of interesting places.
The cold start injector serves no real purpose in UK temps & usual recommendation is just to unplug its lead. Did that just after I bought it, in 1994, & its made no discernible difference to starting.
The LR factory manual for mine gives the setting of a slight gap (0.002inch or 0.05mm) measured at the bottom of the butterfly as you mention. It does affect the idling. Clean round the bore & set the gap then see what happens. Set the throttle pot with it in that position.
The extra air valve is on the top front of the inlet manifold, is open when the engine is cold & closes as both the manifold warms up & its own heater comes into play.
Worth checking that the breather - from the tower on the offside rocker cover and its passageway in the plenum chamber are clear. Mine wasn't, the passageway in the plenum was blocked solid with crap. Result was that the engine pressurised & oil leaked out of all sorts of interesting places.
Edited by paintman on Monday 10th March 20:43
Tried mine fully closed & it does make a difference. If there is a gap then air can pass which will obviously affect the mixture, if no gap then it can't so I'm not sold on the 'stops it jamming' argument.
The manual is specific about the gap, its not 'thereabouts' or as the OP says 'between 2 & 5 thou'. As said, that's LR specific to mine & later hotwire vehicles have the stepper motor air valve at the rear of the plenum.
ETA. I've had a very quick look & the update in my manual doesn't give any gap on the hotwire, stating that when adjusting the throttle levers the throttle valve must be kept at its 90deg vertical setting - which is fully closed. The stepper motor adjusts air at idle to keep the idle speed constant. The usual symptom of one failing or sticking is the idle hunting.
I'll have a look through RAVE later to see if there's anything else.
Don't forget that the above is specific to mine & other vehicles/engines etc may well do other things.
The manual is specific about the gap, its not 'thereabouts' or as the OP says 'between 2 & 5 thou'. As said, that's LR specific to mine & later hotwire vehicles have the stepper motor air valve at the rear of the plenum.
ETA. I've had a very quick look & the update in my manual doesn't give any gap on the hotwire, stating that when adjusting the throttle levers the throttle valve must be kept at its 90deg vertical setting - which is fully closed. The stepper motor adjusts air at idle to keep the idle speed constant. The usual symptom of one failing or sticking is the idle hunting.
I'll have a look through RAVE later to see if there's anything else.
Don't forget that the above is specific to mine & other vehicles/engines etc may well do other things.
Edited by paintman on Tuesday 11th March 08:47
paintman said:
Tried mine fully closed & it does make a difference. If there is a gap then air can pass which will obviously affect the mixture, if no gap then it can't so I'm not sold on the 'stops it jamming' argument.
The manual is specific about the gap, its not 'thereabouts' or as the OP says 'between 2 & 5 thou'. As said, that's LR specific to mine & later hotwire vehicles have the stepper motor air valve at the rear of the plenum.
ETA. I've had a very quick look & the update in my manual doesn't give any gap on the hotwire, stating that when adjusting the throttle levers the throttle valve must be kept at its 90deg vertical setting - which is fully closed. The stepper motor adjusts air at idle to keep the idle speed constant. The usual symptom of one failing or sticking is the idle hunting.
I'll have a look through RAVE later to see if there's anything else.
Don't forget that the above is specific to mine & other vehicles/engines etc may well do other things.
I didn't say fully closed The manual is specific about the gap, its not 'thereabouts' or as the OP says 'between 2 & 5 thou'. As said, that's LR specific to mine & later hotwire vehicles have the stepper motor air valve at the rear of the plenum.
ETA. I've had a very quick look & the update in my manual doesn't give any gap on the hotwire, stating that when adjusting the throttle levers the throttle valve must be kept at its 90deg vertical setting - which is fully closed. The stepper motor adjusts air at idle to keep the idle speed constant. The usual symptom of one failing or sticking is the idle hunting.
I'll have a look through RAVE later to see if there's anything else.
Don't forget that the above is specific to mine & other vehicles/engines etc may well do other things.
Edited by paintman on Tuesday 11th March 08:47
my point was it is not to be used as a supplementary air bleed idle bypass that's the job of idle bleed screws and idle valves either stepper or the electric/bi-metallic air valves 
obviously if you open it no matter how slight it will affect things including the TPS idle reference point for the ECU 
Had a chance to look through RAVE. The RAVE covering the Classic covers the later hotwire, not the flapper which is the older paper manuals, in the case of mine SRR660ENWM.
When setting the throttle butterfly on the hotwire Classic, the butterfly must be at 90 degrees to the bore of the plenum. Which is fully closed with no air passage, extra air for adjusting running idle being ECU controlled via the stepper motor.
The flapper doesn't have a stepper motor & once warm the extra air valve on these is closed. They do have a bit of a tendency in the autobox for the idle to drop slightly when in gear. Worst case will see the engine stall when low speed manouvering due to the increased load of the power steering.
The idle adjustment screw in the plenum sets the out of gear idle speed at 700 to 800 rpm.
As I've said, these are from the LR manuals specific to my vehicle. I can only suggest the OP sees if it makes a difference.
When setting the throttle butterfly on the hotwire Classic, the butterfly must be at 90 degrees to the bore of the plenum. Which is fully closed with no air passage, extra air for adjusting running idle being ECU controlled via the stepper motor.
The flapper doesn't have a stepper motor & once warm the extra air valve on these is closed. They do have a bit of a tendency in the autobox for the idle to drop slightly when in gear. Worst case will see the engine stall when low speed manouvering due to the increased load of the power steering.
The idle adjustment screw in the plenum sets the out of gear idle speed at 700 to 800 rpm.
As I've said, these are from the LR manuals specific to my vehicle. I can only suggest the OP sees if it makes a difference.
Edited by paintman on Tuesday 11th March 21:19
Many thanks for the replies boys,
Especially the people who looked at documentation for me..
I took the plenum off one evening last week and spent 1/2 hour or so carefully adjusting the throttle stop, put it back together and eventually run it on Saturday morning... I can only conclude that the settings are correct for the hotwire injection setup... I couldn't get the tickover down to anything below 1100 RPM. Spent the rest of Saturday putting it back together, engine now worse if anything...
Called in assistance and another pair of ears, eyes and a brain... Many thanks Martin
Martin has a very similar (it's the same Red!) but later 350i
I'd been pondering over the symptoms and decided to check the fuel pressure again (I have a FSE fitted in place of the standard fuel pressure regulator)
Pressure was OK at 40 psi, but I noticed that this pressure dropped to zero over 2-3 minutes or so, the SD1 manual I have says it should not drop more than 10.6 psi/minute. When we clamped up the outlet hose the pressure held up dropping very, very slowly.
So we took off the FSE and replaced the standard regulator, the pressure on this was a fair bit lower at 30 psi, but only dropped a fraction when the pump was stopped and even without clamping the outlet hose the pressure held up... Result....
Car now started up and warmed up nicely and now started up when warm just on the starter, allowed it to cool down a bit, then took it for a test drive... Plenty of power (for a 350 anyway) and popping and banging on the overrun...
So there is a problem with the FSE, well maybe... We took out the four bolts holding it together, and on opening it up we immediately spotted a small piece of rubber hose floating around inside the regulator.
Not very big, but enough to screw up the fuel pressure and cause all sorts of odd running issues...
The moral of this (long) story, look very carefully at everything, then look again.
Regards,
Brian (and a Red 350i)
Thanks for the thoughts, assistance and moral support Martin
Especially the people who looked at documentation for me..
I took the plenum off one evening last week and spent 1/2 hour or so carefully adjusting the throttle stop, put it back together and eventually run it on Saturday morning... I can only conclude that the settings are correct for the hotwire injection setup... I couldn't get the tickover down to anything below 1100 RPM. Spent the rest of Saturday putting it back together, engine now worse if anything...
Called in assistance and another pair of ears, eyes and a brain... Many thanks Martin
Martin has a very similar (it's the same Red!) but later 350i
I'd been pondering over the symptoms and decided to check the fuel pressure again (I have a FSE fitted in place of the standard fuel pressure regulator)
Pressure was OK at 40 psi, but I noticed that this pressure dropped to zero over 2-3 minutes or so, the SD1 manual I have says it should not drop more than 10.6 psi/minute. When we clamped up the outlet hose the pressure held up dropping very, very slowly.
So we took off the FSE and replaced the standard regulator, the pressure on this was a fair bit lower at 30 psi, but only dropped a fraction when the pump was stopped and even without clamping the outlet hose the pressure held up... Result....
Car now started up and warmed up nicely and now started up when warm just on the starter, allowed it to cool down a bit, then took it for a test drive... Plenty of power (for a 350 anyway) and popping and banging on the overrun...
So there is a problem with the FSE, well maybe... We took out the four bolts holding it together, and on opening it up we immediately spotted a small piece of rubber hose floating around inside the regulator.
Not very big, but enough to screw up the fuel pressure and cause all sorts of odd running issues...
The moral of this (long) story, look very carefully at everything, then look again.
Regards,
Brian (and a Red 350i)
Thanks for the thoughts, assistance and moral support Martin
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