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Has been a little while - so thought i'd send an update
Needed to rebuild the AAV - have done this according to the great guide from Grant Francis
Have also replaced the TPS and reset successfully as i thought the old one was giving inconsistent readings
Remembering also the throttle plates were set to a zero gap - so i adjusted these also
After - i've done all of this, i now (still) have a super fast idle speed (2000rpm) which i can't bring down as well as some missing on A bank i never had previously.
Yes - I've checked and double checked and i can't find an airleak anywhere.
Sooooo - my current thinking is that the timing is set too far advanced as i dial down the fast idle with on the distributor. I'm thinking this as the throttle plates were previoulsy set to zero - and maybe the timing was advanced to mask the issue??
The car used to be a pig to start - but ran really well, so i'm a little wary of heading in the wrong direction on this
Anyway - presumably the next step would be to check and adjust the distributor to allow for the correct range of adjustment to bring the idle speed down - however i wonder if i'm chasing the wrong thing here and creating work where there isn't actually an issue
How much work does this involve and am i on the right track?
There is a timing plate under the car at the front, and a raised car, brave (very brave) human is needed to see it.
BUT,
The timing ring on the crank front pulley has a terrible habit of slipping, so the timing mark is useless. Gotta LUV the V12.
Sooooooo, when delving into the unknown I do it Grants way. I then wrote it up for you all, and for when my memory really crashes, its in writing, clever hah.
The early V12 HE had a stupid 15 minute timer thingy, that held the idle at about 1500rpm for that 15 minutes whenever the engine is started. I will have to look waaaaaay back in the Grey Matter, and my huge stack of notes regarding this thing. I disconnected it, and then removed all of it. I think?? the prime item/s is the thermo vac/electrical sensor at the rear of the RH water rail, and the solenoid sitting in the backing plate of the RH aircleaner, which can simply be unplugged, and any vac hoses plugged.
Last edited by Grant Francis; 03-12-2017 at 04:57 AM.
Reason: spelling sucks
If you are idling at 2000 rpm you DO repeat DO have an air leak, do not go off fiddling with timing until you find and fix the leak. Either your rebuilt AAV is not working properly, or one or more of the huge number of ways for air to get into the manifold are incorrectly open. The 15 minute timer, if fitted to your car (it will be if a non-cat car, will not be if it is a cat car as all in the USA were) I am pretty sure (although disagreeing with Grant is a brave thing to do) will enrich the mixture but NOT increase the idle speed.
Some tests to prove the leak:
remove B bank airbox and block off the exit to the AAV, do the engine revs change. Be SURE that the dizzy breather tube where it joins the flexible to the AAV from the airbox is not broken and then also block off the breather tube from the dizzy top.
Place a HUGE ball of rag over each of the throttle bodies, butteflies closed, (so it cannot be sucked into the intakes), and see if the RPM drops. If they do not, and the AAV is blocked off, you have a huge leak elsewhere that is letting in air to the manifold.
go round each manifold blocking off every spigot you find until you find the one that drops the revs. Do not forget the large spigot unde the A bank TB that powers the vac for the cruise control, hard to see and often drops off.
Ok
Have blocked off the AAV - minor drop off in revs but nothing significant
Also shoved a couple of tee shirts in the respective throttle bodies and this certainly dropped the revs more from 2000 to 1500
Also blocked off the Distributor breather pipe
The engine still runs so that would suggest an air leak I presume. I still can't find where but will work my around each plenium and block off holes to see what difference that makes
btw - I did have that timer device you mentioned at the rear of A bank.
Just out of curiousity, if the RPM at idle is sitting at 2000rpm, shouldn't the engine also be "rev hunting" due to the auto shutoff of the injectors at around 1500rpm? Whether the issue is a broken AAV or an air leak, wouldn't the rev hunting issue still present itself?
Just out of curiousity, if the RPM at idle is sitting at 2000rpm, shouldn't the engine also be "rev hunting" due to the auto shutoff of the injectors at around 1500rpm? Whether the issue is a broken AAV or an air leak, wouldn't the rev hunting issue still present itself?
Yes it should, but we do not know what year or model the car is. best not to worry MM at this stage, let's just get the tickover leak solved!
Greg
Ok
Have blocked off the AAV - minor drop off in revs but nothing significant
Also shoved a couple of tee shirts in the respective throttle bodies and this certainly dropped the revs more from 2000 to 1500
Also blocked off the Distributor breather pipe
The engine still runs so that would suggest an air leak I presume. I still can't find where but will work my around each plenium and block off holes to see what difference that makes
btw - I did have that timer device you mentioned at the rear of A bank.
MM?
that had me scratching my (bald) head
1982 HE v12 auto (that's the next project to fix)
Thanks, put it on your signature I suggest. Your car will have the earlier 6CU version of the ECU, which may, repeat may, be the reason the normal cycling of revs at tickover above 1400 rpm is not happening. This is NOT a worry at all (basically a fuel saving measure on a trailing throttle), but once you have sorted the tickover problem, changing the ECU for the later 16CU model, which is a direct plug in and go swap, is a very good idea. This later version is far more reliable.
Not all 16CUs are the same (depends on ignition (you have Lucas) and whether there are cats on your car or not. But they are easy enough to find.
Greg
Ok
Have blocked off the AAV - minor drop off in revs but nothing significant
Also shoved a couple of tee shirts in the respective throttle bodies and this certainly dropped the revs more from 2000 to 1500
Also blocked off the Distributor breather pipe
The engine still runs so that would suggest an air leak I presume. I still can't find where but will work my around each plenium and block off holes to see what difference that makes
btw - I did have that timer device you mentioned at the rear of A bank.
OK,
X300 finished, so catch up time.
If you have the AAV plugged,AND T Shirts up the throttle bodies, and its still running, frame the bloody thing, it is indeed a rare V12.
Couple of things:
1) On top of the AAV is a rubber 90deg elbow. These split all by themselves, and usually on the underside. Quickie fix, Insulation tape, wrap it aroung in copious layers. It will last about 3 hours, but will diagnose YES or NO very quickly. DO NOT take it off without a NEW elbow on hand, you will need one, no matter what.
2) The Balance pipe that runs across the rear of the engine, and connects the 2 inlet manifolds. The rubber hoses at each end also split, so read (1) above for a temp fix.
3) Brake booster diaphragm is split, common now with age. Remove the booster vac hose at the rear of the RH Inlet manifold, and plug the spigot. DO NOT drive the car like this, your legs are NOT strong enough to stop that car, trust me.
4) Look below the area where the Booster vac hose is, and you will see an end plate on the manifold, triangle in shape. It has a few hoses attached, well should have, and ONE rubber cap on a "spare" spigot. Is that cap still intact??, and are the hoses intact??, as a huge vac leak from here will rev the engine significantly.
5) The solenoid that sits in the rear of the RH Air Cleaner backing may be activated, and that will raise the idle by about 400rpm, so unplug the electrickery leads just to be sure.
6) The Inlet manifold gaskets are split. Some early, and your is early, have 12 Inlet gaskets, and they do split, and allow heaps of air in.
7) The square section seals on the BOTTOM of the injectors are split, or shrunk, or missing.
8), You probably have Overrun valves on the front of each Inlet manifold, PITA on a good day, they leak, reek havoc. Take them out, make a plate to seal off the manifold.
I will keep thinking.
Last edited by Grant Francis; 03-13-2017 at 04:48 AM.
Just to refresh - still have a ridiculously high idle @ 2000rpm and have been chasing an air leak for the past couple of weeks
Have disconnected and blocked off all the vacuum pipes to the pleniums and managed to get the idle down too a resonable level at around 1000rpm although it was increasingly running very very rich - smoke everywhere and missing badly. This seemed to get worse over time
Then throughly inspected and added the pipes back on - the rear balance bar seems to be the issue with the idle jumping immdediatly back to 2000rpm when this was reconnected - although the engine certainly ran alot better with no significant smoke.
There is a smaller vacuum pipe at the rear of the balance pipe - and i traced this to a module in the boot. i couldn't find any issues with the pipe itself - so the next question is what is the module in the boot and how does this effect the high idle?
There is a smaller vacuum pipe at the rear of the balance pipe - and i traced this to a module in the boot. i couldn't find any issues with the pipe itself - so the next question is what is the module in the boot and how does this effect the high idle?
The module is the ECU---Electronic Control Unit. It's the brain of the fuel injection system. Inside the ECU is a barometric pressure sensor; that's what the vacuum pipe/hose goes to. It's the primary player in mixture control. With no vacuum applied the fueling will be very rich...as you found out.
The ECU itself cannot create a high idle. Only additional air will do that.
Have disconnected and blocked off all the vacuum pipes to the pleniums and managed to get the idle down too a resonable level at around 1000rpm although it was increasingly running very very rich - smoke everywhere and missing badly. This seemed to get worse over time
That may be because the TPS is way off, or because the ECU thinks the throttle is wide open because of there being no vacuum signal to it, and is fuelling accordingly. The TPS is a little electronic unit under the throttle capstan which tells the ECU how open or closed the throttle is. It must be set to 0.32 volts at the closed postion, and rise to 5 volts, or close to it, at WOT.
Then throughly inspected and added the pipes back on - the rear balance bar seems to be the issue with the idle jumping immdediatly back to 2000rpm when this was reconnected - although the engine certainly ran alot better with no significant smoke.
The rubber hoses that connect this balance pipe to each inlet manifold, or the pipe itself are letting in air. Check also that the vacuum signal pipe to the ECU holds vacuum (the pipe you describe below). The purpose of this vacuum signal is to tell the ECU what the manifold depression is, and thus how much air the engine is calling for, and thus also is used to set the fuelling. Check this pipe by blocking the pipe at the ECU end and seeing if you can suck air at the engine end where it joins the balance pipe.
There is a smaller vacuum pipe at the rear of the balance pipe - and i traced this to a module in the boot. i couldn't find any issues with the pipe itself (see above)-
so the next question is what is the module in the boot and how does this effect the high idle? The 6 CU unit is not nearly as reliable as the 16CU, The 16CU is a direct replacement for the 6 CU and well worth doing. If the barometric pressure reader Grant referred to is not working, or the circuitry is not (very common) this will also fool the ECU into thinking the throttles are wide open.
You are making good progress and have narrowed down the causes, well done and keep at it! Greg
In that vac hose in the boot, just near the battery, is a Black Plastic cylinder. This is a pulse damper for the vac signal TO that ECU (nodule), and they split, as does the hose AT the ECU spigot.
Also, as Doug again stated, LOW vac at the ECU = Rich mixture, High Vac at the ECU = Lean mixture.
If that Black cylinder is split, simply use a hose joiner, new length of hose, and run the hose direct to that ECU. Mine has been that way for 20+ years.
Since you have found that hose at the balance pipe, unplug it again, suck on it, and ensure it actually HOLDS vacuam, and if it does, then the hose, pipe under the car, hose in the boot, and ECU are just fine.
I'll just add the item #13, the hose to the solenoid, goes to the underside of the inlet manifold....out of sight. It's a pretty big hose, 3/8" or 5/16 " inside diameter. If it's broken or has fallen off the intake manifold it would let in quite a lot of air.
Following up from the last few posts, the engine idle is sitting at 2000rpm after I've tried to retune the car and opened the throttle plates to the correct gap as part of this process as they were set fully closed. Have also replaced and reset the TPS To the correct voltage reading at closed throttle and have rechecked
The general consensus was an air leak, so I removed all the components from the pleniums and blocked them off accordingly. The idle dropped back to 1000rpm until I attached the rear balance bar and it shot straight back up to 2000rpm
i have then rechecked the rubber hoses and bar and can't find any air leaks - all looks very good.
I then removed the vacuum pipe to the ECU and checked it for any leaks and again - no problems with the integrity of this pipe including the black damper thingy close to the ECU
Could it be something wrong with the ECU itself?
Maybe someone has reset the idle on it??
it looks like it was replaced in 1998.
See attached photo
Remove the vacuum hose to the ECU from the balance tube and reattach it to a difference vacuum source....like one of the nipples at the rear of the RH inlet. Now remove the balance tube.
Any change?
I beginning to wonder if the baro sensor inside the ECU has ruptured. This would give a very rich mixture....which is masked by the 2000 rpm engine speed but evident at a lower engine speed.
Attach a vacuum hose to the nipple on the ECU and give it a good suck. Does it hold vacuum?
01-29-2017, 06:46 PM
