Chasing serious lean out EA82T

steptoe · Post by **steptoe** » Mon Mar 31, 2008 6:49 pm

Involves using a portable Vane air fuel ratio meter chasing a lean backfire condition on a new LPG installation BUT PLEASE DON"T LEAVE THE ROOM YET !!!

Me mate "MacGuyver" suggested we look at what the meter does on petrrol, and bargger me does the same.

Car idles nicely on both fuels and runs well on petrol, not on gas due to backfire

This Vane measures tail pipe emissions and was running nice ordinary looking figures until it suddenly swung to the maximum lean reading at idle on both LPG and PETROL then back to normal then up to max lean again.

Nice stoich for petrol is 14.7:1, LPG is 15.5:1 at idle, max 13.2: rich for LPG under load, and this gauge reads 29.9:1 LEAN for both petrol and LPG on the swings !!

If it was petrol only relying on the O2 sensor you'd look at its readout next, but for simplicity sake I have eliminated the O2 sensor from the gas system, until I can get it sorted in BASIC first. Unless it is coincidental dodgy O2 sensor giving same fault lean mix readings.

It could be sticking valve ? re my miss I get on cold drive off and engine brake drive but disappears once op temp. Could be an air leak but it is all new intake man gaskets.

The lean to rich comes and goes like a wave , as if something pollution/vacuum release is causing it. Thinking that sticky valve may not feel or show as easily on an efi set up until you go shoving a fuel charge in there like LPG to be suddenly upset by fresh air released into its equation somewhere.

Blocked off the auto tranny vac line - nothin'
The EGR is plated off and I disconnected the wire plug for it just in case
Surely other than the purge canister hoses there can't be another sort of air leaking diaphragm that would open and shut to cause this ?

Disco ? got your thinking cap on ?

any takers???

Gannon · Post by **Gannon** » Mon Mar 31, 2008 7:35 pm

Could you please explain the details of how your fuel system works.

Is it an LPG carby, or are you injecting the LPG through an EFI system?

Check your gas pressures, see if they fluctuate in sequence with your lean swing.

Matatak · Post by **Matatak** » Mon Mar 31, 2008 7:55 pm

that is seriously lean if it actually is going to 29.9:1

id be unsure if it culd even run being that lean.

BlackMale · Post by **BlackMale** » Mon Mar 31, 2008 10:26 pm

steptoe wrote:It could be sticking valve ? re my miss I get on cold drive off and engine brake drive but disappears once op temp.

HOw cold is it when you drive? maybe there is an issue with the auto choke? I am anial about driving mine until the auto idel almost turns itself off.

steptoe wrote:Car idles nicely on both fuels and runs well on petrol, not on gas due to backfire

if i have read this correctly i do not see how it could not be a leak in the air system as it would backfire on petrol.

What's the difference between the burn rate on the fuel and the LPG? Sorry if this is unclear... i know what figures i am looking for and its probally more for my info.

Again this is probally more for my info but was the system istalled and tuned by someone professional? (Note that i am suggesting that if you and mate did it its not a professional job or anything).

Sorry i am not much help but you have a PM.

discopotato03 · Post by **discopotato03** » Tue Apr 01, 2008 7:27 am

If the EGR plumbing is plated I'd leave the valve connected just incase the ECU has hissy fits . It should know if the valves disconnected but not if the plumbings plated .

Sounds silly but make sure the dizzy is doing what its supposed to do timing wise as well .

If the symptoms are exactly the same petror/gas then I think it must be an air problem . I don't know if they ever fail or go eratic but you could also check that hexagonal steel boddied FICD valve (fast idle control valve for AC idle up) though you'd think it wouldn't matter because all the air in theory is being metered .

A collapsed PCV valve could make it do strange things as could cracks in the inlet trunking . If you disconnected ALL the crank case breather system from inlet manifold plumbing that isolate lots of potentials for test purposes . Don't seal the breathers if you do this even temporarily or it could pump oil out the front and rear crank seals . A little oil vapor in the bay wont hurt anything temporarily .

The thing to also check is how good the AFR gear is that you are checking this out with . If you can find a Dyno facility run by petrol heads the may do a quick diagnostic run just to check AFR without being too greedy .

Lets know what you find - I'm suspect the breather system because they have 101 old hard rubber hoses so many leak points .
Lastly check inside you airbox just in case the filter element is collapsed or has a large loose object is floating around inside the box .

Lets know how you go , cheers A .

discopotato03 · Post by **discopotato03** » Tue Apr 01, 2008 7:33 am

Another couple of thoughts , check the vacuum line to the dizzy AND the brake booster as well .

Cheers A .

steptoe · Post by **steptoe** » Tue Apr 01, 2008 8:47 am

The Impco 200 mixer is force fed filtered air through a silicone bend hose. The PCV system feeds before the turbo so no leaks here. Mixer then goes straight into another silicone hose to throttle body. It is all sealed. And for elimination it is non feedback at the moment so it is an old fashioned free air set up I specced with some good assistance in the US, using an L converter. All components overhauled. I am the one who has installed system. Conversion #3 that has not been a box of components already sorted and delivered. My experience with gas goes back to the dark ages and have trained a mate to licence level (so I got a gas licence now that comes with me 100kg mate) and done a few - AND STILL LEARNING !!

the copper line you may see has been replaced with straight out of the Impco fittings and 1/2 inch ID line. This is the balance line

Something (air) is getting in somewhere between mixer and cylinder. Thinking if exhaust valve sticks fuel is not compressed or burnt so oxygen escapes to the tail pipe reading. I don't think efi gets a backfire with sticking exhaust valves like carby coz fuel enters just before the valve.

Just thinking, I noticed an oily looking weep about the EGR valve body, may need further inspection, but off to find a sensitive RYCO vac gauge

Love to have used the vapour injection technology but steering away from two fuel systems (injection needs petrrol for start up/warm up). Mate is doing his V8 VI at the moment and been observing heaps spring up. I may wait for liquid injection - kits are here now

, but still need petrol warm up !!

You'd think I could hear any manifold air leaks under boost through my clutch cable hole (got no clutch and I heard my boost yesterday coming out of the IAC hose I forgot to hook up both ends

came boosting out of the alloy cross pipe

Cold start meaning not run for about 8 hours or more , rather than brrr cold air outside temp.

The miss goes like this, if I start it up , cold, warm up to a nice temp (coz tranny won't move until its warm), drive down road 50 M in low held and back off using engine / gears as brake, come to a STOP and car returns to idle but running properly only on three cylinders, missing on #2. Continue to drive off and away we go engine and tranny all warmed up the miss does not show until again engine has cooled completely and will miss again until warm. The big BUT is if I drive the first 50M in DRIVE using brakes as brakes and not assisted by engine and tranny in LOW the miss of #2 will not always be there ??

I can also produce this same miss if I run engine from cold on the spot to op temp and just blip the throttle or thrash it up and down, on its way down the miss will be there and can just settle out OK, rev it up or blip it again , same miss on return to idle.

The Vane is quite new and not mistrusted at all, in fact the sensor is brand spankers as the old one slipped off a pipe recently and sustained more than gravel rash, mind you it is gonna be looked at again with another known vehicle, just in case.

discopotato03 · Post by **discopotato03** » Tue Apr 01, 2008 11:14 am

Your call but accurate wide band AFR sensors are best and quickest reading .
Because they are used in virtually everything wide band pump cell probes are not that expensive for what they are .

Just on the gas install , one problem I can foresee is the gas carby downstream of the turbocharger . What a turbocharger does is increase air density (boost pressure) , carburettors are not density sensitive only air speed sensitive . Under boost manifold pressure can go up without air speed rising and its doubtful if you can made a carburettor meter in these circumstances .
The other problem you have is that manifold pressure is rising in relation to the gasses stored pressure system so its getting difficult .
If I wanted to do the gas thing I'd do it as a suck through rather than a blow through because everything upstream of the turbo works just like it would in an NA installation .

Cheers A .

steptoe · Post by **steptoe** » Tue Apr 01, 2008 6:34 pm

A.

This Vane unit is available from mainlineauto.com.au It IS wideband

http://www.mainlineauto.com.au/products ... /index.htm

Me local gas guru suggested suck through giving lots a room for boom if things go wrong (like now!!), Impco staff in Sydney say must go mixer as close to throttle as possible. I jump on rasoenterprises propane forum and there are turbo Impco set ups using same stuff I have and run well I believe. My Impco books of the 80's say that their stuff can do it either suck or blow but all diagrams are in blow through - less wear on turbo bearings. I am getting good info from both directions, so made a decision for myself .
A balance tube is used to balance mixer and converter. Me guru has described a Falcon on gas mit turbo and the mixer was four foot away down ducting. Given my 'miss', I reckon I went the right way so far.

steptoe · Post by **steptoe** » Tue Apr 01, 2008 6:38 pm

Second trial of the Vane and I only once saw at idle , no foot on throttle, a spike of 29.9 lean just appear out of nowhere. Took it for a belt up the road getting 14.6, 14.7 on light to medium throttle down to 10.2 rich on foot to floor stuff and learnt of the 'injector cut' on back off or TPS closed , until about 1500rpm when ecu turns injectors back on. An efi stunt apparently and one that continues on with vapour injection. This gave lean of 29.9 too !!

steptoe · Post by **steptoe** » Tue Apr 01, 2008 6:40 pm

The decision is to buy a set of new hydraulic lifters and do the LHS bank, suspecting an exhaust valves lifter #2 has a little Viagra lurking in his veins

Gannon · Post by **Gannon** » Tue Apr 01, 2008 7:11 pm

I still dont understand your fuel system.

I assume you have LPG and petrol and can switch between the two.

Lean when idling or deceleration isn't a problem, slightly lean on light cruise isnt all that bad either. Its when you are accelerating and working the engine hard that lean is a bad word.

If you are getting 14.7 on cruise and 10.2 on accelerate. Thats near perfect. If you are getting just a spike of 29.9 momentarily at idle or when decelerating, thats quite normal too.

I also suggest you reconnect your o2 sensor, preferably a newish one.
That way the engine will can readjust itself as you are driving

steptoe · Post by **steptoe** » Wed Apr 02, 2008 10:09 pm

Gannon, it was designed as a dedicated LPG but it takes fewer minutes each time to remove gas carby and silicone pipes and refit turbo pipe and plug the ecu back in to run on petrol , and swap my fixed open afm with the good one- that sort of 'switch' only

From check number two, other than the one off spike on idle I'd say it was all rosie, the O2 sensor does good but to get the lean backfire on gas -it is not driveable. What the sensor is reading is unburnt oxygen and that has come from somewhere, so reading into it the miss I chased from day one almost and this lean backfire I have no choice now other thanto change lifters first. Ordered them today - not as cheap as they were - negotiated $20 ea should arrive Thursday. Just waiting to place a bid on a bucket of motivation on ebay

I don't think it is the fuel system leaning out causing the backfire - more a flash from exhaust valve holding open

Gannon · Post by **Gannon** » Thu Apr 03, 2008 5:29 am

If the engine is misfiring (even caused by bad spark) and the cylinder of air/fuel doesnt get burnt, that can cause the a/f meter to read lean momentarily.

steptoe · Post by **steptoe** » Mon Apr 07, 2008 12:35 am

yep, that's the way i understand it - seen it on both fuels so cannot blame gas until i attend to the cause, not many options left considering
heads recoed, good compression, many new plugs, injectors done, new leads, cap, rotor.....

SCOOBIDOO · Post by **SCOOBIDOO** » Fri Apr 18, 2008 3:51 am

Hi Jonno...around a year ago i told you what the problem was with your engine..the 29:1 spike you have discovered with the wide band is cause by the valve not closing completely, due to the weak valve spring.this allows the lifter to pump up and hold the valve open for a short time...then slowly goes away after a few seconds..the spring cant over come the oil preasure of the lifter..so it tops out and holds the valve open..i thought you soughted it then..as you stopped talking about that problem..chase it all youl ike..but come and thank me when you find the weak spring dude....ive been in the trade for 35 years....search and yee shall find...did i forget to mention your valve is being held open by the lifter???cheers

steptoe · Post by **steptoe** » Sun Apr 20, 2008 11:15 am

Yeah Scoobi, I have not discounted your diagnosis, just reasoning that if a head reco joint has done my heads you'd hope that the guys check for these things. I think I will be good at striping LHS cam gear to do the lifters first then the next time to prove you are right - in the stubborn belief in trying one thing at a time so you know for future reference even if it takes more time and effort.

The problem went away in the way that if I drove it through this miss it would not miss once driven a few kilometers each time. The problem was always there if the car was stationary and warmed up and free revved on the spot. Have done about 7000km since engine rebuild and the only time this miss occurs is on cold start up and just blip the acc pedal or using 1st gear auto as an engine brake down the first part of the road. It has never reared its ugly head once warm ??? And NOW with change of fuel

Have you found similar to mine in that the weak valve spring comes OK with driving? Oil thinning out as it all becomes hotter.

ta,

SCOOBIDOO · Post by **SCOOBIDOO** » Mon Apr 21, 2008 10:37 pm

steptoe wrote:Yeah Scoobi, I have not discounted your diagnosis, just reasoning that if a head reco joint has done my heads you'd hope that the guys check for these things. I think I will be good at striping LHS cam gear to do the lifters first then the next time to prove you are right - in the stubborn belief in trying one thing at a time so you know for future reference even if it takes more time and effort.

The problem went away in the way that if I drove it through this miss it would not miss once driven a few kilometers each time. The problem was always there if the car was stationary and warmed up and free revved on the spot. Have done about 7000km since engine rebuild and the only time this miss occurs is on cold start up and just blip the acc pedal or using 1st gear auto as an engine brake down the first part of the road. It has never reared its ugly head once warm ??? And NOW with change of fuel

Have you found similar to mine in that the weak valve spring comes OK with driving? Oil thinning out as it all becomes hotter.

ta,

IDENTICAL SYMPTOMS......i took my rocker covers off..and with my thumb..pushed on all the rockers arms..and sure enough..there was one noticebly softer spring..mind you my engine is in a vw type vehicle and access is dead easy...you have to thumb them pretty hard..but you will find 1 softer spring..mine was right beside the turbo..i think this was just a hugh coincidence..cheers

steptoe · Post by **steptoe** » Tue Apr 22, 2008 9:27 pm

Scoobi, it may be a good chance that I will prove you right and many wrong on this one. I was talking to the old and experienced guys at my other machine shop today re my MY heads and told of these symptoms - yeah lifters likely cause, but then again i respect your experience and offering of probable fix, just have to wait 'til i make time....

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Chasing serious lean out EA82T

Chasing serious lean out EA82T

Weak Valve Spring