Injectors firing too early?

[Rokassileika]

Hello. ive seen that it is possible for injectors to open up too early. What is usually the cause of it and how is it fixed? I have a car with 2GR-FE engine. Stag 600 computer unit, zavoli zeta and aeb injectors. My problem is that the car has very inconsistent power output. For example, today i went to work and i could not recognize my car- it felt like driving a very powerful sports car. Yesterday i drove it and it felt as sluggish as a 1.0 Toyota Yaris would be. There are many things done with this car- new spark plugs, filters, cleaned reducer, new vacuum lines, cleaned MAF, serviced automatic transmission 2 times. By the way, on hot summer days it is usually very strong and fast, this happens more when it is cold outside. Noticed that power increase on rainy days- this is not the first time i notice it with lpg car. And, the engine noise that is produced by combustion sometimes is heard as a very smooth and quiet running engine and sometimes it is significantly louder. Any ideas?

[Gilbertd]

Not sure where you saw that injectors can open too early as they are slaved off the petrol injectors so there would be nothing to fire them early. I would say it is something different but can't help with what I'm afraid.

[LPGC]

The 2GR-FE engine is a Toyota V6 but it's spec and the spec of it's fuel system depends on the year and model of vehicle. Some feature both port fuel and injectors and direct fuel injectors, some only port injectors, some have different intake manifold designs to others.

What year and model of vehicle?

It is a long shot at this stage to assume 'injectors are opening too early'. As Gilbert said, particularly if the engine has only port injection, the LPG ECU 'slaves' from the petrol ECU so only tells LPG injectors to open when it has received respective (per cylinder) petrol injector pulses... This is true if 'routing' is correct (correct routing being petrol injector pulse on a cylinder causes LPG injector pulse on the same cylinder as opposed to a different cylinder). If routing isn't correct then some cylinders will get fuel too early and some cylinders get fuel too late, or too late could happen if the point of LPG gas entry into the intake manifold is too far away from the intake ports on the cylinder head.

There could be many causes for it seeming more powerful sometimes than other times, a few examples: 1. If it isn't setup and calibrated correctly it could seem more or less powerful if it runs in 'limp home mode' compared to running in closed loop mode. 2. If temperature compensation isn't correct it could be leaning mixture off too much when the weather (under bonnet temperature) is cold. 3. Injectors could be gummed up or failing. Could go on and list many more potential reasons but to suggest a likely reason we'd need a lot more information including fuel trim readings under various conditions.

If you only drive it on petrol does the engine seem to run OK with expected power? Does the engine warning light come on?

[Avensist]

Simon is correct, the 2GR series engines have variations. The 2GR-FE is a simple port injected engine. The ones with direct injection will be 2GR-FSE, 2GR-FKS and 2GR-FXS.

[Rokassileika]

As I mentioned before, mine is 2GR-FE, no dual injectors. I do believe that it could be something off with temperature calibrations. Lambda is always showing a bit rich on both banks. One bank is slightly leaner than the other

[LPGC]

As I mentioned before, mine is 2GR-FE, no dual injectors. I do believe that it could be something off with temperature calibrations. Lambda is always showing a bit rich on both banks. One bank is slightly leaner than the other

But which model of vehicle is it in? This could make the difference between type of inlet manifold. E.g. If it's fitted in a Lexus RX the LPG installer may have fitted (or maybe should have fitted) straws (that run inside intake runners to make for point of gas entry close to the engine inlet valves) at least for the rear bank of cylinders.

"Lambda is always showing a bit rich on both banks" - Lambda signal should flick rich lean during closed loop operation and constant rich when putting your foot down, is this not the case on LPG? How about on petrol?

What are the fuel trim readings at idle when cold, idle when warmed up, same again cold and hot trim readings at a few other rpm/load points such as (say) 2500rpm 0.5bar manifold pressure cruise. Readings on petrol and readings on LPG? Make sure that it stays in closed loop mode for all the tests and isn't misfiring, or obviously mention if it switches to open loop/error mode or misfires. What are the gas temperature readings during all these tests?

[Rokassileika]

As I mentioned before, mine is 2GR-FE, no dual injectors. I do believe that it could be something off with temperature calibrations. Lambda is always showing a bit rich on both banks. One bank is slightly leaner than the other

But which model of vehicle is it in? This could make the difference between type of inlet manifold. E.g. If it's fitted in a Lexus RX the LPG installer may have fitted (or maybe should have fitted) straws (that run inside intake runners to make for point of gas entry close to the engine inlet valves) at least for the rear bank of cylinders.

"Lambda is always showing a bit rich on both banks" - Lambda signal should flick rich lean during closed loop operation and constant rich when putting your foot down, is this not the case on LPG? How about on petrol?

What are the fuel trim readings at idle when cold, idle when warmed up, same again cold and hot trim readings at a few other rpm/load points such as (say) 2500rpm 0.5bar manifold pressure cruise. Readings on petrol and readings on LPG? Make sure that it stays in closed loop mode for all the tests and isn't misfiring, or obviously mention if it switches to open loop/error mode or misfires. What are the gas temperature readings during all these tests?

Thank You for explanation. It is a Toyota Camry from 2007. The hoses are near inlet valves, the points were made with drilling holes in aluminium inlet manifold (p.# 17111-0P030). I guess I will upload a Youtube video with all the specs at same moment. When starting the car in the morning (cold start) I have LTFTs with a big minus -10 to -20 if i remember correctly. Both lambdas are working normally it is going from 0.1 V to 0.9 V to 0.1 V all the time, but STFTs are on the minus pretty much always. Forgot to mention that when I bought the car it was going very strong on gasoline and just after LPG installation the power dissapeared somewhere, I could really notice it. Switching to gasoline does not improve this situation. I have never actually gave attention if it is in open or closed loops when there is a significant change in power outputs, will definitely check on that. But wouldn't i get an engine error code if this would happen? Ive been through many forums, but this is the first time I have a very good feeling that You guys know what You are talking about. Big Thank You for that.

[LPGC]

Sometimes negative fuel trims shortly after switching to LPG during engine warm up at light engine loads should be expected.

What can be happening in that case is that although the petrol system has switched to closed loop fuelling, the petrol map during the cold engine conditions still expects that (due to the cold engine) not all of the petrol being injected will atomise properly so won't be burned.. So although closed loop the petrol map is compensating for the cold engine by still applying what would be (in the old days of carb engines) a bit of 'choke' effect. But when we switch to LPG we don't need any choke effect because the LPG is injected as a vapour so atomises and mixes with air anyway, so since the LPG system bases its fuelling on petrol injector pulse duration we get negative fuel trims at light engine loads shortly after switching to LPG decreasingly during the engine warm up period.

Other things that can happen during this period is that the LPG injectors are cold so respond differently... They make take a little longer to open and/or to close. If they take a little longer to open it results in more positive fuel trims, a little longer to close results in more negative fuel trims. Pressure can also have an effect, pressure is compensated for by the ECU but the pressure compensation doesn't take into account how varying pressures affect injector opening or closing time, the default ECU pressure compensation assumes an ideal injector that doesn't have opening or closing time in itself affected by varying pressure. Same with gas vapour temp compensation.

The above effects can be exaggerated if the injectors fitted are particularly susceptible to varying response for changing pressures and/or temperatures or if the injectors fitted are pulsed for a relatively short time compared to their opening and closing time.

You need to find out what is going on regards mixture and/or misfires when power seems much different to what it would be if the engine was running properly on petrol, because it should feel the same to drive on LPG or petrol once it has switched to LPG and only mixture or misfires should account for such differences. Sometimes location of components such as position of gas entry into the manifold and pipe lengths etc can cause momentary (during transient conditions i.e. changes in throttle position, rpm, temperatures, etc) can cause incorrect mixture sometimes leading to misfires - pics of your installed positions and other info such as pressures and nozzle sizes etc might help us help you.

[Rokassileika]

Will definitely make some photos. At the moment im struggling with the power being inconsistant whenever the engine is cold or hot. Lets say i drive the car for 1 hour straight, city driving. Lets say i'm pressing the gas pedal at 25% it is now driving like a rocket. 20 minutes later, the power is gone- i use the same amount of throttle it goes like s***. 25 minutes later the power magically comes back, it starts driving strong again. It is completely random. The rainy (high moisture) days somehow makes the car run better. Im pretty sure my LPG Map is pretty messed up by now, but it definitelly somehow runs better with a messed up map vs when it was calibrated by specs. I have negative STFTs when the engine is fully warmed up and at idle. I nnoticed if i hold gas pedal steady at about 25% power eventually kicks in, I have like a "v-tec" feeling from 2k-3k rpms and it is not always like that. I have to play with the gas pedal to kinda find its "sweet spot" or something. I've had a vw golf 1.6 77kW before and i remember it did absolutely the same. I wish the engine could release its full potential when I have WOT and not just on 25-30% on the gas pedal. I mean WOT usually feels much worse than these 25 ish percents of throttle. But I was wondering maybe a streched/ loose chain would cause such symptoms, or low oil pressure maybe, bad tappets not letting to fully open the valves maybe? Anyway, the engine sounds normal, no codes regarding to such problems

[LPGC]

What do you mean be 'calibrated to spec'?

If you only drive it on petrol (if you don't switch to LPG at all from a cold engine start) does the same problem of low power still occur?

From memory a common issue with some of these engines is over-sensitive knock sensor circuit designs causing the ignition timing to be retarded causing a lack of power but this is just one potential problem that could cause lack of power.

[Rokassileika]

I mean the LPG and gasoline MAP curves don't look even anymore since i cleaned the reducer. Now that would explain a lot of things with knock sensors. I was thinking about replacing them, but i dont think this would solve this kind of problem since it is over-sensitive, neverthless i had a code related to knock sensors after i drove this car after it was left untouched for about a month. The transmission was working very erratically back then, but after a few drives everything went back to normal. I mean its the ECU who takes care of sensitiveness. Have You ever heard of engine tuning for them? I know it should be possible to correct that, but i'm not sure if anyone does that. Sorry I can't take the pictures for now, working a lot at the moment.

[LPGC]

I'm still not sure if you mean the problems only happen when running on LPG or happen when running on petrol too?

If it drives OK on petrol but only drives OK on LPG at a certain throttle position it points to an LPG problem that causes fuelling to be correct only at that throttle position, which could be a mapping problem, injector problem, etc.

The transmission may seem to act erratically if for whatever reason the engine doesn't make expected torque for a given rpm and throttle position anyway... But besides that both the transmission and engine may act erratically if a component that both rely on to work properly (usually things like throttle position sensor, map sensor, maf sensor) are not working properly.

[Rokassileika]

uploading a photo of LPG part locations. The unconsistant power is on LPG and gasoline, but sometimes LPG feels more torquy than gasoline.

Link: https://we.tl/t-g8ZeGOEJRD

[LPGC]

You can upload pictures directly to your post on this forum but I have downloaded and viewed your pictures.

Seems like the installer has made some effort with the install and fitted 'spuds' (brass gas outlet bits) in a decent location in the lower metal part of the inlet manifold and pipe lengths aren't too long. The Zeta S reducer might be borderline for the engine but overall the install looks OK, obviously we can't see the setup (set pressure and injector nozzle sizes) or calibration from the pics.

Unless the problems running on petrol are petrol injector related (as opposed sensors or vacuum leaks etc) you shouldn't expect to get it running any better on LPG than it runs on petrol. You should first fix the problem that causes it not to run properly on petrol, then move on to setting up and calibrating the LPG system. It is possible that if the LPG system isn't properly set up or calibrated that the mixture can be very different between petrol and LPG and this can cause problems for some time if/when you switch between the different fuels but by running solely on petrol you can rule this out.

As a bit of an aside - Just the other day I repaired the LPG install on a Lexus RX350/400 H (hybrid). It also used a Stag ECU and Zavoli reducer but originally used Stag's own injectors not the AEB injectors. The reducer on this install (with it being a hybrid which has hybrid components fitted in the location where your reducer is fitted) was fitted at the very rear and bottom end of the engine bay just above the engine undertray. I'm not sure where you are or where this one was converted but I wouldn't mind betting yours and this one were converted by the same installer. I've seen the RX350/400H before, a few years ago I replaced the worn out Stag injectors with Baracuda single injectors and shortened the pipe runs between injectors and manifold. On this occasion the 12mm rubber pipe that runs from injectors to reducer had burst where it had rubbed on the antiroll bar (and probably also suffered over pressure), a problem realised due to how the original installer had fitted it and made it rub on the antiroll bar. I also found and fixed broken vacuum pipe between reducer and vacuum T. I used to quite like the AEB injectors, get a couple of good and well matched rails and they're very quick to open and close and well matched in terms of flow, longevity is also good and much better than Stag injectors, the only downsides being they won't flow a lot of gas (so are only good for engines with up to moderate size cylinders and/or low boost) and they're not great at opening when the rail bodies are cold, far better than the slower Stag injectors which always have a few percent difference in terms of flow from channel to channel (but not to the same extent as the later poorer performing AEB injectors). I never liked any of the Stag injectors and went off the AEB injectors after a certain date when it seemed they started to be made with one outlet on a 3 cylinder rail flowing around 5% more than the other 2 outlets.

[Rokassileika]

I just had a thought that my transmission could be shot, leaking the pressure internally.. Every winter when i switch from R to D or vice versa, i get no drive condition in D, i have to put it into N and then again in d to start driving it. Somebody changed the valve body before me to a newer one that hasn't got pressure sensor switches needed. I'm not sure anymore where should i start by now. I've read multiple articles and it was mentioned that it should not impact transmissions functionality. But maybe it has something to do with pressure internally, i dont know anymore. Anyway, I will still upload the journey on youtube with STFTs and LPG injector times when I can.

[LPGC]

Hehe "Just had a thought that my transmission could be shot"... It reads like you've had good reason to suspect the transmission for a long time!

Not sure about your 2007 Camry but lots of vehicles with automatic gearboxes will throttle back the engine or retard ignition timing during gearshifts or if clutch pack slip is detected. Maybe your car feels down on power because it's detecting AT clutch slip and backing off the power.

[Rokassileika]

But the weird part is that it is driving great in summer time, great when there is moisture and just randomly great. And the fact that im having this issue for 3 years now and the transmission is still working the same is driving me nuts! no slippage codes by the way, I only have codes for pressure switches, but it is a known problem when people change the valve bodys that belong to newer model U660E transmissions. And as far as I was digging into this, no one reported this transmission being lazy, slippy enough to lose power. All is known that they stop working out of the blue sky.

[Rokassileika]

Ok so I noted some very important stuff today. Recorded my live engine and transmission parameters after rewriting transmission compensation codes. What I noticed here is some interesting stuff (I will only upload a few photographs, since the recorded files are ~20 minutes long. I will try to explain it here. So when the engine was more to the cooler side STFTs were pretty much the same between the bank 1 and 2 on 56 engine load I was getting enough power- the way the car should pull- strong and good. After doing these stops and go's I noticed that there is a HUGE difference between bank 1 and 2 (adding photos) ~70 engine load there was not enough power- it even felt less than it was with only 56 engine load!!! So my question is now WHAT could be causing such uneven fluctuations between these two banks? Why only on higher loads? Where should I start looking?

[LPGC]

Were you running on petrol or LPG?

First I looked at the fuel trims as they're what you pointed us to. Fuel trims are steered by lambda sensor readings, lambda sensors detect unburned oxygen in the exhaust, if the engine misfires it pumps both unburned air and unburned fuel into the exhaust and this can affect the lambda sensor readings in a chaotic way... the readings from lambda sensors will always reflect unburned oxygen in the exhaust but when there's a misfire we don't know to what extent the unburned fuel and air pumped into the exhaust are burning before they reach the lambda sensor.

Looking at the misfire count, the engine ECU counted 1 misfire between the 2 screen snapshots but the engine ECU might underead or overread misfire counts.

STFT goes up to around +20% on bank 2 at the higher load, often a misfire will make a lambda sensor give a lean reading (but as implied above not always). This does give support to a theory that there's a misfire on bank2 though. But again not necessarily, because from a static screenshot we don't see the transition of the figures or know if engine load or rpm were accelerating - if these are accelerating sometimes OBD readings will reflect momentary higher fuel trim figures on one bank than than the other. If 'transition state' were true we could be seeing a fairly normal high STFT on bank 2 and the misfire could even be on bank1.

Why is coolant temp reading low at 92.7F (only around 30C)? If the engine is supposedly fully warmed up this reading should be higher.
Why is intake air temp reading fairly warm at 95F? I forget where in the world you are.
Why is intake air reading hotter than engine coolant temp? This shouldn't be true.

[Rokassileika]

I was running on LPG. I live in Lithuania so the climate is +- the same as in UK, maybe colder. That is very interesting, I never paid any attention to initial temperature readings, they really look off, but once the car is running they seem to be logical (~55 F intake and 140-180 F coolant). This static picture is taken exactly when the engine was constantly accelerating. I do randomly hear some kind of a ticking noise on bank 2 since i purchased the car. I guess it will be a compression test time for me. Well, maybe ignition coils, but doubt that.. But before that, i've made up a theory in my head, what if it's the LPG injectors? Adding a picture. What if this is caused by under-fed injectors because of their position? Is it just me or doesn't it look like that the bank 1 injectors would have a higher pressure vs bank 2 injectors just because of their location?