1jz with lean miss

[jampac]

I have a 1jz-gte in a soarer that some months back developed a problem of a lean miss which is random, but most of the time its crap. Basically spark plugs are white tipped.

I've replaced all the coilpacks with new ones from toyota. I've replaced the ignitor, changed ecu, tested all the temp sensors (coolant and air) and they appear to be in range of the factory manual. I've tested the fuel pressure and its ok, but it does jump around a little, like a psi or 2, but it was doing this when it ran fine. I've pulled out the injectors to have them tested, to see if they are dribbling/not atomizing correctly (be done within next week). Spark plugs have been changed many times using BKR7E and BCPR7E both gapped to 0.8mm and all 5 sets now have the same lean miss problem. The o2 sensor has also been replaced and the mixtures were tested and idle/lite throttle was around 14.7 mark, and richened up under boost as expected, but still missed, but its random, could give full power, or start missing at 1500rpm with vaccum, its all over the place.

I've only been able to get the car sort of running by increasing the idle and lite throttle timing by 10 degrees using my powermod piggy back ecu, but it still stuffs up eventually, just not as quickly.

Now while pulling out the injectors I broke the wires off one of the cam angle sensors. They were so weak, they just snapped off. Checked the other one and the insulation was cracked around the base of the wire. I'm wondering if this has been my problem all along. Now it gets a bit weird cause the new ecu I have doesn't throw up error 13 which indicates bad cam angle sensors, but the old one does, and over the course of owning the car it has thrown this code at some point or another, then clearing itself, but it was getting worst over time.

Note that I do have a piggy back ecu, but before you point in this direction, problem occurs without the piggy connected. Its actually even worst without the piggy back. At least I could still drive the car around with the piggy back. The engine also has a hks type dli for ignition but this has also been pulled off to test, and problem actually was worst.

So there is 3 things I'm going to try before I burn this car,

1. replace the cam angle sensor wiring/plug with new good stuff (this is proving to be next to impossible as I have no part no. for the plug and no one wants to cut a efi loom up.
2. Test the injectors for dribbling.
3. Test for vac leak, which I've been told could cause a lean miss.

So does anyone have any ideas? Anyone seen a prob like this before? I've shown a couple of mechanics and they all talk shit about the mods being the problem. I'm fairly certain prob is factory related, so I've been targeting this, but have checked aftermarket gear to be sure.

Basically within 10 minutes of putting in new plugs, they are showing as lean miss without even hitting boost or revs over 3000rpm.

[BeRad]

if the a/f is fine it shouldnt be running lean... how did you test the a/f

is the whole end of the plug white? white doesnt just mean lean..

bits of white on the plugs can mean preignition meaning the timing is advanced to much, or that the plug isnt rated for the right heat range for your engine, lack of engine cooling may also cause it.
white sought of spots sometimes mean detonation....
is it white or an ash deposit, if its that valve guide seals may be worn etc....

and are you sure your gapping them right to the engines requirments... usualy if there for the engine there not to far off being what they should be...

[jampac]

It was tested with a wide band sensor on a dyno. Yes whole end is white, no ash.

http://bburgess.customer.netspace.ne...%20(Large).JPG

They should be brown/tan colour.

I originally thought it was fouling, but have been told by a mechanic is lean miss. Yep positive gapped correctly, checked with two different feller gauges, one a professional workshop one as I didn't trust my one.

I've used 7's before without a problem. All the probs started when one of the coil packs blow up and blow the ignitor as well. So near 2 months later I figured out what I needed and ordered from japland and america for the parts, and now its not working ever since.

[BeRad]

have you checked the timing?

how much does the piggy back control...

[jampac]

No haven't checked base timing, as nothing like that should have changed. Piggy back only modifies from what the factory does. So when I say 10 degrees, its 10 degrees on top of whatever the factory ecu is doing.

[camrygt?]

Be carful using the lean bit as part of your diagnosis.

If the engine misses it doesn't burn the fuel air mixture corectly and the engine pushes the unburn mixture down the exhaust causing high O2 and a lean reading on a wideband o2.

I have seen a reputable dyno place advise someone to fit a bigger fuel pump due to a miss that appeared lean on o2 gauge. Replaced spark plugs and it was perfect.

maybe adding some LEDS with resisitors to the primary side of the coils and watching what happens to the pulses as the car plays up might give you some clues

[urantia]

one thing i've always wondered is if the o2 would really register 1 cylinder running lean.

say for exampke the 1jz with 6 cylinders, 5 of them are running beutifally with 1 cylinder running lean. (1 injector might be abit below par)

The overall exuast readings to the o2 would look ok to the ECU?

I suppose if this were the case they'd have moved to having an o2 on every cylinder exuast outlet for individual monitoring.

[camrygt?]

the o2 sensor only really reads the average. bad if you have a leaky injector as it will make the ecu lean out the other 5 cyls. Thats why o2 sensors only have a limited control over the base maps like 10-20%

[jampac]

All 6 cylinders produce the same spark plug colouring so its a common cylinder prob. I can totally understand the miss causing o2 sensor to misread. I was advised this by a friend, but this would mean the prob is just in my plugs. This doesn't make any sense as I used the exact same plugs before and had no issues. Really confused here.

The HKS dli does have an led for spark, but only one for all six, you can see it change with revs, perhaps I can use this, but still wouldn't standard computer throw an error 14 which is coilpack or ignitor failed to fire if the led did actually change in pulse when missing occurs?

[chris davey]

I would check base timing for starters as it is easy. Make sure 100% that what the powermod is telling it to do, it actually is.

I run exactly the same plugs and gap (bkr7e at .7mm) and I have had a very slight miss on the odd occasion but my plugs were definitely not white tipped like yours.

That is all I can think of.

[camrygt?]

I wouldn't trust the fault codes in my experience they don't pick up some problems all that reliably.

[BeRad]

as i said and chris said timing is easy to check and the fact that there the same on all 6 cylinders leads you to something that controls all 6 cylinders with one thing, i wouldnt think about injectors as there is 6 individual injectors, if anything maybe some fuel treatment to see if theres any shit in the system

[thechuckster]

have you tried to put a timing light on the engine to see what the timing is doing? missing and crap performance could be timing way out courtesy of faulty timing sensor (e.g. crank sensor)

zorst popping might be sparking too late and the plugs - dunno, need a manual to refer to first.

does the zorst have an unburnt petrol odour? or some other kind of weird smell?

[Enchanter]

I have seen just recently with a 2jz a problem with the CAS, the "star" that triggers the pulse from the sensor was loose and caused some problems.

In a nut shell I agree with the others on timing being the first port of call here, check the CAS and CPS.

[Maverick]

Perhaps the ecu is crook? i`ve heard of toyota ecu`s leaking shit from resistors (due to age i presume), and thats whats ultimately controlling the show, try swapping with someone to see if thats the problem (if you haven`t already)...