Lean Misfires at 2700-2800 rpm

[StealthCRF]

Originally Posted by ProwlerGT

From the engine service manual page 11E-79 (lash adjuster/lifter check procedure:
"3. Remove the small wire and press the plunger. If the plunger is hard to be pushed in, the lash adjuster is normal. If the plunger can be pushed in all the way readily, bleed the lash adjuster again and test again. If the plunger is still loose, replace the lash adjuster.
Caution
Upon completion of air bleeding, hold the lash adjuster upright to prevents the inside diesel fuel from spilling."

Newb to engine internals question: Are the lifters responsible for the compression in the cylinders?

I know the manual says Diesel, but what do ya'll think of cleaning/installing with seafoam for this procedure instead of Diesel? I mean regular motor oil and seafoam (if you put it in the engine for a cleanout) go through them in normal usage anyway right?

TSB-99-11-006 gives the SPECIFIC updated method for cleaning and prepping the lifters. I've done it more times than I can count and it works. Use diesel.

quick edit: has anyone actually taken the valve spings out and checked them for height and proper direction yet?

[badass3000]

I didnt get any yet. Progress this weekend

[DoctorDex]

Deleted my last 2 posts because they were too complicated to make any sense.

[DoctorDex]

Scoped the injectors today and I'm not sure what to make of the findings or if I even found anything at all.

As I'd increase the rpms to the 2600 - 2900 rpm range, the AF would get leaner and the injector pulse widths would gradually increase until the point it would stumble, the rpms would drop, and the injector pulse width would shrink. When I examined a series of pulses I couldn't detect any missed pulses which would explain the sudden drop in rpm. In the end, I was unable to determine whether the injector pulse width was shrinking because of the drop in rpm, or if it was shrinking and causing the drop in rpm.

After running numerous tests, the tech guy I had helping me out thought it must be the ECU cutting fuel. I can't say I'm convinced either way. I guess one way to find out would be to buy a used AEM system and if it doesn't fix the problem, I can always sell it for the price I paid. Now if only I could come up with $1500 for this little experiment...

I think I'm going to try changing the rear lifters first.

Badass: You have an Emanage Ultimate unit right? With that setup can you fully override the stock ECUs injector pulses and can you see the stock ECUs pulses on a log? How are you making out? Have you changed your lifters yet?

[TurboBob]

can you scope the ignition outputs? watch the dwell times.

[badass3000]

Originally Posted by DoctorDex

...Badass: You have an Emanage Ultimate unit right? With that setup can you fully override the stock ECUs injector pulses and can you see the stock ECUs pulses on a log? How are you making out? Have you changed your lifters yet?

to do that with my Ultimate I would have to buy a few extra parts (to avoid a CEL) and totaly rewire. Guess I could tho. sounds interesting.

I have my stock injectors in now so I could be sure it has nothing to do with my bad tune. After a mile or so of driving I didnt notice any missing, although the loss of power still seems to be there. Its actual all the way up to 3000rpm. Its like at 3k someone turns on my VTEC or something. I ment MVEC
Thats why Im still thinking about a *soft* lifter.

[badass3000]

holy sh!t, I was just joking when I wrote that about VTEC, but the more I think about it mabey it makes sense!
I mean what is VTEC/MVEC/NVEC? its a way to open the valves less during cruze to get better gas milage but at a loss of power. If we had an exhaust valve that didnt open untill 3000rpm, then that would exsplain the power loss, possibly the pressure pulses (2 intake valves, 1 exhaust valve might not be able to vent all the gas before it closes and then the intake valve opens).
and we both have a (suspected) noisy lifter(s).

[3000hybrid]

This thread is really interesting. I have the same dayum problem that started last week. The cars weaker than normal until 3K and then it feels normal again. Plus I'm getting 1-3 counts of knock from cruising all of a sudden. You guys have done everything that I would have done or checked from the beginning. The lifter theory does make sense.

[TurboBob]

Originally Posted by badass3000

holy sh!t, I was just joking when I wrote that about VTEC, but the more I think about it mabey it makes sense!
I mean what is VTEC/MVEC/NVEC? its a way to open the valves less during cruze to get better gas milage but at a loss of power. If we had an exhaust valve that didnt open untill 3000rpm, then that would exsplain the power loss, possibly the pressure pulses (2 intake valves, 1 exhaust valve might not be able to vent all the gas before it closes and then the intake valve opens).
and we both have a (suspected) noisy lifter(s).

I have a hard time believing an unstable valvetrain could recover that abruptly and repeatably as the 3000 RPM blast-off that these cars do.

I'm sure its related to the ECU going into WOT/open loop/enrichment mode.

Its quite possible that the coil dwell is increased at that point, thus fixing a weak spark condition.

Bob

[badass3000]

all of last year I was too thinking something electrical, but after replacing every unit/plug/sensor that could be related I have to start looking somewhere else.

Bob, are you thinking that even though we have tried known good ECU's, that our ECUs are still faulty -or- perhaps receaving an improper signal causing faulty results?