Okay, I removed the thunder racing maf, it helped a little. I resetted the pcm and it is ok now so far (about 6 hrs ago). Here is the problem though. If I am in 4th gear, at around 40 mph and push the gas pedal down over 60 percent and jab it kind of, I hear a bad knock. This is not normal. I don't know if this is knock, or something bent, IE pushrod. I have never misshifted...never. Any suggestions would help.

I also have a rough idle, there are no engine mods at all except a FIPK. If I obd2 it, the o2 sensors (bank1 short term) jump around alot. I am not sure if this is in relation to that or not.

If anyone can help I would appreciate it.

Thanks

 

what car do you have, what year, mileage? Could be a lifter/pushrod, need a little more info...

 

I'm gonna assume you've got a Z28 or T/A with the LS1. From what you're describing, I honestly think that the "rough idle" is normal..........the LS1's have a compression ratio somewhere around 10.2:1, which is getting high(er) for a street engine (and FWIW, my car has idled "rough" since day one..........remember, it is a ~300+HP engine.........it's high performance).

The "knocking" you were describing (heard mostly under quick loads being applied) is "pinging", or "detonation" as some refer to it as.................what this means is the timing is too far advanced for the fuel grade being used (or in other words, maybe you're not using a high enough grade of gasoline, ie: using 87 octane instead of 91, or maybe 91 when your car might like 92 or 93 better). If you do experience pinging frequently, switch to a higher grade of gasoline (on a stock engine, that should be able to curb the problem). An engine that has a higher compression ratio requires much higher octane levels, and that's where octane booster and 110 octane gasolines come into play.

I guess there could be a problem with your engine, but if you're saying it's relatively stock, I highly doubt you've got bent pushrods and what-not................the rough idle is normal (well, unless it's really rough, like the engine has a miss or something ), and pinging can usually be fixed by using higher octane gas, which doesn't ignite as quickly.

HTH (hope that helps) .

EDIT: had I read your user name, I would have seen it says "WS6", so at least I know what kind of car you have...........but you've still gotta give more specifics.

 

Yeah, here are some more details. I have a 02 WS6 LS1 m6. It is pretty noticeable under part throttle (over 50%) it seems to knock then go away. I can hear a tap sound at idle if I am outside the car, but honestly I don't know if it is normal or not. I ALWAYS us 93 octane, and have filled up 3 times since, all different gas stations. On my way home last night, I put the car in 5th gear at 50 mph, and jabbed the gas about half way, the car made a loud knock sound, I almost thought it sounded like a spun rod bearing. It did this once then stopped. I have no SES lights though. If anyone else knows anything, please post.

 

Engine mechanical noises don't respond to throttle position.
A lifter / pushrod click will not get louder as you give it gas.
Its load and action are the same at a given RPM, regardless.

Pinging will.

Because it "goes away" pretty quickly, I think you may have
a situation where your "predicted" A/F ratio is wrong, and
you are depending on closed-loop operation to bring it into
line. On a throttle transient the computer has nothing but
the raw calculation to go on, and it gets it wrong (lean)
at first, then refines it. This is the "TRIMs" thing the tuner
guys go on about. If you have the data adjusted so that
the car makes the right calculation -for your vehicle's
particulars- then this might be taken care of. For power
you want the PCM to miscalculate just slightly rich (rich
enough to suppress knock retard). Knock retard may
also be the reason the knock goes away.

One basic cause of problems can be fuel pressure (low).
The pressure regulation is back at the tank, demand
surges and acceleration can result in a significant engine-
end pressure drop. People report 5PSI drops or more.
Out of, what, 35PSI setpoint? That's a 12% mixture error
if uncorrected.

"Tricker" mods like fooling the IAT, dicking with the MAF,
etc. will also induce lean mixture error. The '02s (and
probably especially the WS-6 ram airs) are tuned
pretty right, and have good airflow, puts them in a
place where they don't respond as well to the older
"mixture fooling" mods (and in some cases, respond
negatively).

I suggest that you remove the "tricks" and take it on a
road "teaching trip" where you exercise the mid - to -
WOT for a while, see if it'll learn its way out of its
behavior with proper hardware configuration. The best
way would probably be tuning (pro, or buy your own
gear & software and "track tune"). But this is a long
road. If you did go for the tuning, then you could keep
the MAF ends etc. and get the (minor) benefits of that
little airflow increment.

 

I have removed the maf ends. From what I can tell it is still there. I will remove my FIPK this weekend, and retest with the cleared pcm. I will post my results. Thanks again guys for the help!!

Last night i hooked my computer up to the obd-2 port (I use virtual dashboard, not autotap) and my car's shortterm o2's were all over the place. This is definitely a lean situation, I am suspecting the fuel pump.

 

I sit alot in rush hour traffic, I think that the heat is building up and causing it. However, even 5 minutes later when I get on the highway, it is still doing it. Any suggestions, the stock maf is on, and I filled up with 93 octane.

 

I have a 99 trans am. When I crank my car up in the morning it ticks and by the time I get out the driveway its gone.,This is normal right?

 

Yes it is normal.

 

Good. Thanks.

 

this is not accurately true, in fact, engine TOP end noises will most probably go away or die down @ higher RPMS due to higher oil pressure. and sound worse @ idle. Engine BOTTOM end noises sound (usually) all the time, but get worse as the engine temp goes ^ due to metal expanding, and larger oil clearances. Now the information provided on engine control systems I 100% agree with. Sounds like you have a air:fuel / engine load compensating problem. I say your problem could be a MAF, the ECM might not be getting accurate readings, and using another sensor as it's, it's main point for fuel deleivery, such as a TPS or MAP sensor. I've heard of over oiled k&n filters causing faults, and miss readings on our over delicate MAF meters. Also maybe you have a fault with your tps it's self, since you claim it to be upon acceleration. That usually causes a hesitation, and/or a richer mixture. I say the same, remove any "back yard" mods you've performed, reset ECM and put the car through a relearn process, which takes some driving, it may take you a couple of days, for teh ecm to relearn all the correct values, and the car to return to normal.