davebalkevitch

I have a 93 Firebird.
LT 1 Motor. After the car warms up it has a slight Miss and
if you put the pedal down it will spark knock and it lacks power
I Have replaced the IAT Sensor, IAC, coolant temp switch(front of water pump), fuel filter, New Plugs, Wires, MSD Coil, Hypertech Chip, 160 temp TSTAT, knock sensor, Air Foil. It did this before I added
and changed stuff... thought this would help. Car only has around 125,000 miles. The previous owner ran 3 tanks of 87 Octane.
Cat conv. is empty also. I use 94 Octane gas and added marvel Mystery oil and B12 Cleaner.
After about 7 min it starts acting up. If you ease the gas it's better.... after about 2500 to 3000 rpm it totally clears up and is all power.
If your driving 70 in OD and step on the gas.... hesitates, spark knocks. If you drop to 3rd and the rpms are raised it's better. still has a little hesitation.


Would this be O2 sensor or Dirty Injectors,?
I get no codes and has been on a basic scanner and no trouble codes.

Please email me at davebalkevitch@yahoo.com
for your suggestions..
Thanks,
Dave

pcgamer4life

Chances are, if it's bumping your timing down, then you've got real/false knock. Any exhaust leaks, or more likely, lifter ticking? Same problem with my car... lifters tick + exhaust leak = bumping timing down like 26 degrees under WOT. If knock sensor is bad, it'll throw a code probably, so I doubt it's your knock sensor. You could get an LT4 knock module, which might pick up less of the knock, or just buy an AKM cable and tune it out like I did, and I'm dealing with the lifters this weekend and putting headers on this summer.

Stl94LT1

Can't use an LT4 KM in a 93.

pcgamer4life

That's right, older PCM, missed that part. Guess tune it out, or find the source of the knock.

davebalkevitch

How do you adjust Optispark timing on a 93?

The car has no power when it spark knocks.
When you give it gas no power and spark knocks.
Had Exhaust checked. No leaks. Exhaust leak will not lose power and
do all the hesitation

Thanks
Dave

Stl94LT1

The timing is adjusted through your ECM by tuning. I would find the cause of the timing retard before changing the stock timing.

pcgamer4life

Unless your 93 is different than any other Lt1, its possible that it could. Your knock sensor is like a pseudo-microphone, it determines if there's any abnormal noise (typically a ticking by lifters, which can sound very similar to an exhaust leak) and it retards timing accordingly. So exhaust leaks are often a cause of that. But you had yours tested, so obviously that's ruled out... probably a lifter clicking.

davebalkevitch

I have 2 noisy injectors. number 2 and 4
would that cause the knock sensor to do that?
Can I delete the knock sensor? I will check the lifters.
I have some 1.6 roller tips to put on....

pcgamer4life

You can have it tuned out, or tune it out yourself. But unless you know exactly where it's coming from, I wouldn't tune it out. I don't think injectors would cause enough noise to trigger spark retard.

Injuneer

You say you get "spark knock". Did you determine this by observing knock retard with a scanner, or did you actually hear a knocking noise?

davebalkevitch

I heard the Spark knock and when it does the power lacks....
When the car is cold for the 1st 5 min...........
Nothing... Runs Perfect......Put the pedal to the floor.... no issue........ Car Gets hotter........... step on it.... no power and spark knocks...........
Ease into the pedal slow........... runs smoother....... no knock..........

after 2500 to 3000 rpm... engine clears and runs fine.............
shift gears........... anything under 2500 no power runs bad...........

so My thoughts were ign module or maybe O2

Also............ going fast............. back off the gas to slow down..........
a little popping........... maybe needs valve adjustment?

Cleaned throttle body and such....
ran injector cleaner but haven't checked fuel pressure or volume yet.
next on list

pcgamer4life

Ignition module is a possibility, but it usually either goes or it doesn't when it warms up... there's not a lot of inbetween there. You can take it to a parts store, and have them check it. Make sure they run the test 4-5 times, to allow it to heat up (which is when they generally fail, when hot.) As for the O2, I'm not sure if that would cause it or not.

Not sure why within the first 5 minutes it doesn't do it when you punch it, but if makes sense if your lifters are ticking or something that it would do it under load.

If you can physically hear a knocking under the hood, though, that's the problem. If there's an audible knock, your knock sensor is going to pick it up and say "Eh, something's wrong... I better retard the timing to keep the motor from exploding." And it will retard your timing accordingly. Not sure why you're so concerned with other options (ignition/o2) if you can clearly hear a knock or tick or ping or whatever while you're driving.

davebalkevitch

the knock is the spark knock that I hear in the car.
No rod knock. I hear the spark knock under the load...
When it spark knocks there is no power in the car.
Lacks horse power when the issue happens.

Injuneer

If you can hear spark knock, you have a serious problem. The stock tuning/knock sensor allows the PCM to pull up to 15-degrees of ignition advance, to eliminate knock before you could even hear it. If pulling 15-degrees of timing isn't enough to eliminate audible knock, there's a big problem somewhere, with the potential to damage the engine.

davebalkevitch

I am hearing the spark knock because Something is causing the
ECM to advance the timing while driving it.
If the ECM wasn't advancing so much it would not be lacking power and
spark knocking. spark knock is the noise.... but The POWER is LOST when it spark knocks.... Something is making the timing advance......
That's what I am trying to figure out.
Had it on the Sun machine..........
O2 Has good numbers, Fuel Pressure and Volume are great. EGR working,
All sensors were reading good even the ign. module. ect....... On the machine.... under a load......... give it gas slowly it's fine.... Step on it.... timing advances to far and have the spark knock....
if you ease into it ... it is not there.

Maybe Intake leeak or bad valve adjustment?