Stephen68

Hey everyone, here is some new data logs i just did today. Can someone please take a look at them and give me any feedback or suggestions and let me know if there is any problems...My brand new LT4/LT1 is running like crap.....

GaryDoug

Seems like the knock counts are rising almost all the time. Then going way up on acceleration.

Stephen68

GaryDoug, what would or could cause this to happen as i did see that while i was running live?

Thanks!

GaryDoug

I know next to nothing about tuning, but do you have the correct/best knock module for your setup?

Stephen68

Gary, i just got to thinking when you mentioned the KS....This LT4 block i have came from a 1996 Corvette that had been burnt. When i purchased the motor i noticed that there had been a couple other sensors that had melted from the previous fire. I never thought to swap the KS from my 95 LT1 block after my rebuild lol. This could be causing me some problems...Whats your thoughts?

GaryDoug

Like I said, I know very little about this but I did just notice this topic:
https://www.camaroz28.com/forums/par...module-884088/

Ask around about this.

Stephen68

Gary, i misunderstood you a second ago, your speaking of Knock Module, i was speaking of Knock Sensor lol. Would me having a LT4 Knock Sensor in my 95 LT1 make any difference or is the Corvette Knock Sensors and the LT1 Knock Sensors the same thing?

Injuneer

A 96/97 knock sensor for an F-Body - 100 Kohms - would set a code if used with a 94/95 PCM, which is expecting a 4 Kohm sensor. To my knowledge there is no LT4-specific knock sensor, just like there is no difference between a Y-Body LT4 block and a Y-Body LT1 block. But the Y-Body has dual knock sensors, as does the B-Body LT1. I don't know what the impedance of the 96 Y-Body knock sensor is, but I think it is 100 Kohms.

Increasing knock count means nothing if it is not accompanied by knock retard.

Very busy but I'll try and look at the logs.

Stephen68

Thank you Fred, much appreciated sir!

Injuneer

Looked at the first one in your list. Lot's of problems.

Knock retard all over the place. This seems to be a response to incrementing knock counts, but not in all cases. When you have opened the throttle and increased RPM, the knock count increases from 34,000 to 65,000 with only two minor retard numbers in individual frames. The problems are occurring with the throttle closed.

Right after the knock count field reaches it's maximum limit (65,536), and resets to "0" the problems start. Here's a case where the knock counts stay at 360, but there is knock retard reaching more than 6 degrees, and then tapering off.

I wish I understood what GM does in the knock count field. As you can see, knock counts can increase dramatically without producing knock retard, and knock retard can occur without the knock counts increasing.

Retard also appears to be a response to the right O2 sensor going dead lean (

Injuneer

This is a continuation of the above.... for some reason it truncated my paragraphs, and even after I edited and retyped them, it doesn't show up.

Retard also appears to be a response to the right O2 sensor going dead lean (less than 200mV) for an extended period of time - up to 8 seconds. The sudden lean condition causes the idle speed to drop and it appears you blip the throttle to keep it from stalling.

Something appears to be intermittently dumping air into the exhaust. It's not an injector (electrical) fault since no fault code. Could be a mechanically sticking injector. Maybe a sticking valve. Don't know what else would cause that.

No knock sensor code. But probably wouldn't hurt to measure the resistance of the sensor. Connector off sensor, measure ohms from the single pin on the sensor to a good block ground.

Stephen68

Thanks very much Fred, i appreciate and value your input sir. One last question...With the above problems mentioned, would that be enough to cause my car to smoke constantly and smell like fuel or exhaust fumes very strongly?

Injuneer

I see you provided a lot more detail on the problems you are having in the new post on LT1 Engine Tech. Probably would have been a good idea to provide that info in this thread. If you have excessive oil in the combustion chamber, it can cause knock.

Check the vent line from the throttle body to the passenger side valve cover. Could be full of oil. If so, it's a sign that the rings are not seated. Make sure your PCV valve is operating.

What make this engine an "LT4" other than the LT4 HOT cam? The LT4 had some weird "twisted" piston rings to control flutter, and prevent some problems they encountered with the rings sealing.

Next, I looked in detail at the second log in your list (170913). I has a huge number of blank lines of data, and a lot of lines that are corrupt, with totally erroneous/impossible values. Sometimes the corrupt data results from RFI interference from the ignition system. But why the blank lines? Are you shutting off the engine during the logs, and then restarting it without starting a new data log? In any case, the problems with the log prevent me from using my normal numerical analysis via Excel to look for issues.

Maybe Gary can look at that log to see if he can discern why there are so many data errors, why there are void lines (if you aren't shutting the engine down). For all I know, the PCM is not well.

However, there is the problem of huge amounts of knock retard, some relate to the increments in knock counts, others not. Nothing new here.

And the problem with slow response of the O2 sensors is even worse in this log. There are cases where the Left bank sensor hangs up at very rich values for 6 or 7 seconds. Or both sides hand very lean for 6 or 7 seconds. I wonder if you are fouling the O2 sensors?

The end result is you have a mild case of "split BLM's". Do you have an aftermarket throttle body? The LT4 HOT cam should not have enough overlap to cause split BLM's. Has the PCM been tuned for the cam?

Stephen68

Fred, as always thank you sir for your input. This block is out of a 96 Corvette is why i referred to it as an LT4/LT1. Basically just a 4 bolt main from a Corvette but with regular LT1 heads and internals. As for the blanks in my data log there was a couple times that i did in fact shut the motor off without starting a new log, I was actually adjusting my rockers, sorry. If you would please take a look at the attached bin file that is supposedly custom tuned for stock heads and the lt4 hot cam, the timing looks strange to me but i am new to the tuning aspect of this. The motor in question is like i said, a 96 lt4 block with lt1 heads and internals. Stock MAF, stock TB with long tube headers and no cats into a Magnaflo cat back. Stock injectors, stock air intake, upgraded springs and an Accel ignition coil. I will check the PCV hose and PCV itself. Again, thank you for all your input sir and if you want i will delete my other post as to not confuse anyone.

Injuneer

I'm not a tuner, at least not with the LT1 PCM. I switched to an aftermarket system 16 years ago. I can look at the timing in the data logs to see if it appears to be unusual.

Are the LT1 heads stock or ported?