When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I GOT A 1995 Z28 M6. CAR WAS SUPPOSEDLY STOCK WHEN I GOT IT.
OKAY SO CAR HAD A BLOWN HEAD GASKET. I GOT TO PULLING ENGINE OUT AND PUT IT ON A STAND, REPLACED OIL PUMP, PICKUP SCREEN, TIMING CHAIN, LIFTERS, INJECTORS WITH BOSCH IV 24LB FLOWED AT 3 BAR (43.5 PSI), LONGTUBE HEADERS, OFF ROAD Y-PIPE, NGK TR55IX PLUGS, OMNISPARK PLUG WIRES, SUMMIT RACING OPTISPARK (HAD GOOD REVIEWS). ALSO TRIED 3 AUTOZONE OPTISPARKS AND RUNNING ISSUE STAYED THE SAME.
I DELETED EGR AND AIR PUMP AND DID NOT REINSTALL EVAP PURGE VALVE. ALL I HAVE CONNECTED VACUUM WISE IS OPTISPARK, BRAKE BOOSTER AND FUEL PRESSURE REGULATOR AND PCV VALVE. EVERYTHING ELSE IS BLOCKED OFF.
I HAVE TESTED FUEL PRESSURE AND IT IS FINE WITHIN SPEC OF 42. WOT IT JUMPS UP NORMAL. ENGINE VACUUM IS AT 10" HG. PULLED PLUGS AND THERE ARE FULL OF BLACK SOOT WHICH MEANS CAR IS RUNNING RICH. DID A COMPRESSION TEST ON CYL 1 & 2 AND I GOT BACK 220 LBS. I HAVENT TESTED THE OTHER 6 CYLINDERS.
ANOTHER THING TO NOTE IS THE HEADERS TUBES GET HOT BUT RANDOMLY 1 OR 2 WILL GET COLD AND THEN ANOTHER 2 TOTALLY DIFFRENT CYLINDER WILL GET COLD.
NEW TPS SENSOR, IVE TRIED UNPLUGGING MAF SENSOR AND ALL THAT DOES IS ALLOW IT TO IDLE MORE STEADILY BUT AROUND 950-1200 RPM IT JUMPS AROUND EVEN WROSE WITH MAF CONNECTED.
NEW ICM
NEW COIL
NEW O2 SENSORS
IVE TRIED 2 DIFFERENT PCMS
IVE TRIED FLASHING A STOCK TUNE TO CAR.
I TRIED FLASHING A CC306 TUNE I FOUND ONLINE AND NO CHANGE.
IN THE VIDEO BELOW I HAD A 02 WHICH WASNT READING BUT I HAVE SINCE FIXED THAT AND DIDNT HELP.
I HAVE ALSO SMOKE TESTED THE INTAKE AND FOUND NOTHING OTHER THAN THE INTAKE ELBOW LEAKING WHICH I HAVE REPLACED ALREADY AND NO CHANGE.
I HAVE A ALDL CABLE AND ALL SOFTWARE REQUIRED TO DATALOG OR FLASH AND READ PCMS. I OWN A AUTOMOTIVE SHOP AND OUT OF THE 3 MECHANICS WORKING HERE NOBODY HAS FIGURED IT OUT ON OUR FREE TIME. I HAVE ANY TOOLS I MIGHT NEED. I ALSO THINK IM WAY OVERTHINKING IT AND IM JUST OVERWHELMED AND FUSTRATED BY IT.
I believe I've responded to this on ltxtech.com, under the name “91TransAmGTA”.
While the Bosch Gen IV injectors are stated to flow 24 #/HR (factory programs I've looked at actually use 24.9 #/HR for stock injectors) in another post here you indicated they have are “faster” and have “shorter response times”. That detail would seem to suggest it would be critical to program the correct injector offsets. Unless the PCM knows they open and close faster, it will still be setting injector pulse widths based on the slower stock injectors. That would result in the engine running rich, forcing the PCM to use the long term fuel trims to lean it out. You indicate in the post on the other site that “blm is at 112 at idle for both banks”. That indicates that the idle cell (16) is subtracting 7.8% off the normal fuel supply, and your plugs are still showing rich.
What are the BLM's (LTFT) in the other cells?
Stock program target idle speed, fully warmed up with the M6 is 800 RPM. What are your IAC counts? If they're bottomed out at “0” and still can’t reduce idle, either the IAC is not responding, or the engine is getting air from some source other than the throttle body.
The engine vacuum that I suggested you check is only 10” Hg. That's only 1/2 of normal stock cam vacuum. Did that improve any with your two attempts at getting the valve adjustment correct?
I need to look over my data log, i did today while driving car. It started bucking super hard but would clear up with more throttle. But was still missing. It threw some codes as well. Seemed intermittent though. Car sounds like it has a cam no doubt about it. Engine vacuum never changed when adjusting valves stayed around 10” average entire time. Iac counts bounce from 55-90 while its idling. Also i cannnot get it to idle with the maf connected
i have a guy looking over data log and tune i have on car. Im getting knock retard of about 9-10 degrees. And knock counts climb up into thousands. I logged it with eehack.
no intake leaks exist. Ive smoke tested it twice and nothing.
i got these codes while the bucking occured. Seems to me a intermittent wiring/connector issue.
while data logging i had MAF unplugged due to it not wanting to stay on.
Knock count is somewhat meaningless. It is a field that starts at “0” and appears to sometimes increase for actual knock or sometimes reasons other than actual knock. Appears to increase under conditions that might produce knock. The number continuously increases, so you could see numbers in the 60,000’s, resets to “0” when it reaches ~65,536 which suggests that it is an 16-bit field) even with no knock and no knock retard. The absolute value is not important, it is how fast it is increasing that matters. Not unusual to see it increase a couple thousand when the starter is cranking the engine.
Actually, there's not much more happening here than on ltxtech.com. I'm the one trying to keep both sites from dying. Otherwise the LT1 is “old news”.
Looking at a freeze frame of your video, the engine has been running for 237 seconds (206 seconds is the norm for entering closed loop) coolant temp is 185°F (above 140° will usually enter closed loop) but the O2 sensors appear to be “stuck” at ~450mV. They aren’t working. As a result the PCM isn’t going into closed loop.
I think in the other site I recall you mentioned something about disabling fan #1 in the program. Why did you do that? It appears to be setting a code (DTC 77) for the relay control circuit, so it isn’t “programmed out”. Did you just remove the relay for some reason?
DTC 51 indicates an EEPROM Programming Error. That could explain a lot of the problems if it's an active code rather than stored.
Did the MAF code set because you unplugged the sensor, or is that code there with the sensor plugged in? The video shows 471 (GPS?). That's a typical default with an open circuit.
Something wrong with the PCM's failure to pull the IAC counts down when the idle speed is above the 800 RPM target.
That scanner video shows a major disaster. Where is the log file you claimed you posted? What did you use to log? Is the file in .csv format?
My Formula had a moderate custom solid roller cam 230/242 114LSA 0.590 I / 0.590 E and it didn’t sound that wild. Guy who bought the car bumped the cam up to 253/261 109LSA 0.684 I / 0.681 E and it still doesn’t sound as wild as yours. I still think there's something wrong with the timing or the plug wire sequence.
Looking at a freeze frame of your video, the engine has been running for 237 seconds (206 seconds is the norm for entering closed loop) coolant temp is 185°F (above 140° will usually enter closed loop) but the O2 sensors appear to be “stuck” at ~450mV. They aren’t working. As a result the PCM isn’t going into closed loop.
I think in the other site I recall you mentioned something about disabling fan #1 in the program. Why did you do that? It appears to be setting a code (DTC 77) for the relay control circuit, so it isn’t “programmed out”. Did you just remove the relay for some reason?
DTC 51 indicates an EEPROM Programming Error. That could explain a lot of the problems if it's an active code rather than stored.
Did the MAF code set because you unplugged the sensor, or is that code there with the sensor plugged in? The video shows 471 (GPS?). That's a typical default with an open circuit.
Something wrong with the PCM's failure to pull the IAC counts down when the idle speed is above the 800 RPM target.
That scanner video shows a major disaster. Where is the log file you claimed you posted? What did you use to log? Is the file in .csv format?
My Formula had a moderate custom solid roller cam 230/242 114LSA 0.590 I / 0.590 E and it didn’t sound that wild. Guy who bought the car bumped the cam up to 253/261 109LSA 0.684 I / 0.681 E and it still doesn’t sound as wild as yours. I still think there's something wrong with the timing or the plug wire sequence.
i didnt disable the fans. they work, im guessing the code is from the fan relay being triggered on with ignition power. i have it wired that way.
i have a .eehack log file. i dont know if you can read that or how do i convert it to .csv
MAf code only sets if i unplug it. Never sets if i have it plugged in but with it plugged in i cannot get it to idle or run at all.
Oxygen sensors are brand new Walker brand from oreilly. but they have extension harness to reach on the longtube headers, can the extra resistance cause this
The O2 sensors either aren’t warming up, or have an open circuit. The PCM supplies the 450mV reference voltage, and it doesn’t change until the sensor thimble reaches about 600°F. That's how hot they have to get in order to work. At that point the sensor starts adding voltage (rich) or subtracting voltage (lean) from the PCM reference voltage.
Im working with Strong Speed Works, Hes working up a tune and im datalogging it for him, its getting better, car is cammed afterall, he said he could tune it without me having to pull cam and check specs. only problem im getting now is car is stalling and wont stay running when it enters closed loop, and car acts like it been shut off all random with any throttle. like a bucking issue. i got code 42 the other day. i do have a oreillys icm in it. should i put back the gm one? i changed the pcm and flashed it with strongs tune and it still has code 42 and bucking.
DTC 42 sets when the PCM detects 84 crankshaft revolutions without any ICM activity. That DTC only sets during cranking.
At this point, your tuner should have the data log required to analyze the problems, and he should be able to figure out whether the ICM needs to be replaced. There's not much more I can do at this point.
Out of curiosity, did you address the problems with the O2 sensors? You seem to be ignoring my input.
I found my o2 extension wiring had got cut when the starter housing broke in half, i replaced the extension harness and now the o2 sensors go to something of 730 mv around there when in closed loop and they move around they arent stuck anymore.
04-13-2023 | 03:11 PM
