1994 Z28 No WOT Power-Datalog
02-27-2017, 10:02 PM
#1
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1994 Z28 No WOT Power-Datalog I've recently learned how to use Scan 94/95 after getting my ALDL cable in the mail for my 1994 Z28 that's been having a lot of issues lately. Is there anyone here that could possibly check out this datalog for me? I know it's a massive amount of data and I honestly don't see how you guys decipher it so easily lol
Well I let it warm up from a cold start then drove it for a few minutes while holding it at certain rpms and gears after making sure it was in closed loop. The car just has no power at all. WOT from a stop feels like it's taking off in 3rd gear and if I stand on it while holding the brake, it won't even attempt to spin the tires like it use to a few months ago. But it's not throwing any DTCs besides a short DTC 16 that popped up while cranking but never came back after clearing the code. (I've been told that can happen from time to time). It still runs, drives, and idles just fine. But it just doesn't have any power if I give it any gas.
All I've been told so far is that the pcm is dumping a ton of fuel into the engine to a point where it could possibly be washing down the cylinder walls.
152,000 miles with no cataylic converter, an airfoil, SLP 160* Tstat, and a Moroso cold air intake are all that I know has been done to the car. Along with AIR and EGR delete.
Im honestly stumped at what to do next since it's not showing any DTC codes. Since I've had spare and new parts from my 1996 Z28 project laying around, I've swapped over the 96 MAF meter and sensor, 96 IAT sensor, 96 ICM, a new AC Delco coil and a new MSD coil wire (old one was arcing badly), and a new driver side AC Delco o2 sensor (couldn't get to the passenger side without having to remove the Y pipe). I also put a new fuel pump in it that holds 43psi with the key on/engine off and will hold that pressure all night long. Along with similar pressure at idle and WOT. So I know it's not a fuel issue. The car also has NGK TR55 Iriduim plugs and Accel Extreme 9000 plug wires done by the previous owner a few years ago. And a Richporter Optispark
Any help would be greatly appreciated. I just want to enjoy this car but I can't because I'm worried it will leave me stranded a 3rd time
https://www.mediafire.com/?er75q5o8ama7hs2
Well I let it warm up from a cold start then drove it for a few minutes while holding it at certain rpms and gears after making sure it was in closed loop. The car just has no power at all. WOT from a stop feels like it's taking off in 3rd gear and if I stand on it while holding the brake, it won't even attempt to spin the tires like it use to a few months ago. But it's not throwing any DTCs besides a short DTC 16 that popped up while cranking but never came back after clearing the code. (I've been told that can happen from time to time). It still runs, drives, and idles just fine. But it just doesn't have any power if I give it any gas.
All I've been told so far is that the pcm is dumping a ton of fuel into the engine to a point where it could possibly be washing down the cylinder walls.
152,000 miles with no cataylic converter, an airfoil, SLP 160* Tstat, and a Moroso cold air intake are all that I know has been done to the car. Along with AIR and EGR delete.
Im honestly stumped at what to do next since it's not showing any DTC codes. Since I've had spare and new parts from my 1996 Z28 project laying around, I've swapped over the 96 MAF meter and sensor, 96 IAT sensor, 96 ICM, a new AC Delco coil and a new MSD coil wire (old one was arcing badly), and a new driver side AC Delco o2 sensor (couldn't get to the passenger side without having to remove the Y pipe). I also put a new fuel pump in it that holds 43psi with the key on/engine off and will hold that pressure all night long. Along with similar pressure at idle and WOT. So I know it's not a fuel issue. The car also has NGK TR55 Iriduim plugs and Accel Extreme 9000 plug wires done by the previous owner a few years ago. And a Richporter Optispark
Any help would be greatly appreciated. I just want to enjoy this car but I can't because I'm worried it will leave me stranded a 3rd time
https://www.mediafire.com/?er75q5o8ama7hs2
Last edited by LT11996; 02-27-2017 at 11:03 PM.
02-28-2017, 11:27 AM
#2
At WOT you are getting about 3 degrees of Knock Retard. Looking at the entire log you have something going on with your Knock Sensor as it is constantly reading a slight amount of Knock Retard regardless of RPM / Load. It's as if the Knock sensor is too sensitive and picking up erroneous noise. Perhaps when the Knock sensor was installed it was Torqued on too high.
You are running very Rich on the Left bank for most of the times. I would check for perhaps an exhaust leak on the Left side .
Just from experience I know you could use a tune to clean things up much more better all round.
You are running very Rich on the Left bank for most of the times. I would check for perhaps an exhaust leak on the Left side .
Just from experience I know you could use a tune to clean things up much more better all round.
02-28-2017, 12:38 PM
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At WOT you are getting about 3 degrees of Knock Retard. Looking at the entire log you have something going on with your Knock Sensor as it is constantly reading a slight amount of Knock Retard regardless of RPM / Load. It's as if the Knock sensor is too sensitive and picking up erroneous noise. Perhaps when the Knock sensor was installed it was Torqued on too high.
You are running very Rich on the Left bank for most of the times. I would check for perhaps an exhaust leak on the Left side .
Just from experience I know you could use a tune to clean things up much more better all round.
You are running very Rich on the Left bank for most of the times. I would check for perhaps an exhaust leak on the Left side .
Just from experience I know you could use a tune to clean things up much more better all round.
02-28-2017, 04:46 PM
#4
If the car had been running a long time with the exhaust leak it would cause the car to run Rich. Now this opens the question as to how long it was running Rich because now your Cats are suspect to being Clogged. I suggest you drop the exhaust before the cats and see if any difference in power
Last edited by FrankieD; 02-28-2017 at 04:53 PM.
03-05-2017, 09:41 PM
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Bump. Could a misfire caused by bad plugs or wires be causing this knock retard? Any ideas would be great. Please help me get to daily driving this thing guys lol
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03-06-2017, 11:22 PM
#8
TECH Resident
On a mostly stock engine, why would he need a LT4 knock module?
His momentary sig of a 1996 vs the 1994 title could confuse things.
Bank one is pulling fuel for some reason. At times during 0 throttle his O2's go dead lean, but I guess that is fuel cutoff for coasting. The majority of the time the long terms for bank 1 are bottomed out...however the bank 1 short trim is still relatively centered, so I'm not sure if you are washing down the cylinders just yet....but I do think you are on the edge. If that short term stops cycling and bottoms out you really do have trouble.
You mentioned it left you stranded.....how did it leave you stranded?
Have you performed a compression check? How do the plugs look? Does it have power when the engine is cold(open loop)? Have you swapped injectors around to isolate if you have a bad injector(all of bank 1 to bank 2 and vice versa to see if the problem switches banks)?
His momentary sig of a 1996 vs the 1994 title could confuse things.
Bank one is pulling fuel for some reason. At times during 0 throttle his O2's go dead lean, but I guess that is fuel cutoff for coasting. The majority of the time the long terms for bank 1 are bottomed out...however the bank 1 short trim is still relatively centered, so I'm not sure if you are washing down the cylinders just yet....but I do think you are on the edge. If that short term stops cycling and bottoms out you really do have trouble.
You mentioned it left you stranded.....how did it leave you stranded?
Have you performed a compression check? How do the plugs look? Does it have power when the engine is cold(open loop)? Have you swapped injectors around to isolate if you have a bad injector(all of bank 1 to bank 2 and vice versa to see if the problem switches banks)?
Last edited by ACE1252; 03-06-2017 at 11:38 PM.
03-07-2017, 09:39 PM
#9
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On a mostly stock engine, why would he need a LT4 knock module?
His momentary sig of a 1996 vs the 1994 title could confuse things.
Bank one is pulling fuel for some reason. At times during 0 throttle his O2's go dead lean, but I guess that is fuel cutoff for coasting. The majority of the time the long terms for bank 1 are bottomed out...however the bank 1 short trim is still relatively centered, so I'm not sure if you are washing down the cylinders just yet....but I do think you are on the edge. If that short term stops cycling and bottoms out you really do have trouble.
You mentioned it left you stranded.....how did it leave you stranded?
Have you performed a compression check? How do the plugs look? Does it have power when the engine is cold(open loop)? Have you swapped injectors around to isolate if you have a bad injector(all of bank 1 to bank 2 and vice versa to see if the problem switches banks)?
His momentary sig of a 1996 vs the 1994 title could confuse things.
Bank one is pulling fuel for some reason. At times during 0 throttle his O2's go dead lean, but I guess that is fuel cutoff for coasting. The majority of the time the long terms for bank 1 are bottomed out...however the bank 1 short trim is still relatively centered, so I'm not sure if you are washing down the cylinders just yet....but I do think you are on the edge. If that short term stops cycling and bottoms out you really do have trouble.
You mentioned it left you stranded.....how did it leave you stranded?
Have you performed a compression check? How do the plugs look? Does it have power when the engine is cold(open loop)? Have you swapped injectors around to isolate if you have a bad injector(all of bank 1 to bank 2 and vice versa to see if the problem switches banks)?
So I had my grandpa come pick me up, came home, grabbed the Accel wire that was arcing and swapped it in place of the new autozone wire, and the engine fired right up and I drove it home. So I figured of course the brand new autozone wire was junk so I returned it and ordered two MSD coil wires. Got them in a week later after letting the car sit that amount of time, only to swap them in and neither one would allow the engine to fire up. Not even with the Accel wire. It would just turn over and over without firing. So then I ordered an AC Delco ignition coil to replace the MSD unit already on it when I bought the car, and that finally allowed it to fire up and run. But it still never regained the power it had before all of that stuff.
The second time was due to low fuel pressure. I swapped in a new 255lph fuel pump and now it holds good pressure at idle, WOT, etc
And no I haven't tried swapping injectors around yet but that is a great suggestion, thank you. I may do that tomorrow.
I haven't done a compression test but I pulled these first two plugs on the driver side just to take a look at them and see what they were
Last edited by LT11996; 03-07-2017 at 10:48 PM.
03-08-2017, 08:43 PM
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Well you know typically it didn't make a difference whether it was cold, warm, closed loop, open loop, it would still have a lack of power. But tonight I cranked it for the first time in two weeks and drove it down the road and back without letting it warm up much and it seemed to have a lot more power. Actually spun the tires and stuff. But I can tell it's still not near as strong as it use to be
03-09-2017, 02:39 AM
#12
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Okay so I just swapped the injectors side to side. Each of them were pretty rusty and nasty looking on the bottom side. I guess that's normal for a 152,000 mile LT1? Also, after swapping them, I propped the rails up on a piece of cardboard and turned the key to ON to see if any were leaking, but none of them leaked.
So then I read on here that to check for an injector not firing, I could unplug one injector while the engine is idling and see if anything changes. If the car idles badly, that means that injector is working. But if nothing changes in the idle while disconnecting one, that means that injector is bad.
So I went through that process on all 8 injectors, and each time, the car idled worse and dropped down some except for when I unplugged the cylinder #4 injector on the passenger side. I went through the process twice, shutting the car off and re cranking it after plugging back in each connector just to make sure that it was firing again. And both times, disconnecting the #4 injector didn't affect the engine at all even idling for another 20 seconds or so.
That injector was originally on the driver side this whole time. So if it hasn't been firing this whole time, could that be a big part of my problem?
So then I read on here that to check for an injector not firing, I could unplug one injector while the engine is idling and see if anything changes. If the car idles badly, that means that injector is working. But if nothing changes in the idle while disconnecting one, that means that injector is bad.
So I went through that process on all 8 injectors, and each time, the car idled worse and dropped down some except for when I unplugged the cylinder #4 injector on the passenger side. I went through the process twice, shutting the car off and re cranking it after plugging back in each connector just to make sure that it was firing again. And both times, disconnecting the #4 injector didn't affect the engine at all even idling for another 20 seconds or so.
That injector was originally on the driver side this whole time. So if it hasn't been firing this whole time, could that be a big part of my problem?
03-09-2017, 11:12 PM
#13
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The driver's side is bank 1, which was where the problem was showing in your logs.
If disconnecting it does not change the idle, then you may have found something. I'm not sure why it would be pulling fuel unless the injector was stuck open at one point. Seems like it's not working at all given your info above.
If you get a mechanic's stethoscope, you can put it to the injector, then listen to see if you hear it opening and closing. You'll know if it's not working...there is a very audible "click, click, click....." when listening to an injector with the mechanic's stethoscope.
If you can, log it...see if the trims are okay on the driver's side now.
If disconnecting it does not change the idle, then you may have found something. I'm not sure why it would be pulling fuel unless the injector was stuck open at one point. Seems like it's not working at all given your info above.
If you get a mechanic's stethoscope, you can put it to the injector, then listen to see if you hear it opening and closing. You'll know if it's not working...there is a very audible "click, click, click....." when listening to an injector with the mechanic's stethoscope.
If you can, log it...see if the trims are okay on the driver's side now.
Last edited by ACE1252; 03-09-2017 at 11:19 PM.
03-09-2017, 11:25 PM
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The driver's side is bank 1, which was where the problem was showing in your logs.
If disconnecting it does not change the idle, then you may have found something. I'm not sure why it would be pulling fuel unless the injector was stuck open at one point. Seems like it's not working at all given your info above.
If you get a mechanic's stethoscope, you can put it to the injector, then listen to see if you hear it opening and closing. You'll know if it's not working...there is a very audible "click, click, click....." when listening to an injector with the mechanic's stethoscope.
If you can, log it...see if the trims are okay on the driver's side now.
If disconnecting it does not change the idle, then you may have found something. I'm not sure why it would be pulling fuel unless the injector was stuck open at one point. Seems like it's not working at all given your info above.
If you get a mechanic's stethoscope, you can put it to the injector, then listen to see if you hear it opening and closing. You'll know if it's not working...there is a very audible "click, click, click....." when listening to an injector with the mechanic's stethoscope.
If you can, log it...see if the trims are okay on the driver's side now.
03-09-2017, 11:57 PM
#15
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I'm going to say around 5%-10% trims are okay. I deal with OBDII, so I'm not sure how that correlates to OBDI numbers. I think 160 is the upper number...128 is the middle..so that is 32 difference.... if the scale is linear then the bottom number would be 96. Doing a little bit of conversion assuming that 96 would be 25% (the max it could pull) that would put 108 at around -15% fuel trim. So...to target -/+10% you would need to be between 115 and 140.
I'll do a little digging through a OBD1 factory manual to see if my numbers are right. I very well may be out in left field with my max and min numbers.
Someone better versed in OBD1 may be able to correct me quicker if I'm wrong.
I'll do a little digging through a OBD1 factory manual to see if my numbers are right. I very well may be out in left field with my max and min numbers.
Someone better versed in OBD1 may be able to correct me quicker if I'm wrong.
03-10-2017, 12:10 AM
#16
TECH Resident
'94 service manual is telling me that the long term fuel trim data range is 0-255...which surprises me. I was thinking it was 96-160 so.....I've got some homework to do. It does confirm that 128 is 14.7:1. Numbers below 128 pull fuel(rich) and above 128 add fuel(lean).
The manual lists the normal range for the long term fuel trims between 118-138. So, I was not far off the mark with my 115-140 guess.
The manual lists the normal range for the long term fuel trims between 118-138. So, I was not far off the mark with my 115-140 guess.
03-10-2017, 12:13 AM
#17
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I appreciate all your advice. I think the highest I remember seeing was 190. I'll go back outside here in a second and run another Scan94/95 log. In that program, all you can really do is monitor stuff but it does give you the option to reset the IAC position and reset fuel trims. Should I try resetting the trims and see how they read? Or would that have negative effects
03-10-2017, 12:19 AM
#18
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Resetting the trims would not be a bad idea. Leaving them will not hurt either. Either way, the PCM will adjust to what information the O2s show. Attached is an excerpt of the '94 manual that I've been reading with the typical data values and ranges.
03-10-2017, 12:37 AM
#19
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This may help as well. Has some good suggestions on what to check when dealing with a rich condition.
Looks like 108 and 160 are when the DTCs for rich and lean(respectively) are set.
Looks like 108 and 160 are when the DTCs for rich and lean(respectively) are set.