Whats the easiest way to save and post an eehack file. I can save and load an eehack file but if I just click on the file without loading it, it wont open. I guess it has to be zipped after that?
Thanks..

 

Take the EEDATA file and ZIP it. In Windows, this can be done by right-clicking the file, going to "Send to," then "Compressed (zipped) folder." Then attach the ZIP to a post here using the Manage Attachments button.

You can open an EEDATA file by double-clicking it, and then when Windows asks you what program to open it with, point it at the EXE for EEHack.

 

hopefully this works..

 

I checked it on my phone and it appears to have worked; at least, there’s an EEDATA file inside the ZIP.

once I’m home from work I’ll try to load the log and see what’s up.

 

I appreciate it.. thanks

 

Okay, had a chance to look at the log. Couple of things I noticed that stood out to me.

1. You have MAF System Failure listed in the log. This could indicate the MAF is on the fritz. Once this error pops, the car should switch over to Speed Density mode, so it shouldn't affect the car...unless the MAP sensor is bad as well, but it usually isn't.

2. Your TPS doesn't appear to be properly returning to 0, or you have a nasty habit of keeping your foot on the accelerator pedal when idling at 0 MPH. To properly engage DFCO and idle code you do need 0.0% TPS. If the problem is that you keep your foot on the pedal, stop doing that. If the problem is that it just isn't returning to idle properly, adjust the part of the throttle cable between the ASR and the throttle body. There's a little button on the cable around the middle (near the ASR module) that allows you to adjust the length. Adjust it so that you read 0.0% TPS on EEhack, but so that there's enough tension that pressing the pedal will move the throttle blades. Basically, you don't want slop in the cable, but you also don't want the resting position to read anything over 0.0% for any reason.

3. Your O2 sensor readings do not match. Your right O2 sensor reads a much narrower range than your left, and during open loop operation your right bank reads way richer than your left. Your right bank reads almost stoich, while your left bank reads almost dead lean. Both sensors are properly fluctuating in closed loop (which is why an error hasn't been thrown), but their readings do not match, and that's strange. Either you actually have an imbalance in your engine's fueling, or you should consider replacing your O2 sensors. To find out which this might be, you can try a cylinder balance test. First, as stated above, make absolutely sure that your throttle cable is adjusted so that the TPS reads 0.0% when your foot is off the accelerator. Then get the car up to operating temperature and leave it idling in park or neutral. Once it's idling, connect with EEHack, click the "Tests" button, then click "Run Test." This will then perform a test to see if any cylinders are operating differently from the others (by dropping them out of service and checking the resulting change in RPM). This is a test you can go ahead and screenshot.

4. The computer is commanding 550 RPM idle but you're only getting down to about 830 RPM. Let's start by fixing that throttle cable to make sure you actually get into the proper idle cells. After that, the usual suspects are vacuum leaks (especially the hose going to the charcoal canister, the one that passes by the blower motor on the passenger side at the back of the engine bay, and the hoses coming off the passenger side of the throttle body, and the hoses going to the cruise control unit on the driver's side of the engine bay, and the brake booster hose), and a bad IAC. But I'm not convinced the IAC is bad; it seems to be reacting correctly to ECM commands. So let's do the easy ones first.

Also this isn't a problem necessarily...but your car is running really cold. I'm surprised. Intake air temps are around 30C, but your car barely cracks 90C when operating. It's so cold that neither of the fans come on at any point. It's warm enough that you get into closed loop and such, so that's fine. Is your car actually running this cold? Have you changed something related to fan operation, like made the fans run all the time rather than being controlled by the PCM?

 

1. The maf failure was caused by me. I had unplugged it and plugged it back in while it was running just prior to recording. BTW, the engine basically runs the same with maf unplugged. Hooked up eehack again after clearing codes and no maf failure code occurred.

2. Adjusted cable etc etc.. With just the key on and eehack connected, the tps seems to work perfectly. Always ramps up smooth and always returns to 0 with gas pedal. However, when you start the engine, the tps bounces around from 0 to 1. something. I think sometimes it even hits 2. It has a new tps on it so I tried the old tps which I replaced because it had a crack in it. Anyway, the results were identical. I also turned out the idle stop screw all the way and that changed nothing either.
Remember, my problem is a high idle with some surging. With the idle screw all the way out, (meaning throttle plates as closed as possible), I'm still getting 1500 rpm at idle in park. It goes down to about 1100 in gear with brake.

3. When I first hooked up eehack I did the cylinder test. If I recall, they were all 27. something. I believe they were all within .3 of each other. Tried to do it today and got a message that test cannot be run because throttle is not at zero. (tps)

4. I've checked all the vacuum lines several times. I have just blocked them off at the source to test. (at the intake) Nothing really changes anything. Even pulling the lines off the engine, it still runs the same. I found no leaks. I also did the brake cleaner thing.

Thanks again man.. Much appreciated.

 

Okay. So first, makes sense on the MAF thing. And as I mentioned, unplugging it shouldn't change the way the engine runs--because it will switch over to running like the 92-93 Corvette which didn't include a MAF. Good to know that's working correctly.

As for the throttle, you still have a problem. It may not be related to the surging issue, but you most certainly have a problem. The TPS being at exactly 0 is what the PCM uses to enter the BLM idle cell and use the idle code (and some DFCO stuff). You got that error message in EEHack for a very good reason, namely that it's not actually reading a fully closed throttle. Something is wrong there and needs to be fixed, or the idle functionality in the PCM just plain isn't going to work as intended.

When you state RPM, are you looking at EEHack or are you looking at your dashboard? If it's the latter, the tachometers on these old cars have a known habit of reading way too high. It can be corrected, but it's not really worth the work. EEHack however displays actual RPM as read by the PCM, so there's that.

If your lines aren't an issue but you're still getting surging, it makes me wonder if you have a serious intake manifold gasket leak or something. Perhaps why your left bank reads dead lean in open loop. I know you said you did the 'brake cleaner thing', but I mean, if the throttle plate really is closed, and all the vacuum sources are blocked off...you'd need a pretty good source of manifold air to make the engine rev up like that, and doing so would lean out the mixture. It really does make me wonder if the odd reading of your two O2 sensors isn't that one sensor or the other is failing, but is rather that one bank really is running differently from the other.

 

As I said with the throttle, the tps worked flawlessly with just the key on and hitting the gas pedal. Always to 0 when the pedal was released and no variance. I also held the throttle closed to see if vibration was causing the variation off zero while running. It still bounced around. Is that possible pcm? Do you think I should try a 3rd tps?
As for rpm, the eeehack file I posted shows the car at idle at the beginning and its running between 12 and 1300 rpm. I guess we'll take that as accurate. Its high..
I agree that it seems to be a vacuum leak somewhere. For ***** I just went out and blew away another can of brake clean to see if I missed something. No change in rpm. Is it possible that the intake leak could be pulling air from the crankcase? I have a receipt from the previous owner that the intake gasket was replaced a few years ago. I also checked the bolts and they were pretty tight for the most part.
My fear of course is just chucking parts and labor at this. So far I've only bought a tps and a iac sensor. if you go back on this thread, theres a bit about the iac that I find baffling. I still think somethings up with the pcm. Maybe it has to do with voltage when the engine is running. Gauge shows 14.7v

 

The PCM is not bad. Let's just get that out of the way to start.

To see what's going on with the TPS, adjust the cable so that there's way too much slack. Then start the car and see if the TPS reading still bounces around. It shouldn't.

If it does, and two different TPS do the exact same thing, it seems to me like the throttle plate itself is fluttering when the engine is running. Again, on a properly-functioning car, the TPS will read exactly 0.0% in EEHack regardless of whether the car is running or not as long as you have your foot off the accelerator pedal and the throttle cable is adjusted properly.

So again, while it may not be directly related to your surging problem, it's still a problem, and absolutely needs to be looked into.

The 94-95 PCM is incredibly sturdy; they don't fail unless they get bricked by an owner flashing them improperly, and I haven't seen one spontaneously fail without being torn apart first. Just sitting there in the engine bay, they do just fine.

I do agree that chucking parts and labor at it is a bad move. Engines are air pumps. There are a limited number of ways that this symptom can happen. So let's just correct one obvious problem at a time and see where that takes us.

 

I'll try adjusting the cable but I'm pretty sure it won't matter. As for the throttle plate, I held it closed and the tps number still fluctuated on eehack. Its just not an easy one..

 

I adjusted the throttle cable. I even ovaled out the holes on the tps for more adjustment and the same results. With just the key on, you actually have to move the pedal a bit of a distance before tps goes off zero. With engine running a bit, it just starts going off zero by itself.
Did a cylinder test. two cylinder read 19.1 and 19.3. The highest cylinder was 20.7. Is that Ok?
I went to the control part of eehack and checked the override and steps box in the idle section. The idle did drop to its target. Around 800. First time I ever heard the engine idling normally lol... However it still had its little surge or miss. Does that idle tool tell if the iac is working? What is eehack doing to change the idle? After removing laptop, idle went back to its normal high. So, nothings changed. Here is the last file after a short drive and after adjusting the tps and throttle cable.

 

No screenshot of the cylinder dropout test? The test results aren't included in an EEHack log file, so I can't see the results just by opening your log. But as long as all the cylinders were that close (you only reference three above), it's fine.

EEHack overrides the IAC position to change the idle in the Control section. So that confirms your PCM is fine (again), and your IAC is probably fine. There is something mechanically wrong, and it's something so wild that the electronics are having a heck of a time trying to correct for it.

Your TPS not going to zero is still a problem. As I've already said multiple times, it may have nothing to do with the surging, but the throttle plate should be able to be shut, and the TPS should always read zero when there's no pull on the throttle cable. If there's no pull on the throttle cable and you're reading anything other than 0.0%, you have a problem, and you need to figure out what it is. I can't get my hands on your throttle body, so I'm afraid I can't help much there.

But hey, as an experiment to rule out the TPS itself, you could always just remove the TPS from the throttle body and then start the car and see if the reading jumps around. That won't test the actual TPS--but it'll test the electrical connections between the TPS and the PCM.

 

I tried it again. When in the control idle section the eehack is changing the iac to 15. The iac normally runs at 60 at its high idle. Do you know what a normal iac count should be at idle?
I tried removing the tps. It just sits at 5.5. Remember, zero is after you turn it a small turn counter clockwise to install it. I'm clueless as to why its going over zero when the engine is running. I have no discernable slop on the throttle plate linkage. I dont know.. thanks for helping anyway.

 

Okay, so remove the TPS and hold it at the zero point yourself then. See if the TPS reading jumps around. Again, we're not trying to diagnose a bad TPS, we're trying to see if there's something wrong with the wiring between the TPS and PCM. If you can hold the TPS at '0' and it reads 0.0%, then that rules out the TPS and the wiring between it and the PCM. That then leaves the actual throttle plate assembly itself as the culprit.

Normal IAC for the LT1 is considered to be around ~30 at fully hot idle. Less than 160 on cold startup.

 

I'll try that with the tps. I had a thought. I think I have an exhaust leak on the pass side between the ex manifold and the pipe. Could that have any effect on anything?

 

It could explain the odd O2 sensor readings, but it shouldn't affect the engine in a way that would cause surging.

 

The tps acts entirely different with just the key on vs the engine running. Very predictable with just the key on. When the engine is running, its hard to keep it on zero. It wants to jump a bit just like when its installed. I've ordered another.I just have to try another before I take all of the time cutting up a wiring harness. The wiring harness looks fine btw. The tps seems to have a feedback loop or something when its running verses with just the key on. Are you sure its supposed to stay on dead zero at idle? When I held it at zero the engine still ran the same. No idle drop or anything.

 

It is absolutely supposed to stay on dead zero. 0.0%. You can see this in the current BLM cell when logging; 0.0% is a different cell from greater than 0.0%.

Best of luck. Like I said many times, it may not be related to the surging problem, but it is still a problem that must be addressed.

 

I need all the luck I can get! lol..

Update... New throttle body, new tps.. Checked all grounds on the car. (as best I could) I cleaned up a few of them. No luck. Tps still likes to dance around 0 to 2 when the engine is running. Perfect with just key on. So, heres a guy that seems to know what hes talking about in regards to tps. Do you know if I can use the eehack flash program and do what this guy is talking about as far as raising the tps threshold?
As always, much appreciated..

" Ground plane issues. Very common on older cars like 98 fbodys. You know you have this issue when you log tps voltage and see a difference between car off and car running. For example you read 0.65 key on not running, start the car and without the throttle ever being moved it jumps to 0.69. I some cases adding and/or moving grounds can help this. Ive seen this problem resolved on f cars from putting the two ground eyelets back on separate bolts after a lazy installer put them on the same bolt on the back of the head. There is a reason Gm took the time and money to have two separate attachment points. To separate digital and load bearing grounds.

Basically its comes from variations or float in the ground voltage of the system at varying points due to to flow. It changes because running you have all this flow taking place, alternator charging, coils and other devices drawing. Turning on the head lights can make a difference. While most things wouldn't notice a variance in 0.02 volts, a tps will. This is why most sensitive sensors have there own ground path back to the pcm, where the pcm references the 5v signal of the sensor not from system ground, but that leg to fight such problems, But internally many of the "seperate" grounds still tie to together and interfere with each other.

Regardless, sometimes there is nothing to be done about it short of rewiring the whole car. Especially in the professional environment when you have limited amount of time to tune a car. The only solution to the problem tune wise is to raise the max tps % the pcm will qualify as "zero". This is done in the throttle follower airflow table. Basically if the follower is not active, the ecm treats the throttle as closed and all idle air flow pid controller and timing routines are allowed to operate. If look at the table you will see the first few cells are zero. If you have a tps problem, take the highest tps youve seen with the throttle closed, lets say 2.1%, and make the table zero past that point, say all the way to the 2.5% cell. This will let the car control the idle properly again. But this can create other problems, especially if youre not actually fighting a ground plane issue, so do this as a last resort."