I've got a 94 Z28 stock with hooker catback and an electric cutout. It's got 133k on the odo, and it hasn't run right since the day I got it. Brand new plugs, wires, fuel filter, and ignition coil.

Now on to the problem, it's really random when it does it... but usually it's either high rpm (4500+) or when you stomp the gas at any RPM. In the said situations, the motor studders, hesitates, bogs, whatever you want to call it for anywhere from 1-10 seconds before it either catches and takes off, or I let off the gas. For example, getting on the interstate, hitting the on-ramp at about 45mph, and then punching it up to 70 or so. In another situation, you can be sitting still... in park, neutral, or in any gear, and hit the gas and it studders/cuts out. It sounds/feels like it's not getting enough fuel or air, but I'm not sure. On top of that, I get terrible gas mileage, around 12-15 mpg highway or city, and the over-all idle is poor. Sometimes it idles high (1100+) and sometimes it dips down to ~400 and almost stalls out.

I'm at a complete loss here, and I just pulled 3 codes off the engine, 83 (TCC code --- reverse lockout? Sometimes I can't shift from park to reverse) Also, code 32 (apparently EGR --- so i think it might be part of the problem) and a 61 (AC low charge, which would explain why my AC blows hot all the time... but I rarely use it)

Any help would be greatly appreciated. I recorded a lengthy log with freescan if anyone is brave enough to sort through it and analyze the data! Thanks.

http://www.mediafire.com/?9csmisg41lg

 

DTC 83 can be the TCC a solenoid fault if you have an A4. Its a problem with the reverse lockout solenoid if you have an M6. Since you mention shifting from "park" to "reverse" can we assume its an A4? If so, the code has nothing to do with being able to move the shifter from park to reverse.

Why not put the tranny info in your signature?

DTC 32 is no flow on the EGR system. Shouldn't make any difference in the kind of problems you have, since EGR isn't used above 3,500RPM or at WOT.

 

Thanks for the reply, Injuneer.

For clarification, it is an A4. I suppose the TCC = torque converter clutch... if so, would this cause abnormally hard shifting? Usually from 1-2 I either notice a rough shift or a delayed shift. Not enough to give me back problems, but it gets rather annoying. However, that's the least of my worries.

Also, the problem isn't always above 3,500 rpm. Sometimes it's at idle and you blip the throttle... or at any RPM and you hit it. It's pretty sperratic and strange... if at all possible, could you (or someone with any/equal qualification) take a look at my data tables from FreeScan... I glanced over them for a short while, but couldn't spot anything bluntly obvious... then again, I've never looked at any data tables before, so I don't really know what to expect. Thanks again!

 

I downloaded it, but its a huge file and I've got several others in front of yours.

 

Oh don't worry about it... I noticed you have a 'dummy's guide' to analyzing some data tables... though it's not FreeScan, I'll take a look at them and try to learn what I can. Off hand, do you know of any other free resources for learning?

 

In line 2283, your MAP hits 100 kPa at 700 rpm and only 43% throttle, which I've never seen before. Also, at that point, you have 3* of timing and it doesn't get much better for WOT.

It's been a long time since I've messed with a stock tune, but I'm almost positive you should not have ~25* of timing at WOT at 4,000+ rpm (as shown in line 2321). Now that I look at it, I'm noticing the immense amount of knock retard you are getting. It seems you are getting it in a lot of places, especially WOT. Then, you go WOT again and the timing starts looking good, but falls off again (referring to line 2379 where you have 31* of timing). Once again, your losing your timing due to knock retard.

Line 3367 shows 2* of timing and then 7* when you to WOT in line 3375.

Lines 14123-14130 (just scrolled to the bottom because of the hugeness of the log ) have some messed up timing as well.

I take it your coolant temperature reading is in celsius? If so, the car is running 220-230* F the whole time. That's way too hot and can cause spark knock. I believe the stock thermostat is 185*.

Have any clues on why the car is knock retarding? Loud muffler? Bad gas (or 87 octane)? etc. I did this quickly and probably missed some things.

 

Thanks a ton for the input! I'm runing an original temperature thermostat, but it's new as of about 3k miles. I've got hooker catback with cutout, and when I did those runs I think the cutout was closed so it wasn't too loud. Any ideas what could cause these problems? And I've never seen the temperature gauge pass the halfway mark... so I'm not sure. Gas shouldn't be bad, and I'm running super, however the tank was about 1/4 full when I did the log. I am going to fill up today and throw in a can of fuel injector cleaner and see if it helps. Anything wrong with my o2 sensors that you can see? 133k, presumably stock O2 sensors, and horrible gas mileage (14mpg)

 

Looks as if the O2's are behaving correctly (they're cycling). Your poor gas mileage might just be from having to push the car so hard, because it's not running at full potential. Your coolant temperature is shown from 101-109*C (which translates to 214-228*F). If that's not matching up with the gauge, then one of the sensors is off (sensor for gauge is in driver's side head and sensor for pcm is in the water pump). You need to determine if that knock is false or not. I bet the car is a dog; you'd definitely be able to notice if you had that extra 10* of timing advance back at WOT.

 

Is there any way to test either of the sensors, I wouldn't be surprised if the gauge is reading incorrectly.

How would I determine if it's false knock or not, what would be symptoms? How might I go about getting this problem solved? Is it possible to tune out the knock, would I have to replace the knock sensor/module?

 

http://shbox.com/1/4th_gen_tech2.html#ect

To test the temp sensors.

 

I couldn't imagine that it is true knock with the car running as little advance as it is, but there a couple of ways to check to see if it's false:
1. Purchase some high octane fuel (100+) and mix with gas. Then, see if the knock retard goes away. If it doesn't, the KR is most likely false.
2. Use TunerCAT (or whatever tuning program) to pull timing out of the areas where it is pulling the timing. If it doesn't affect the KR values, most likely it is false.

You can tune out the knock sensor by zeroing both of the knock retard tables. I wouldn't necessary recommend doing that just yet. You need to locate the source of the knock and fix it. I would first run through and make sure the knock sensor is in check.

http://shbox.com/1/4th_gen_tech2.html#knock_sensor

Then, check for banging exhaust, noisey engine components (loud pulley, whining alternator, etc), anything that can cause noise that the knock sensor would perceive as 'knock'.

 

Well my engine is pretty noisy, sounds like clicking from under the valve covers... so lifters maybe? I really don't know. No access to high octane, so that's out. I've never used TunerCAT, though I do have it (the free trial). I guess I'll check the sensor using shoebox's tutorial sometime when I get.

What do you mean "pull timing out of the areas where it is pulling the timing?" care to elaborate on that? Drop the timing in when it's too high/
Other than a noisy valvetrain, I don't think I've got any other unneccesary noise. Like I said, hooker catback which is moderately loud I guess, but not too bad. I've got a cutout, but it was closed on this log. Thanks a ton for your help!

 

A noisy valve train is plenty enough to cause the PCM to pull timing. You may want to look into issue if you can figure out whether or not this knock is true or false.
Well, what the car is doing is it's pulling (retarding) timing when it is sensing the knock. What I was suggesting is you find the areas where the PCM is pulling the timing due to the knock, go into TunerCAT, and retard the timing in those areas (matching RPM and MAP of the knock retard). If you do this and the knock is true, you'd see less timing being pulled by the computer (because you already took it out of the program). I don't know if your familiar enough with TunerCAT to do this or not. Does this make sense?

Or, you could 'disable' the knock sensor (see method up above) and actually listen for the car to spark knock. You can also check the spark plugs, because those will give an indication of detonation.

I'd get the EGR fixed while you're at it. Either that or use block off plates and get rid of it.

 

Getting rid of it sounds like a better idea, rather than spending $50 on a valve that presumably hurts me. Would a single block-off be all that I need to delete the egr system? Would I have to remove anything else, or would blocking off the valve be all that I need to do?

For clarification, I've never even opened up TunerCAT, only recently got the ALDL cable and FreeScan, and figured I'd download the TunerCAT free trial. When I get enough time to play with it, I'll look into it.


As for noisy valves/lifters/whatever, how would I go about correctig the issue? If it involves pulling the valve covers, and replacing any components, I might as well look into a set o roller rockers, right? However, I know there are supposed additives that can quiet noisy lifters, think that would be worth a shot? And if not, can you perform simple adjustments to fix the situation? I know these are all vague questions for the situation, since I really don't know where the noise is coming from.

 

Do you have emissions testing? If you don't, the only other thing you would need to worry about with removing the EGR (which doesn't hurt you if it is operating correctly) is making some tuning changes. Here's a link to a set of plates (there are 3 holes that must be blocked off), which is all you need to remove the EGR:

http://cgi.ebay.com/ebaymotors/93-97...QQcmdZViewItem

Another thought is to pick up a used one from someone. There are tons of people that remove their EGR setups, even with them functioning correctly, that would sell their's to you for hardly anything.

For correcting the valve train noise, I'd first start by pulling the valve covers and making sure none of the rockers feel loose. There's not a whole lot that can go wrong with the stock rockers, but putting 1.6 rr's on will only help the performance of the car. If you do this, I will suggest picking up an LT4 knock module so that you aren't picking up false knock from the increase noise of the rr's. You may need to inspect your lifters to make sure they are pumping up (possible problem if the rocker is loose and the bolt is tight). You can also listen around with a mechanics stethoscope to try and pin-point the source of the noise.

If you haven't even opened up TunerCAT, I wouldn't suggest going in a dicking around with your tune. It would be very easy to destroy the engine if the wrong adjustments are made to the tune. Just steer clear of the tuning stuff (as far as using it to fix your car) for now. If my computer wasn't in storage, I'd help you out.