Forcing PCM to run diagnostics?

I just bought a scanner/logger from www.obd-2.com. The only problem is I did some work on the car and had the battery unhooked and now the SES light isn't on any longer and there is no history of any codes when I check with this scanner. Also using this scanner and going into enhanced mode it only shows misfires for cylinders 1,2,3,4,7,8...yet is shows a misfire history for all 8 cylinders. Is there a way to force the PCM to run some diagnostics so i can tell what the problem was? I am trying to diagnose this problem...located on dyno graph below:
http://www.daporkchop.com/host/dyno.jpg

I've already changed to an MSD coil recently and bought OVC Taylor wires and new plugs...not sure what is going on.
Any help would be greatly appreciated.

If this is a pretty dead sensor/device then the problem should show up at next startup, like an O2 reading lean. If the probably only shows up in closed loop then wait for closed loop (2-3 minutes or so), if its an exaust leak or something you will have to wait to drive it around more to try and duplicate the problem.

Oh ok...well I have a new cam on stock tuning and the SES light came on all of a sudden but then I unplugged the battery to put in a new coil and the SES light went away. I bought this scanner to track the problem but now it doesn't say there is a problem...besides not seeing misfires for cylinder number 5 and 6 and the weird dyno result. So there pretty much isn't a way to force the PCM to go through some diagnostics then?

If there is a way to do it with OBD II I sure dont know about it, but maybe there is? If there is it likewise may only be a GM thing, so far as I know though it is all real time diagnostics, drive it and if you have a problem it will set a code. This would be no different than it trying to do a diagnostics test really, since it is monitoring sensors at all times, in closed loop and most of them in open loop as well (MAP, etc).

I thought that losing codes with OBD II was more difficult than just unplugging the battery, but perhaps I'm mistaken. For OBD I though, if you unplug the PCM_BATT fuse or the battery you lose the codes.

Your SES light may have been over something "stupid" like HIGH MAP or something, which means that the car is running like crap due to timing (mostly), at low RPM and is unexpected at idle...? Somethings things like this can happen and you may never see the SES again for a long, long time.

I see the cam in your sig now, that will definately need some tuning, but at least the gears will help you out greatly. If your not on the LT1 Edit list yet, or have a reliable baseline tune to play with yet, I'd suggest getting on the list and looking for some help.

Damn I just bought this scanner and now its kind of useless...although it did show me some knock at high rpm and the problem with not registering cylinders 5 and 6 in the misfire...could that be because I didn't make the wires for the plugs correctly...is there a way to test the spark plug wires? My car isn't making the power it should. Thanks for your help Dr. Mudge....where in the bay area?

I'm in 94080, so I'm about 35 miles from you, http://maps.lycos.com

You can test plug wires with an OHM meter for continuity/resistance, if you actually routed them wrong (I've done it) the car would really run badly, and just about not run especially with your cam. Are you confident the chain was put on right? I helped someone not long ago with a Hotcam, and asked if he put the cam/crank gears at 6/12 and made sure they were lined up, what it came down to was us popping the cover and it was off by a tooth, then he said "oh, well I thought that was close enough", a quick guess says thats worth 8º or whatever (count the teeth and you could figure it out) of slop which is

ALOT, the car barely ran and it sounded like a NASCAR cam. Also, since your OBD II you have that CPS which I dont know alot about, but the gears being off or maybe something to do with the Opti would not help things out. I hope you passed smog recently because you wont want to do it again any time soon :)

You'll have your hands full with low RPM stuff now, dont worry about WOT for awhile, especially since you dont know how the car is running, it would not be fun to nuke the engine due to fuel or timing problems.

I'm hoping I put the timing chain on right. I'm not going to lie I did "accidentally" move the crank a little after I took the chain off but I put it back to where I last remembered it was. If I didn't it wouldn't run correctly nor would it make 302 rwhp, correct? But I do have that high rpm miss. The car runs pretty good and has a little cam surge if I let off the gas at say 1200-2000 rpm but I try not to do that. I'm just trying to figure out what would cause that high rpm miss. Oh and I won't need to do smog till '04, I think...I'm hoping to make friends in the smog industry ;).

The key is to have checked with the gears on the car, if you moved the crank/cam gears a little its no BFD at all, but you really needed to see if they lined up before you put the cover on. It would be pretty obvious if they didn't line up at 6/12, there is a fair difference between dead on or not, so it could be 10º or something, dunno.

You should hit 340-350 RWHP with stock heads and running right, you do have headers right?

Work on low end first is my opinion, just like knock, once it starts it will effect everything thereafter until you let off the gas, poor running low end doesn't usually make for a spectactular transition to full throttle either.

How did you fit your NSA rockers under the covers, are you using Vette covers or something? I cutup my LT1s as a temp solution and those suckers leaked, bad idea.

Oh ok now I know what your talking about. When I put the chain back on it was lined up perfect(6/12). If you look at the dyno sheet its fine at first but at about 4500rpm+ it goes haywire. Plus the torque isn't anything to brag about. I'm guessing I might of made a couple of the wires wrong (5 and 6) cause they're not showing up on the scanner. Would the car still run fine if 5 and 6 weren't running? Thanks again for answering all these questions. Oh and I do have SLP 1 3/4 shorties on the car.
Oh and I also cut those metal tabs out of mine....leak a little, nothing to worry over though.

It should run pretty cruddy if 5/6 were not hooked up, I dont know how to explain that one. Plus working with OBD I I dont get to see stuff like that.

Did you run a wideband setup or did you just strap on for 3 runs?

I believe it was wideband as well since they checked afr. I was running good till about when the car start missing and it dips down to around low 11's. Waiting for the OBD-2 version of Tunercat to come out so I can tune cause LT-1 Edit is pretty expensive. I don't drive the car daily either.

No kidding its expensive. I heard TC for OBD II was going to be available this spring (heard that a year ago), I hope they can live up to that but I really have no idea.

Why not just go OBD I? If the car is running that rich at least you wont blow it up though probably, but thats going to put a ton of carbon buildup in there.

I don't want to switch over just in case they swap smog over to where they just hook up to the PCM. That way I will still have my PCM and might have a way of passing. If I did swap and they brought the new smog then I would have to buy TunerCat for OBD-2 anyway and well too much money spent. I don't see you having a mod list for your car, besides the 240Z link...I still have my 280Z, not running though.

I know what you mean, but at least the car would run right for now instead of carboning up, even a stock car with an exaust leak can look pretty nasty very quickly. I would hope that you would spend $20 for a definition file, and they would send you a new FLSHREAD/PROG and not charge you for it, but I've never talked to them directly about it.

I'm not big on making webpages, and I hate big 1/2 page sig files with every little mod like ported and polished blinkers, neon wiper blades and etc I ran a heads/cam car with SLP shorties, Non SA Pro Mags, Cmolly pushrods (still have those), 30# SVOs, jumped on the dyno and made most of my power by the 2nd or 3rd run, even basic tweaking cleaned it up in a HUGE way and it was like driving a different car. I made 411 RW.

The 240 has an N33 intake, N42 head, dual 32/36 DGVs (probably going to change soon), and a couple suspension mods, steel brake lines, 15x7" wheels etc I am pretty sure that I'm going to throw a 2.8L turbo in it, and sell my spare F54 flat top, and 2 N42 heads, one of them is ported. I was looking to make nice NA power but the thought of 27 MPG and 300 RWHP just picks at my brain in a huge way, if I run race gas on the track I wont have to worry about heat, because I didn't want to spend $900 on an intercooler either, I will do what ducting work I can though to cool it. On the street a single or dual GN intercooler should get the job done with no problems, I dont drag and I wont hardly be in boost long enough to overpower the ICs on the street. This way I can go with a 3.54 rear and stay in the gears longer on the course, instead of my 3.90 R200 that I have now for an NA car.

So, lots of good things with a turbo setup.

I'm saving for some heads now...are yours stock ported or different heads? 411 rwhp...nice, 400 rwhp is my goal. My 76 280Z is stock and slow...last I remember. You got some nice running cars from what I can read.

Ported stockers from my 94, and the cam would not pass smog without serious work. I am considering going with some AFRs and maybe a stroker in the future, I really have little idea what I'm going to do and I suffer from indecisiveness ;) I have 2 cars to work on and 'hop up' now which is also going to slow things down and force me to prioritize, I like the 240Z for its road handling abilities, but I'd also like to get some serious road stick on the Camaro too, because driving a 240Z all the time just about makes you clausterphobic, so I miss the land cruiser every now and again.

Have you emailed Tunercat about an ETA on OBD II stuff? I'd be curious to hear whats doin over there on that end. If you every go OBD I though I'll always be around to help, there are fair number of folks in the south bay also, and some Fremont guys.

I forgot to mention the early 5 speed in the 240Z, I want to try to hunt down a late model NA 5 speed, its a close ratio and has a much nicer .745 5th gear. Right now the car runs a mid 15, but I dont drag it myself, the guy I bought it from is a gearhead as is his dad. The dad is a tool and die guy, with a couple 240Zs, one of them with about 400 HP with a T5.

A guy in Sac just ran a 12.07@ 119 with a stock LS1/T56 setup, no posi!

Originally posted by sherwinZ28
Also using this scanner and going into enhanced mode it only shows misfires for cylinders 1,2,3,4,7,8...yet is shows a misfire history for all 8 cylinders.....


Are you saying that the scan software shows the total misfire count for all 8 cylinders, but it only showing a misifre code for all the cylinders except 5 and 6?

Or are you saying that it has a field for total misfire count for all 8 cylinders, but there is no data registering in the space in the data fields for 5 and 6? If its this one, call the company that sold you the software and ask them to look into it. Seems to be a bug in the software.

"not making the wires up correctly" can cause a misfire, but it isn't going to cause the misfire data to disappear from the PCM. The misfire data is generated by the PCM based on the spacing of the signals from the crank position sensor. No way a poorly made wire is going to fubar the crank sensor. That's why if you are getting data in 6 of the fields, and missing data in two of the fields, it may be a software bug.

Can you watch the misfire counts and see if they start to mount up right at idle? If so, that would indicate a problem with the low load cam programming.... the idle will be too choppy, and it will continue up in the rpm range at low loads.

Well there are fields for misfire like this:
Misfire Cylinder 1
Misfire Cylinder 2
Misfire Cylinder 3
Misfire Cylinder 4
Misfire Cylinder 7
Misfire Cylinder 8
Misfire History Cylinder 1
Misfire History Cylinder 2
Misfire History Cylinder 3
Misfire History Cylinder 4
Misfire History Cylinder 5
Misfire History Cylinder 6
Misfire History Cylinder 7
Misfire History Cylinder 8
So I was wondering why there weren't any fields for 5 and 6. I emailed Alex Pepper but no response yet...I emailed 2/8. I thought maybe cylinder 5 and 6 weren't firing or something...just looking for a way to explain whats going on with the car from the graph in the first post.
There are a few misfire counts but very rare...very very rare. It just goes something like this:
Misfire Cylinder 1 0
Misfire Cylinder 2 0
Misfire Cylinder 3 1
Misfire Cylinder 4 0
Misfire Cylinder 7 1
Misfire Cylinder 8 0
The History field still shows 0 for all cylinders though. Also I am getting a lot of spark retard like 12-20 degrees at idle and much higher at higher rpms say 38 degrees or so...why? The car does run fine though and I haven't had any problems beside the high rpm miss...at idle it is usually fine if its warmed up. Idles at about 8xx(from the scanner) but shows up as 1000rpm on the tach...I noticed its off by a few hundred(the tach that is). Also is there a way to update how fast this software updates the screen...is freescan or autotap this slow as well. It takes about 15 seconds or more to update the data...the virtual dashboard becomes pretty useless.

Freescan lets you select latency, I think Datamaster does to but I dont like it, so I dont really use it. However of course there is a limit to how fast things can be. Even on my 486/25 MHz, with Freescan I'd get about 1 frame a second which is WAAAAAAAAY slow. OBD II is faster than OBD I, so I'm puzzled that your getting a frame every 15 seconds? Thats pretty much worthless for tuning, even 1 FPS is not going to cut it in my opinion.

4 frames per second starts to get workable (subject to each cars power level/setup and user opinion), but to some degree the more the better.

The more input I'm getting the more I'm thinking about just returning this product and switching over to OBD1 and using TunerCat and FreeScan. My laptop is a pentium 166 running NT so I doubt thats what is slowing it down. It did show 11degrees of knock retard when I did a WOT run but it said the knock occured at 2280 rpm...I don't think it was correct because of the slow frame update. I will wait for a reply from OBD-2.com before I make up my mind though. I just didn't want to lose OBD-2.

I sort of see what you mean, and I dont know the book on swapping over, but it doesn't seem like that much of a hassle.

As for smog, some guys that are doing the PCM checks just shrug and let you pass, I dont doubt that may happen as well as it may not last very long, who knows at this point, if and when it comes. By that time though hopefully something will be out, but I really am supprised you expected the car to run decently on a stock tune ;)

Thank goodness we have knock sensors eh? :)

I had various computers with Freescan, and with my P233 that I had with Winders 98, I believe I was getting 5-6 FPS, which was plenty fine for me to work with. I didn't run the lowest latency either, just standard 100ms. While the OBD II port is faster, I really dont know how much more data is coming through, certainly not so much though that you get 4 frames a minute, thats obsurd. Thats a question for the LT1 Edit list, this forum is still pretty much the dead area of the site.

How do I get on the LT1 Edit List?? Seems you are getting lots of info from there.

I am not on the list anymore, but yes there is tons of info. There are various subscription options, you can read via the web or get it in digest mode (one or two big emails intead of individual).

www.lt1edit.com