The ECM does an EGR system check at ignition-on. In the older systems with the EGR temperature switch it checks to see if the switch is closed (which indicates hot exhaust gasses flowing through the EGR pipe), which should never happen at ignition-on. Unfortunately GM didn't differentiate between that error and the other "running down the road" EGR problem, so we have to guess which one it is. In this case he gets the SES right away, so we know it's the initial check.

It is my understanding that MAP cars do the EGR test by looking for an change in MAP reading when the EGR valve is opened. I don't know what it checks at ignition-on so I don't know what causes the error. The FSM would probably be the best source of information on this.

 

Well I put a new fuel pump in from racetronix, the pump ran but no fuel pressure and no fuel whatsoever, I removed the new pump hooked power to it and it ran but would not pump fluid out of a container, I then switched polarities and it worked, I rewired the connector that came with the pump and reinstalled the pump and have great fuel pressure 47 psi, I will try and finish everything up tomorrow, Hopefully in time for the Pottsville Cruise.

 

Well everything is back together but I have no power to the fuel pump fuse (10amp) I tried a new relay but no luck, I can run the engine but I have to run power to the pump side of the fuel pump and am getting a code 54 and code 42, I believe when I tried running the fuel pump by using the fuel pump test lead located by the battery it shorted or blew out a fusible link, I tested all the fusible links located behind the battery but they all tested good. I need to now if there is another fusibale link for the fuel pump and where to look.

 

I will start a new thread.

 

I don't understand this statement (the "fuel pump test lead" part). I don't know of anything like that. [ EDIT ] I just found out that the fuel pump test point in the ALDL connector was moved to a test point near the battery in 1990 and later cars. A much better place for it... [ /EDIT ]

There is a short wire from the positive battery terminal that goes through a fusible link and a connector. That lead supplies power to the ECM and the fuel pump (through the fuel pump relay or oil pressure switch). Maybe that's what you are talking about?

The easiest method for turning on the fuel pump (in my opinion) is to remove the connector from the oil pressure switch and short the two contacts in the connector together.

 

I will try that, but if there was power to the oil pressure switch as soon as the engine cranks and there is 4 psi at the switch power would go to the pump. Here is a link to the 90 fuel pump wiring showing the test connector, my guess is there is no power going to the switch, I will do some probing this morning.

https://drive.google.com/file/d/0B5d...ew?usp=sharing

 

Im looking at your Spark Adv on your data log and i see way too much timing adv. I can see over 30* at idle and up to 45* at only 1700rpm. Im not sure how accurate the data log is for timing but u should get a timing light and mark your dampner for at least 45* adv timing marks. Then use a timing light with a reliable tachometer to "map/graph" your timing adv up to 3000rpm (no need to go higher). And u could spot check with just a couple of data points for a look.

Im think something in the timing control looks like adding way to much adv but the data log may not be accurate so u need to check manually w/timing light.

Hope this can help.

 

Don't mean to hijack. But what would cause his timing to be off?

 

We dont know if it really is but the timing needs to be verified manually to what the data log says. Most owners have a timing light and this should only cost him time. If it is high/to adv we gonna find out arent we? Stay tuned.

 

I do have a timing light, it has RPM's and Adjustable Advance, To my understanding corvette L98's have a lot of timing tuned in from the factory. I believe when I checked it in the past with the EST wire disconnected and timing adjusted to 6 degrees, then the EST wire connected, it would run about 22 degrees at idle. Tomorrow I will be using the FSM to troubleshoot a code 42 it has, after that I will look into the timing. On a positive note with the new injectors and fuel pump I put in this week. It does idle smoother but the idle is hunting a little bit and the engine feels rough when exhilarating.

 

Yea when the engine is lean it can handle a lot of adv and i have seen other OBD I ECM data logs with a bunch of advance. But depending on how the rotor is phased to the terminals under the dist cap 45* is close to firing the preceding cyl. Or 30* at idle maybe cause of pre-ignition though i didnt see much for knock counts on your data log. Its just such a easy test for diagnosis that wont cost u anything but time. And the dist is not a completely passive part that cant wear and fail. Reading your thread the problem starting with a disconnected plug wire seems more ignition related than fuel to me.

Looking at your fuel trims i can watch it go into and out of closed loop and it seems to control with the O2 in closed loop - though mostly rich but it does go lean also as expected. Fueling looks pretty good to me or at least i cant see anything wrong. This also looks like a healthy ECM the way its controlling as expected. My diagnose reference say an intake leak would keep the fuel trims mostly lean so im not looking there (doesnt mean it cant have a leak just unlikely large enough to be a problem).
So my guessimate here is if its not in the ignition then it maybe mechanical. Broken vlv spring? Wiped cam lobe? Timing chain or timing set? 185k mi is alot for those parts. I know u have steady vac but did u know compression and vac will actually rise with a wiped cam lobe? The wiped lobe has short duration and intake vlv closes sooner - trapping more charge. Maybe a compression test to compare each cyl could help with that.
But i think the timing adv curve is easiest test here and would start with that.

Hope this helps more than confuses u. BTW this helps me practice diagnose as much as it could help your issue so i hope i dont start any fires here. No flames intended.

 

If there is a vacuum leak you will see the IAC counts go very low or even to zero as the ECM tries to compensate by removing air coming into the engine.

 

I would think code 42 EST Grounded that I have would effect timing so I will tackle that first.

 

Ok I still have Code 42, here is a list of what I read with a timing light.
Idle: 7 degrees
2000 rpm:14 degrees
3000 rpm:15.5 degrees.

That is way off from what the my data logs shows.
Data Log at Idle is 24.61 degrees
Data Log at 2000 rpm is 52.73
Data Log at 3000 rpm is 49.57

Here is a link to data log. https://drive.google.com/file/d/0B5d...ew?usp=sharing

 

In the past my timing on the timing light was in sync with my data log, I replaced the Ignition controle module with a known good one so my code 42 is either a short to ground or ECM.

Note on data log file BLM's will be low I upgrade the fuel injectors to 24# because of planed future build.

 

IIRC, mine was over 7 at idle. Much over. If you set base to 6, all it gives is 1 degree? Someone correct me. What is base without the advance wire connected

 

Last time I checked it was around 22 at idle, so something is wrong, I would like to find someone close by with a 90 to swap ECM's to see if that makes a difference.

 

Buy a Delco or MSD ignition module. Not like you wouldn't use it ever

 

I already replaced the Ignition Module with a known good one made in the USA, I have had it for a wile now and I keep it around for just in case.

 

Im getting confused when i see over 50* adv at only 2000rpm and the knock counts dont change or increase. Dont know how to explain this. But i havent looked at enough OBD I data logs to make judgement.

Just looking at the data log i see the MAP, integrator (short term fuel trim), O2 mV output all switch at the same time and looks like timing adv does to - this is in closed loop when the O2 is controlling. They all move in step which should not be. The MAP follows throttle position and looks ok to me. The short term trim locks onto a steady O2 output. In closed loop the O2 should be swinging. I dont know why i didnt see this before. When was the last time u replaced the O2 sensor? Did u know they are a normal wear part and should be replaced 'bout the same mileage as the tires or brakes?

U can test the O2 by pulling a vac line and allowing a intake leak and u should see a lean output but u need to be monitoring the O2 output somehow - with a meter or datalog or whatever. Next u can use a propane bottle to add propane fuel the same intake leak and watch the O2 output again - it should go rich.

I know im saying 2 things here but i think the O2 sensor is the easier test here than any further ignition tests and overdue for replacement anyways. And i dont have an answer for the large timing adv - sorry. But for an O2 sensor that doesnt swing in closed loop i do - its bad.

Watch'a think?

BTW u need to update the ECM with the new injector constants when u change injectors. Did u do this? That shouldnt make all the variables lock into step though as logged here but something to correct when ready.