Engine Missing

[tomtom72]

Originally Posted by c4zr1

Here are the codes I think I got when I did the A B pin cross
Code #34: Manifold Absolute Pressure Sensor Circuit Low - High Vacuum.
Code #42: Electronic Spark Timing (EST) Circuit.
Code #44: Left Oxygen Sensor Circuit Lean.
Code #54: Fuel Pump Circuit (Low Voltage)
Here are the codes I think I got when I did the A G pin cross
1. C12 9. H72

Where do I go from here?

Hi, I thought I would try to share some thoughts.

1. the EST code could be from a PROM ( MEMCAL ) not seated fully. You swapped chips & it might be worth a look. Unless some one disconned the DIS box connector and going back on they had it upside down. That will bend a pin on the box and give a 42...ask me how I know that one!

2. MAP low volts/high vac. Take a look and see if the MAP hose has oil in it, even the MAP itself can get oil into it and if it does it will simulate high engine vacuum. Our motors pass a bit of oil vapor from the PCV system into the plenum and then it can get into the MAP hose and sensor. Also, the MAP hose can get soft and collapse under engine vacuum and give the same code.

I would, after checking the MAP & hose and the PROM seating, disconnect the battery for a minute or two to clear the codes and start her up and see what there is to be seen. Not trying to be a wise guy. It's just sometimes multiple codes throw me for a loop till I remember to start with the lowest number code. Stupid Q: do you have a FSM? FWIW, two tools that I rely upon with this car are my scanner & software pkg and my FSM. Best money I spent besides Marc's chip!

A senior member ( Jerry, our VP ) told us when you get multiple codes that don't seem to be related start with the lowest number code for the diagnostic procedure.


Tom

[c4zr1]

Tom,

Where is the DIS box connector? I am new at diagnostic stuff on my car. I do not know what all of your lingo means. I have not had any trouble with it since I have had it. I think it is from lack of driving it. I am going to start driving it more.
I do not have a FSM? FWIW, scanner & software pkg.
Tell me more where is the best place to get these things?
I will start with your advice. I have looked at the hose to the MAP and it has not come off. I think it has a small zip tie on it. I have not looked to see if it has oil inside of it. I will also check the prom again.

Thanks!
Don

[tomtom72]

Hi Don

Okay sorry for the "lingo"

FSM = Factory Service Manual, it's a set of three books, or at least it was when I bought mine. Try this link:http://www.helminc.com/helm/homepage.asp?r=
These guys do GM's printing so they have the real stuff. Try to stay away from the Motors or Chilltons versions as they leave stuff out sometimes.

You will eventually need a scanner. I bought mine used on e-bay. The important thing is that you have to get the right software with any scanner or else it can't talk to your car.

MAP hose with a zip tie is not such a good thing. Our MAP hoses are supposed to be blown off in the event of a misfire when a start attempt is performed. Usually our LT5's back fire if we don't hold the key over in "start" position long enough for the motor to actually run. If you let off too soon it will back fire. The hose blows off to save the MAP sensor from damage. The zip tie on yours makes me suspect that the hose maybe oil soaked or soft or both. The OEM hose is made up from a hard small plastic bent line section that has two preformed rubber connector ends. The MAP hose can actually be taken apart into it's three pieces, plastic hose & two rubber ends.

Okay, so none of this trouble with you seeing any trouble codes & an SES light started till recently, after a long sleep? Just another fwiw, our electronics package is a power hog. If the battery has weak cell or cells it sometimes drives the ECM crazy....usually it wont start or crank but there is the odd chance that low cells upset the ECM. I bring my battery back every 3 to 4 yrs & it always tests "marginal" so I get a warr replacement. Sorry for all this stuff. I'm trying to think & write fast so you will not think we are leaving you flat!

Check the chip ( PROM ) and take a good look at the MAP hose for softness and or oil fouling. Let's start there..oh, forgot after you check that stuff do the disconn on the negative cable to clear the codes. Drive her and see what happens with the SES light. If it comes back then pull the codes and let us all know what is there this time around.


Tom

Don, sorry I forgot to answer the Q about the DIS connector. You really can't see it as the DIS box is bolted to the underside of the plenum at the rear. If you take the MAP sensor & bracket off and look up under the rear of the plenum you will just see it, actually you will see the connector a 12 wire son of a B. If no one has had the plenum off then dismiss that because they rarely fail.

[tomtom72]

Originally Posted by Dynomite

Tom: I always enjoy watching you think on line....you are superb in diagnosis and explaining things (especially when it comes to codes).......there is another codes issue accuring at this time also http://www.zr1.net/forum/showthread.php?t=12754

Which I am thinking there is a simple solution since ALL codes are showing at the same time.....

I am learning ...and thank you

Cliff, I need a brain to think with....my SES light is telling me that there is no ECM in the system!

Straight up, thank you for the kudos. My problem is that I can't type as quickly as I think, and sometimes I can't think too quickly either! Senility, that's my story and I'm sticking to it!!

[c4zr1]

I checked the pins on my prom. All is good and straight.
I disconnected the battery to try and clear the codes.
I am still getting codes 42, 43, 44, and 54.
I have not take the MAP hose off yet.
That is my next step. It is zip tied. Sort of hard to get too.
I did take the top plate off above the MAP. Is it easier to take the torqe bolts out of the braket holding it to the plenum?

[tomtom72]

Okay Don, I smell a rat somewhere. It deleted one code and added one code.

I'll have to look over all the diagnostic trees in my FSM to see what I come up with.

The MAP bracket to plenum bolts are a bit of a bitach to r&r. Be careful or you will drop them onto the top of the transmission ( trust me done that one ).

I'll have to run down 42 in the "intermittents" section B of the FSM.

Tom

[c4zr1]

I did get the zip ties cut off of both ends of the rubber elbow of the MAP hose coming frm the plenum. It does look like a little oil residue in that elbow.

[tomtom72]

Okay, I don't like this. All these codes have one thing in common, faulty ECM, DIS, ESC.....bad grounds or shorted wiring, bad ECM plug terminals.

Humor me for a minute Don, also please don't be insulted either.

Your chip is from Marc Haibeck? Which kind did you get, a replacement PROM or the "piggy back" that you must insert into the backside of the PROM? If the latter, recheck your work on the install because the piggy back one must leave the first 13 slots open as they are the cylinder ID's, and obviously the PROM must be seated and the levers locked.


The last time something like this happened to one of our members it was the holes on the big plugs that go into the ECM, the holes opened up some how and made for some weird goings on! Search user name "tccrab". I'm just shooting in the dark at this point.

The only other thing all these codes have in common is bad wiring, lost grounds or shorts. Okay, so I left out that the DIS box failed, ECM failed, ESC module failed....you see where this is going, right? The car would not run in MHO if all that stuff was bad at once. This is proly something stupid.

btw, a scanner is of no help with 42. A test light and a digital VOM are the weapons of choice here. 43 you scan for knocks, 54 is bad relays besides wiring issues.


tom

[tomtom72]

Originally Posted by c4zr1

I did get the zip ties cut off of both ends of the rubber elbow of the MAP hose coming frm the plenum. It does look like a little oil residue in that elbow.

Okay clean that stuff up well and see if any oil made it to the MAP sensor. I use a tissue rolled up to go into the hose port. Make sure the hose part is not at all soft because these motors create quite a vacuum. At idle an LT5 will suck in a hard cover loose leaf binder! Serious, it will actually break the cardboard covers from the suction thru the T/Body.

I still don't like what's going on with all these other codes. Let's do this one step at a time though.


Tom

[c4zr1]

I cleaned the MAP hose and MAP tube, put it back together.
I disconnected the battery for a few minutes hoping to clear the codes.
Took the car out for a spin. SES light was on when I started it. The LTPW light does come on from time to time. Will this code keep the secondaries from coming on?
SES light never went out when I was driving it.
It does seem to be running on all 8 cylinders, but not opening up the secondaries.
Pulled into the garage and read the cods again.
Still getting 42, 43, 44, and 54
I cannot seem to be able to clear the codes by disconnecting the battery.