Engine Missing

[c4zr1]

I need a little help. I have a 92 with 17,200 miles on it. I know I do not drive it enough. It developed a miss and the engine service light is staying on. The secondaries are not coming on. I have changed out the plugs and fuel filter. Did not help. I am not getting any codes. The engine is idling right at 500rpm. I did do a reverse vacuum check and the vacuum does not hold constant, it leaks back down slow, but the vacuum pump does not stay on all of the time. It comes on about every 15 seconds and stays on for about 5 seconds. I did notice plug #1 and #8 was pretty black, but not wet with fuel.
I wish there was someone close that I could take it too, but Dallas is 6hrs away. Does anyone know of a good ZR-1 mechanic in Oklahoma City? I am only 4 hrs away from there.
Any help would be appreciated.

[Pete]

I think Jerry Downy lives in Oklahoma don't know where in Oklahoma he's at Carlilse this weekend try him on Monday.

Jerry is good people.

You can contact him at www.jerrysgaskets.com

I would say spark plug wires or bad injector.
Pete

[Paul Workman]

My engine is missing so bad...I can't even find it in the car!! (Just kiddin...sorta. Actually the engine IS missing from the car at the "moment" [sigh])

What Pete says is where I'd look first as well. But, if you have an SES situation, the secondaries will not be commanded open by the ECM. And, there should be a code too; at least while the SES light is on.

You can have it scanned at many of the auto parts stores; many do it for free. Scanners are great diagnostic tools, however they don't always point to the problem; but sometimes to the result of a problem.

For example, a leaking or stuck open injector will not throw a code or invoke an SES light - directly. However, if excessive fuel forces the O2 sensor out of range, the scanner will pick it up instantly, and if the condition is sustained, the ECM will finally light the SES light - as long as the ECM is operating in CLOSED LOOP configuration.

It sounds like you have a slow leak in the secondary system's vacuum circuit as well. That might be another item on you list, but not the one causing the miss - the scanner will shed some light on the path.

Like Pete said, my suspicions too lie with the injectors at this point, and since you changed plugs with no affect, then possibly wiring. Try pulling one plug at a time while it is idling and see if you can detect which "holes" are not firing and let us know.

Gotta run!

P.

[c4zr1]

Update on the miss

I put in a set of NGK Iridium IX plugs. Put in some Lucas Injector cleaner ran about 3/4 tank of gas through the engine.
I did decide to take it to the local chevy dealer to let them run an engine analysis on the engine. Had an appointment at 8:30 yesterday morning. I never did hear anything from them so I went back at 5p.m. and ask the service adviser if I could have an update on my car. He told me that they have not been able to look at it. That did not set too good with me I certainly did not want to leave it overnight so I told him I would just take the car. When I got back home and in my driveway the engine service light went out. It seem to be hitting on all 8 cylinders. I decided to take it out for a spin. It did pretty good, the secondaries started to kick in. When pulling up to a stop the engine service light did come on a couple of times, but after I set there a couple of minutes letting it idle a little faster the light would go back out. I made it back home then without the service engine light coming back on.
3 hours later
I started the Z no engine service light. Great!
I put the Marc Haibeck chip back in. The engine was already running bad when I purchased the chip from Marc. I took that chip out and put the stock chip back in while trying to dianose the engine miss. I was hoping that might cure my problem.
I took the Z for a test drive.
It drives like a ZR-1 should now. The chip makes it even run better.
I think I had dirty injectors and eventually the Lucas Injector Cleaner cleared up the injector or injectors that was not working.
I feeeeel a whole lot better now.

Thanks to those that responded!
Don

[Paul Workman]

Originally Posted by c4zr1

Update on the miss

I put in a set of NGK Iridium IX plugs. Put in some Lucas Injector cleaner ran about 3/4 tank of gas through the engine.
I did decide to take it to the local chevy dealer to let them run an engine analysis on the engine. Had an appointment at 8:30 yesterday morning. I never did hear anything from them so I went back at 5p.m. and ask the service adviser if I could have an update on my car. He told me that they have not been able to look at it. That did not set too good with me I certainly did not want to leave it overnight so I told him I would just take the car. When I got back home and in my driveway the engine service light went out. It seem to be hitting on all 8 cylinders. I decided to take it out for a spin. It did pretty good, the secondaries started to kick in. When pulling up to a stop the engine service light did come on a couple of times, but after I set there a couple of minutes letting it idle a little faster the light would go back out. I made it back home then without the service engine light coming back on.
3 hours later
I started the Z no engine service light. Great!
I put the Marc Haibeck chip back in. The engine was already running bad when I purchased the chip from Marc. I took that chip out and put the stock chip back in while trying to dianose the engine miss. I was hoping that might cure my problem.
I took the Z for a test drive.
It drives like a ZR-1 should now. The chip makes it even run better.
I think I had dirty injectors and eventually the Lucas Injector Cleaner cleared up the injector or injectors that was not working.
I feeeeel a whole lot better now.

Thanks to those that responded!
Don

Ummmm....OK. A good WOT now and then does wonders too. But, I've had the same set of symptoms which turned out to be O2s. A free scan from AutoZone would tell us a lot.

Just a thought. Hope it continues to please!

P.

[c4zr1]

Well things have changed some. I took my car back out today and I and I am still getting an SES light on from time to time. It will start up sometimes with the light on and some when I start it the SES light is out. When the SES light comes on I can drive it for a few miles and the light may go off, but when I get to a stop light it will come back on.
Puzzled.
I went by the local Auto Zone and they said they only scannd vehicles 96 and above so I could not get the codes read.

[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?

[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.