1 Cyl miss, out of ideas, might sell cheap..LOL

[Spanky1965]

heres the story, have miss on cyl #6,

I have so far changed fuel pumps, fuel filter, new Accel inj, new Borg Warner coils, checked all vacuum lines, new NKG spark plugs, New Oxygen sensors. checked all conectors and set TPS

Cly #6 has spark, but a miss, I am getting lean code on pass side. I am open to all ideas,

:dontknow:

[Spanky1965]

forgot to add also did a compression test, 180lbs

[tccrab]

ECM.

TomC
"Crabs"

[Spanky1965]

ECM??? is that the one under the plenum? how do I test? replace?

[Pete]

Try the easy thing first and change #6 spark plug.

I know you said the plugs are new you just never know if the ceramic has a crack.
Had same issue and drove me nuts for a couple of days.
Cheap,easy and nothing to loose by trying it.

Pete

[tomtom72]

ECM??? is that the one under the plenum? how do I test? replace?

That is the DIS, ignition control module. The one, ECM, TC is talking about is over next to the brake master cylinder, and over the clutch master cylinder.

You ran down the diagnostic chart for a DTC 64? I just looked it up and the hardest step is checking the connector at the right O2 sensor.

Car in closed loop @ 1200 rpm, coolant temp 95F to 203F, does scan tool read O2 voltage below .35volts ( 350mV)?

If Yes, discon O2 harness @ sensor, with car @ idle speed, scan tool should display O2 sensor voltage between .35 and .55 volts ( 350mV and 550mV)
Does it? If NO, refer to aids on facing page.

If Yes refer to aid on facing page. If NO, then PPL ckt 998 shorted to ground or ECM faulty.


The miss, I stick with what Pete said....:o Or that injector is stuck shut?

[Spanky1965]

have changed plugs 2 times, and I ohmed? the inj and at 14, would it ohme ok and still not work?

[tccrab]

If you're SURE of spark, then I can think of only two conditions that will cause a a misfire with an associated Lean code.
#1: Fuel injector stuck shut.
#2: ECM not firing injector.

TomC
"Crabs"

[Spanky1965]

I am 100% sure of spark, but injector ohmes ok, could it still be bad? they are brand new

[gbrtng]

I am 100% sure of spark, but injector ohmes ok, could it still be bad? they are brand new
Yup, could be - did it start acting up when you changed injectors?

[tomtom72]

I am 100% sure of spark, but injector ohmes ok, could it still be bad? they are brand new

Yes the injector could be stuck shut and I do believe that it would OHM out okay. The ohm only gives the condition of the coil, but that will not say anything about it's spraying out fuel. Usually the plugs are a fair indicator. I found when my injectors were not spraying fuel the plugs looked like nothing was happening in that cylinder. They were as white as snow, there couldn't have been any gas going in as there was no evidence of combustion.

I hope that is some help.

:cheers:
Tom

[Spanky1965]

yes thanks,,,I am goign to switch one of them

[tomtom72]

I just thought of this. I was reading another thread by ZRWON. His injectors were shipped with some kind of wax like protective coating on the tips....his laid around for a long while before he used them, and one was stuck shut from the wax. Don't know if that's any use either.:o

:cheers:
Tom

http://www.zr1netregistry.com/forum/showthread.php?t=9944

[Spanky1965]

well I swapped 2 inj and #6 still does not fire, so ust be ecm?? where do I get one of those?

[tccrab]

I am 100% sure of spark, but injector ohmes ok, could it still be bad? they are brand new

Remember, you are only measuring the OHMs of the magnetic coil inside the fuel injector.
All that measurement tells you is if the coil is shorted out or not.
If the pintle is stuck for whatever reason, then it doesn't matter if the coil is good or not.
This "Pintle" is a little spring loaded magnetic needle that moves up and down when the magnetic field is triggered by the ECM. When current passes through the coil of the fuel injector it produces a very intense magnetic field. This magnetic field pulls up on the pintle and gas sprays out. When the current is stopped, the spring snaps the pintle back to it's shut position and the gas stops spraying.
Pretty simple stuff actually, it's amazing how simple our best technology is.

TomC
"Crabs"

[tccrab]

well I swapped 2 inj and #6 still does not fire, so ust be ecm?? where do I get one of those?

*sigh*

ECM's are specific for ZR1's.
The ones for LT1s look the same, but they don't work in our cars.

There are none in the GM inventory *right now*, nor have there been any for at least a year.
That may change (I hope, I hope, I hope...)

There's a guy over on the CF forum who has one for sale, $285 if I recall correctly. It's used and there's no guarantee.

There's a few on eBay, but prices are north of $450 each.

We need to find a reputable rebuilder who will work on these.

TomC
"Crabs"

[SharkPilot]

Just a thought...

Have you verified the wiring continuity from the ECM to the actual injector connector? I realize it may be a long shot but maybe there is a failed connection somplace in there that's keeping #6 inj. from getting a signal. There is a contact at the ECM connector and at the injector. I don't know if there is another plug along the line anywhere.
Can a test lamp be used to verify a signal to the injector?

All the best and I hope you find the trouble,
SharkPilot

[Spanky1965]

we are ohming the inj from yhr computer so the conection should be good, but thenk you,,,I am open to all ideas, might even take it to the chevy dealer,,,LOL

[secondchance]

If there is someone nearby w/ a 90, best way to find out if ECM is bad would be to borrow and run a good ECM and see if that fires all cylinders.

[lbszr]

well I swapped 2 inj and #6 still does not fire, so ust be ecm?? where do I get one of those?

If you still might need an ecm I've saved these sites but haven't checked them out. Some have said the 95 will work in the 90, but I've heard it won't work also. If it would work Corvette Central has them for 95. Hope one of these helps.


http://www.parts123.com/parts123/yb.dll?parta~partsort

http://www.autopart.com/ecc/ECC1990CHEVROLETCORVETTE.htm

[lbszr]

Rock auto lists the 16163993.

[tccrab]

If you still might need an ecm I've saved these sites but haven't checked them out. Some have said the 95 will work in the 90, but I've heard it won't work also. If it would work Corvette Central has them for 95. Hope one of these helps.


Corvette Central has no stock.
Just called.

TomC
"Crabs"

[Spanky1965]

I will look, thanks

[Spanky1965]

oops...

[Tyler Townsley]

Having had a simular problem many years ago I can tell you the best way to troubleshoot and what the steps tell you. First what color is the spark plug tip?

1. Pull the # 6 plug wire put a spark plug in and lay it on the plenum and start the car. Look at the spark across the plug. Choose another cyl and do the same. If the spark across the gap is not the same you have a spark related problem in the # 6 cyl.

2. Given that the above is proved OK you then go to the fuel side. You can measure the resistance on the injector, if it is off then you have a bad injector. You can also swap the injector with say the #4 cyl and see if the miss follows the injector, if it does then you have found the problem. Given that you show the pass side lean then you probably have a bad primary side injector on # 6.

3. If neither of the above happens then you have what I had, a broken valve spring, mine was exhaust and took me 3 months to troubleshoot and diagnose. The only way you can verfy this is to pull the cam cover and cam and take out the spring, something I am not sure you can do with the head still on the car.

It would be EXTREMLY unusual for the dis or the ecm to only effect one cyl.

Tyler

[Spanky1965]

good call, but wouldn't a compression test show if a valve was not opening? I am asking?? I don't know

[Tyler Townsley]

good call, but wouldn't a compression test show if a valve was not opening? I am asking?? I don't know

No, what if effects is closing. It acts as a lazy closing that either keeps the exhaust open too long or the intake open too long, the cam lobe will open it no matter what the condition of the spring. A comprssion check rpm is too slow for it to effect the compression reading. I finally figured mine out from looking at the plug and elimination of everything else. IE I move plugs and the discoloration stayed with cyl 6, I moved injectors and the miss stayed with cyl 6. The spark was strong across the plug when I laid it on the plenum. The compression was good what was left? I actually did not put it togeather until I was talking to a friend about it and he mentioned that he had a simular problem on a BBC but he could see the spring was broken when he pulled the valve cover. He did say the compression was good, which had been the part of the puzzle that did not make sense to me until we talked about it.

Once I figured it out I even knew when and how it happened. I had been getting a trouble code for the shocks and I could clear it for awhile by turning the car and restarting, it would stay off for ablut 15 min or so. At first I would put in the clutch turn off the motor coast and start the car then let out the clutch. After awhile i just turned the car off left it in gear and turned it on and let it start. Bad move, with the LT 5 you have a wasted spark that fires whichever cyl has enough fuel, aparently there was enough fuel in the off cyl to fire it with a partially open exhaust valve and it broke the spring when it fired.
To this day I can remember it was running fine and I reached turned it off then back on and it was missing. It took 3/4 months to connect the dots.

Tyler

[Spanky1965]

wow, ok so if I pull the valve cover I cant see it? car only has 30,000 miles

[SharkPilot]

Tyler,

How does a valve spring get broken when the cylinder fires with the valve part way open? I'm not doubting you at all it just seems puzzling to me.
Does it send some sort of shock up the valve and stress the spring?

Thanks,
SharkPilot

[Pete]

Another thought came to mind.

Make sure the injector plug has seated right on the injector or did not mix up the secondary plug with the primary plug.

I know it sounds silly but sometimes it's the silly stuff that drive us nuts.

Pete

[tomtom72]

Tyler,

How does a valve spring get broken when the cylinder fires with the valve part way open? I'm not doubting you at all it just seems puzzling to me.
Does it send some sort of shock up the valve and stress the spring?

Thanks,
SharkPilot

Wouldn't it make sense that the explosion could slam the valve back into it's seat sending a shock wave thru stem & to the spring? The impact would have a lot of energy to transmit somewhere? I could see the hydraulic lifter acting like an anvil with the sudden attempt to squeeze all the oil out of it, from the missfire, very quickly and the hole is too small to handle the oil flow? :dontknow:

If you don't have some one close by to lend you a known good ECM. I have a spare that will work for a 90 with a stock 90 EPROM in it. It's not a 90 ECM by the numbers, but one of the later ones that will work on a 90. Hit me up if you think you want to go in that direction.

Did you run down the flow chart in the FSM for a DTC 62? That could tell the state of your ECM also.

One other thought. I'm embarrassed to mention this. What happens when one of the 90's "quad drivers" malfunction? Could that cause just one injector to go dead?

[Spanky1965]

flow chart in the FSM for a DTC 62? ???

Quad drivers??

[GOLDCYLON]

You mentioned aftermarket coils which have known to be a problem. Is it possible to swap out the approriate coil with a Delco unit? Great ideas guys keep em coming also can anybody close by Hook a brother up to test the ECM problem with a swap to rule that out as well?

[Spanky1965]

well had the problem before I changed the coils, I 100% have spark, and yes please keep the ideas coming

[Tyler Townsley]

Tyler,

How does a valve spring get broken when the cylinder fires with the valve part way open? I'm not doubting you at all it just seems puzzling to me.
Does it send some sort of shock up the valve and stress the spring?

Thanks,
SharkPilot

Your guess is as good as mine. I just know what did it.

[Tyler Townsley]

OK we need some info from you. What did you see when you tried the things mentioned especially what the plugs look like. Take them out put them in order by cyl take a picture and post the picture. Without feedback on the tests we are blind.

Tyler

[tomtom72]

flow chart in the FSM for a DTC 62? ???

Quad drivers??

Sorry, my senility is showing.:o I meant to write DTC 64 the right o2 lean condition. If you run thru the flow chart steps you will know with a good degree of certainty if the ECM has crapped out on you. At least a definitive answer would be nice to have.

Quad Driver = Secondary Injector Relay = official GM name for the part. These can't be the issue, sorry I always forget which injectors they control.:o

My apologies, sometimes my fingers are in gear and my brain isn't in the loop!

:cheers:
Tom

[gbrtng]

"Quad Driver = Secondary Injector Relay = official GM name for the part."

Not so much - the quad driver is an output transistor in the ECM (probably CMOS) that provides current to 4 injectors. There are no relays in the system.

[Spanky1965]

Ok guys, after $2000 of parts and Jeffvette even gave up helping me or returning my calls, I took it to the local dealer, turns out the PCM conector had poor terminal tension, they removed the bad ones and soldired and pluged it back in

Car now 100% perfect, thanks for all the help,

Just an FYI to all, watch out for some of the "experts" on here, they like to have you change parts, its not there money.:blahblah:

[Spanky1965]

just to be clear on my last post I am very thankfull for everyone that offered ideas, I am taking about the guys that claim to be the experts

[Kb7tif]

Ok guys, after $2000 of parts and Jeffvette even gave up helping me or returning my calls, I took it to the local dealer, turns out the PCM conector had poor terminal tension, they removed the bad ones and soldired and pluged it back in

Car now 100% perfect, thanks for all the help,

Just an FYI to all, watch out for some of the "experts" on here, they like to have you change parts, its not there money.:blahblah:

Good deal. :dancing

[Jeffvette]

Ok guys, after $2000 of parts and Jeffvette even gave up helping me or returning my calls, I took it to the local dealer, turns out the PCM conector had poor terminal tension, they removed the bad ones and soldired and pluged it back in

Car now 100% perfect, thanks for all the help,

Just an FYI to all, watch out for some of the "experts" on here, they like to have you change parts, its not there money.:blahblah:


Spanky, glad you found your issue. I am sorry that I was not able to diagnos your car which is approximately 2,000 miles away. If it truely is a ECM connector issue it should have shown in doing random diagnostics. Sorry you were not able to relay that portion to me.

On a misfire you will have a couple of issues that boils down to the problem. Installing new coils or injectors solves those problems at a rate of 99.9999999%

[Spanky1965]

Jeff I thank you for your help, I was only mad you would not call me back or answer emails except to say you would call and never did, But no big deal you were doing a stranger a favor and I do thank you,

[-=Jeff=-]

Ok guys, after $2000 of parts


Hey Spanky, I am curious on what parts you replaced that cost $2000

[gbrtng]

I took it to the local dealer, turns out the PCM conector had poor terminal tension, they removed the bad ones and soldired and pluged it back in.

PCM = ECM ? The ECM has four connectors. This is a very weird failure since the Weatherpack connectors are pretty much bullet proof. How many hours did the dealer charge you for? I'd still be looking ....
:occasion1

[GOLDCYLON]

Yeah I was kinda wondering about that as I was not sure where the PCM was Im assuming the ECM as well. I heard those connecters can corrode as well as the connectors to the Quad drivers

[Pete]

I also have changed parts,taken parts off just to put them back on i did this a bunch of times,i lost count.
I have ported parts and reported parts.

It's wierd everytime i take it down the track i have this silly grin on my face looks like this:-D

It's all Chevrolet and Doug Rippies fault for making the Snake Skinner.
I am so mad at them i can scream.

Pete

[Spanky1965]

new parts list
Fuel pumps
fuel filter
Oxigen sensors both sides
Accel Injectors
New coils
2 sets of plugs

and just for fun a new stereo and Nitto drag radials...LOL