New Accel Injectors, same problem different hole.

[tccrab]

I replaced my fuel injectors because I came up with a miss at lower RPMs, diagnosed primary fuel injector failure, and after measuring them with a volt meter, one was obviously bad and two others were on their way.
Put in the new Accels with the special 'O' rings from Haibeck. Installation was a breeze and everything went back together just as it should. To be honest, I was just a little worried, my first plenum pull and all.
Engine fired right up and became obviously clear that I still had a miss.
Before, cylinder 3 was not firing, pulling it's spark plug wire when idling did not make the idle worse.
Now cylinder 5 does not fire.
Got spark, have ohm'ed the fuel injectors and they're fine, and I don't have a connector that's not seated.
No big obvious vacuum leaks, the secondaries hold vacuum and the idle however rough is under 1000 rpms, so I'm fairly certain it's not a leak.

The miss seems to go away when the secondaries open. Under hard acceleration the motor smooths out and the miss appears to go away.

Taking off from a stop is almost painful, the miss is that obvious. It's not an occasional misfire, it's a dead hole.

I've not yet pulled the sparkplug, this cylinder was firing prior to the fuel injector replacement, and the spark plug wires were replaced by the P.O.'s mechanic.
The motor has 10,800 miles.

I'm playing with the idea of pulling the plenum back off and taking that fuel injector down to the local speed shop to get it flowed. Even though it's coil measures fine, it might have junk in it.
I'd like to have a few more diagnostic tools under my belt before I go yanking the plenum.

Guys, got any hints, helps, ideas, WAG's?
ANY help at all right now would be SINCERELY and thoughtfully appreciated.

TomC
'90ZR1 #792

Did you happen to remove the spark plug wires for the coil packs while you were under there.

Also how strong is the spark at the plug?

[tccrab]

Jeff:

I didn't mess with the spark plug wires at the coil packs.
It was actually pretty clean under the plenum, all things considered.
Spark seems OK, don't have any real way of testing them, I don't want to fry my DVM.
I was going to check at the local auto parts store for some kind of tester.

TomC
'90ZR1 #792

[RZR]

I found this thread and had to register to reply ASAP. I too am in the same exact dilemna as tccrab. I have replace the primaries with Accels, checked connectors, plugs, etc. same steps tccrab performed and yet have a consistent miss during normal driving. I have logged data using Datamaster and have definitely found a lean condition on the left side based on long term and short term fuel trims. ALSO, significant knock counts occur during higher MAP sensor readings. Spark plugs confirm the lean condition. I would be VERY interested to hear any suggestions at this time and wuold be happy to share anything I find. Interesting thing is WOT does not produce knock counts but does show a slightly lower 02 voltage reading for the left side.

[tccrab]

Originally Posted by RZR

I found this thread and had to register to reply ASAP. I too am in the same exact dilemna as tccrab. I have replace the primaries with Accels, checked connectors, plugs, etc. same steps tccrab performed and yet have a consistent miss during normal driving. I have logged data using Datamaster and have definitely found a lean condition on the left side based on long term and short term fuel trims. ALSO, significant knock counts occur during higher MAP sensor readings. Spark plugs confirm the lean condition. I would be VERY interested to hear any suggestions at this time and wuold be happy to share anything I find. Interesting thing is WOT does not produce knock counts but does show a slightly lower 02 voltage reading for the left side.

RZR:

I'm sorry to hear that we're in the same boat.

I've called around to a few of the ZR1 tuners and i've got a few more simple tests that I will be performing to hopefully diagnose my failure. Just want to share them with you in the hopes that you havn't tried them yet.

First thing I'm going to do is to see if the connector on my dead hole's primary fuel injector is not seated properly. Mark Haibeck (thanks for the tips!) suggested fashioning a hook with a strong piece of wire (coathanger) and try to pull the connector off. There's just enough room to do this without pulling the plenum. If the connector moves, then it's not seated properly and could be the culprit. I don't give it much hopes for success as I've already ohm'ed the injectors at the ECM and my bad one ohms correctly, but you never know....
Next, I will go down to the auto parts store and buy a in line spark plug tester like this one:
http://www.drivewerks.com/catalog/sh...CAT450_pg6.htm
This will help in determining if I'm getting the same amount of spark at the plug on the dead hole vs. all the rest. (Thanks Mike Ebert @ ESS)

If still no joy, the plenum comes off.

Next thing to check is to see if the primary injector is spraying. With the plenum off, turn the ignition on, this will cause the fuel pumps to pressurize the system and energize the fuel injectors with 12 volts. Then ground the appropriate pin at the yellow connector (Connector A, pin 3 which is the primary injector on cylinder 5, my dead hole) on the ECM. This will cause the injector to spray, as the ECM controls the fuel injector by opening and closing the ground ciruit. This can be done without taking the injectors out, just look down the primary hole while having somebody ground the appropriate pin on the ECM connector.
If no spray, then injector is at fault, unless there's no 12v at the injector, then the ECM or wiring is at fault.
If it sprays, then ignition most likely culprit, although it could still be ECM.
(thanks Mark Haibeck)
In my case, I'm hoping for just a bad connection on the injector plug, but more likely it's the injector itself.
I don't even want to think about having a bad ECM...

TomC
'90ZR1 #792

[RZR]

Tom, thank you very much for the detailed action steps for further diagnosis, I will monitor the thread for your progress. I have not tried ohm'ing the injectors via the ECM and am not sure which specific hole is misfiring as there is not one spark plug with the telltale signs of a no-fire condition. Can you please point me towards a 'how to' on this procedure? I do not currently have an ECM pin reference. I am beginning to really miss the ZR1's normal performance..........

Where are you in Washington?

[RZR]

Hi Jeff,
Seattle. How about you?

Battle Ground, I was up in Seattle this past weekend though. Met up with a few other ZR-1 guys.

Dropped a part off for another ZR-1 guy to test on his car.

Check out www.pnwzr1.net

[tccrab]

Originally Posted by RZR

Tom, thank you very much for the detailed action steps for further diagnosis, I will monitor the thread for your progress. I have not tried ohm'ing the injectors via the ECM and am not sure which specific hole is misfiring as there is not one spark plug with the telltale signs of a no-fire condition. Can you please point me towards a 'how to' on this procedure? I do not currently have an ECM pin reference. I am beginning to really miss the ZR1's normal performance..........

In my case it was easy to find the dead hole, I just fired her up and got her to operating temp. Then you just pull one plug wire at a time and listen for the engine to stumble. Because of how well the engine is balanced, cylinders 3,4,5 & 6 don't cause all that much imbalance if they're not firing, so you have to listen carefully when pulling the plug wire. It might take two or three go arounds to home in on the bad cylinder. The key is that when you pull the plug wire on the bad one, the engine sounds exactly the same.

I'll scan and .JPG the appropriate electrical diagram page from my Helms manual later today or early tomorrow morning.
It's pretty easy to measure the injectors at the ECM. All you need is a DVM with fairly long leads.
Remove the negative battery cable. Open passenger door and remove the INJ fuse, it's a yellow 20A, top row about halfway across. Remove the "A" connector on the ECM, it's the yellow one closest to the outside drivers side. Using your DVM, measure between the correct pin on the ECM (don't have the Helms book here at work, otherwise I'd list them) and the right hand side of the INJ fuse connector. Just stick your black probe from the DVM into the INJ fuse hole that is closest to the firewall, make sure it's got good contact.
My probes were too big to fit into the pin holes yellow connector on the ECM, so I cut a 2 or 3 inch piece of 3/32 wire to stick into the pin hole, then I could clip the Red lead of my DVM to it.
The actual ohms read from the ECM connector will vary depending on temperature and wire resistance. If you were to have measured at the fuel injector itself, the Ohms at room temperature should be 13+/-1 ohm.
What you are looking for is a variance between injectors, it'll be obvious if you've got a bad one or one out of spec.
No ohms at all would indicate a bad connection or a shorted coil in the injector.
Low or high ohms indicate coil failure in the injector itself.

Good luck!
Keep me posted!

TomC
'90ZR1 #792