An enigma insues... - ZR-1 Net Registry Forums

Paul Workman · 08-15-2010

If y'all haven't gathered by now, after a long difficult surgery, the patient is having trouble in the recovery room!

It fires, but is missing badly at idle, and no change in the missing under some throttle up to 2500 rpm, except some of the missing clears up momentarily.

On fire up, there is sometimes some sharp "barking" thru the exhaust - which lead me to thinking ignition. The coils were new two years ago, and FWIW they ohm out between 5.8 to 6.2 across the posts.

The plugs were new at the time the coils were installed; platinum with 3k miles - they look "perfect". And, inspecting the plugs after a short run, I find a couple plugs that are wet with fuel, yet the plug on the opposite side of the coil are firing. And, some plugs appear dry, but fouled and a bit cooler to the touch - so I'm guessing they have been firing at least some of the time...

My pressure washer and a Honda I owned both suffered gummed ports in the carbs after storage over the winter, so my injectors came into question (reason for the earlier Accel parts# request.)

However, I got to remembering that since I run with secondary throttle plates and actuators removed, my secondary injectors come on just off idle (via the Marc Haibeck chip design), but there's no appreciable difference in the missing characteristics when throttle is added: point being it would be highly unlikely both injectors on the cylinders not firing would be equally plugged.

Injectors??? The injectors had been replaced at the time I bought the car - friend showed me the receipt for $1200+ at time of purchase. Just to check it, I ohmed them all and they checked out. So, I rigged up a pair of wires from the battery to alligator clips, clipping one clip onto one of the posts on each individual injector in turn, and with the fuel rail pressurized, I momentarily bumped the other alligator clip against the remaining injector post while looking down the IH runner to observe the individual spray pattern. All 16 injectors made a crisp "click-click" sound i.e., they didn't sound gummed up - is my point. And, the spray pattern characteristics appeared identical to the eye: marginalizing injectors as the issue, for now anyway.

The one item I changed in the interim before first turning the switch was the knock sensor - as the plastic connector piece was damaged. There are no codes, but the scanner did show only 17* advance at 1500 rpm...THAT seems a tad low, and come to think of it, the engine runs like the timing was waaay retarded (e.g., the "barking" and the sluggishness of throttle response, etc observed over the years fussing with SBCs.)

Oh, the O2s readings are a bit wacky, but they haven't had much time to heat up (burn off un-burnt fuel). Besides, it was running in open loop still and so the O2s wouldn't be having an effect in open loop anyway. The left and right integrators are both at 128.

So! Some of the plugs are fouled up now, so I'm going to replace them with some fresh ones this morning...AND reinstall the original knock sensor and see what happens to my spark advance...I'm running out of options pretty fast. Have I missed anything?

Stay tuned...

P.

PS: At times like this I am soooo thankful I cut off the coolant ports to the plenum. If I had to drain the coolant and then try to get the air pockets out each time...I'd be a little nutz by now! Now it is about a 20 minute job - if that -to pull it.

08-15-2010	#1
Paul Workman Join Date: Nov 2007 Location: Squires (near Ava MO in the Mark Twain N'tl Forest) - Missouri Posts: 6,466	An enigma insues... If y'all haven't gathered by now, after a long difficult surgery, the patient is having trouble in the recovery room! It fires, but is missing badly at idle, and no change in the missing under some throttle up to 2500 rpm, except some of the missing clears up momentarily. On fire up, there is sometimes some sharp "barking" thru the exhaust - which lead me to thinking ignition. The coils were new two years ago, and FWIW they ohm out between 5.8 to 6.2 across the posts. The plugs were new at the time the coils were installed; platinum with 3k miles - they look "perfect". And, inspecting the plugs after a short run, I find a couple plugs that are wet with fuel, yet the plug on the opposite side of the coil are firing. And, some plugs appear dry, but fouled and a bit cooler to the touch - so I'm guessing they have been firing at least some of the time... My pressure washer and a Honda I owned both suffered gummed ports in the carbs after storage over the winter, so my injectors came into question (reason for the earlier Accel parts# request.) However, I got to remembering that since I run with secondary throttle plates and actuators removed, my secondary injectors come on just off idle (via the Marc Haibeck chip design), but there's no appreciable difference in the missing characteristics when throttle is added: point being it would be highly unlikely both injectors on the cylinders not firing would be equally plugged. Injectors??? The injectors had been replaced at the time I bought the car - friend showed me the receipt for $1200+ at time of purchase. Just to check it, I ohmed them all and they checked out. So, I rigged up a pair of wires from the battery to alligator clips, clipping one clip onto one of the posts on each individual injector in turn, and with the fuel rail pressurized, I momentarily bumped the other alligator clip against the remaining injector post while looking down the IH runner to observe the individual spray pattern. All 16 injectors made a crisp "click-click" sound i.e., they didn't sound gummed up - is my point. And, the spray pattern characteristics appeared identical to the eye: marginalizing injectors as the issue, for now anyway. The one item I changed in the interim before first turning the switch was the knock sensor - as the plastic connector piece was damaged. There are no codes, but the scanner did show only 17* advance at 1500 rpm...THAT seems a tad low, and come to think of it, the engine runs like the timing was waaay retarded (e.g., the "barking" and the sluggishness of throttle response, etc observed over the years fussing with SBCs.) Oh, the O2s readings are a bit wacky, but they haven't had much time to heat up (burn off un-burnt fuel). Besides, it was running in open loop still and so the O2s wouldn't be having an effect in open loop anyway. The left and right integrators are both at 128. So! Some of the plugs are fouled up now, so I'm going to replace them with some fresh ones this morning...AND reinstall the original knock sensor and see what happens to my spark advance...I'm running out of options pretty fast. Have I missed anything? Stay tuned... P. PS: At times like this I am soooo thankful I cut off the coolant ports to the plenum. If I had to drain the coolant and then try to get the air pockets out each time...I'd be a little nutz by now! Now it is about a 20 minute job - if that -to pull it.