Nistune Forums

checked everything within the FSM.
replaced all ignition components twice.

only thing I haven't replaced was the subharness from the distributor/CAS to the main harness- but I was getting 1 degree and 120 degree pulses on my o-scope. also getting pulses on pin #3 and #5 - which come directly from the power transistor.

Car starts and runs- but when I jab the throttle from a closed position, it stumbles. If I let the idle coast back down and jab again, it stumbles. If I jab before the idle settles- it seems to rev fine.

It's just the initial jab that makes this thing stumble. Going to check TPS harness perhaps tomorrow but I don't think that would be the stumble issue.

21 = Ignition signal issue

Mismatched coil feedback against what was expected when spark was produced

There is a feedback wire used to determine ignition problems by the ECU. During/after the coil has been charged, discharged if the feedback line doesnt match accordingly then this error is raised

Code is a result of problems including spark plug leads (if applicable), coils/coil pack issue, power transistor, spark plugs. Just a fault in one of these can trigger the code

Matt wrote:21 = Ignition signal issue

Mismatched coil feedback against what was expected when spark was produced

There is a feedback wire used to determine ignition problems by the ECU. During/after the coil has been charged, discharged if the feedback line doesnt match accordingly then this error is raised

Code is a result of problems including spark plug leads (if applicable), coils/coil pack issue, power transistor, spark plugs. Just a fault in one of these can trigger the code

So any recommendation as to what to check? I checked everything as per FSM. even busted out the o-scope and tested certain things. I'm going to change the sub-harness at the distributor-CAS, as it's the last thing.

Kinda thinking this has to do with a lot of my ignition problems. I would like to fix this before actually going ahead with more modification. Last thing I need is my IGN signal taking a crap when I'm having fun.

poor earths possibly?

may be hard for a scope to pick up missing signals when they are happening hundreds of times a second, but enough to cause the car to run crap

wondering if its isolated to a particular coil pack/spark plug. gets a bit difficult to track down but just an idea

I had a small crack in a spark plug which could cause it to start cutting out at high rpms. took a while to find

Thanks for the replies, fellas.

I recently redid the entire ground cable from the battery to the starter bolt using 4ga "ground wire" from the autoparts store.

I redid some grounds on the engine harness, but only the terminals where they bolt to the chassis or engine. I did not actually redo the entire ground wire. What i did do is make some small jumper wires that plug in between the pins and sockets on each connector so that I may run a separate wire to the battery negative pole while still running the component... Still not a change with whatever I tinker with.

I've checked resistance, and they're all under 1 ohm. closer to 0.5 ohms or 0.3 ohms. I don't know if that's ok but the FSM says "approximately 0 ohm", whatever that is. The multimeter's probe-to-probe test reveals a 0.3 ohm resistance with no wiring as a load. I changed probes on the DMM (it's a Fluke 75, and I have 3 of them to test with), and still 0.3ohm.

One thing I noticed yesterday. While driving my engine noise/sound did not change but the digital tach jumped to max and then shot back down passed my current RPM to 0 and suddenly reappeared at 3000 rpm which was where the engine was currently running at.

Any indication of any circuits I can check?

What sucks is that I have an extra engine harness but the ignition wires are not even on the engine harness. They are part of the Engine room harness- which goes under the dashboard.

boooooooo!

any tips for checking more in depth? I'm running out of ideas here.

that digital tach signal would come from the 1 deg CAS wire I would think. But I would think that would affect how the engine ran also

hmmm. serious? that's where the tach signal comes from for the Digital models?

well then. we may be onto something here.

i used a logic probe and got pulsation on 1 and 120 degree signal wires at the ecu, but it could be intermittent. I just got another CAS plug so I'll try that out. I switched distributors twice, so maybe it's time to switch that plug.

Thanks Matt. Hopefully this fixes my issue. I know it's the last thing I've yet to replace short of the harness that goes into the body, as the EFI harness does not encase the ignition module and coil parts of the engine electrical.