Car ran fine, now it runs horrible. Whyyyy!:cry:
 

So the car ran totally fine 1&1/2 weeks ago. Had a bunch of fun for a period of time after finishing the new 3" exhaust system. Drove to my sister's birthday, and home, all was good.

Car sat for that short period of time. Today I decided I would start fixing the problem where mega squirt was reading different voltage than the battery. I figured today was the day to check the voltage at the injectors, and calibrate megasquirt to match it. In order to dial in the battery voltage correction.

/ME Time to finally proceed on with *completing* the tune for this summer of track awesomeness!!!
/LIFE: NOPE, NEVER HAHAHA

So I pulled my Multi/voltmeter outdoors and turned the ignition key ON.

I unplugged injector #3 from the harness because that one was the easiest to get my hand on. (FlowForce 640cc's)

I attached the multimeter probes 1 to the #3 injector harness connector, the other probe was grounded to the engine's cylinder head.

It read 12.2-12.3 volts. I held the probes to the injector harness and engine ground for like 35-45seconds to try n get a decent read out of the voltage.

I checked megasquirt on tunerstudio, and it read the same thing. 12.3volts. So bingo, it's already calibrated fine!

I unhook the multimeter, I plug the injector connector back to the harness connector and close the hood.

Start the car up and:

At idle, the engine shakes. It's not a considerable amount, but when the revs start to drop below 1000, it's enough to be felt and visually seen at the shift knob as well as seen at the engine bay. The whole driveline shakes. (it also has AWR poly engine mounts and delrin diff bushings less than 1 year new)

The exhaust sounds like it has a bit of a burble, and the overall sound level coming from it is half as loud as it should be. almost as if the car is missing fire, but I took it for a short drive around the block and it felt like it would hardly accelerate for the throttle input. As well as is a whole lot quieter than normal. Yet the weirder part is there's no sudden cut of power, no missing fire, no stumble, no hesitation, nothing. It's totally smooth throughout the range but when I accelerate, 20% TPS feels like 3% TPS. It's only when the RPMs drop below 1000 RPM when the engine starts to shake, most noticeably at idle.

Normally it's a little on the lean side during hot or cold start ups Like 17s or so.
and when I give it a little TPS input the battery voltage goes from 12's to 14.7's and suddenly the AFR targets are hit.
And EGO is always pulling 10% of fuel to compensate and hit AFR targets at warm idle.

This time when the car finally warmed up (through modulating the throttle to prevent it from stalling out) I took a log and ego correction was actually adding as much fuel as it could in order to keep the AFR from being too lean. Completely different from before when the car was warm and alternator was running.
side note: I've always had a problem with the alternator not running for some reason when I start the car until I give it some revs then it lights up n starts working. Unrelated to this tho, just worth noting if you check the log out.

The log included has me starting the car up, letting it idle for a brief moment, then taking it for a cruise in 1st,2nd,3rd gears in a circle on my street.

If I'm not mistaken, the idle vacuum seemed a bit unusual. 45KPA@804RPM? And the RPM graph looks funky too (very wonky). :cry:

So I'm about at a loss for words at this point. So tired/exhausted of always dealing with problems. Getting to the point where I might want to give up, although I've already put way more time and money into the car than I would ever be able to get back. And all I want to do is drive it!!! But I tried my best to formulate something readable. Apologies for the lack of enthusiasm in this

So many words...

Ran good, disconnected #3 injector now runs bad.

Confirm #3 is firing, while car is idling, pull plug boot. You should hear a change in the way the engine runs. While you are in there, do it for the other cylinders as well.

Thanks man. My brain has hit the over-stress protection today when that happened. Just so tired of needing to pull the tools out for her yet again, when it's supposed to be reliable enough to go on road trips by now with the 1,000's of hours of work I've put into it already. I am using a abundance of rambling words to try to distract myself from the way I feel deep inside.

I will be able to try that tomorrow evening...

The ECU trying to dump fuel in is because cylinder 3 is likely not firing and it's pumping a bunch of air into the exhaust, more air in the exhaust makes the wideband read super lean. It's possible you damaged the injector driver or it did not get plugged all the way back in. While running you can try to shake or wiggle the wiring and connector to see if the car suddenly pops back to normal.

There is a test mode. Under CAN if I recall correctly. Can tell the injector to open and close with no engine running. Then go out and listen for the clicking sound.

I'll admit that I didn't comprehensively read the OP, so if he stated that he's running COP ignition, I missed that.

Assuming a stock ignition coil (any year, '90-'05), pulling the #3 plug will also kill the #2 plug.

This is the nature of wasted-spark ignition systems. The current for each ignition event jumps through the gaps of two spark plugs. If you interrupt one, you interrupt the other.

Well would you look at that, it has been so long since I ran the stock coil packs. As an engineer who is required to design fault tolerant systems, that is pretty poor design right there.

I got it fixed. It was spark related. I will elaborate tonight when I'm off work how it all went down. Thank you to everyone

Apologises for not posting last night. Didn't really have time to.


So the problem was actually the coilpack again. It was misfiring on cylinders 1 & 4.

Back story:
About 4 months ago i had a misfire (come to think of it, i think it was after i did some minor wiring work, like reinforcing the grounds behind the intake manifold, and adding electrical tape to the cords to make things look better)
It turned out to be the coilpack. I replaced it with a new coilpack and problem was fixed! I also replaced the spark plug wires too with NGK from fab9tuning.

I've drove the car about 1,000 miles or less since then and that's when this problem started. It was after i messed with the injector harness, so i highly doubed it was the spark related.

But it turned out it was spark related. I pulled plug wires with engine running and upon pulling 1&4 or 1 or 4, no change in idle. So i was running on literally 2 cylinders somehow lol 2&3 like a two stroke engine.

So the day b4 yesterday I changed a good coil from the old pack with the bad one from the new pack and wallaa problem fixed idles good again 👍 all 4 cylinders are sparking, everything is normal. Turns car off after just a few minutes n calls it a day.

Last night after work i start car up and bam SAME PROBLEM AGAIN!! Cylinders 1&4 no spark. So obviously i burned that coil pack AGAIN!!!


conclusions
1) Either i have my ignition settings in megasquirt set wrong to where something is just burning up coils back to back (except I'm just using the up-to-date megasquirtpnp.com 94-95 turbo base tune settings)

Or

2) there's a problem in the wiring. So last night i stripped the harness apart that includes coils, injectors, cas, o2 sensor, some triangle thing on the back of the intake manifold, etc. And all was normal along the wires except the ground wires running from the 2 coil pack connector plugs are janky as anything. They looked like they were twisted back together when they were spliced at some point. Not diy soldered or oem crimped. And the inner copper is rusted green. Super janky. I'm thinking a previous owner tried to replace the coilpack connectors at some point.

Could this be the problem?

I'm ganna replace the wires from the coils to the ecu with new and redo the grounds. Any suggestions on what gauge wire i need for the grounds and etc