jeff spahn

I have my car apart waiting for the paint guy to pick it up and now it's running like crap.
Intermittent spark on many cylinders. Thought it was a fuel issue. Swapped MAF, no change. Put old MAF back. Still same.

Changed fuel regulator and damper (only one as I have supercharger kit and we eliminated one). Runs a bit better.

Ran sharktuner. Running all in the green on sensors. Using correct map and values are still good. Idle control switch is new and functions correctly. Has run for two years (15,000 miles prolly) on this map so that's not it.

Idle was a bit lumpy like I had a hot cam set in it. Cylinder 8 is getting crappy, intermittent spark. Pulled plugs one at a time: Getting somewhere.


So. I put a new cap on the driver side. Improved it a bit. Have weak spark on a couple other cylinders too. Cylinder 8 spark is still not good. 7 and 6 are great, 5 is weak like 8.

Here's what I propose and I want some feedback:

I have new plug wires coming. Mine are older so it can't hurt.
I have new rotors coming. Might as well replace those too.
I put one new cap on, I'll put the other on.

Should I replace the ignition amps? Could they be weak or is it not how they work? On or off and no in between? I did have one go bad 4 years ago and replaced it. Cylinder deactivation light is not on and both banks are firing, just poorly.

Mixture is 14.7 +/- a point at idle. Bounces around. Adaptation is turned off, am running in coding plug mode, not forcing an O2 Sensor or No O2 sensor to computer.

Possibly the coils? They are original from what I can tell from my records. Can they be weak or am I missing something here?

I am planning on a full Megasquirt system in the late fall/ winter but that doesn't mean I don't want it running well. I have all winter to put in the MS system and summer has lots of miles in front of it yet.

What says the peanut gallery?

joejoe

Check grounds for injector harness.

jeff spahn

Grounds will be checked again. Under the maf if I remember correctly. They were cleaned about a year ago.

Swapping the amps has shown that one of them is weak or something. Strong spark when amp leads are swapped. Going to try new amps as well.

jeff spahn

So, it was the ignition amps. Got two new ones and it runs like brand new.

Chalkboss

Nice! You'll be all ready for that new paint.

Mrmerlin

Jeff glad you found the issue,
did you also use fresh heat sink paste on the new amps?
If not they will soon fail from heat damage.
Radio shack has this paste be generous when applying

jeff spahn

slathered the paste on one amp that comes in the package. second package had none so I used my radio shack heat sink paste for processor installs on computers. Sean Ratts told me to use it. wondered why I kept that, now I know. Its squished out the sides on both amps installation.

SeanR

Yep, you did good son.