Intermittent Rough Running Diagnosis

**sturgillbd** · 10-02-2019

You didn't get your datalog to attach to your post. Have you checked fuel pressure? Have you inspected your distributor cap and rotor? There are lots of things that can cause the shuddering and loss of power. Post your datalog and a copy of your bin if you have a way to read the chip.

**tony-baroni** · 10-06-2019

Thanks Sturgillbd

I did a visual inspection of the wires, and cap (without taking it off). Everything looked good. Then inspected fuel injectors with the key on, and then idling, and then just a little gas, it seemed fine.

Then I checked the fuel pressure, and it was too low. Figured a bad regulator, took that out, and found the adjustable set screw that holds the regulator in place was fully backed out. It must have backed itself out from vibration.

I'll have to get on my PC to upload a log and bin....now I'm focused on figuring out what I can put on those threads to prevent that from backing out again, that won't fall apart in the fuel and clog up the injectors, any ideas?

Originally Posted by sturgillbd

You didn't get your datalog to attach to your post. Have you checked fuel pressure? Have you inspected your distributor cap and rotor? There are lots of things that can cause the shuddering and loss of power. Post your datalog and a copy of your bin if you have a way to read the chip.

**sturgillbd** · 10-06-2019

If its a stock style regulator, the threads shouldn't be exposed to fuel. You could use some light duty loctite on the threads of the adjustment screw.

**tony-baroni** · 10-13-2019

Thanks for pointing that out, I have since learned more about this unit. It's been sent back to the guy who sold it to me, he adjusted it and confirmed the adjustable fuel pressure regulator was good.
I have set the FP to 15psi, and put the stock memcal back into it. That hasn't helped at all, I have to check timing next.
What do you think about the state of the distributor cap and rotor? This is with about 10k miles on it.
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**tony-baroni** · 10-13-2019

Okay here's another update. It's idling high, around 1900. The TPS voltage with throttle closed is 0.6V. The TBI is whistling very loudly, a piercing whistle, when the throttle is closed. I was able to make a log file, starting it from nearly cold, getting it to closed loop mode was possible while idling because of the high idle. Then drove it, but tried driving it without giving it any gas really. Then turned around and drove it a bit with around 15% throttle. The driving starts around 6m mark on the log.

I hope the file upload worked properly. The bin is a custom one, based on BNKM, and I am using a definition file for $31.

How can I get the idle down to where it should be?
Is it normal for the knock retard to stay so consistently around 6 deg?

Other items, I checked manifold vacuum and it's in the green around 21 in Mg on my gage with this high idle. When I put it in gear, the idle drops, and then it shows in the red zone, indicating late ignition timing, only around 15 in Hg Vac

**tony-baroni** · 10-13-2019

One more update. I went out again and made a 2nd log, with more throttle, and got onto the freeway briefly. it runs like crap. Tons of knock.

I noticed a few things when I looked at the parameter list, instead of the dashboard.
Knock counts are off the charts, getting up to 50k and reseting every few seconds.

When I come to a stop, the spark advance shows 23 thousand and change, that doesn't seem right.

The check engine light came on at a stop light while the vehicle was stopped. I haven't yet figured out how to see which code was generated yet.

I'm all ears to feedback and what to try next!

Thanks all!