Misfire/rough running 80 series (2 Viewers)

[spencergonomo]

I just finished a head gasket on my 1997 80 series and I started it up and it runs very rough. Pulling spark plug boots, I found no change to the idle on cylinder 6.

I have no check engine light (should this throw one?) I confirmed I have good spark and I can hear the #6 injector firing, the injector reads 14ohms. I pulled the spark plug after running for about 8 minutes and it looks brand new still (not even wet). I confirmed my distributor rotor points just in front of cylinder one wire at tdc, and noticed when I turn the distributor cap clockwise idle increases but the misfire remains.

Where should I look next? Why am I not getting a CEL?

Thanks

 

[baldilocks]

Look for vacuum leaks due to a hose that you didn’t reconnect. Is there an odor of gas rich exhaust? I once pinch an injector wire between the valve cover and the head. Several minutes into the first garage start up the insulation melted off that wire causing that injection to be grounded and it hung open.

Retrace your path. It ain’t the car, it was you. Your distributor rotor might be in the correct location but is the engine 180* out?

 

[landtank]

Pull the connector off the injector and check that the pins aren’t bent.

 

[spencergonomo]

Pull the connector off the injector and check that the pins aren’t bent.

The connector seems to be fine, and I can hear the injector ticking when I put my ear up to a screwdriver touching it.

Look for vacuum leaks due to a hose that you didn’t reconnect. Is there an odor of gas rich exhaust? I once pinch an injector wire between the valve cover and the head. Several minutes into the first garage start up the insulation melted off that wire causing that injection to be grounded and it hung open.

Retrace your path. It ain’t the car, it was you. Your distributor rotor might be in the correct location but is the engine 180* out?

would the truck run at all if it was 180° out? I am almost sure I set it at the correct TDC but will surely double check that. I seem to be getting the same voltage reading to the #6 injector plug as the rest of them.

Another point is the engine won’t rev past about 2000rpm - seems far more bogged down to me than a single misfire.

Will update once I double confirm distributor alignment.

Thanks

 

[GCCFZJ]

Once had the issue after doing a head gasket. I would check your TPS connection. When doing my head gasket I needed to replace my connectors as age and heat takes its toll. I mis-pinned my TPS connector so it wouldn't rev past 2000 rpm. I unplugged the TPS and it revved past 2000 rpm. Finding an issue with the TPS I was able to double check my wiring and correct my error in the pinning of a TPS connector.

 

[spencergonomo]

Update:

Still having the same issue—the most characteristic symptom is the engine not revving past ~1900RPM. Sounds like a random misfire when on throttle whereas idle sounds like a consistent misfire on #6. Finally threw a P0306 code.

Checked so far:

• Spark (looks strong on all cylinders)
• Ignition timing (not off by a tooth or by 180°)
• Fuel injector #6 is ticking
• All injector plugs getting voltage
• #6 injector 14ohms
• #6 injector connector continuous with ECU
• Good compression on all cylinders (150PSI +/- 5PSI)
• No vacuum leaks found
• EGR not stuck open
• TPS resistance values good
• Swapped #6 spark plug wire with spare (no change)
• #6 spark plug looks nearly identical to other plugs (smells a bit like fuel)

The fact that it is unable to rev higher than 2kRPM leads me to believe this is not a simple spark/fueling issue in cylinder #6. Going to try to throw a new distributor cap and rotor at it and see if I get anywhere. here is a Video of it running. Any ideas?

Thanks