1997 5.7 Misfire under load, bunch of parts replaced

[Keeper]

I was thinking same thing, plus crank sensor is easy. Could be connector/harness to it also.

edit: also, did you follow up from prior suggestion to make sure you have enough coolant for coolant temp sensor?

 

[Dud1f3r]

I was thinking same thing, plus crank sensor is easy. Could be connector/harness to it also.

edit: also, did you follow up from prior suggestion to make sure you have enough coolant for coolant temp sensor?

I did a coolant flush with some Dexcool and made sure it was filled up completely. I did find multiple vacuum leaks, mainly around the spider connector. Gonna fix those and see what's going on from there.

 

[Dud1f3r]

Alright, parts ordered. Plugs finally getting here today, along with another set of intake plenum gaskets. Spraying brake clean near the spider while running made the idle drop, along with spraying around the TB and one corner of the intake, right by the thermostat. Just gonna replace them all, torque them down to spec (again) and probably lubricate the inside where the spider seal goes, since I've noticed the last couple of times I've taken them out they like to tear. Hopefully, this will be the last of my worries, and we can finally drive the truck.

Also bought an Autel MS906, gonna use it to set cam retard and check any other sensors. Should make diag a lot easier, and I can use it on my VWs (and my 94 Miata, since it's got a OBD1 port adapter)

 

[WICruiser-97]

Crank sensor or wiring to the sensor are cantidates given the codes that you have.

I am not sure how you disconnect the cam sensor without disconnecting the ignition given that I believe it is internal to the distributor but that may be my lack of knowledge.

Increasing load and warmer being worse sounds like a fuel delivery problem. Any way to evaluate the system fuel pressure under the conditions that cause the misfire? Fuel pressure may be fine with the small amount of fuel required at idle but drop off when you really need added fuel due to load.

 

[Dud1f3r]

I am not sure how you disconnect the cam sensor without disconnecting the ignition given that I believe it is internal to the distributor but that may be my lack of knowledge.

I have a VORTEC motor, which means the cam position sensor is in the dizzy, but the coil + ICM is external of it, mounted to the passenger side of the intake.

Increasing load and warmer being worse sounds like a fuel delivery problem. Any way to evaluate the system fuel pressure under the conditions that cause the misfire? Fuel pressure may be fine with the small amount of fuel required at idle but drop off when you really need added fuel due to load.

I replaced the spider (with FPR), fuel filter, and fuel pump. I can recheck my fuel pressure tomorrow when I go to work on my truck, although I'm not sure that's the issue here.

I'm leaning towards ignition issue, or just multiple vacuum leaks everywhere. With the new scanner, I can see what my vacuum pressure is in the intake, check cam retard, and check ignition timing, so we can figure out more. Looking forward to getting this thing running strong, since I'll be selling my Golf soon so I'll need a new daily.

 

[Dud1f3r]

I'm leaning towards ignition issue, or just multiple vacuum leaks everywhere. With the new scanner, I can see what my vacuum pressure is in the intake

So I replaced my intake plenum gaskets again finally, and it’s actually operating like a truck again (the spider injector seal was torn and stretched). It had positive manifold pressure before I replaced the gaskets. Since doing that, it’s ran super smooth, no hitches or hiccups at all.

Thank you for everyone that’s helped me out along this journey, I look forward to driving this truck/putting it to work, and maybe seeing some of y’all out there!

 

[Dud1f3r]

I lied. Or, the truck lied. Something/someone lied. It's back on it's **** again. It's definitely gotten better, but misfiring under load again, and getting worse when it's warmed up.

 

[Dud1f3r]

Alright, back at it like a bad habit. Replaced the CKP and the plugs (finally) and it got a lot better, but not perfect. I think the only sensors I haven't touched are the O2 sensors, and when I do those I'll check to see if the cats are clogged (hopefully today at work). Gonna also see about a PCM? There's a bunch of express vans near me at local junkyards, so it's worth a shot to get them chooching.

 

[Dud1f3r]

Ok, it seems to be the O2 sensors, but I cant get bank 2's off. All the nuts decided both to round off and rust weld themselves to the exhaust (understandable) and the O2 on bank 2 won't come out. I replaced bank 1's and it's running a lot better. Not perfect, but a whole lot better. I'll probably end up just replacing the whole exhaust on this thing just to get rid of the cats, the rusted out hardware, and all that good stuff.

 

[1998_K1500_Sub]

So I replaced the intake manifold gaskets, and put the dizzy in wrong (d'oh)

After getting that sorted out, I have P1345 coming back, along with it not running at all if the cam position sensor is plugged in. I swapped out the old dizzy's cam position sensor, and same thing. Current codes are P1345 (Crank cam correlation code), P0340 (Camshaft position sensor circuit A malfunction), and P0300 (Random/multiple misfires).

Re: P1345 code, did you adjust the distributor to eliminate the code? You hinted at this in your prior post (#13).

The process is described in the factory service manual and elsewhere. See the LAST page of the attached .pdf, although the rest of the pages are relevant for a distributor re-install.

As you may already know, the distributor can be installed WAY off its optimal position and the engine will still run, but it may run poorly under certain conditions. The procedure described in the 1st and later pages of the attached .pdf describe one method of installation that avoids the issue. While you OP may not benefit from this information, some other reader may. I hope this helps

FWIW, the contents of the .pdf came from the 1998 FSM.