OBD1 codes 33, 34, 45.... and more great news....

DeCaff2007

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I'm SO confused. The fuel pump doesn't pump oil, why would it have a switch for such a thing?

Regardless, I'll check what's there and it's condition.
 

PlayingWithTBI

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I'm SO confused. The fuel pump doesn't pump oil, why would it have a switch for such a thing?
The OPS on the china rail is a backup to the ECM turning on the fuel pump relay by bypassing it. When it sees ~4 PSI, it'll turn on the pump too. Anyway, the OPS is directly plumbed in to the oiling system. This drawing is for an 88 but it's good for VIN Z (4.3L) too. Again it's for an 88 but, the 2 years are almost the same other than dash and gauges.
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Schurkey

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Does it misfire ALL the time, or just under power, or is it random?

If it's consistent, you could figure out which cylinders are not running with a cylinder-balance test. Connect a vacuum gauge to manifold vacuum. Blunt the sharp edges of six SMALL nails, lube 'em with silicone dielectric grease. Slide them BETWEEN the distributor boots and the wires, so that you don't puncture the insulation. You'll feel when the nail touches the metal plug-wire end. Start engine, allow to idle. Then use a grounded jumper wire, or a grounded incandescent test light to touch each nail in turn (not longer than ~5 seconds each) while watching the vacuum gauge. As each nail is touched, the vacuum should drop. If the vacuum doesn't drop as much as the others, that cylinder is weak. If it doesn't drop at all, that cylinder is dead.

V8 distributor shown.
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This test will probably set it's own code for lean exhaust.

You need to download a service manual for your truck--or buy one on eBay.
 

DeCaff2007

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Misfire is all the time. I've never heard of that test before and now I'm super curious to try it and see what happens.

Question: Won't spark jump between those nails with the engine running?

EDIT: @Schurkey: My brain is so flustered right now, that I had to re-read that paragraph about 5 times before I realized that that test grounds out the spark for the respective cylinder. Plus, you wrote it right there in black and white... a cylinder balance test. OMG I need a vacation. I've never put a vacuum gauge on manifold vacuum to see the results of such. This will be interesting.

I need figure out why the passenger side is spewing oil. It's bothering me. :(
 
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DeCaff2007

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The balance test is done. Interesting, but inconclusive.

I connected a vacuum gauge to port vacuum to get a reference reading. The gauge I'm using is the one in this video @ 0:06. I'm linking to this video for a pictorial reference of the tool I'm using. Nothing more.

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For me, the needle stayed at 40. Vacuum drop per cylinder (the needle reading, not how much it actually dropped):

Cyl:
1 - 38
3 - 38
5 - 37
2 - 38
4 - 38
6 - 38

Then, I went ahead and checked every vacuum line I could find, disconnected it, and used my vacuum tester to verify no leaks. Wow! The vacuum line feeding the MAP sensor was 100% bad.

Lastly, that gauge said "Ignition Timing Late". I didn't think it was possible to adjust ignition timing on these engine, seeing has how the computer wants control.

It would make sense, though. Lack of power, seems like its missing, and sorta low vacuum. Hmmm.
 

DeCaff2007

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See if the EGR valve is holding vacuum.

I can do that. I'll post up the results as soon as I can.

Might have to put this whole thing on hold for a while. We noticed a massive puddle of oil under the Wife's Jeep. The oil pan is rotted straight through and finally gave up the ghost. Gotta pull the engine to get the pan off. Done it twice (pulled the engine) already so a third time would be cake, right? NOPE. Been at it for about 6 hours now. That Jeep is the single most aggravating vehicle in my life. It fights me every step of the way.

Well then I hopped up on the front bumper to lean over the engine bay, to access the last two transmission bolts. The hood is off so I have all the clearance I need. Hmmm couldn't quite see down between the firewall and the block so I leaned in a little more. The front fascia gave way and my footing went with it :eek:. Down I went, and my left shin caught one of the front tow hooks on the way down.

Ever see stars in the daytime? Unreal [email protected]#$ The neighbors probably heard me scream a mile away. When stuff like this happens, it means STOP for the night.
 

DeCaff2007

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Gents, we are waiting on parts for the Wife's Jeep, so I can get back on this project in the meantime. Aside from the EGR valve (which I have yet to check, what else is there?

I see myself pulling this engine to fix the oil leak. #notfun.
 
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