Running terribly

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Jeepwalker

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LOL! Vacuum tubes refers to the rigid plastic (often molded shape) tubing used around the engine compartment of vehicles (if/when present). It's really not a hose if a hose is a 'flexible conduit of air/vacuum'. Therefore I refer to those as tubing, and I believe that would be found in factory manuals too. Even hose is referred to as flexible tubing a lot of times. But yeah ...different people say or 'think' different things when hose/tubing is used. I get that :)

Plastic tubing can crack, and when it does, it can be difficult to spot. Rodents can chew a hole in the non-visible backsides. Just because it's plastic don't overlook it -- it could be a hidden problem. The rubber molded ends can and often do become brittle and split. Been there. In the OP's case, not knowing the history EVERYTHING should be inspected in terms of the basics. The first thing at the top of the page on factory troubleshooting trees is to ensure all the basic things have been inspected and known 'good' before proceeding down the troubleshooting tree.

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Sle-z_90

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I inspected and cleaned my grounds today. Despite some of the nuts and bolts looking pretty bad, it ran the same afterwards. I also checked the timing. It was a little advanced but I brought it back to 0. Runs the same. I confirmed the msd is not connected but was hooked to the battery. I removed the battery connection and the msd. I found a couple connectors that are completely disconnected but could not find where they should connect. Can anyone I’d these?
 

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PlayingWithTBI

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I found a couple connectors that are completely disconnected but could not find where they should connect. Can anyone I’d these?
The 1st one looks like your water temp sender for the gauge. Does it reach the sender in the left head between cylinders 1 & 3?

The 2nd one looks like it's for your A/C high pressure switch that goes to the back of the compressor.
 

Sle-z_90

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I forgot, the 1st one may be for your O2 sensor (I forgot about the 1-wire sensors).
Thank you. I will check out both tomorrow. The temp gauge doesn’t work. I don’t think it will reach the driver side though. The o2 sensor might be good though because reconnecting it may resolve my other problems.
 

victor II

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I recently purchased a 1990 GMC C1500. The truck came from the factory with a 350, I have not been able to verify that it still has the org engine though. Mileage is 28X,***. I bought it running poorly so I cant really give a history on it. Truck idles very rough and shakes significantly. I pulled the codes and got 33, MAP sensor signal high, low vacuum. I tested the MAP sensor according to the procedure laid out in https://troubleshootmyvehicle.com/gm/4.3L-5.0L-5.7L/how-to-test-the-map-sensor-1 . It worked fine, signal dropped under vacuum as it should, power and ground checked out as well. I changed the vacuum tubes to the MAP sensor, EGR valve, egr sensor. The vacuum line to my canister looks good and holds a vacuum. I also changed the hose for the PCV. Still running rough, still throwing Code 33. Very strong smell from the exhaust and very loud. Backing out of my driveway today it died twice. Backing out of my space at the grocery store it died as well. It will sit in the driveway and idle for a as long as I've let it. Sometimes it will die right after start up but once its idling, it will stay running unless I put it into gear. Brakes are not great. When I press the pedal that seem to react as expected, a little spongy but more or less responsive. However, when actually coming to a full stop they truck creeps further a bit further than expected.

I think it is "running rich" because of the smell and stumbling. I am, admittedly, not a super experienced mechanic so I could be wrong about that. If the MAP sensor is working and the vacuum tubes are as well, it suggests to me that the engine is producing low vacuum. This may also be causing the brake problem. The troubleshootmyvehicle.com article suggests that in my case I should test my cylinder compression and fuel pressure, but also mentions that the PCM may be fried. I doubt fuel pressure is the problem because it seems to be running rich, not lean. Also, prior owner replaced the fuel tank.

My plan is to check out the EGR valve and sensor next. If they check out or replacement doesn't solve the problem, I will check compression. If that checks out, I suppose I'll start looking at the spark plugs, wires, distributor. The wires look new, haven't pulled the plugs yet, and the shaft of the distributor looks corroded. There is a MSD box on the passenger side, but the best I can tell its not hooked up. The wires I see coming from it are disconnected.

I welcome any questions, criticisms, suggestions etc. I have a tendency to bite off more than I can chew so hopefully this isnt another example of that, lol.
Have you checked the distributor cap, rotor, wires and plugs? Also, run some Seafoam through the fuel system to clean the injectors. Also check the air cleaner and pcv valve and it’s hose. Lastly, spray wd-40 around the base of the throttle body to see if you have a vacuum leak there.
 

Sle-z_90

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Sle-z_90

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