90 Suburban runs rough and dies shortly after filling up.

[Irish_Alley]

also see this

[90_suburban]

It does smoke just a little occasionally but it did that before. Little bit of white I think it’s a little oil burning. Clears up pretty quick though.

Looking at the testing you posted for code 34 it shows it is an intermittent code being my voltage is around 1.5 while idling. I haven’t actually checked the timing I’m pretty sure it hasn’t been adjusted since new being the bypass connector is still taped to the harness can’t unplug it without taking the tape off. The lean showing on the screenshots bounces every 2ish seconds between rich and lean which I assume would be normal ( constantly adjusting).


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[Irish_Alley]

should of added this first

[90_suburban]

should of added this first

Looking at that it’s possible I set the code from having the throttle over 20% when trying to get it restarted. Possibly. I can reset the codes and see if it comes back and try not giving it any throttle while starting as to not set it from that.

I have to get a new fuel regulator tomorrow for it. I pulled it just for peace of mind that the spring wasn’t broken or diaphragm torn. The diaphragm is too soft to reinstall without the guide pins supplied with a new one.


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[zieg85]

Have you checked timing?  A loose timing chain possibly?

[90_suburban]

Have you checked timing?  A loose timing chain possibly?

I haven’t checked yet my timing light only wants to work occasionally so I will be picking another one up tomorrow. Loose chain is possible with 190,000 on the clock. Hopefully it’s not.


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[zieg85]

If the timing is jumping all over it would explain a lot of what is going on

[90_suburban]

Just checked the time and it’s 0* with the wire disconnected and 24* connected and idling. I did reset the codes and was watching the live data. All of a sudden lost all voltage to the map and it died started back up and can’t get any voltage reading on the map. Swapped the map out with a different used one same thing. I’ll be looking into what is causing no voltage reading.


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[90_suburban]

Checked the map sensor wiring. If I jumper terminal BtoC I get 5 volts. Check resistance back to the ECM and all check good readings were grey wire 1.1 ohms lt green wire 2.5 ohms and purple wire 1.1 ohms. According to the troubleshooting diagram above the ECM is bad.


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[bd]

Before condemning the ECM, disassemble and clean all ECM ground connections to the cab and engine.  Turn on the windshield wipers and verify there is zero voltage drop between the cab sheet metal and the battery negative post.  Similarly, verify the ground connection between the engine and the battery negative post.  Disconnect the harness connectors from the ECM and wash the wire terminal ends and PCB edge contacts with CRC QD Electronic Cleaner or equivalent.  Using care not to deform the board edge terminals, slightly raise the terminal ramps using a pointed, narrow, curved scribe or similar tool to subtly increase the tension between the harness terminals and the PCB.  Remeasure the continuity of the MAP to ECM wires while very gently wiggling the wires to make sure none are severed internally.  Then retest.  Note that disconnecting the ECM will clear all stored codes and reset the adaptive memory.

[90_suburban]

Definitely is a wiring issue. Wiggling the wires for the map I can lose all voltage or get voltage back. I’ll dig into to harness and get that fixed and see where I’m at then.


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[90_suburban]

Got the wiring issue for the map sorted out. Loose connection on factory crimp for the 5v reference. Now I have 0.1 ohms on all 3 wires. Only issue I still can’t figure out is why it is idling at 1000 with the higher than normal iac counts. 


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[zieg85]

Check all the connections then.  You may find more bad ones

[90_suburban]

Went through pretty much all sensors and the wiring checks out. I checks for vacuum leaks again and finally found the intake manifold leaking between cyl 3 and 5.

I also noticed that it will idle fine at 650 in park and 550 in gear until I turn the scanner on? What would cause the idle to go up when the scanner is turned on?


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[90_suburban]

Looks like as long as I don’t hook the scanner up it runs perfectly fine even with the slight vacuum leak in the manifold. Drove it into town and back around 15-20 miles stop and go traffic and even stopped got some food and it started right back up and drove just like it did when I bought it.


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