Dies in gear when throttle applied

[92GMCK2500]

I'll report back here once I figure this out.

 

[92GMCK2500]

I am still chipping away at this as time allows, which isn't very often.

Truck recieved a new fuel pump, tank, and lined. Problem aside, I said F it, the old, 30 year old fuel system is getting replaced in prep for the inevitable engine overhaul/replacement that is ultimately looming.

Circling back, the problem persists. No surprises there. I am wading my way through some diagnostics.

Interesting, scanned a code 15, coolant temp sensor. I remove it yesterday and bench tested it, got real wacky ohm readings so a new one is on the way. The multimeter was showing 38k ohms at room temp, but it kept raiding all the way to 200k. Weird. Tested again in boiling, then cold water. Same thing.

Next up the new sensor goes in, and then chasing the wiring. I am only getting 3.7V at the CTS plug. Can a crappy battery affect this? My battery tested at 11.95V. I charged it, it reached 12.75V but also dropped to 12.2V after 2 hours.

I will try my yellow optima next. It's on the charge so we'll see what the CTS reading is. Hoping it's the Batt, but could be wiring, my favorite...not.

 

[1990Z71Swede]

I believe the CTS is feed by 5 Volts from the ECU. That means; without anything connected you should see the full 5Volts at the Connector BUT if you plug it in there will be some current flowing with a corresponding voltage drop, depending on the temperature at the CTS. That voltage drop(or sometimes current flow) is how the ECU reads Coolant temp. If that 3.7 Volts is with nothing connected, I would start with measuring voltage to the ECU right at the ECU connectors. If that checks out to be about the same as bettery voltage out my next test would be ECU ground. Now if you measured these 3.7V between the block and one of the pins in the connector I would try measuring voltage between the pins instead, just to verify its not just a 1.3V difference in ground plane between engine block and ECU.

 

[92GMCK2500]

If that 3.7 Volts is with nothing connected, I would start with measuring voltage to the ECU right at the ECU connectors. If that checks out to be about the same as bettery voltage out my next test would be ECU ground.

Yes, I get 3.72V at the CTS connector, with the sensor unplugged, measured between pins A & B.

Where does the ECU ground?

 

[92GMCK2500]

I also ordered a new connector as the clip is broken and the pins shows signs of corrosion.

You must be registered for see images attach

 

[1990Z71Swede]

Yes, I get 3.72V at the CTS connector, with the sensor unplugged, measured between pins A & B.

Where does the ECU ground?

There might be more than one ground. You can find the Wiring Diagram here:

88-98 Service Manuals

Over the years I have collected a bunch of GM service literature. Links to PDF Scans of service and STG manuals and a links to the Parts manuals. You'll need the FREE Adobe Acrobat reader to open these files. Get it directly from Adobe here {http://get.adobe.com/reader/} If you're not...

www.gmt400.com

ECM stuff starts at page 72. 5V Return B and 5V reference might be of interest too.

 

[someotherguy]

Vacuum test of the EGR valve can really only show you that the diaphragm is still good, IMO. Can't tell if the spring inside is broken.

If you want to quickly eliminate whether the EGR is the issue, temporarily install a block-off plate for testing. If you pull the valve you'll need a new gasket anyway, so go ahead and get one, and use it as a template to cut a little piece of scrap steel for the block-off. If you only run it a short time as a test, the gasket will be 100% re-usable when you replace the valve.

In terms of EGR failure on the vacuum EGR's, it's almost always the valve, rarely the solenoid, just as an FYI. If your EGR is bad, picking the correct replacement is critical.

Richard

 

[92GMCK2500]

Are there any precautions that must be taken when testing electrical at the ECU?

E.g. battery ground connected vs not? Or, risk of static electricity etc?

 

[92GMCK2500]

Vacuum test of the EGR valve can really only show you that the diaphragm is still good, IMO. Can't tell if the spring inside is broken.

If you want to quickly eliminate whether the EGR is the issue, temporarily install a block-off plate for testing. If you pull the valve you'll need a new gasket anyway, so go ahead and get one, and use it as a template to cut a little piece of scrap steel for the block-off. If you only run it a short time as a test, the gasket will be 100% re-usable when you replace the valve.

In terms of EGR failure on the vacuum EGR's, it's almost always the valve, rarely the solenoid, just as an FYI. If your EGR is bad, picking the correct replacement is critical.

Richard

Thanks Richard.

I've got my hands on a vacuum tester now, I have your Chevytalk EGR article pulled up and will be following that to figure out my code 32.

I have a new Delphi EGR Valve btw

 

[someotherguy]

Thanks Richard.

I've got my hands on a vacuum tester now, I have your Chevytalk EGR article pulled up and will be following that to figure out my code 32.

I have a new Delphi EGR Valve btw

I still say try the block-off plate. Might save you from trashing a good OEM EGR valve if that's not the issue.

Richard