92 Truck+Camper Build

[92GMCK2500]

Nice! I bet that was an SUV spare that was stored inside the vehicle. My Suburban's spare is the same six lug steelie even though it came with the aluminum saw blade wheels.

You almost had it.

Came from a 97 express van. I paid 30 bucks for it. My wallet was very happy yesterday, I treated it to buying other new parts

 

[92GMCK2500]

Truck has been sitting since Sept 2022. Life has got in the way, kids, no $$...

Currently have a problem where the engine dies when put in drive. Idles ok in park. Dies in drive. Fuel is almost 2 years old so I've got to drain that juice out first and foremost. Maybe spring time when it warms up we will get this pig running again.

Getting this set of problems sorted. Go over to this thread to check out the full going on's.
https://www.gmt400.com/threads/dies-in-gear-when-throttle-applied.61750/page-9

Truck was dying in gear. In short, it seems to have been the coolant temp sensor giving wonky readings causing all kinds of issues.

Still getting Code 15 but getting closer to resolving. I suspect circuit 410 from CTS to ECM problems. Have yet to dive deeper into the harness &/or ECM.

Done recently:
- New fuel pump - upgraded to a 96+ Delphi unit.
- New fuel tank - Spectre premium, (made in Canada)
- New fuel lines, from LinesToGo. Highly recommend, great quality. Also made in Canada.
- Inspected & cleaned engine, pump & tail light grounds. Cleaned up wiring looming beneath truck, in frame rail etc.
- checked & fixed suspected vacuum leaks, redid some EGR hosing.
- tested EGR system, still resolving possible spring failure in valve. Stay tuned...
- New CTS sensor.
- Moved ECM ground to water outlet stud (thermostat housing).
- Redid PCV hose. Sh1tty Dorman replacement cracked & failed.
- tested & verified TPS function. Within spec.

That's all for now.

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[92GMCK2500]

Got to get this thing back on the road before end of month!

 

[92GMCK2500]

The pig has driven and done its work for now. We set up at our summer camp spot.

I ran the bags on less pressure so that the overloads were engaged. I can vouch that this is my preferred way of hauling the camper. In theory it gives 6 points of support, rather than 2 with the bags over inflated, no overload engagement. If you get my drift.

Still working out CTS wiring gremlins. See thread above. I'll cut & paste my update from there in another comment so that it's captured on this thread.

Next tweaks include (listed in rough order):
- Wrap Y pipe with header heat tape. Currently oil dripping onto Y pipe from rear main seal and smoking pretty good. This is a temp fix of course.
- Clean spark plugs w propane torch due to oil fouling. Engine sounds like it is faintly missing.
- Test O2 sensor. Replace anyway possibly. I've got a new GM genuine part on the shelf.
- Reset IAC Valve due to weird IAC step counts. See other thread.
- Figure out CTS wiring ****.
- New AGM starter battery.
- Replace incorrect brake calipers with 8600 gvwr ones. I ordered the wrong calipers when I did the hydroboost upgrade. Currently have 'low drag' type which do not match the MC I have. The brake still suck imo.
- full & complete brake bleed, including ASB unit.
- Trans flush, fill, filter. It is looking nasty in there.

 

[92GMCK2500]

(Pasted from other thread linked above....):

Reporting back on this. Haven't had the time dig into the harness nor ECM. Too many life things going on at the moment.

HOWEVER, some good news. I took the truck on some shake down runs. It drives ok, not perfect of course, but ok. I even loaded up the camper & drove to our summer camping spot without too much hassle. It's about a 30 min drive.

Truck warns up to op temp. CTS reads as it should. This is what I noticed on the drive, I was reading the scan tool along the way:

- Commanded desired idle rpm is 1000 rpm regardless of gear, or driving conditions. If I turn engine off, then restart it goes to 600-650 rpm, which seems more appropriate.
- The actual rpm at idle, in gear matches desired idle speed. However, in P/N is idles at 1500-1800 rpm. After the truck has been driven it slowly drops but only to about 1200 rpm.
- At the same time as this is happening, the IAC steps are 155. Really high. Spec is 5-30 steps at 525 RPM.
- Furthermore, regardless of gear, or driving conditions, IAC steps are always pegged at 155. Even cruising, 0% throttle, no AC, no lights or other loads. IAC reads 155.

Would this explain the high rpm at idle or high commanded desired rpm?

Another theory, could the ECM be opening the IAC Valve more, to add air, to try balance the rich fuel condition due to the Code 15, low coolant temp, aka add fuel?

What do the block learn numbers mean?

Ok my brain hurts. I'll see if anyone has anything to add. Cheers

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[Supercharged111]

I think block learn numbers are trim numbers, @PlayingWithTBI could speak better to that. But if commanded and actual match, then you need to figure out why it wants to idle so high. You said it has a low coolant temp code, which if pegged at -40 would definitely raise the idle, but you also said that the sensor was reading correctly on the data stream?

 

[PlayingWithTBI]

I think block learn numbers are trim numbers, @PlayingWithTBI could speak better to that.

Yes, and @Schurkey explained it in the other thread. In a nut shell Stoichometric is normally 14.7 AFR (it varies with alcohol content), in terms of INT and BLM, 128 is Stoich, anything below is rich and anything above is lean. When it's below 128 the ECM is commanding INT for leaner fueling until BLM gets back to ~128. This is all assuming the O2 sensor is working properly.

Something weird is going on with the idle and IAC, the reason it's only commanded to 155 is that's the maximum allowed in a stock .bin. Something is telling the ECM it needs to keep a high idle and it's trying to increase the idle by opening the IAC. We need to find out what that something is.

There are other things that can effect the IAC such as "ALDL" idle speed. If you short out pins A & B with a 10K Ohm resistor (used for older ECMs and TPI systems), it'll raise the idle to ~1000 RPM. Throttle Follower can raise the idle too. How's your TPS working? If your system voltage goes below ~8.7, the IAC will shut down. As discussed earlier, the CTS can cause this too.

Sorry, that's all I have.

 

[92GMCK2500]

I think block learn numbers are trim numbers, @PlayingWithTBI could speak better to that. But if commanded and actual match, then you need to figure out why it wants to idle so high. You said it has a low coolant temp code, which if pegged at -40 would definitely raise the idle, but you also said that the sensor was reading correctly on the data stream?

When I follow the scanner, the CTS reading starts at ambient temp, then slowly warms up in 5*C increments until it reaches 90*C (194*F) when the thermostat opens. I have not seen the CTS higher than this temp, yet. This is what I am calling '"the CTS reading correctly".

However, please note, the actual voltage at the CT sensor is only 3.75V with KOEO, not the 5V spec the FSM calls for.

We've disussed this in the linked thread, there is a problem in the 410 CKT wiring, I just haven't got off my a$$ to investigate further thus far.

 

[92GMCK2500]

Yes, and @Schurkey explained it in the other thread. In a nut shell Stoichometric is normally 14.7 AFR (it varies with alcohol content), in terms of INT and BLM, 128 is Stoich, anything below is rich and anything above is lean. When it's below 128 the ECM is commanding INT for leaner fueling until BLM gets back to ~128. This is all assuming the O2 sensor is working properly.

Something weird is going on with the idle and IAC, the reason it's only commanded to 155 is that's the maximum allowed in a stock .bin. Something is telling the ECM it needs to keep a high idle and it's trying to increase the idle by opening the IAC. We need to find out what that something is.

There are other things that can effect the IAC such as "ALDL" idle speed. If you short out pins A & B with a 10K Ohm resistor (used for older ECMs and TPI systems), it'll raise the idle to ~1000 RPM. Throttle Follower can raise the idle too. How's your TPS working? If your system voltage goes below ~8.7, the IAC will shut down. As discussed earlier, the CTS can cause this too.

Sorry, that's all I have.

Cheers for the explanations.

Interesting, 155 IAC steps is max. How on earth would it do that...

TPS seems to be working normal 0.58V at 0% throttle & 4.27V at WOT.

System voltage? You referring to supplied 12V to the ECM?

My batteries are on the way out, they are ok but hover around 12-12.4V depending on there charge state. Not sure if this is a problem. I haven't checked anything at the ECM yet

 

[PlayingWithTBI]

Interesting, 155 IAC steps is max. How on earth would it do that...

It's a setting in the .bin on the EPROM, max is 256 but GM has it set at 155.

TPS seems to be working normal 0.58V at 0% throttle & 4.27V at WOT.

That's pretty good there.

System voltage? You referring to supplied 12V to the ECM?

Yes, what voltage the ECM sees. It's designed to protect the sensors and system.