Andy’s 1995 CCLB 7.4L TBI to Vortec Swap

[andy396]

I went to start it and it would fire right up, seemed like it wanted to run for a second, then it would just die. I decided it's an ignition thing and thought I was probably off a tooth on the distributor. I'm getting really good at pulling the coil and distributor all at this point. Sure enough it was off a tooth, oh and I left the cam position sensor connector off. I even looked at the spark advance output on my scan tool and it said zero, which I didn't think much of at the time but should have gone, duh! you forgot something. This iteration went pretty quick though, I had it all timed and back together in probably 30 minutes. That and I put hose clamps on the two power steering return lines I forgot and were leaking.

Turned the key and it fired right up and purred nicely. My son comes in and says, "why's it so quiet?". I said because you're used to hearing it running like crap!

Topped off the antifreeze and trans fluid, but was out of power steering fluid. Put the transfer case in neutral and ran through all the gears. Didn't hear anything weird, so I re-engaged it and put it in reverse and forward. Still seemed good.

June 26, 2019 it officially moves under its own power again, a little over two years since throwing a rod through the oil pan.



Backed it out and washed off all the power steering fluid and antifreeze I spilled. Pulled it back in and parked it.

My nice looking self rebuilt alternator doesn't seem to be working, so I'm going to just go buy one and get some more power steering fluid next.

Definitely feeling much better. I'm cautiously optimistic at this point. I still have to bolt on a bunch of stuff, finish putting the dash in and tie up a few loose ends here and there before I can give it a good test drive.

 

[andy396]

Putting the dash back together I finally got the interior lights fully functional. It was just a matter of splicing two wires together at the headlight switch, just not the two I had initially thought. It took me way longer to figure that out than it should have. I didn't help that the '95 GM wiring diagram left that part of the circuit blank! 1995 was such a ******* year for these trucks. All I had to do was splice the small grey wire to the white wire on pin C. After '95 that little grey wire goes to the remote locks receiver to make the interior lights come on when you unlock the doors. I'll be okay without this feature. Heck, I've gone this whole time without even remote locks. I never got the key fob from the previous owner and never got around to getting and new one programming it.

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Above is the splice needed to make the interior lights work as intended in 1995.

I also figured out the issue I was having where the radio won't illuminate. It works as a radio, you just can't see anything. I decided it's a radio thing. When I plugged in the '95 radio it illuminated as normal. Looks like I'll be getting an aftermarket radio. I wouldn't mind having Bluetooth and hands-free calling anyway.

 

[kennythewelder]

Blue tooth is grate. I love mine.

 

[andy396]

A couple days later I add power steering fluid, but it's still not building any pressure, which also means no power brakes. It's a new reman. pump. I pulled the pressure fitting out of it and the one out of the pump on the old engine. Sure enough they're different. The '95 had an extra little hole in it that the '00 fitting didn't have. Put the old one in it and it works now. Must have something to do with the speed sensitive steering that was on the '00 truck. I thought I could just leave that valve off and just hook my old line right in, but apparently not. It's now leaking PS fluid from somewhere...probably the fitting I just put in.

The 4WD isn't engaging. Come to find out the '00 actuator is shorter than the '95. It looks like I can just make a spacer to put in the hole where it mounts as that's what Dorman sells with their kit when converting from the thermal actuator to the newer servo mechanical one.

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This shows both actuators fully extended. I'm so happy to be getting rid of the thermal actuator. When I want 4WD, I want it now! Not eventually when the thermal actuator gets warm enough.

 

[andy396]

Took if for a small test drive around the neighborhood the other day. I got as far as 3rd gear. Seemed to shift okay. It's definitely a firm shift. I assume that's coming from the enlarged orifices I did when I rebuilt it. I hope I like it long term. When I switch to the 0411 PCM, maybe it's something to tune?

The latest big problem is that once it was warmed up, it would stall every time I came to a stop. I'm thinking the issue is that the TCC isn't unlocking. Once it stalls, I can start it back up and it's fine. I'm pretty sure that its not getting the signal from the brake switch that is supposed to signal it to unlock the TCC whenever you step on the brake pedal. I think this is another '95 to '00 thing. I reused the '95 brake switch because I couldn't find the '00 one. I had to change the connector and move wires around to make them match up. I didn't think much of it at the time because I just figured it was an improved design, not a different design. I checked the pin at the PCM that's supposed to toggle between 0 and 12V when depressing the brake pedal and only ever got 0V. I eventually did find the '00 brake switch, so I guess my next move is to reinstall that one and see if that fixes it. Really hoping it's not a transmission problem.

I also can hear a slight ticking coming from what sounds like the transmission when idling. I don't know if it's anything to be concerned with or if I'm just being paranoid.

The engine seemed to run good. Definitely more peppy than the old TBI engine!

 

[andy396]

Got the brake switch changed and took it for another test drive. Still stalling when coming to a stop. I can keep it going if I through it in N or left foot brake and give it a little gas. Just watching the tach when I give it a little gas, I'd say I've never even reached lockup yet driving around the neighborhood. So maybe it's not TCC.

For all I know the engine had this issue when I bought the parts truck. I didn't drive it very long. It might not have even warmed up. It only does it warmed up. The fact that I can keep it running with left foot braking and working the throttle has me thinking it's an intake thing.

I think I also found what that ticking sound was that I thought was transmission. I think it's coming from the aftermarket cat that I welded in place. It only does it when the exhaust gets warm. I tried dimpling the outer case a little, but I think I need to get more aggressive with it. It's superannoying!

The next step is to borrow a friends HPTuners Scanner and really see what's going on. My scanner just doesn't show enough parameters.

 

[andy396]

The next day I take it out again, but this time with the HPTuners hooked up. I soon hear a huge exhaust leak coming from the engine area, pull over and there's a smog plug in the RH replacement exhaust manifold that I either forgot to tighten or worked it's way loose. It's still sitting in the hole. Knowing it's too hot to touch I opt to just leave it there and hope it stays there until I get back home. The whole time I was driving it said the transmission input shaft RPM was 0rpm. It eventually threw a code for that. The other code I got this time was P0401 - Exhaust Gas Recirculation Flow Insufficient Detected. I'm guessing that's because of the huge exhaust manifold leak! I also got P1626-Loss of Serial Communication with VTD. Not sure what that's all about? I haven't had and VATs issues yet preventing me from starting it.

When I get back, the smog plug is gone! I walked back to where I think it fell out, but it was getting dark and never found it. Of course it's some odd ball size that I later figured out was M22-1.5.

I pull the connector of the input shaft speed sensor and it's terribly corroded. When I rebuilt the transmission I couldn't get either of them out. I messed with them for a bit, but was affraid of breaking them. Well, when the rear one (which is just a plug) saw pressure it started leaking. Being a little lubed up I managed to get that one out now. I couldn't get my muiltimeter on the front one to test it, so I tried to rotate it. When I did that it broke off and I got just the inside part out. The insides were all corroded also. So apparently it had been cracked and letting moisture in for a while. When I tested it, sure enough it was bad. I was able to get the casing out by threading a tap into the plastic and working it loose. Stole a good one out of the '95 trans to replace it with.

 

[andy396]

This brings us to present day. My wife went for a walk this morning and found the smog plug laying along side the road! Yah! She's awesome. I was sweating where I was going to find such an odd sized plug.

I took it out for another test drive. NO STALLING!

It seemed to shift even better than before. Without the input shaft speed signal I think it was commanding full line pressure the whole time.

I think I've put about 13 miles on it so far.

My list of loose ends is still pretty long, but hopefully the biggest issues are behind me? (knocking on wood).

 

[andy396]

Still getting P0401 - EGR Flow Insufficient. It's a new EGR valve, pipe is good. I took it off and tested the pintle movement by commanding 100% and watching it move. Looked good. I do have a very slight leak in the exhaust flange under the cab.

I don't understand what the PCM is trying to do. I can see where it looks like it's commanding the ECR to 0% a total of 8 times. I'm assuming that's where it's testing the EGR, but it's not doing it how it is described in the manual.

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In the manual is says:

"The VCM tests the EGR system during deceleration by momentarily commanding the EGR valve open. The pressure in the intake manifold increases when the EGR valve is open. The VCM monitors the Manifold Absolute Pressure (MAP) sensor signal during the EGR system diagnostic in order to determine the amount of EGR flow. The VCM calculates an error based on the difference between the actual MAP increase and a predetermined value. The VCM records the error and adjusts an internal fail counter towards the fail threshold if the error is too great. The VCM sets a DTC P0401 when the fail counter exceeds the fail threshold. The number of test samples required to exceed the fail threshold varies according to the magnitude of the detected flow errors.
The VCM allows only one EGR flow test sample to be taken during an ignition cycle. Following a scan tool Clear Info or a battery disconnect, the VCM allows twelve test samples during the first ignition cycle in order to aid in verifying a repair."

Is there some sort of ECR test or learning sequence that I need to do? I see this test mentioned in the manual:

"Run Test
• Stabilized MAP (valve closed) recorded and EGR valve ramped open over a time interval and peak MAP value recorded and MAP change computed.
• EGR valve closed
"

 

[andy396]

Still at a loss as to why it's giving me the P0401 code. I double checked that all EGR passageways are clear and open. I also checked out the MAP sensor. Seems correct at 4.8V when engine is off. I moved the EGR valve to 100% at 1500 rpm and MAP went from 30kPa to 50-55kPa. Does anyone know what the intake pressure increase should be when doing so?