454 TBI swap from refrigerated box truck, timing problems I can't figure out

I can't figure it out. My research has led me here.

It is a gen V 454 TBI from a refrigerated box truck manual trans, 1227747 ECM (no knock sensor or ESC could be found) . I put it in a 1988 C1500 with a turbo 400 trans. Picture album of build http://imgur.com/a/6VPoZ

When I unhook the timing bypass wire and try to set the timing to 4 degrees BTD it will barely run there. If I advance it a whole lot, like almost to the next plug wire, is where it runs best with and without the bypass wire hooked up. When I hook up the wire the timing does not change. It does advance when I rev it. It misses some at idle and runs weak like the timing is off. Some spots around 1/8 throttle seems OK with power. Giving it good throttle is a toss up. Sometimes it runs OK and most times it falls on it's really weak with a small misses. I have no codes showing. I was thinking it jumped time, but that wasn't it either. I don't think it is fuel related because it sprays good but doesn't want to idle at 4 BTDC.

I replaced, timing chain, ICM, cap, rotor, plugs, wires.. The distributor and firing order are set correctly and double checked no less that 5 times each.

I'm pretty much down to the ECM and or the lack of knock sensor and ESC. I did read that some ECMs didn't use knock or ESCs. Maybe the mapping for the box truck is just not compatable for my set up? Could the lack of back pressure from having headers and free flowing exhaust be the problem? I did install dual O2 sensors. Also I used the C1500 wiring harness because the box truck harness was to short to work, but I was told elsewhere that wouldn't be a problem. The harness I am using does has a spot for a ESC and knock sensor. The box truck harness didn't.

Thanks in advance.

Howdy.


Sounds like you've got a neat project when you get the bugs worked out.

Some of the very early calibrations required you to jumper the ALDL A and B connectors before setting the timing. Do you have the original emissions label because the instructions would be there.
The dual O2 could cause a problem. The 7747 doesn't have an input for a second O2 and you won't get correct values if you tie two sensors together. Try disconnecting the sensors and see how it runs. Check the the MAP sensor line to ensure no vacuum leaks. You can try disconnecting the coolant temp sensor also... the ecm might be thinking the engine is hotter and pulling timing back.

Use Tunerpro or a scantool to see what the ECM is seeing and you might get some good clues. Otherwise you're just guessing.

I've been doing more research. This 1227747 ECM came with the 454. Is that normal? So basically I am using the ECM from the 454 with the other truck's wiring harness. Maybe that is causing the problems. That is how I was able to connect 2 O2 sensors because the harness had 2 spots for them. I don't have the original emissions label.

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Originally Posted by yellowsnow

I've been doing more research. This 1227747 ECM came with the 454. Is that normal? So basically I am using the ECM from the 454 with the other truck's wiring harness. Maybe that is causing the problems. That is how I was able to connect 2 O2 sensors because the harness had 2 spots for them. I don't have the original emissions label.

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I never have seen a TBI truck with dual 02 sensors or even dual o2 sensor inputs to the ECM.

What is the BCC (Chip four letter code) on the chip in ECM.

No it's not normal for that truck to have a 1227747... it should be a 1228747.

There is no extra spot in either of those ECMs for an extra O2 sensor. Not sure what your seeing?

Motor must be warmed up to set timing, even then they do not run well, barely idle.

Wonder what year motor that BB is? Could have been a swap from 94-95 which require higher fuel pressure? Can you get the number off the top of injectors?

The four letter code is "ANVA" which doesn't show up in the search.

The truck was an 89 but with a gen V goodwrench crate motor. I don't know the history of it.

The injector number is "GM 52352 (8 or3) 1 * ? PD

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Maybe that is causing the problems. That is how I was able to connect 2 O2 sensors because the harness had 2 spots for them. I don't have the original emissions label.

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Is it a single wire plug? What color wires are on the ECM side of the connector? If not purple (probably green or black w/ white stripe) it's not O2.

4 letter BCC means not an early calibration. There are some 7747 BBC calibrations.

We'll get this figured out. ;)

Both O2 sensor wire are purple/violet one is by the relay on passenger side and the other on drivers side close to the brake booster. Both had the O2 sensor clip on the end, so I just bought some O2 sensors and hooked them up. But the harness was from the truck, not the engine but it also had a 1227747 ECM.

Someone has messed with it. That ECM can not run 2 O2 sensors. Check wiring and remove one!

No luck in my search of a ANVA But ANUA comes up as a 7.4L Manual 1227747

5235231 - Red / Blue - 80pph - 7.4L / 454 - 88-90 Got the big injectors! :thumbsup:

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Both O2 sensor wire are purple/violet one is by the relay on passenger side and the other on drivers side close to the brake booster. Both had the O2 sensor clip on the end, so I just bought some O2 sensors and hooked them up. But the harness was from the truck, not the engine but it also had a 1227747 ECM.

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The connector on the passenger side is not for O2. Disconnect it. I can't remember what it is... possibly TCC diagnostic wire. But as I remember, O2 should be on driver's side

Alright, I fixed it some how. I replaced the riming chain which was stretched with a lot of slop, That was getting finished up when I started this post. I unplugged the passenger side O2 sensors, and I installed a knock sensor just for the hell of it.

So now I set the timing to 4, then hook the wire up and it goes up to about 16. It would never do that before. It was stuck in limp mode before. That was like the main thing that didn't make since.

So now it seems OK through out the throttle range. It seems kinda of week for a big block though. Makes me wonder if the ECM mapping is really tame.. My brother is a computer programer and programs microcontrollers for a living. Maybe I can get him to tweak the chip. But he has never messed with vehicle chips before. I probably need a better cam though. The stock cams are tiny.

Even if you have the correct ESC and Knock sensor for the 7.4L hooked up... it will not work until the parameters in that chip are changed!

The reason it feels weak is the advance is set so safe! Why... well it did not have a knock sensor! That's the way all these BB are that came with no Knock sensor, plus the fueling is on the rich side to keep things cool! The heavier trucks did not have as stringent emissions to meet so this is how they were calibrated, to be safe with a heavy load and any driver.

It was running pretty clean when I got it done and drove it the first time, but coming home from work last night it seemed to have a fuel issue if I stomped on the gas. At least it's not a timing problem any more. I thank you guys for that.

I already have the knock sensor. If I get the LXE30 spark controller I should be able to flash the chip to a regular chevy 3500 pickup mapping. Or did they not run this ECM? I would just have my brother do it since he already has the equipment. I need to put a rebuild kit in the TBI, MAP sensor, fuel filter, and a fuel pump. The previous owner conveniently cut a trap door in the bed to get to the fuel pump.

And if I did all that and got the connector cable, could I get good results by fine tuning it even more? I don't have to pass any emissions stuff where I live (Illinois). So I'm not running a cat and I have free flowing exhaust.

Just a funny thing, when I went to change the oil in the motor after I got it in I found that it has a 8qt oil pan. Jeez it cost me a bunch just to change the oil.