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Help With 87 R-30 please:

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conoverbandit

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Ok,
I've posted about this truck a couple of times and got some really great help.
But I'm not out of the woods yet.... What I need to know is this: Is there another "computer" that would work in this truck or am I going to have to find another 87 R-30 with 454 and get it's puter? I had a fella tell me it might work from another truck because each one has it's own "card" type thing to tell the computer what to do.I'm trying to post this as simple as possible, I guess what I'm asking is can I find another 80's model "computer", take my card out and pop it in there and it work?Or is it going to have to year/model specific......
Thanks for your time,
 
First off is probably the question "why" do you need another computer?

I believe the TBI ECM's up until 1990 were all 1227747's, and if thats the case, then yes, ANY ECM with that same number will work. It's on a sticker on the ECM case if GM, but there are multiple resources found on google that will tell you the applications that the '747 was used in.

The PROM is the swappable "card" that the other person was talking about. That is what is "calibrated" to the specific vehicle, for things like fuel curve, engine size, etc. So instead of having a completely different computer for each application, GM used the same ECM and was able to just use a different PROM based on the specs demanded by each specific vehicle.

But there are many, many different ECM's as well, so making sure you get the PROM for the right ECM is critical.
 
Ok,

I'll try to answer your "why" question. I got a 87 R-30 crew cab with 454 motor,
It has this "high idle problem" it acts like as if it has a "choke" and it's hung up of sorts. Engine hot/cold it doesn't matter, it still does it, no "service engine" or "check engine" light comming on. Light is working, when you turn the switch on and crank the truck it comes on and goes out about 2-3 seconds after it's running, tried retrieving any codes from ECM but it says there aren't any. I have replaced the fuel pressure regulator,all the gaskets on the TBI,new IAC sensor, new coolant sensor,and swapped in some other injectors. All this to no avail. Still loading up like crazy,fuel stays on top of the "Butterflies" all the time. Everyone tells me that you have to have the proper injectors and all, others say as long as it's the same "type" injectors that they'll interchange since the ECM is telling it what to do anyway. I talked to a couple mechanics in my area, and they suggested replacing the ecm and trying that. If you don't mind my asking what did you type into google to get the resources for the ecm's? Thanks for your time,
 
I don't even keep links anymore, so here is what I just used as a search. "gm ecm application 1227747"

The result I went to is http://www.cruzers.com/~ludis/c3xref.html and the ECM IS a 1227747, so it shows you which will interchange.

When you tried to retrieve codes, did it at least flash a code 12, as it is supposed to? You've established the bulb works, so that rules that out.

With injectors, the ECM commands the amount of TIME they spray as I understand it, and the regulator governs at how much pressure. (which bases that on engine load obviously)

In my case, I went with a 350/350 injectors, running off of a 305 PROM. Since the 350 injectors are proportionally larger to the displacement of the engine, the duration of the "spray" stays the same for both applications, if that makes sense.

In your case, running a 454 on a 350 ECM would be a bad idea. I guarantee the spark timing and fuel map is MUCH different, and would likely allow the engine to run, but nowhere near optimum. Along the same lines, however spark is handled (ESC module like early TPI?) can also be a problem, as the knock sensors are different between engines, and if the ECM handles the knock portion, a there would be more issues.

If the ECM gives you a code 12, I would REALLY stay away from getting another one. It is extremely common to blame the ECM when other parts don't fix the issue, and just like the other parts, it probably won't solve anything. (not saying it WON'T, just not likely) A GM service manual is a huge help, as will be an actual scanner that shows data. Parts add up quick, I suspect as much as you've spent on parts now, would have bought a scanner or GM manual.
 
Hello,

It's been an adventure to say the least. Yes, the ECM will flash code 12, but that's all I get. But like right now though, I have the o2 sensor out of it, so you would think "immeadiate" check engine light right? NOPE! lol, crazy thing comes on when you crank it then still goes off 2-3 seconds later and the o2 is not even in the mainfold.......That's another reason I think this things fried......almost to the point of pulling motor, swapping everything on it over to "bone stock" carb,regular dizzy, adding fuel pump, ect, and dropping it into my K-10 and letting my buddy take the body.............Got a fella on here that has a TBI complete unit I'm trying to get the $$$$$ for, I'm hoping that and maybe ECM will do it. I had a guy tell me to pop kick panel off and rap heck out of the ecm with a screw driver handle and this would re-set the computer?Something about a "hard jar or knock" would re-set it's self? He said if it ran good after that then ecm was bad.......Any Ideas?
Thanks for your time and help. I looked up the ecm #'s last night and got some info. Thanks again,
 
t.b.i info

the ecm isnt in the kick panel it above the glove box . and the o2 out will only come up no comunication after full operating temp is reached. as for the injectors thay are sized to each motor. 4.3,5.0,5.7,7.4 and so on. yes thay will work but wrong amounts of fuel at the pulses will come out. i know you said you changed the gaskets on the t.b.i but did you change the base gasket also, big blow out problems with them. if this isnt it try a can of brake cleaner around the intake gaskets ( BUT BECARFULL OF FLAMES ) and see if the rpms go crazy. if so where ever you sprayed that it has a leak. get a good shop manuel and check the voltage and resistance values on the sensors , such as throttle position, iac, map and so on. it could be out just a bit and not set a code, have seen it many times before. if you or someone else has changed the iac or the throttle position sensors thay may need to be set to a specific range or position. thay just dont drop on and run. hope this helps you and get a good book and try the test procedures.:cool1:
 
Ok,

So there is a deffinet difference between a 4.3, 5.0 and 7.4 injectors. I took the injectors out of a 5.0 caprice and put in this rig, the "loading up" did not change, but it started "surging" and will eventually die...I am working on geting a 89-90 model 7.4 TBI from a member of this baord, so hopefully this will help it out. My truck has some sort of "heater box"? between TBI unit and intake, I changed gaskets on both sides of it as well, but you can hear a "hissing" sound pretty loud when running, it was real bad, but changing the gaskets I did seem to help this alot. I just figured this noise was the air going down into the TBI unit, since the butterflies are almost completly closed off. Thanks for your help,
 
You'd be right. The butterflies aren't, "almost completely" closed, they ARE completely closed if everything is working right!

I'd look for a vacuum leak after you fix your O2 sensor. Don't blame the computer because it can't see the fact that you removed your O2. OBD I isn't THAT smart.
 
Id check for carbon build up. Not sure if chevys do it, but my toyota had a high idle and was due to carbon build up. Cleaned it up and it went away.
 
ECM will reset if you pull the fuse for 10 seconds.

As was mentioned, O2 isn't really looked at until the engine gets warmed up.

Code 12 is telling you that the ECM self test checks out.
 
So the ECM it's self should be ok since it's pulling a 12 code? ok then idea's please, if timing is out somehow would this cause the irradic operation? I want to get this other TBI unit and bolt it on a try it to see if this helps.Thanks,
 
When you pressurize the system in the morning when the engine is cold, do the injectors drip?

You really need injectors that are "matched" to the setup, however, if it was doing the same thing with other injectors, probably not them then.

TPS checks out ok?
 
I would check out the temperature sensor in the intake. This is the one that the ECM will read, not the guage. Sounds like it might be bad and making the ECM "think" the engine is really cold, and therefore causing high idle/too much fuel. Also, check the connections at the temp sensor and the wiring between. BTW, I could run and drive my '87 TBI 454 on an 89 TBI 350 ECM. It would start, run and drive about normal, just a little down on power.

If that checks out OK, PM me, I still have access to my ECM for an 87 454 for you to try. You and I have done business before, so I know you would be OK to ship it off for a loaner. Let me know.
 
Hey,

I have replaced the coolant sensor twice thinking the first one was bad, I have also replaced the IAC.I bought a new TPS and it ran worse so I took it back, with the new one it just poured the fuel in, My friend runs a towing business and he told me to find out if any other ECM was compatible with mine and he'd let me go through his yard and see if I could find anything. So far I 've found 87-91 was the same ECM in trucks and 87-92 in vans all had the same ECM just different prom.I had someone tell me from this board that he's running a 383 with 4.3 injection unit with no problems. That's why I hi-jacked the injectors from the mom-in-laws 5.0 caprice. But that didn't work either.......If I don't find a ecm here anywhere I'll give you a holler and borrow yours for a test to see if that's it. Thanks again,
 
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