Hello everyone I'm new to fuel injection but not swapping motors. I just put a 305 tbi in an astro in place of 4.3. thanks to this forim I've fixed everything but one. when the temp. is 60 or below, when the engine starts it run fine [ idles @ 1000 for a few seconds then down to about 750] but when it warms up to normal temp. it wants to idle @ 350 or 400. yes it's had a tune up fuel filter will be tomorrow, replaced the cts. put all new vacuum hoses etc.
Anyone thats got any idea's? Thanks

 

You do have the 305 injectors in the TBI and a 305 ECM or chip on it. Otherwise the computer will be running weird timing, idle speed etc. If you still have the 6 cylinder engine prom in the ECM it is in 6 cylinder mode. The reference pulses recieved from the V8 will actually make it idle abou 3/4 speed and in general run poor.

You may also have to reset the minimum air rate if the TBI is from the 4.3.

 

ok, thanks 355, that makes since. I do have the tbi from the 305 and one thing I noticed that when I advanced the timing that it ran better until the ecm readjusted. Where is the best place to buy a new prom? this project was to pull with and better fuel milage than the old 4.3 that was shot.
Thanks to all that use this forum, this is a welth of infomation for all that takes the time search.

 

Since it looks like you have a 1986 astro that would be controlled by a 7747. Your best bet would be scoop up a 305 Van ECM and just plug it in. Best place would probably be a wrecking yard. You should be able to pickup one for under $30.00 certainly under $50.00. Most yards seem to get around $20.00 but will usually take $10.00 to $15.00. Your ECM is in the passenger side kick panel in front of the door, under the dash.

 

The ecm in my astro says serv no. 1227137, is this what I go by when trying to find an ecm or chip? I took the lid off to see if the chip in the rs that i took the 305 from would work in the astor but it was different. I thunk this is starting to sound like I'm in the wrong forum but I thought it was a tbi problem.
Thanks for all your help, this is very good learning experience.
DksAstro

 

Switch the ECM from the camaro to the van and see how it runs.

 

I tried that,it wouldn't evan fire at all. The only difference that I could see is the part# The plug must be wired differnent on the RS. It's 1990 and the astro is 86. but the chip inside looks like it would plug into my ecm.
Thanks again

 

Thats odd!!! I haven't found a TBI ecm yet that didn't have all the major stuff in the same locations. I don't have the wiring diagrams in front of me but possibly the injectors are on different pins. The chips although they look the same are coded different. The car ecms and the truck ecms are coded different. Your best bet would be get a wiring diagram and compare the two. If needed swap the wires in the pins. You pull the blue retainer and use a tiny screwdriver to release the tabs. Then the 305s ecm would run the 305 using the modified astro harness. It will throw an IAT code for not having the air intake temp sensor but it will run better than the 4.3 ecm will.