What efi system is best for a 4.5 pfi cadillac engine7

[S.O.B.B.]

interface2.gifthis is the first cable I made for the 7747.I'm not getting a connection to 7427.do I need to have this 2 transistor set upScreenshot_2018-10-28-17-11-46.jpgany help is appreciated. Thx

[sturgillbd]

That cable will not work on a 7427. The 7427 requires bidirectional communication. Easiest cable I have found to make is use a USB/serial TTL converter and hardwire to PCM. I just plug a USB cable into my PCM and it works. Here is what I use https://www.ebay.com/itm/FT232RL-FTD...-/121821751277 There are a few posts here on gearhead on how to use them. Basically you tie RX and TX pins together and this is the serial data terminal. The other connection you use is ground.
Simple and it works well

[S.O.B.B.]

That's the info I was after.thanks for your time.that will let me see what's up.the engine won't run with out pushing throttle so I'm suspecting iac not wires correctly.plus timing not set.hopefully the weather cooperates so I can finish up the rest of the reassembly and get running and tuning again.thanks again for the help

[S.O.B.B.]

Got the usb to ttl functional.very cool.thanks for that tip. Got it idling.it ran Decent until I set the timing. It was at 30 and I put it to 10.plugged bypass back in and no change.like no advance.I am getting a code 43.need to check knock sensor and circuit. As for the timing I am going to check at distributor for continuity at bypass wire to pcm.any advice on what else I should be checking for in ignition system.the advance worked on the other set up and this is same distributor and harness.thanks in advance for any help��

[sturgillbd]

Did you pull power to the pcm to reset codes? If you did, then you have a problem with the esc circuit. Check wiring from distributor to the pcm. That's where I would start.

Brian

[S.O.B.B.]

Thanks for that.I did reset 2 times and got the same code before setting the timing and the same code after and after clearing codes once timing bypass plugged back in.it seems the code comes only after reving it.checking the wiring to distributor and knock circuit is first on the list.will post what I find. Appreciate the help

[S.O.B.B.]

Well I won't get to drive this till tomorrow but I do have it running and going into closed loop and no codes so that's awesome. I don't know if the knock sensor failed or was the wrong one.the one I had laying around seems to have stopped the code 43 and the advance seems to work now.I did another search for the Chrysler iac and found I had it incorrect.I'm not sure how to tell if it's correct now but it seems to respond as it should.the data seems a little glitchy but it does not seem to interfere. Once I go for a drive and log some data I have the wideband ready to install. The tune feels better than the tbi 7747 that's for sure.will update once I get the drive time in.thanks for all the help.I doubt I could have accomplished this mpfi conversation with out this site.