Okay, here is the problem. I put a tbi setup off an 88 on my 85 350 and I have a problem I cant sort out. The engine is very lazy off the line, will backfire sometimes if you try w.o.t and will hardly pull itself up a hill. I have checked fuel pressure replaced the injectors and filters, installed new map and tps, and installed a new distributor when I put in the new crate engine. It has a new knock sensor, and I have tested the esc and it is working fine. With the timing set at 0 degrees it is not drivable, but is much better as you advance the timing, the more the better....up to the point the computer cant compensate for det. and retards the timing 20 degrees.I am not running a speed sensor, but did hook up the prndl so the computer knows when it is in gear.I have set the minimum air to idle at 475 and the tps works better if I set it at .9 volts at idle as compared to .5 volts. The problem did not change with an engine replacement very much, maybe it worsened a bit even. I am stumped, nothing seems to help, and I am tired of changing parts that dont help. When I initially installed the tbi it ripped for a short time and then went down hill and has stayed there.  

When you are setting the timing I assume that you are disconnecting the wire to disable ESC. Also for what it is worth, I have long not used TDC from static timing on TBI. I use 6 to 10 BTDC depending on fuel and vehicle. They will run much better this way with 89 or 93 octane fuel too. I generally find TBI's somewhat slug like with TDC and 87 octane fuel. I am not sure what roll that VS sensor plays in ECM management but it does watch it and this is a concern. Also, your Eprom may not be mapped properly for your engine because TBI engine have higher CR and a different cam profile than a carbed 350 from a few years earlier. This may not be total cause of problem but it is not helping it. Try this, set static timing to about 6 BTDC with wire disconnected then hook it back up and then pull ECM fuse for several minutes to clear its memory and place it back in learn mode. (this reboots ECM) see if it helps at all.  

It does help for sure bumping the base timing with the bypass unplugged, yes. My buddy has the same setup as me, and his truck runs as it should, far from a power house, but at least he can spin the tires and go up a slight hill. Mine is DEAD for power, and I mean dead. I have done the reboot thing to no avail as well. My experiences in the past have always been that if a carb backfires when you hit the throttle it is too lean, and that seems to be what mine is doing. I have driven it around with a pressure gauge in clear view and it does not move. The injector spray looks good with a timing light on it, and I did change the one injector that I thought was suspect. It seems like it needs more fuel and more timing.... I swapped out the cam in the original engine to a stock profile tbi cam, and I put in a comp tbi cam with the new engine, along with an edelbrock tbi intake. Any other ideas?  

Have you checked the ECS (Engine Coolant Sensor) There are two, one in head for gauge and one near thermostat for ECM. If it is bad, it will throw mixture off. Also you might check MAP sensor and wiring. At engine crank, map sensor senses altitude data and it together with ECS sets pass line mixture. THose ECM had what was called a CalPak in them that was designed to run engine in limp mode when ECM failed internally or due to bad sensor data. It kinda sounds like you are in calpak mode. ALso have you watched timing response with a light when wire is hooked up? One the knock control, the way it works is it does a vibration noise level check of engine at idle to set threshold for knock detection. If this in in fault mode, you will only have base line timing with no electronic advance and it will be sluggish and tend to backfire at times.  

I have not tested the coolant temp sensor, no. I dont have a fault code for it but it could be reading wrong. How do you test this without a scan tool? I have swapped the map out and it made no difference to the way it runs, and the engine dies if you unplug the vacuum line from it, so I didnt go any farther with it. I think you are getting on the right track with the limp mode idea. I dont know if the computer stilladvances the timing in limp mode, but I have ran it alot while watching the timing and this is what it does, when you inintally hit the throttle the timing retards, alot. then it advances to only a total of 27 degrees. when I do the same test on my buddies truck, his also retards, but much less, and much faster, and advances to a total of 37 degrees. I have ran mine with the knock sensor unhooked, and the esc unhooked and no change in performance, it just sets off the light. I have also tested pin b7 on the ecm for a drop in the 9.34 volt signal from the esc, and have got nothing. Does calpac mode still have the ability to advance the timing, but in a limited fashion? and how do I tell if it is in limp mode?  

What happens to timing when sensor is disconnected? Does it visible act the same or does it change it? ALso on these timing observations of your,you mention total advance and retard and then advance when throttle is opened. That revision of ESC cannot retard below base line timing so I am assuming that you are reading advanced timing at idle to retards toward base line then advances again. As I recall the version ESC can have different advance curve depending on model and hardware so do not read too much into the difference between yours and your friends TBI. (not to say it is not a issue but not likely mean a fault) Furthermore as memory suggests, that version ESC has 20 degree retard limitation for knock control (it can subtract up to 20 degrees from programed timing when a knock is detected. TBI is pretty simple in theory (not being cocky here) so your problem is curious. In summary, when you start it up is reads AMP to set altitude and combines with ECS to set mixture. It also uses IAT (Intake Air Temp) to adjust it as well. The only purpose of O2 sensor is to fine tune mixture. The TPS's main function is to enrichen mixture when you advance throttle. I have a 89 factory manual around here somewhere but I cannot seem to lay my hands on it a moment.  

The timing stays the same with the sensor unplugged. I was just reading some other forums with similiar problems and someone mentioned over tightening the knock sensor makes it read too much? ever heard of that? And yes, I am reading the total timing and it is retarding the timing, but not below base. When you say it reads AMP, I assume you mean MAP? There is no IAT on this set up either. Thanks again for your input. I am heading back out to the shop now and play some more...  

There is supposed to be a IAT sensor on that engine. If I recall correctly in is in intake but it has one somewhere. I has too. It needs data from it to set mixture properly when combined with MAP and ECT (not ECS typo) and then uses O2 fine tunes it when it warms up. Does it run any different cold or warm?  

It rns about the same cold or war, I cant say for sure because I never really gas a cold engine hard.  

It runs about the same cold or warm, I cant say for sure because I never really gas a cold engine hard.  

You need to research IAT and confirm ECT operation and TPS signal. Even if IAT, MAP and ECT is correct, without good TPS data, it will tend to fall flat until ECM catches up using MAP data and enrichens mixture. TPS also is used by ECM for advance control of spark. It is a simple system in theory but can be a royal PITA when something is not right yet is not obvious.  

There is no IAT sensor for sure, they did not start using them until 96. ECT is good for sure, tested for 10 volts at pin b7 on ECU and it is good, and I can manually induce det. by hitting block near det. sensor. I just hooked up a scan tool and tps and map, etc. are all good. coolant temp is right on, and O2 is switching well, running in closed loop. Knock sensor will retard timing at WOT with base timing advanced to 10 degrees. I did take apart the pressure regulator and bumped the fuel pressure to 15 psi and it runs much better, the spring must have softened up in the reg. as it was down to 9 PSI, and I had checked it recently. Almost runs as it should now, just need to get the timing sorted out. What do you think about trying a different ECM? I have tried, changed and checked everything else I can think of.  

Well pressure regulator is supposed to be set at about 10 PSI. I am wondering, did your TBI setup /ECM come from a 305? It would explain a few things.  

I wondered the same thing, the engine sticker is missing on the donor vehicle, but the snap on scanner says it was a 350 from the vin #. I understand the fuel pressure is supposed to be 9-13 psi according to my service manual? The extra pressure fixed the back firing and it will actually sorta spin the tires a little. Keep the ideas coming, you obviously know alot about this system.  

I found my Dealer manual for fuel system and engine controls for a 89 model year TBI engine. Very detailed. Your right, no IAT but some engines that year had a MAT (Manifold Air Temp) but not that engine (I knew I remembered some engine having something like that) I have complete diag info on sensors in system in book here. BTW, TPS is supposed to be .6 at warm idle and over 4.5v WOT.