Hey ya'll, new to the site. It has been said over at fullsizechevy that you all are the "tbi gods", and I humbly beseech your aid.

Just got a datalogger for my 7747 ecm 1989 350. Logged with Winaldl. Would anyone care to look it over and see if anything jumps at you? I swapped the 4.3 that was there for the 350, and I don't think everything is quite right. Thanks ahead of time.

I have a 5-speed manual tranny, and I took it out for a short trip around town and then out on the two lane to open it up a bit. Log rate is only once every second and a half or so, and at least it makes for a quicker read, I guess.

 

Welcome to the site, and lets see if we can help you out. I'm not expert but I do help with the tuning aspect of TBI around here. You are in luck becuase I've tuned several 4.3 to 350 swaps for guys local to me. The surpising thing is that your tune isn't that far off. It stands to reason that since you swaped from a v-6 to v-8 that the thing probably would't even run, luckily it doesn't work out that way.

Your ecm injects fuel every time it gets a reference pulse from the ECM, now that you have a v-8 in there your getting 2 more pulses every time your motor turns over, and your ecm injects two more burst of fuel. Also 4.3's have the same cylinder size as a 350 and the calibration bases everthing on cylinder size not engine size.

So this is why your truck even runs, I bet it even runs pretty decent. All is not perfect though, your pump shot is not bases on cylinder size, so that is all out of whack. Also your ecm thinks that your turning much higher RPM's than you actually are, which will scew your fueling a good bit more so at high rpm's.

The easy fix is to get a hold of a 350 chip, injectors, EST module, and knock sensor. Your TB is the same as a 350, only the injectors are different. The not so easy, but better solution is to get into DIY chip tuning. This way you can burn your own stock 350 chip for about the cost of a new one from GM. Then you'll be all set when you start modding your engine.

As always mail order SUCKS!!!!! I think I'm going to put that in my sig.

 

I'd like to chime in on this one. i recently replaced a smaller engine in my 3rd gen for a 350, got all the sensors, and the car ran ok. I recently hooked up with BMmonte for tuning purposes and wow what a difference it makes, it runs now the way it should, maybe even better, and we are not even done yet. Just let me say, if DIY chip burning sounds scary, its not at all, just a little understanding of what your looking for. Im a beleiver where as just a month ago I wasnt. About $150 of equipment and some time and your running the way you want! Check out the thread named "come in for a free tune" Where BMmonte and I have been working together on showing everyone else the step by step almost on what you need to do. Bmonte has been doing most of the instruction and my car has been the guinea pig. He knows his stuff!!! So dont be affraid to tune, it pretty simple and fun, with instant results. Just my

 

xjcamaro89.

Thanks for posting that. Several of us talk about tuning all the time, and people seem to think that it isn't needed, and very hard. It definatly makes a huge diffrence, and really is not all that hard to pick up. BMonte, myself, deminted, etc. All started out where everyone else is. We know what it is like to start out, and the learning curve. In fact there was much less information available to learn from, when many of us started. Especialy now that RBob has his EBL stuff out, there is no reason why anyone should bother paying for a mail-order chip, and deal with a car that doesn't run pefrectly.

tbiguy --

Feel free to post you logs up here, that way several diffrent people can look at them , and give you feed back. If you are still using the 4.3 chip, that is going to be the issue.

Do you have specs on the 350 that was put in? was it a stock LO5, or was it a built motor?

 

This may be suprising, but I already have a complete 350 ecm out of a '91, which I also snatched the tbi unit from, as well as all the sensors. THe actual motor itself is from a '93 suburban, which had been rolled. Everything but the heads intake, and oil pan had laready been sold off of it. I was originally going to buy the motor from the '91 pickup, but when the guy started it up I could hear a rod knocking. So he let me strip the '91, including the flywheel, and put it on the '93 motor. It is a stock 350. It has 5.7 cast into the block back by the left rear of the block, above the bellhousing. NO ideahow many miles. I only gave $300 for everything.

I have done the ultimate mods, save for the AFPR and injector pod spacer, an air cleaner lid flip, and I have a very free flowing exhaust, save for the cast manifolds. I am unsure why it seems to be running rich. I also noticed that when I hooked up to the aldl port that the idle went from 650 up to closer to 1000, not sure why.

I agree with you guys, it's a miracle it even works. Mileage sucks worse than it should, that be the running rich thing?

Chip tuning sounds appealing, I'll have to start reading up on this stuff. I still have my 4.3's ecm, (also a 7747, just a 4.3 prom instead) could I program it, and swap it in alternately with my other one to tune it?

Thanks guys, I appreciate your wisdom and your hospitality.

 

BTW, there are calibration differences between standard and automatic transmission 350 trucks. Standards typically see much higher loading at lower rpms than automatics do. Some of the differences can be seen there.

Have you checked for vacuum leaks? Especially the base gasket under the TBI. Vacuum leaks on the base gasket will typically effect the MAP sensor reading and actually make the engine run rich.

The reason your idle picks up with the datalogging cable is because your cable has a resistor that is needed for CCC carbs. When used with the TBI, the idle is brought to 1,000 rpm, the timing advance is at a fixed position, and the air/fuel ratio is richer.

 

BOth my truck and the '91 whose ecm I am now using were 5-speed manual, and 4x4 too.

Vacuum leak is possible, but I haven't found one. the most likely place would be around my homemade tb spacer, but I did not notice any real change when I put it on.

I di this swap in late nov. after the 4.3 started beating itself to death. I haven't driven it an incredible lot since then.

 

If the 350 ecm is a 747' just swap the chips. Also your ALDL cable has a 10K resistor across pins A and B, you don't need this for your ECM. See about getting that removed, with it installed you enter ALDL mode which disables teh knock sensor raises the idle and several other things. Your ecm will still log without it.

 

Does this mean I need to remove the resistor and leave the circuit open?

 

yes, it will be fine.

 

I'm not quite sure, but I think he would be OK with the EST module and knock sensor. I beleive they are tuned to bore size, which is the same between 4.3 and 5.7. A little advanced maybe, but just wanted to point that out that he may only need the 350 chip and injectors.

 

Which I already have... I have all of the sensors for both the 350 and the 4.3, but I went ahead and used the ones for the 350. I have the tb off of the 350, and I put in the 350's ecm.

 

New(er) datalog. Before I removed the 10k ohm resistor between a & b. Starts from the gas station in town, then I hit the interstate at the 391 second mark, and then got off the i-state at 1317 seconds, followed by a short drive up a two lane highway. Very long. Haven't datalogged since I fixed my aldl connector as my head gasket seems to have finally gone. Noticed yesterday a suspicious amount of smoke from the left tailpipe, and a lack of half a jug of coolant. ALways figured it would happen sooner or later.