350 TBI issues

[john86]

I swapped a 350 into my dd, it had a 305 TBI before. everything that was hooked up before is hooked back up and the timing is dead on zero when ideling, but when you rev it up or try to drive it, it'll spit a flame back through the TBI. according to all the part stores the emission equipment and ECU stuff are the same. So i am stumped, Anyone gone through this yet???:confused:

[bigassjeep4u]

Have you disconnected the purple wire when you set the timing... If not it will stay in safe mode and wont advance the timingwhen you try to drive it. It should be near the distributor.

Nick

[john86]

yep sure did,.....next??

[bigassjeep4u]

Disconnect the IAC (4 wire on side of TB) and see if anything changes and next check the Coolant Temp sensor... I have had both make it do crazy things nlike that and also had both go out for no reason including 2 of the IAC's in a year... Good luck

Nick

[Bill usn-1]

How about some specs on what you are running?
ECM#/BCC ?

Start with the diagrams at the bottom of this page...
1227747 diagrams (http://www.diy-efi.org/gmecm/ecm_info/1227747/)
Start with reading any codes that might be stored in the ecm.
Connect pin A and B on the aldl plug then turn the key on.
read codes.
then remove jumper.

Sheet 1 is the ecm pin out. note there is also voltage checks listed on the outside. they are key on and engine running.

Now look at sheet 6.
This has your ignition circuit.

First thing you need to do is figure out if your timing is even working.

The est is designed to give 20° of advance at 2000 rpm if the ECM does not control the timing.

Start the truck and let it warm up.
Check the timing ...what is it at?

Now rev the motor to above 2000 rpm. What is the timing now?
Did the timing slowly rise or did it jump 20°?

Now disconnect the bypass wire and do the same tests.

are there any differences?
If the timing is the same in both test then your est is not being controlled by the ecm.

when done turn off and unplug the ECM to clear any codes.
reconnect.
Then perform the voltage checks listed on sheet 1.

If the timing is working correctly then the voltages checks will be good to continue troubleshooting.

Measuring the fuel pressure will help also.

[2manyprojects]

have you triple checked the firing order. I've seen # 7 and 2 swapped, idled great. Popped and farts when reved up.

[yager]

had a similer issue after a TBI swap, fuel pump was 9psi at idle, any acceleration or load it droped to 4-5psi followed by the pop and fireball.. Get a fuel pressure guage on there.. Along those same lines its possible your injectors just arnt getting the job done...

funny aside - coming down my street blew the air cleaner /plastic speed nut clean off and i drove over it, :(

[J Bruce]

Replace your 305 knock sensor with the 350 knock sensor. :D

[Bill usn-1]

Personally I would just remove it and the ESC before I would spend money on another knock sensor.

[82FB]

X2 on rechecking the plug wires for correct order.

[john86]

i have been reasearching and i think it's an injector issue, b/c that is the only part on a 305 that is different than a 350 and everything worked on the 305 when i pulled it out. So i am gonna give that a whirl (they got 200,000 miles on them so there pretty tired anyway) and if that dont fix it i will have to go through it like Bill usn-1 told me.

keep your fingers crossed:( :D

[john86]

i have been reasearching and i think it's an injector issue, b/c that is the only part on a 305 that is different than a 350 and everything worked on the 305 when i pulled it out. So i am gonna give that a whirl (they got 200,000 miles on them so there pretty tired anyway) and if that dont fix it i will have to go through it like Bill usn-1 told me.

keep your fingers crossed:( :D

[82FB]

i have been reasearching and i think it's an injector issue, b/c that is the only part on a 305 that is different than a 350 and everything worked on the 305 when i pulled it out. So i am gonna give that a whirl (they got 200,000 miles on them so there pretty tired anyway) and if that dont fix it i will have to go through it like Bill usn-1 told me.

keep your fingers crossed:( :D


Just how do you think a different injector would make it backfire through the intake? It sure sounds like in ignition timing problem. Either timing is wrong, or a couple plug wires are out of order. I guess you could have a valve problem too, but I really don't think a slightly different injector could possibly cause your symptoms.

[Bill usn-1]

If you think the inj's are too small for the 350 then just turn the pressure regulator up a couple pounds.

You seem to only want to spend money and swap parts till you luck into it.

Why not save money and learn something????

Maybe even buy or build a $10 serial cable to hook up to your laptop. Then you can actually log the data coming out of the ECM and know without a doubt if it is lean or not.

Popping is normally timing wrong or way too lean.
Unless as mentioned there is a mechanical problem.

[MrWillys]

As Bill USN1 already asked, Did you change the chip in the ECM? If not your base pulse width calc's are way off. You can try and mickey mouse it by turning up the pressure, or contact AFI and get a new chip. Also, someone already mentioned, you have to change the knock sensor...

[Bill usn-1]

AFI told me they were getting out of the chip bussiness.
I think bumping the pressure up is a viable way to make the smaller injectors work on a larger motor. It's just not the final answer.
I feel it's much better to learn the system yourself..
And for $130 you can convert the ecm to an EEPROM, and do all the tuning yourself, with your own chip burner.

A new chip from someone else is probably going to cost at least $100.
And if it's not right...then you pay again.
Change to headers, pay again.
Change cam, pay again!!!

You get the idea.....

Knowledge is the most valuable tool in you in your tool box!!
And it will save you the most money!!

[1ton383]

well im new here and i dont want to make any one mad cuz im new here but i have a qusetion about what moter is best for a mud bogger a 383 stroker or a 377 i dont no anything about a 377 infact i just found out about that moter its for a 1 ton ext cab long bed with 4.88s and 38s on it but i want to rev sky high and leap off the line like lightning i dont no were to put a new pst at or i would have don that plz help me about the moter and if you could tell me were to post new threads at thanxs

[Wicked_S10]

well im new here and i dont want to make any one mad cuz im new here but i have a qusetion about what moter is best for a mud bogger a 383 stroker or a 377 i dont no anything about a 377 infact i just found out about that moter its for a 1 ton ext cab long bed with 4.88s and 38s on it but i want to rev sky high and leap off the line like lightning i dont no were to put a new pst at or i would have don that plz help me about the moter and if you could tell me were to post new threads at thanxs

Big green button in the upper left hand corner of each main catagorey, says "POST" in it will allow you to post new threads. It is in the exact same place that you found the "REPLY" button, but without actually opening a topic first. Anyhow, if you dont want to make anyone mad, read the sticky threads at the top of the forums, the one labled "newbies read this before posting" would be a good start. Also the thread about searching, and learn how to search, either with or without a star (i.e. google). And last but deffenitly not least, I would suggest based on your piss poor 4th grade hooked on phonics spelling, that you type all of your posts in MS Word, or another word processor, have it spell check and for good measure do a gramatical check, and then cut and paste it to make your post. Your reply to this thread was almost unreadable because of all of the spelling hacks.

[J Bruce]

i have been reasearching and i think it's an injector issue, b/c that is the only part on a 305 that is different than a 350 and everything worked on the 305 when i pulled it out.

The injectors are different and changing them will help.

The knock sensor is your real problem though. The 305 uses a different one than the 350 does. Once the motor is warmed up and it goes into closed loop, the computer uses the knock sensor to determine how much to advance the timing. It advances until it pings then backs off. If you've got the wrong knock sensor it will screw up the timing and cause problems. Some people leave the knock sensor off but you won't get the best performance from the motor doing that.

As others have mentioned, the calibration pack in the ECM also needs to be changed. You can order these direct from GM and they don't cost much. The same TBI ECM system is used on 4cyls, V6 motors, 305s, 350s and 454s. The ECM uses a calibration pack to determine the fuel mapping for the specific vehicle, motor, and transmission combo it's in. Different weight, gearing, and driving needs are all factored into those calibration packs. A 350 in a camaro uses a different cal pack than the 350 in a 3/4 ton suburban. When I swapped the TBI motor into my CJ I grabbed a cal pak from an '88 blazer with a 4spd. Works great in my 4spd CJ.

[Bill usn-1]

Once the motor is warmed up and it goes into closed loop, the computer uses the knock sensor to determine how much to advance the timing. It advances until it pings then backs off. If you've got the wrong knock sensor it will screw up the timing and cause problems. Some people leave the knock sensor off but you won't get the best performance from the motor doing that.

Not exactly how it works AFAIK!!

The ESC-electronic spark control- is the flat square module between the knock sensor(microphone) and the ECM (computer).
The timing is advanced based on the timing tables in the bin file on the main chip.
If ping or knock is detected by the knock sensor it sends a signal to the ESC which then sends it to the ECM. The ECM will retard the timing based on tables within the bin file. The amount of retard and the rate of recovery is in the tables.

You can run your motor pefectly fine with out a knock or ESC to retard the timing.(what did you do on a carb motor?)
In some cases they may actually cost you power and mileage if you try to run a very agressive timing table.
The ECM will be continuosly retarding the timing to eliminate the ping.

Headers and noisy lifters can also cause false ping and will cause the timing to be retarded for no reason.

Some people leave the knock sensor off but you won't get the best performance from the motor doing that.

I don't think you will see any difference if the motor is properly tuned. The stock timing tables are pretty generic. Those big money chips you buy only add a couple degrees of timing in most cases.

I played with ways to eliminate the ESC/knock for quite a while. I was looking for a way to do it with out the need to reclibrate the chip.

The ESC sends a constant 9V(high) to the ECM to tell it all is good.
If the voltage varies from that signal the ECM retards the timing.

Now if you just remove the ESC the computer will apply the retard all the time...not what you want.

So to fool the system you have to place a high signal there.
The only voltage sources avail are 12V and a 5V reference on pin C14 of the ECM.

So I remove the ESC from pin B7 and tie that wire to pin C14. (I wasn't brave enough to hook 12V to a signal input on my ECM.)

Now the computer sees a high signal all the time and there is no retarding of the timing and no ESC/knock error code.
I have been doing it this way for about 4 years.

If you followed the link I provided in my sig you already knew all this!!:D


The same TBI ECM system is used on 4cyls, V6 motors, 305s, 350s and 454s.
If you are referring to the 1227747 then they were not used for 4cyl applications. I have reset the cyl select in the chip and have successfully ran the V8 system on a 4cyl.


As for the calibration itself...you have to have logged data to know if it is wrong or not.

I'm no "Guru" and no "expert"...I'm just a guy that like's to know what is making my engine run and how to make it better.

[MrWillys]

Unless you've datalogged your motor and know for sure you're not seeing any knock. Do not remove, or disable your knock sensor. Knock sensors look very similar, but detect different levels of harmonics. I usually recommend isolating it using a brass extension. You can then wrap it with header tape to help reduce simple vibration detection.
The knock sensor is a good thing and should only be disabled on very high compression motors with large cams that create lots of vibration. Everyone else should use it as a tool to realize something is wrong.