It's a riddle

[Hybrid]

Hey guys for those of you who know me, this is Jacob and I still have a tbi problem!! I can't get this 350 to run right. I have installed a tbi system with a brand new wiring harness, and i couldn't get it to run right so i started replacing things, like knock sensor, coil inside the distributor, and the harmonic balancer. When i pull the ground on the computer to set the timing to zero while on TDC it is really really hard to get it to zero without it stalling. Then when i get it pretty close i reconnect the ground and fire it back up. It will run really nice for a little while, but when it warms up the rpm's drop gradually until it eventually stalls. Oh and I have also checked the ECM and it works great when hooked up to another rig. If you guys have an answer to this riddle please let me know. Thanks

[94Dodge Truggy]

Does it have an oxygen sensor and are all of the wires to it ok? I gave up on my wiring gremlin and had it professionaly rewired as simply and cleanly as possible by JN electric. I have yet to get it back and try her out though.

[Hybrid]

The O2 sensor is brand new. I know the system runs in a closed loop until it gets warm, then it runs on an open loop. So I would think that since it runs pretty well until it warms up, that would suggest that something, maybe a sensor, is sending a bad message or maybe no message at all as soon as the loop opens. That is why I starting replacing sensors, but nothing has worked yet. Although when I replaced the knock sensor it run a whole lot better during that cold time.

[mckeddie]

is your oxygen sensor in the right place? i know it sounds dumb, but we've solved a few by measuring the distance from manifold, to make sure it is the proper distance, and getting the correct reading. this has worked a couple of for 5.0l's that we've worked with.

greg

[Hybrid]

I will measure the distance of the O2 sensor from the manifold and let you guys know. What would be the correct distance for a 350 with headers?

[Mike F]

GM TBI and most all OEM EFI systems run in open loop until the oxygen sensor warms up then goes into closed loop. The older GM truck TBI usually idles in open loop even after being warmed up.

Sounds like it could be a bad temperature sensor or IAC, hard to tell. The oxygen sensor should not effect idle. The sensor on a header needs to be placed in the collector near the flang in order to see all the cylinders. The problem is if it will heat up to 500* in order to read correctly, you may need to install a heated 3 wire oxy sensor so it gets up to 500* or more. The old GM TBI computer is to slow to worry about the slight amount of time it takes the exhaust gas to get to the oxy sensor mounted out on the collector. I have a buddy with a one wire one that we put in the collector and I know it works in the summer but I do not know about the winter time, it runs OK in the winter so I have never hooked to it then.

GM TBI is a pretty simple system but it would be nice to hook into it to see what the problem is.

[Hybrid]

I have a dual exhaust with separat mufflers for both sides of the motor, 4 cylinders each. I put the O2 sensor (which is a single wire) on the passenger side exhaust, so it does not even see the other 4 cylinders. Would this be a problem? I also know that I didn't replace the IAC sensor, so i have no idea how old it is. I tried searching for codes the computer might be throwing by counting the engine light blinks but no codes came up, as far as i can tell anyway.

[Mike F]

Just one side of the motor is fine for the oxy sensor as long as it can see all 4 cylinders. A code 12 will come up when in the error code mode to tell you that you are in error code mode, the error codes will be between the code 12s.

A bad IAC will probably not set a code. The IAC may or may not be your problem. IAC stands for "idle air control" it is not a sensor but a little stepper motor controled by the ecm used to open and close a air hole that bypasses the throttle blades to control idle.

[jfiscus]

Yous hould be able to run w/o the IAC, if it runs well till it's warm then there is a sensor that kicks in when its warm, possibly a crank sensor? Also, are you buying name brand sensors or AutoZone/Advance sensors. Sometimes the sell you bad/wrong "new" sensors at these stores & you pull your hair out cause it's a new sensor & replace everything else when the new part itself was bad from the store.

(Had a couple buddys spend over a grand to finally diagnose their supposedly new/good sensors were bad.)

[Mike F]

NO the GM TBI setup uses the IAC to maintain idle at all temperatures and conditions along with a dozen other modes of control at other RPMs.

GM TBI does not use a crank sensor, the motor has a distributor along with a ignition module that sends a signal to the ecm that takes it and looks at the operating condition and decides how much spark advance is needed and sends a signal back to the ignition module to trigger the coil like any older electronic ignition.

GM TBI only has temperature, oxygen, knock, MAP, TPS, and speed sensors.

I can program older GM TBI systems and have set them up to run other brands of motors such as the AMC V8.

[sarge]

Jacob , you need to take the Chero to MikeF and let him get that thing running for you .

MikeF are you one of the MV4W's ? and did you wire Shawn B.'s YJ ?

Sarge

[Mike F]

MikeF are you one of the MV4W's ? and did you wire Shawn B.'s YJ ?

Sarge

Yes and yes, I talked to you at the swap meet.

[sarge]

I thought so , Jacobs rig is my old one , it ran great with a quadrajunk on it so I know it's a FI problem. He sure could use some help on this one , and I really want to see the old girl on the trail. You rarely ever get to see your vehicle in action and not be behind the wheel. :D

[Hybrid]

Yes, I am out of ideas. i really want this thing running right! I have purchased all the sensors i replaced from NAPA. I have replased the ingnition coil in the distributor, the oxygen sensor (which now that I think about it, that one was from Autozone), and i replaced the knock sensor, which was from NAPA. Mike F. if you think you can fix it that would be great!! Send me your info and lets talk. Thanks so much for all the help so far!

Jacob

[Mike F]

What model ecm do you have? I just need the last 4 digits of the number. If they are 7747 I can program that one, if it is another number I may only be able to hook into it and see what is going on depending on year and model and what is left of the harness ;)

Ignition COIL in the distributor? If that is true it sounds like it is a car setup and a early one at that, what exactly do you have? We may have to go through it bit by bit to make sure it all matches somewhat.

[sarge]

Mike , I will start listing the parts that I sold him with the rig :

I got the intake and TBI off of a suburban with a 350 in it , it had a Holley TBI unit on it ( I guess Jacob found it was bad ) . I can't remember the year , but I would say it was early 90's .

Jacob ,
just to make sure , get the numbers off of the block , I never second guessed the guy I bought the K-5 off of as to it truely being a 350 , it may be a 305 and this would cause problems .......

[Mike F]

sarge, Did you pull the entire TBI system off the suburban?

I have the casting numbers for chevy V8s up to 86. At some point after that GM started to cast the displacement litre size (like 5.7) into the same spot as the casting numbers on the rear top of the block in front of the trans.

Hybrid, We also need to ID the replacement TBI you picked up to replace the bad holley TBI.

I can trace some of the numbers for some of the original GM parts. I can only read the info off the chip for the 7747 ecm to see what it is but it realy doesn't matter for that one because I can change it if need be.

[sarge]

the intake and TBI were already off the burb sitting inthe rear seat , I pulled the ECM out from under the dash and I can't remember is I found the dist. or not . The guy I got the K-5 from worked at GM and told me that he blew the 305 and put a crate 350 in it a few months before I got it . It looked like the standard Mexican 350 with the perimeter bolt valve covers that you can get for like $1400.00 .

The burb ( if I remember correctly ) was not the old square style ( 80's ) but more like a 90's . I have a 90 and it was still the square style so I don't know when they changed. I think the ecm is the 7747 , I think I checked when I was going to order a harness.

[Hybrid]

The number on the ECM is 1228747. Where on the block is the number for the motor? That motor might very well be a 305, b/c i bought a new 350 harmonic balancer for it and I can not get it to TDC for the life of me. The coil i replaced in the distributor was a little plastic thing with copper wire coiled around it. It sat underneath the rotor button and it was connected to the sensor in the distributor.

[Mike F]

I do not have any info on the 1228747 ecm but do for a 1228746, if it is a 8747 I can not hook into it and the only option would be to convert to a 7747 ecm if I was to mess with it.

The block numbers should be on the top rear edge of the motor.

That coil was probably the pickup and the sensor is the ignition module.

[sarge]

Jacob , don't freak if it is a 305 , I have all the 305 stuff off my Camaro.

[Hybrid]

The number on the block is 14010207

[Mike F]

The number on the block is 14010207

That comes up as a 80-85 350 casting in the book I have. Looks like the guy may have not been to truthfull. Look at the top of the block (cylinder deck) right in front of the left head as you are looking at it, GM would stamp part of the vin code for the vehicle the motor was originaly installed in unless it was a crate motor, but I have the casting numbers for those up to 88.

I can run the casting numbers off the heads also. They are under the valve cover though on top of the head.

What wire harness do you have?

[Hybrid]

The place you are describing sounds like where I got the number for the block. The only other number I could find was on the intake manifold which is 14057055, i don't know if that helps or not.

I used a brand new wiring harness from a place called Affordable wiring, or somthing like that, it was awhile ago.

[Mike F]

The casting number was behind the right head and was in the mold when the block was cast. The other number in front of the left head is on the cylinder deck (ledge) right in front of the head and is a small number that was stamped on the block when the motor was put in the vehicle. It may or may not have one if they stoped doing it. It is where the saying "matching numbers" comes from with the old muscle cars and how you would know the motor was original to the car.

[Hybrid]

It doesn't look like any numbers are stamped on the ledge. Does this mean it is a crate 350?

[Mike F]

Maybe, maybe not if they quit stamping them. The target master blocks have different casting numbers. The casting number says it is a 1980 to 1985 regular production 350 block but my book only goes up to 88 and they may have brought that number block back for crate motors maybe, but why if they already have a block in production? Also 86 and later blocks have the displacement cast in the block.

The older target master blocks also had Hecho en Mexico above the casting number.

The head number may shed some light, the target master blocks supposedly use a 3998993 head at least untill 88 but so did some production motors.

I have found sights before on the net with curent casting number info I may get a chance to look for one.

[Hybrid]

I will check the numbers on the head, and post up as soon as i get them.

[Hybrid]

The numbers on the head are 462624 and there was another number below that one which was D290. Sorry it took so long, it was a busy weekend!

[Mike F]

That is a 77 to some time past 1988 350 cylinder head that has 1.94 or 2.02 intake valves and 1.50 or 1.60 exhaust valves depending if the head was for a intermediate or high performance motor.

The book also said that head is a light casting and will not take getting hot!

Looks like the motor is a stock 350 truck motor.

[Hybrid]

What should I do to fix this thing, now that I know it is a 350 I am completely out of ideas.

[Mike F]

You still need to tell me what the throttle body you have came off of and what the colors are on the tops of the injectors or what the part number is stamped on top of each injector if the paint marks are gone.

The IAC will retract when you turn off the ignition and should move to close off the port hole when the motor is started, if it does not the IAC could be bad. It will also move when you open up the throttle quickly. You can see it through the the hole on the top left rear corner of the trottle body.

I do not have a lot of extra time right now to mess with it, I have my jeep and others to get ready to wheel. (It was to cold to mess with this last winter.) I would end up rewiring if needed if the harness is compatible to install the 7747 ecm (the ecm used to cost $25.00 local) so I can get in it and get rid of the things you do not need. Maybe in a couple of weeks.

[Hybrid]

Thanks so much for your help so far! I will get those numbers (or colors) of the injectors and let you know. I don't know what the throttle body came off of, but sarge should know since he gave it to me.

[94Dodge Truggy]

Thanks so much for your help so far! I will get those numbers (or colors) of the injectors and let you know. I don't know what the throttle body came off of, but sarge should know since he gave it to me.

In an earlier post Sarge stated what the throttle body was from. Hopefully you will be able to get that beast out on the trail soon!

[sarge]

The second TBI I got was off of a full size Chevy panel Van it was a 350 but I do not know what year it was . the van was crushed . they took the motor out to sell and I snagged the TBI off it .

[blazerbrad]

It may already be a moot point, but whether or not the TBI unit came off of a 305 or 350 it should not cause the issues you are having.

[Mike F]

It may already be a moot point, but whether or not the TBI unit came off of a 305 or 350 it should not cause the issues you are having.

Maybe, maybe not, we now know it came off a 350 and that was not posted before. The system sarge said he had pulled had a holley throttle body on it and that it was supposidly bad. Now I would still like to know I am dealing with a 350 TBI and not a 4.3 TBI or even one for a 454 that is wired different from the others but plugs in the same!

If it is a 454 I will take it in trade to get it running! :D (I will help you out anyways.)

The IAC may be bad and I posted how it should act and that also needs to be checked.

[sarge]

Mike ,

I can 100% say that the TBI was not from a big block or a 4.3 L . As far as it being a 350 or a 305 ..... I can not see them pulling a 305 , they are not worth anything . I knew the previous owner of the van and set the deal up for the van to be hauled in and the previous owner even said it was a 5.7 , but with that being said ..... I have run into alot of people who think GM put 350's in every V8 camaro made :eek: :eek:

[Mike F]

The 4.3, 5.0, and 5.7 throttle bodies look identical and are mostly except for the injectors and some yards do not know the injectors are different hence you could get the wrong one. It is probably a 5.7 one, but it is easy enough to make sure by looking at both the injectors. It should only take a couple of min to check them.