TBI Tuning - running rich

[Murfys_1]

Okay, I finally got all the major problems worked out:

- TPS set wrong (may still be a little off)

- IAC wired way off

- replaced both injectors

- replaced computer

- new fuel pump, filter, and lines



I got it to where it will idle all day long, and when it\'s cool I can rev it up. However, when it\'s warm, it doesn\'t want to rev. It seems to favor a bog situation. It doesn\'t die, just acts as if there\'s a load on it and it can\'t rev. Furhter, you have to wear a good mask or it will kill you. It\'s so rich it burns your eyes. I have played with a few adjustments, but I don\'t know what else to do. http://www.s10v8.com/images/smilies/icon_confused.gif



Can anyone recommend ideas on how to get it running better? It\'s a 305 with a slight RV cam and a Holley TBI unit, using the stock TBI ECM with a custom chip for the combo in a 94 4x4 Blazer.



There is a possibility that the gas isn\'t the greatest, but I have put the STA-BIL in there along with HEAT to dry it and get it better. I also topped it off with some good fuel conditioner and a couple gallons of good fuel. Just over half tank now.



ANY input is desirable, as everything makes you think and possibly come up with the answer!!



Thanks in advance!!



Joe

[riotpolice75]

have access to a scan tool? not a code reader, but an actual scan tool. either the gm tech 2 or a snap on scanner (brick, solus, etc)



now the questions:

have an o2 sensor? does it work?

check engine light on?

is the check engine light hooked up?

how many miles have you put on it so far since the swap?

what fuel pump is in it?

whats the flow rating on the injectors?

what does it idle at? is the idle stable?

have you actually verified that the voltage the computer is seeing at idle from the TPS is about .5v?

what adjustments exactly did you do to it?

is this a fresh motor? rebuilt? etc?

what is your timing set at at idle with the connector unplugged?

you said it dont wanna rev. it wont rev in park or neutral? or in wont rev in drive?

what kind of shape is your coolant temp sensor in? reason i ask is that if they go bad it goes to a default setting which is usually between -30º and -40ºF. thatll make it run richer than hell.



- shitty gas isnt gonna make it run rich







smith

[Murfys_1]

*have an o2 sensor? does it work?

- Have the original one in there, can\'t verify status



*check engine light on?

- It is only one before starting or during the code reading - no codes



*is the check engine light hooked up?

- see previous



*how many miles have you put on it so far since the swap?

- None, that\'s the problem



*what fuel pump is in it?

- Brand new TBI pump for this truck



*whats the flow rating on the injectors?

- They are new Holley units as shipped on a 502-7 TBI. Their pt# is 522-80 (72 lbs/hr)



*what does it idle at? is the idle stable?

- Idles around 600-700. Stable



*have you actually verified that the voltage the computer is seeing at idle from the TPS is about .5v?

- No, but I will if I have the directions!



*what adjustments exactly did you do to it?

- Adusted so it was .5v at idle (engine off)



*is this a fresh motor? rebuilt? etc?

- It\'s a mildly used rebuild that I have had for a while. Late 70\'s 305



*what is your timing set at at idle with the connector unplugged?

- Haven\'t set it that way. Right now it\'s about 12-degrees BTDC at idle. Where is the connector?



*you said it dont wanna rev. it wont rev in park or neutral? or in wont rev in drive?

- When warm it doesn\'t want to rev in Park



*what kind of shape is your coolant temp sensor in?

- 149K miles, original equipment 4.3





Some of the other research has pointed to one or both temp sensors being bad or the MAP sensor. Can I verify any of these with a VOM?



Smith, you are a HUGE help!



Joe

[Murfys_1]

I am also considering ordering the ALDL cables and getting the software (TunerPro) to check out all the functions on a laptop.



Thoughts?

[riotpolice75]

gimme 20 minutes to shit shower and shave. this is gonna take me a little while to reply to. yea, i got a lot of thoughts. youll hgave a reply within the hour







smith

[Murfys_1]

You ROCK!

[riotpolice75]

OK. HERE WE GO.





*have an o2 sensor? does it work?

- Have the original one in there, can\'t verify status

- disconnect o2 sensor. start truck, you are gonna have to wait a few minutes till it warms up. after it gets some heat in it hold the throttle to between 2 and 3000 rpm (helps to have a helper to hold the throttle open) set your voltage meter to volts. youll see a small voltage coming off of the o2 sensor. .450 volts is right on the money. not rich, not lean. below .450 volts is lean, above is rich. ground your black lead, hook the red up to the sensor. hold it to between 2 and 3000 rpm. look at the meter. it should be fluctuating between rich and lean.



while youre looking at it itll say, for example .150 - .800 - .300 - .950 - .80 - .670. so long as its switching between lean and rich youre good. it should switch AT LEAST once or twice a second. the faster the better.



*check engine light on?

- It is only one before starting or during the code reading - no codes

- good



*is the check engine light hooked up?

- see previous

- duly noted



*how many miles have you put on it so far since the swap?

- None, that\'s the problem

-we;ll get back to that



*what fuel pump is in it?

- Brand new TBI pump for this truck

- make sure the return isnt clogged somehow.



*whats the flow rating on the injectors?

- They are new Holley units as shipped on a 502-7 TBI. Their pt# is 522-80 (72 lbs/hr)

- HOLY CHRIST. dude youre getting on big block territory. them injectors are WAY TOO BIG. id be willing to bet thats your problem. OE injectors are only 40 PPH. get some smaller injectors.



*what does it idle at? is the idle stable?

- Idles around 600-700. Stable

- good



*have you actually verified that the voltage the computer is seeing at idle from the TPS is about .5v?

- No, but I will if I have the directions!

- the grey wire should be your 5v constant. the black wire should be your ground. the dark blue wire should be your signal. ground the black lead and check the voltage on the blue wire with the engine running. should be .5v. dont disconnect the sensor when youre doing this.



*what adjustments exactly did you do to it?

- Adusted so it was .5v at idle (engine off)

-if its a half a volt with teh motor off then itll be a half a volt with teh engine on. ok its a non issue.



*is this a fresh motor? rebuilt? etc?

- It\'s a mildly used rebuild that I have had for a while. Late 70\'s 305

- ok



*what is your timing set at at idle with the connector unplugged?

- Haven\'t set it that way. Right now it\'s about 12-degrees BTDC at idle. Where is the connector?

- you should have 4 wires coming off of the back of your distributor. white, purple/white, red/black, and a fat tan/black (i have seen a fat tan/white wire in place of the tan/black wire) the fat tan/black wire should come off of pin B in the back of the distributor and plug into pin B2 on the #2 connector on the computer. follow this wire from the distributor towards the computer. somewhere along its path from the distributor to the computer theres gonna be a connector on that wire. it should be outside of the wiring harness, so if your following the wire loom youll all of a sudden run into a random connector outside of the loom. theres nothing else on the connector, just a single wire. this wire is what the computer used to control the spark timing so you need to disconnect it to set the timing. its gonna throw a check engine light - disregard it. set the timing to the fatory spec for right now.



*you said it dont wanna rev. it wont rev in park or neutral? or in wont rev in drive?

- When warm it doesn\'t want to rev in Park

- f. it. dont use park



*what kind of shape is your coolant temp sensor in?

- 149K miles, original equipment 4.3





Some of the other research has pointed to one or both temp sensors being bad or the MAP sensor. Can I verify any of these with a VOM?

-coolant temp sensor, pull the connector, take a resistance reading across the 2 terminals. if its near 100k ohms or near 70 ohms its bad, replace it. do this with the engine cold. remember or write down the number the meter gives you. plug the sensor back in and run the motor for 2 - 3 minutes. check the resistance again. it should have dropped by at least 200 ohms. if it didnt replace it.

map sensor - back probe the green wire with the engine at idle, take note of the voltage reading, should be between .5 and 1.5 v. give it gas and the voltage should increase.



im gettin up to go get a beer and grab a smoke.







smith

[Murfys_1]

The 502-7 is intended for a 4.3 V6, according to holley. I think they rate the injectors at a much higher pressure than normally run (like 22psi vs 13-15 psi). Remember, it\'s got the larger 2\" throttle bores. It seemed to make sense that it work well on a 5.0... *shrug*



With most of these tests, I will have to wait till tomorrow morning. I have to take care of the family stuff now. I have the day off and I hope to get it taken care of early.



As for the temp sender, I am going to replace it as I have to replace the other one anyway. The gauge isn\'t reading so well, and I was having some significant problems when I took the 4.3 out that could be equated to the sensor (now that we are digging in to it).



SO, first thing in the a.m., I am going to replace the sensors, set the timing, and then try it again. If still no good, I will do the tests for the O2 sensor and the MAP sensor.



I am starting to feel confident about this set of inputs. Like I said, you ROCK!



Joe



p.s. my wife said we are going to have to send you something for helping to figure this out! 6-pack and a pack o\' smokes? http://www.s10v8.com/images/smilies/icon_biggrin.gif

[riotpolice75]

that reminds me, you got 2\" throttle bores. thats all fine and well. what about the intake manifold? got 2\" bores in the manifold as well? if not then the 2\" bore TBI unit dont do you alot of bloody good. see what happens after you get the rich problem solved. it may not rev real fast due to the throttle bore size.



some other things i had in mind - the reason i was asking if you had access to a scan tool was to look at whats called the integrator. the integrator goes hand in hand with block learn. what all of this b/s is is GM\'s name for short and long term fuel trim. the integrator is your short term fuel trim. the median number is 128. if you ever get the chance to look at one its a table with a grid in it and a different number in each square. if you disconnect the battery everything gets put back to 128. meaning that the computer isnt adding or taking away any fuel. any number above 128 means the computer is adding fuel to the system. any number below 128 means the computer is taking away fuel. the whole system is based off of the number 256, so 128 is right in the middle. if you look at it it really shouldnt differentiate off of 128 by more than +/- 10. if it does you got a big problem.



block learn is based off of the same thing. the computer looks at the integrator, if it sees it needs to add or subtract fuel at a certain RPM for X period of time then it changes it in the block learn (long term fuel trim). now im wondering if this chip you got in there is making it dump fuel into the motor. if you can, get it to a shop and hook it up to a scan tool and have them look at the fuel trim. if its running that rich then it should be taking away massive amounts of fuel. provided your o2 sensor is working the right way.



whats your fuel pressure set at by the way? the regulator on them things is adjustable aint it? did you get a stock chip with that computer by chance? if you did then throw it in the computer quick and see what happens. if its still shitty then at least you eliminated the chip as a problem.



lemmie know.







smith



p.s. youre very welcome. i beat myself senseless with this shit when i did the swap on my truck. its frustrating beyond all belief. as far as sending me something - i kinda need a million dollars. i accept pay pal, cash, money orders and checks.



make checks payable to matt smith http://www.s10v8.com/images/smilies/icon_biggrin.gif



enjoy your day off. the rest of us poor white folk gotta go to work in the morning.

[mzoomora]

I second the map sensor. 1.5-1.7 is good at idle. Im guessing if you are rich thet you will be higher, like 2.0 or better even, Check your vacuum lines to the map, make sure it reacts to throttle. Check your idle vacuum. I reccomend an adjustable MAP sensor from turbocity. It worked wonders on my cammed TBI. All the jet chips in the world couldnt fix it. Speed density vehicles are very sensitive to vacuum changes since that is how they calculate load. If your cam is limiting idle vac* it will tell the computer that the truck is under a load and send more fuel.

[Murfys_1]

I agree with what you have said, but I have a ton of vaccuum at idle. This is a low revving truck cam and it really pulls through the TBI.



That doesn\'t appear to be my problem, but if the map sensor is bad that could still be my problem.

[Murfys_1]

Alright, so I replace both of the temp sensors, and now my gauge works and I am reasonably sure the computer is getting the right info. With reserved hope, I started the truck and to my suprise it was the same crappy running as before. So, I swapped in the new MAP sensor that I got for insurance and that made no difference as well. Stumped, I decided that it was finally time to get the truck out of the garage that it has been in far too long.



Cleaning all the crap away that had built up over time (under, in, around, on) I dropped it off the jack stands, cleared away some more clutter, and backed it into the driveway. I was also tired of the smell and the fumes that built up in the garage and found their way into the house. Let the monster breathe a little...



Anyway, I was about to come back in and post my tales of woe when I remembered something smith said: did you get a stock chip with that computer by chance? if you did then throw it in the computer quick and see what happens. if its still shitty then at least you eliminated the chip as a problem.





So I pop the 4.3 TBI junkyard chip into the computer and fire it up again. Expecting to get the same crappy running, imagine my suprise when it ran great and revved like a monster! It still pops occassionally through the TBI, but everything else is fixed. At least I can use it now.



I know, I know, I was told many times that I need to confirm the chip. I swore that it was custom burned for my combo and dismissed everything all of you said. For that, I am humbly sorry.... http://www.s10v8.com/images/smilies/icon_wink.gif



I got the hood back on, topped off the radiator, refilled the power steering, topped off the tranny, greased all the fittings underneath, changed the oil again, cleaned off the tools, and parked it outside for the first time in almost nine months (most of which was just sitting and waiting for me to work on it). I will be putting some miles on tomorrow to let it \"break in\".



Thank you all!



Joe

[riotpolice75]

On 2006-06-16 21:40, Murfys_1 wrote:

So I pop the 4.3 TBI junkyard chip into the computer and fire it up again. Expecting to get the same crappy running, imagine my suprise when it ran great and revved like a monster! It still pops occassionally through the TBI, but everything else is fixed. At least I can use it now.





still pops occasionally thru the TBI? check your spark timing.



so they got way too much fuel goin into it with that chip huh? i\'d call em and raise some hell.



glad you finally got it running. congrats dude. lemmie know how it runs.







smith