hello...hows everyone... I spent a lot of time reading the posts here but im not finding a answer to my problem.... I got an 89 k2500 4x4 with a 350 and i put on a set of vortec heads and vortec intake for a tbi... hoping to increase performance a little but ended up with a sluggish pig... truck has cold air intake and shorty headers and high flow exhaust... and a crane compucam slightly larger than stock... setup worked fine untill i changed heads and intake. what do you ya think the problem could be....get an occasional backfire through tbi as well... thanks in advance ..

 

probably needs to be tuned and/or the timing is off.
vortec heads and any type of cam is a far cry from stock.

 

your probly right... it has the stock chip ... its the 747 type ecu... Id like to learn how to program the epromm myself so can you suggest what programmer and software i should look for.

 

when I had my truck i was gonna get the autoprom as i felt it was the best way for me but there are many options and your better off checking out the moates site and checking the diy prom section they have all the answers you need

 

Need a 12 pin ALDL cable.IIRC its 16 pin for ob2 and 12 pin for obd1.Smart mover tuning it yourself better then spending money on a mailorder thats leaving hp and tq on the table.

 

You can probably get it to run better if you can increase your fuel pressure. You can mode yours for pressure increase, or buy one, I see jegs/summit. You could even try the quarter trick, place a quarter under the regulators spring.

 

lots of great info...thanks guys...had a minute tonight so i moved the dizzy counterclock wise a bit...it revs much better. I assume thats advancing. i didnt put the timing light on it so not sure what degree its at. I also put a new harmonic on this weekend so maybe the mark is off on it. timing was set at 0 degrees advanced in bypass mode before i changed heads and that worked fine. let yas know in the morning how the drive to work went with it

 

well it ran better...has more power now but still not right. took a look at the autoprom from the moates site. looks like thats the best option for me 2. its a bit steep at 350$ but ill use it on more than 1 truck.

 

I did the quarter trick today to the regulator spring and that made a huge performance increase. still a small stumble off idle but it runs much better. the idle is a bit high now at 1200 rpms. had another iac valve so i swapped it out and that helped get it down about 1000 rpms. Im thinking maybe a new iac is a good idea.

 

did the idle go up when you added the quarter?

 

add winALDL to your laptop and buy/make a aldl cable. find out where and how far off the tune is.

 

Well just today I ended up with a mt2500 snap on scanner today. So I scanned the truck and I see lots of info. It says code 34 lean exhaust and code 44 map sensor faulty or vacume leak bla bla... Iac was at 58 i think at an idle. o2 mostly lean. switches to rich occasionaly. why is there no "good" setting only rich or lean? bunch of other stuff as well im not sure what it all means so im learning as i go.. Im in process of getting the autoprom from moates.com. So untill that shows up all i can do is read what the scanner says. also theres a spot thats says backup spark and fuel and in that it says the ecm is in limp home mode? ... It runs good for being in limp home mode!!

 

A NB02 is designed to move over stoich .45V continuously and adjust the BLM(long trim) by the INT(short). More info in stickies at DIY-Prom.

OK you are in limp mode. Need to check out the sensor and check or Vac leak if sensor is good. Maybe your scanner can read MAP at idle. should be 25-35 MAP. also as you accellerate MAP values will increase as VAC decreases

 

i believe the scanner can see the map value... forgot it at home today... Ill check it later and post all the values... I have other used map sensors but ill see what a new 1 costs... All vacume lines are new... Im sure they are all routed correctly... Still have to finish hooking up the egr system...need to weld a bung on the header

 

sensors can be tested.

 

My Vortec TBI was terrible with the stock spark map. The B-body LT1 table is much much better. I use an Autoprom to tune and I like it.

The MAP issue needs to be sorted out first. How is your EGR blocked off at the moment? That could be the source of a vac leak.

 

The sensor was 38$ so I ordered it...grab in morning on my to work... The egr is blocked off with a pipe plug in the intake...its a vortec intake so it comes out the driver side of intake... I have the egr air tube to goto header but still havent had a chance to weld the bung on... ya the pipe plug fits a little loose so i wrapped it with teflon tape and put it in....but all the rest of egr stuff is there... tested egr valve with vacume pump and thats fine...

I put the scanner back on after clearing the codes and went to the road test portion of scanner to check and this is what i got...
rpm_625
o2(mv)_243
integrater_158
loop_open
exhaust_lean this would switch from lean to rich constantly at idle
tps_.62
block learn_133
iac_42
coolant_75 c
prom id_5851
map(kpa)_29
map(v)_1.04
esc counter_13
knock_13
a/f learned_yes
battery_14.5
high battery_no
low battery_no
air divert_div
air switch sol_conv
speed_0
a/c_no


after i finished checking i went and checked for codes and they came back within the 5 mins the engine was running for...

 

BLM 133 and INT 158 indicates that it is running lean and ECM is trying to add fuel. However, do you ever see your O2 voltage close to 800 mV when it is cold and engine just started (allow a little time for O2 to heat up)??

Another question - where is your O2 located and if it is a single wire or three/four wire NBO??

A false lean condition could be attributed to a cold O2 sensor (single wire NBO's do not have heaters). This is a common problem for long tube headers (shorties can be cold as well). Another common contributor to a false lean condition is a poisoned O2 sensor. O2 sensor can killed with antifreeze or with fumes from common household caulking silicon.

//RF

 

What kind of air cleaner are you running? An open element? These tbi need the thermac to run good in cold weather.

 

I installed a new map sensor today. cleared the codes and then went for a drive. idle was very erratic at first but then smoothed out at 600rpm.. overall it does seem better. however the scanner still shows code 34 and 44.. map voltage low and lean exhaust. also still in limp mode...

dont know about the voltage when cold. I will check that.

headers are shorty style with o2 in collector driver side single wire

the air cleaner is a cold air type. cone filter on the end of 4" tube. no brand name on it. what is a thermac?

 

It was suggested to me to try a tbi from a 454 and install a fuel pump with 15 psi. I called around today and havent located 1 yet. I do have a holley inline fuel pump 15psi sitting on the work bench. a fuel pressure gauge may turn up tommorrow so when it does ill check the current pressure. another option would be to just install the 454 injectors into the tbi.

 

Thermac is the stock type air cleaner assembly w/ the tube that goes to the exhaust manifold.

 

ya I tossed that out a long time ago

 

That generally does not work when enviormental temps low. It did not work for me in WI for spring and fall. Car stored Nov-April.

 

I would strongly recommend that you switch to a heated NBO (for example AFS-73). Use a separate relay controlled circuit to turn on heater circuit when ignition is on.

//RF

 

Yes I did just that! I bet I saved on gas as well...

 

well up untill i changes the heads and intake the truck ran fine without the thermac. never scanned it befor so not sure if ecm was always in limp mode. milage always sucked

 

Forget about 454 injector parts they will not help you, what you need is tuning.

Get a pump that can make some pressure, not likely to need more than 35psi.

94-95 big block tbi, and smallblock TPI pumps are popular choices.

 

I installed a new o2 sensor today and the old 1 was cracked and had black soot on the wire. still get a lean exhaust code. I cut the map sensor hose real short to get sensor as close to tbi as the wiring would allow hoping that may improve vacume signal. wire harness shows 5v across a and c pins so its getting the right volts.

 

So id like to add a higher psi pump so can that be done inline instead of having to drop the tank.

 

What to do with the pump in the tank?

some prefer in tank due to it being quiet.

 

figured id just add a secondary pump to build pressure. its easier then dropping the tank however the intank pump is cheaper to replace

 

So you are adding a more powerful pump ahead of the stock TBI pump? Will that work? seems that it may not. I dont know just asking Q.

 

I dont see why not but im sure someone must have done this befor.
i supose if i needed high volume then ya the stock pump would add to much restriction in the line. but at this point more pressure is what i think im looking for


my autoprom showed up today... now i have to figure out how to use it!

 

so i been messing around with this autoprom and now have some questions. i seem to unable to read my stock chip to get the bin from that. I took it off the ecm and put it in the zip socket on the autoprom and cant get a good read. im using tunerpro rt . I soldered the new pocket on another ecm and I found a bin that I could test with. so now i can test with a spare ecm. I can read and write to the new chip with no problem. I tested the truck with the bin i found and it runs. Although not as well as the stock chip. So where is the limp home info stored? I havent tried to data log yet. can the bin be read from the ecu through the aldl port?

 

ok the offset needed to to be changed. now it appears i got a good copy of my original bin.

 

so now that my hardware is good im not sure where to start tuning...what should i be looking at to begun tuning? Im not sure what parameters to change. havent seen a guiide that explains this. perhaps start with a datalog of the current setup?

 

First change you make to tune is to accurately set for the BPC. It is CID vs injector size vs fuel pressure. That is a calc or if you provide the info I can give you the number.

do you have a specific .bin in mind to start with? some are available at Craig Moates under downloads. Or maybe at TunerPro. Odds are the 7747.bin in your ECU is close. May need to tweek it for tranny.

Yes start a data log after confirming the BPC. Then modify the VE table to achieve 128 for BLM.

did you read stickies DIY-Prom and free tune in TBI?

 

I did read the stickys however its a lot to take in... The fuel pressure reads 17psi. Its a 350cid. the bpc stands for what? and I have stock injectors so im not sure how to tell what size they are. sorry but some spoonfeeding is what i need to get rolling!!!

 

base pulse constant is used for fueling calcs by ECU. You need to verify correct if not correct set it and forget it. The injector part # is etched on top of injector there are 2 numbers I recall. 17 lbs is not stock so BPC has to be corrected. It is the the longer # of two. fuel press + CID + injector size = BPC

 

well I dont see a parameter for bpc. Im using tunerprort. Is this something I will see when datalogging?

 

so i tried datalogging on the way to work and i couldnt get it going. have to figure out whats going on. my definitions file may not be correct

 

No BPC is in TP. Not TPRT. It will be in constants. three numbers like 134 132 etc. Mine is 92 I recall.

 

ok downloaded tp and still no luck. I dont see any constants. lol. this is realy frustrating. had the datalogger working for a couple minutes now cant seem to do it again. im lost!

 

Maybe post that TP Q in another thread. What ECU and what definition file? I once had a 7747 ECU(truck) and $42 file. Magnus(TP) often watchs for TP specific questions. Once TP is loaded it will be there for ever. FYI constants are like one value variable. Like "invoke PE" constant may be "60" for TPS %. I am not very well educated in TP software. Since it is there I just use it. No thought on my part.

PS ask Moderator to move this to DIY-Prom. TBI is more mechanical Q's

 

ya i agree this has become more of a "learning how to tune" thread instead of why I originaly started it.