New member- but I have a few crazy issues with my Franken engine and I can't seem to figure out my problem, I got recommended to ask here. My vehicle is a 1968 GMC long bed 1500 other than lowering and my engine it's a pretty stock build, I just want it running smoothly I'm not looking to make power at this moment just drive it. MY drivetrain is a fully rebuilt 96 Vortec short block ( Chevrolet Performance zz350- true flat top pistons, forged internals) with 91 TBI- L05 swirlport heads- stock vortec (heads were changed to TBI heads before I bought it), intake, and front dress. matched harmonic balance and timing tab( all 91 tbi based). old skool Muncie SM318 3 speed manual, Dana 44 with a 3.07 rear gear or 3.08 however you look at the final count. Painless TBI harness 60101- with the orange/ black stripped park selector wire not grounded so the ECM thinks the truck is in gear for my manual trans( and yes I have tried it grounded very little to no noticeable change, ECM 1227747 had a stock ASDX( I know its an 88 Chip) chip now changed to JET Stage 2 (29108-S), I have tried 3 ECM's with same stock cal-pak and same prom in all 3 no cahnges. I am new to datalogging so I'm learning that using Tunerpro rt V5- I made 2 so far 1 being cold start to op temp. and the other after op temp. with a few throttle revs. My alternator is Powermaster GM cs130 style 1 wire( has the function of using excitor which I hooked up after some research about tbi and 1 wire( just 12v+ to Field teminal)). Alt. jumps between 14.4- 14.5v once running. It has full length Dual exhaust h-piped no cat, 180 Thermostat and running 91 Octane(1/2 tank), new fp, filter, tank, lines and tb rebuilt. Everything is brand new or refurbished on my Engine. All new sensors(some twice for testing my problems). I have bench tested every sensor or sender and still can't solve my problems. 3 new distributors timing at 0 with est unplugged here's where it gets funky even though timing chain is on compression stroke, distributor rotor at #1 and timing mark on balancer and tab point to 0 when its running no matter what I do It consistantly wants to run better at the 12 o'clock position under the water pump. otherwise it acts retarded. I have a hard start issue (starts when primed) where a noid won't flash until I throttle it or WOT. FP runs constant at 10.5 PSI, fp relay runs and primes the system for 4 seconds . if I plug off my return line psi jumps to 17 psi and holds, if I start it while return is plugged off its constant and 15psi. Oil PSI climbs to 50 PSI as it starting the Oil PSI switch turns on at 3psi checked continuity. Fp stay running if I unplug the relay after the truck starts. 3 new distributor( meaning new ICM's and pickups) fuel injectors are 1.2ohm have 12.75v + key on( spray pattern looks great when its running). Im running MSD 6A ignition box with all MSD ignition system(distributor, cap rotor, plugs, wires coil( tried that unhooked no difference in the system)). followed my wiring to a "T" (pink/ black stripped wire- to Coil (+) ( drops to 10.5 V while cranking, also tried direct to batt. no difference), red wire to constant 12v+( orange if its stock harness), Purple/White stripped to starter solenoid, grounding to rear of pass. head, same head used for engine ground(opposite end)( tried direct to battery- no difference, also went over every ground on the truck twice!)).

Next problem I have is also strange its a crazy surging issue( runs like its got cam(its a stock Vortec roller cam)). I never get a check light for any of this. I Vacuum tested( Chemical, Propane as well smoke tested- only bleeding smoke around the throttle blades). when I run a vacuum gauge it detects a vacuum leak it jumps between 16-20KPA during surges and the needle is erratic Map shows constant vacuum at 19 in TunerPro. Engine surges about 100 RPM hot or cold at 1000 rpm base Idle. So I did an IAC reset several times all with the same conclusion. when I have the IAC pintle fully seated the surging goes away almost entirely, so I adjust my throttle screw out enough to keep it running and all should be fine after I unplug the battery and plug the IAC back in and restart the truck after a minute but its not! now the truck races rpm to 1500- 1700 and stays at that rpm, so I go back out the idle screw to find a sweet spot and the surging immediately comes back as it gets closer to my 1000 rpm base and the IAC opens and starts its hissing. In Tuner pro it shows my TPS dancing around ( both Voltage and %) not much but enough to notice though I'm not touching the pedal. so I checked that wiring just key on good ground, .78V at rest and rises to 5.0v, and a 5v ref.- TPS is working and doing its job! next I unplugged my ESC and tested all those wires- everything checks out and is secondary verified in Tunerpro. along with knock reads which get up a little bit in my data-logs, but no codes are set.

last issue is when I actually try to drive it down my street, as soon as I let out of the clutch full amount as I'm trying to take off in 1st the fuel cuts off for 2-3 seconds almost sounds like the trucks dead during this time never actually stalling out. If I maintain my pedal it stays out for this 2-3 seconds of time, but if I start throttling it it comes back in sooner. the truck usually seems to continue through its gears with out trouble after this initial fuel cut out. so far with all these problems I've been able to get up to 40mph and rowed through gears up into 3rd gear on my short neighborhood street. but regardless it seems too dangerous with these problems to drive on city streets.

I have been in contact with a few people that understand this tuning stuff better than I do but my question is can I tune these problems out- hard starting, surging, and fuel cutting off??? I feel like I just keep throwing money at this engine to get little to no results. I could really use some help as 1 of the guys I've been talking to that is well versed in this stuff recommended I post here and see what others think. he has also watched my log files and can't see what's going on or why it's doing any of this. I also got connected to a local that tunes as well, and since I have very little knowledge on any of this and am learning as I can. he wants to use the 1227747 ECM with Moates 28 pin chips and tune using a Ballenger afr in lambda as just a tool( foreign talk to me at this point) and emulate using the Ostrich 2.0 and end up burning a chip. IDK enough about this but I have learned a lot of the guys I've talked to on a few FB groups from various locations in the U.S. went with the Dynamic EFI ECM and all seem to have there same engine combo's vortec short block, tbi heads, intake etc.- running and good Probably some tuning I'd assume. IDK if 1 is better than the other in overall terms as I'm not building a race vehicle I just want a more stock tow pig with EFI, I have done and spent a lot to even get this far, but I'm still very very out of the knowledge loop when it comes to tuning. I'm lacking the knowledge to actually start tuning by myself.

I may have forgot something, so If you can help- just ask if I haven't listed anything.

TY in advance

 

The EBL is a good way to go IMO. If you had one and it was a CF motor, I could give a stock tune that would at least be a great starting point and would run just fine given everything else is ok. GL with your issue.

 

Response in progress. Need to work on my own crap first.

I need some time to work through those walls of text.

What I can say now: Connect a scan tool, look at the data stream when the engine isn't running right. Is the computer getting an RPM signal, or is the RPM signal intermittent? If the computer doesn't get a steady RPM signal, it's going to turn the fuel pump off when the RPM signal is missing.

TPS working properly?

DON'T check the sensors at the sensor with a multimeter. Verify the sensors using the scan tool, because that also verifies the wiring harness and the computer's input connectors.

This is an automatic trans PROM used on a manual transmission vehicle?

 

Thank you for your input. How do I check or what test should I use to check if the ECM is getting signal During cranking? Or what wires specifically or pin on ecm pigtail? The fuel never cuts off at the pump during crank cycle. I just have 0 injector ground pulses at the injector pigtails. Only once the throttle is cracked does the pulse come in. Then once it gets fuel it fires up and runs But not without a pre prime or some pedal. After its running I do not have to throttle it, Only to get it to start. Which to me would mean there is some sort of a pulse to trigger ignition fire that quick. When I set timing my light is old school so I use a jumper off the wire that has a light in it. It has pulse at plug 1 on cranking and also when I use the coil pulse to check fuel injector spray.

No- its a manual prom for a 5 speed but my trans is only a old 3 speed with mechanical drive speedo. So I run the 2 pulse vss off the cable drive. From my understanding I don't think the ecm or prom is smart enough to detect the difference between a 3 speed manual or a 5 speed manual. Just that the truck is physically moving and not in park as it would do if it were an automatic.

I'm using aldl cable connected to my laptop running tuner pro rt. I don't think there too many better types of scan tools at that degree of information coming into my laptop. If your not familiar with it you may want to look into it and what information it actually provides at your fingertips. There is other programs this is 1 I already invested into and started learning.

 

Thank you. Being im super new to this side of things I started buying things like burn 2 some chips etc. I just haven't got the understanding quite yet of what I need to do to calibrate. I feel slightly overwhelmed with it all at the moment. Im sure im making it harder than it actually is. There's still things Im not sure of- if adjusting 1 thing effects another bad or good? how to properly adjust ve tables? how to turn things off like EGR signal? How to keep my IAC more closed than open? - less steps im guessing. At the moment I've learned how to write chips so I can burn a stock chip from a factory bin. Im not sure if I could damage my engine or ECM from playing without some know how... 😆

I do appreciate the offer but I'd rather learn. I had someone already burn me a chip and it was useless😵I mean no offense but now im cautious with how I approach this. But I'm open to any help along the way.

 

Was the block already drilled for the coolant bypass system? Some Vortec blocks are, most aren't. TBI uses the drilled hole and matching water pump, Vortec doesn't. If you have the small hole just under the right side water pump mount, the block is probably already drilled. If you have only the two bolt holes and the big coolant opening between them, the block isn't set up for coolant bypass. IF (big IF) there's no valve on the heater hoses, so coolant is ALWAYS flowing through the heater core, you may not need the bypass hole.

I'd expect 87 to work just fine. Watch your knock sensor output to verify.

Don't bench-test. Use the scan tool. (or "data logging", I guess that provides the same info as a proper scan tool.) Takes 1/10 the time, and includes the wire harness and all connections back to the computer. Tests better, faster.
My '88 K1500 TBI 5.7L is INTENDED to have the marks at 12 o'clock. That's how the damper and timing pointer are machined. 12 o'clock is TDC/0 degrees. I'm running a few degrees advanced from that. Timing light shines straight down through a hole in the engine accessory mounting plate--holds the alternator, PS pump, A/C compressor, etc. Damn pain in the tuckus.

But I don't know if the car (not pickup) timing marks are the same. Over-advanced idle timing does tend to make the engine run faster, better, with more manifold vacuum. But then you run into too much timing advance at high speed.

Are you sure you have a matching TBI set--damper and timing pointer/front cover?

Needing throttle to get injector pulsing is a mystery to me. How fast does it crank? TPS reading correct voltage at idle?

WOT should kill the injector pulses when cranking. That's intended to clear a flooded engine. Does having the gas pedal on the carpet actually give you WOT? Common for the pedal assembly lever to bend, giving about 3/4 throttle instead of WFO. Verify using the scan tool to look at TPS voltage at WFO vs. idle.

That all sounds good, although most folks would want higher regulated pressure--12--13 psi on a stock engine. Mine has 11.5 last time I checked, I'm hoping to boost it some.

What is battery voltage when the coil + is getting only 10.5V? It's normal for the starter motor to reduce battery voltage due to the high amperage demand; 10.5 might be normal. Mostly, I want to make sure that the OEM resistor wire is not in the coil circuit--it should turn the MSD on, but the coil gets power direct from the MSD box.

What coil are you using? MSD Blaster II? OEM TBI coil? Ancient Points-style canister coil?

You're using the MSD TBI distributor...right? Has the "8-pin" module? Not the old coil-in-cap 4-pin module job, or an MSD Ready-To-Die?

I had an MSD 6T for a year or two on my '88 K1500. Used the MSD adapter harness so it plugged into the TBI coil easily. Worked good until it failed one day. Popped the adapter harness out, reconnected the stock wiring, drove away. Never bothered to get the 6T repaired.

1. Was the cam degreed when it was installed?
2. What is the cranking compression PSI?
3. Any chance the valves are adjusted too tight?

How do you know? It'd have to be a huge vacuum leak to show up on a typical vacuum gauge. You'd probably hear the whistle.

You're saying the vacuum gauge is more sensitive than the MAP, according to TunerPro? MAP defective? MAP vacuum hose restricted? I don't get this at all. NORMALLY I'd trust the MAP over the vacuum gauge.

Why is your idle speed so high? I'd expect ~650--750 rpm, not a thousand rpm. What is idle RPM spec?

Set the base-idle screw according to service manual procedure.

No idea why the TPS reading isn't stable.

This is a CABLE throttle from pedal to throttle body...right? Not a mechanical linkage?

I wonder if that's related to having no injector pulsing when cranking, and having to step on the gas pedal to get fuel spray. Fix one, you fix both?

Wild Guess: This is not a "tuning" problem, it's defect(s) that need to be fixed. But I don't do "computer tuning" so what do I know?

DON'T dick with the pins or ECM pigtail. All that info is available on the SCAN TOOL, or--I guess--your data logging system. Crank the engine, look at your data logger to view the RPM. If it's showing RPM, the computer should be firing the injectors. If there's no RPM showing, you've likely got a weak signal from the pickup coil or the ignition module that somehow isn't showing up at the ECM. Thus no fuel spray. Might as well look at the TPS voltage while you're cranking, too. Seems like when you stab the gas pedal, the injectors begin to fire. So maybe this is TPS related.

 

The block does have the coolant bypass factory drilled. The timing tab and balancer are matched, hand turning points everything at 0 on that tab tdc and distributor and rotor set at cylinder 1, from a 91 tbi. Msd street fire coil, distributor, 8.5mm wires, iridium msd plugs. I backed out of my valve lash and only have 1/8 turn of pre-load using EOIC method. Compression I haven't measured yet but ill put it this way if I carb it ill have enough compression or more than enough. I have no pops bangs or misses through the tb or exhaust. The cam is a stock roller can with 1.5 tbi rockers. I do hear a whistling sucking noise but only when the IAC fully opens and chooses to stays open even after hitting op. Temp.. Tunerpro shows the map staying steady not fluctuating. TPS moves in both % and in voltage but im definitely not touching the pedal. Tps at rest is .78 and wot 5v. It is mechanical linkage to the throttle with swivel ends on the linkage- Jegs item, kinda like a link bar with heim joints. Used 2 new TPS newest being Delco, same response, better with Delco though.I will run another log and watch my rpm as I crank. Rpms stay near 1000 when idling but dance ☝ as it try's to find idle and surges, steady 1000 with the IAC unplugged and seated.

 

WHICH "Street Fire" distributor? Does it have the 8-pin TBI module?


I'm not asking about compression RATIO. I'm asking about cranking compression PRESSURE. The two are barely related.

Was it installed properly?

But your vacuum gauge fluctuates. Which one is right?

First Guess: Engine shakes on the mounts, mechanical throttle linkage jiggles the throttle arm enough to give the TPS some movement--accounts for the varying TPS voltage/percentage.

1000 rpm is WAY TOO HIGH. Set the throttle base idle screw per the OFFICIAL procedure.

 

Yes its the 8 pin just like o.e. I guess i could see the engine vibrations causing some. But its not a crazy wild shake or anything more than stock vibration. Im using a Mityvac to test at vacuum port on tb. The map stay pretty consistent about 19 according to tunerpro

 

Compression stroke

#1 TDC

plug #1