A question for all folks with MARINE intake on board, please comment!!!

[Aksl]

Hi everyone, so, i bought and installed MPFI spider injection on my track, could feel the difference straight away, it started working more powerful i would say, even sound. While installing, i noticed that when i wanted to drop fuel pressure before taking the fuel line of, the was no pressure in the line, so i gues, after shuting of the engine, fuel just doesnt stay in the line and dropes to tank straight away. I have a taiwan after market fuel pump installed, 280l power. Dont know if that may be the cause, or something else, but i still have the idle problem i described earlier. The engine works, but sims to may be not inject onse in some cycle.. May be its the pump, may be the PCM, dont know. If anyone have any idea, would appreciate!Here is two videos i recorded, you can see and hear, from the exhast, how it just stalls for a second in every some of a cycle.https://youtu.be/kCDyOP1qC6U https://youtu.be/HzucmfJvTcM

[Hog]

Good day sir.

In your 1st video, I noticed that while viewing your clear distributer cap, that we are able to see sparks continuously while the engine idle is cycling. That tells me, that your issue is NOT ignition/coil related. But its tough to 100% verify this in your video, so since its in front of you, make sure that your coil is firing 100% of the time to eliminate your ignition as the cause of this issue.

What is your fuel pressure doing while this is happening? Since you have installed a nice brand new FPR, your fuel pressure should sit there and idle at around at least 58 psi, and if you shut off the engine and measure the fuel pressure WITH THE FUEL PUMP RUNNING, like when you 1st cycle the key and the fuel pump primes the fuel system for 2 seconds before you start the engine, it should read between 60-66 psi. The Key On ENgine Off pressure should be the same as the pressure you would get if you put you taped you fuel pressure gauge to the windshield and held the throttle WIDE OPEN. Wide open throttle and engine off fuel pump running pressures should be the same because the Fuel Pressure Regulator is seeing almost 100% atmospheric pressure therefore does NOT need to reduce fuel pressure like it does when the FPR sees engine vacuum like it does when the throttle is closed or partially open.
If you hook up a fuel pressure gauge and you see pressure fluctuations that follow the up and down cycle of your idle rpm, then you may have found your culprit.
What is the idle speed? Seems awfully fast.

Are you running the 2 Precat(O2 sensors positioned in between the exhaust manifolds and the catalytic converters) O2 sensors and the 2 Postcat(O2 sensors located after the catalytic converters) OR just the 2 Precat O2 sensors? Does your PCM go into Closed Loop?

It would be great to see some data from your IAC Idle Air Controller.


In regards to your lack of fuel pressure after your truck has sat for a while. The system should hold at least some pressure for hours after you shut the engine down. It can only bleed away from a)the injectors b) the Fuel Pressure Regulator but both of these are brand new now that you have completed the CSFI to MFI retrofit. That leaves you fuel pump. A good pump will not let fuel pressure bleed back into the tank. Of course this assumes solid, leak free fuel lines and plumbing. So long as it starts, this isn't an issue I would worry about.

Sitting there at idle is one thing, but what is the engine doing at idle in gear? Does your idle decrease as the engine warms up? It should.

What are you plans for this beast? Do you plan to daily drive it? What do you desire from this engine?

This all could be a calibration issue as well. It would be nice to have a bone stock PCM for you to diagnose with.

peace
Hog

[Aksl]

Hello Mr.Hog, nice to hear you again! Well concerning the distributer and my see through cap, you are correct, I can now see all of my sparks, and they are all good, as well all no faulty code from the engine. I thought to check my wires and spark plugs, all thaw the spark plugs are new, and the wires have been checked before, but i got that out of my head, checking them again, because as you can see the misfire goes once in a cycle, shutting all the cylinders, so the engine every some cycle, just chokes all cylinders and continues running, then again and again, but the distributer, distributes the spark continuasly. Fuel pressure has been checked as well many times, and it is correct at all working modes, except when i shut the engine it just disappears. No leaks from fuel line, injector and fuel pressure regulator are new, so i'm pretty much sure it's the fuei pump, that does not hold the pressure in the system after shutting the engine off. Anyway, the fuel pump cant be the issue, due to steady pressure while the engine is up and running.I have no catalytic converters, i have straight line out exhaust from both sides, they are not joint together at any point, so have just two 2O sensors, and no EGR, cut as well, in the pcm all that set to run with this setup.IAC Idle Air Controller, is the main thing now i'm looking in to, the second is the problem with the PCM tune. It it hard for me to find a stock pcm from a working car, that has same setup as mine (( So, when thecar is on a run, there is no such a issue, as long as i am continuing to accelerate, as soon as i take my leg off the pedal, here you are again.What is my plan for my track, well, long distance runs around russia, hunting, motocross, and continuing to restorate, sound, leather, boxes for tools implemented in to trunk sides, even folding in to floor seats, may be, to carry more than 2 people and the driver..)) dont whant to sell it, i bought it from a friend, who bought it from the street, we just so it standing for 2 years on breaks in the hood, found the owner and got it, becouse its a pitty when somethong like this truck is dying on the street, got it up running, then my friend had a problem with cash, due to credit, i bought it, and if i sale it, than only back to him))) anyway i doubt it, and he can take it any time, if he needs. That's its story.

[Aksl]

Ow yes, and it does drop the idle down, when warms up, all thaw it was set to a higher idle by the PCM, becouse when it set to normal, 0.8 it shuts of often because of this issue.

[Aksl]

Dam, I don`t know why, but when I type a message, replying to threads on this forum, and move to new paragraph, or make big spaces, or start from new line, the forum does not recognize it, and just splashes all together, one after the other, really annoying !

[1project2many]

In my experience the "Black box" pcm like you have installed doesn't idle well in non-stock configuration. In some cases it also does not seem to compensate fuel delivery properly for voltage fluctuations experienced during idle. If system voltage crossing 12-12.5V during idle, finding a way to stabilize system voltage can be enough to reduce idle speed fluctuations. Using a "jump pack" connected to the battery as a diagnostic test can raise system voltage just enough for idle to smooth out. After checking all the basics, I have found that watching the idle parameters such as desired speed and IAC position on a scantool or laptop can help diagnose whether or not the programming is causing the problem. Adjusting the tables involved in spark based idle speed control and the closed loop idle speed control PID loop can help reduce this tendency.

[Aksl]

Hi mr.Hog, well i didn`t know that, I`m really confused, there are alot of people who have made swap like mine (TBI to Vortec), do they all run in to the same problems as me. Didn`t anyone right a guide for such a swap and what to wait from it, what under water stone you will run in to, and how to ovecome them.
Any way, I have invested alot in this truck, will do more, untill i get it perfectly on the go. I planned to get the 12200411 PCM-based RoadRunner for a swap, it`s really expensive thaw 600$, plus i need a program for it, and that is another 250$, may be then i can get my PCM well tuned and runing properly with my setup.
http://www.moates.net/roadrunner-ls1....html?cPath=95

[1project2many]

I'm sorry if I have forgotten the details of your swap. Is your engine the same as a stock Vortec engine?

[Aksl]

Hello, no no no, it's not stock at all! Its a 1990 chevy silversdo z71 short bad step side 5.7l tbi, with engine rebuild, kb pistons 0.25 bored, head swat to vortec with all top (intake manifold, injector, and so on), spider acdelco mfi, and an after market cam (comp cam 08-467-8), and uder hood wiring, blackbox pcm, from same 1998 vortec Tahoe as everything else. PCM has been tuned, the cheap was remooved, and flashed several times, a bracket for the chip was installed in PCM, so now it can be removed any time and reflashed via EEPROM programmer.