88 5.0- Truck won’t start on its own, blowing black smoke rings from the tail pipe while cranking, brake cleaner in the intake will get it running on its own but it has a very bad miss, sounds like it’s running on 4 cylinders..maybe. Throttle position has no change in RPM
Truck has new:
Fuel tank and in-tank pump, high pressure pump
Fuel filter, injectors, rails and FPR,TPS, ECT
Plugs, wires, cap, rotor


12 volts on all injectors
All wiring has been checked from ECM pins to the injectors for ground signal to fire on both banks
All injectors have been checked for proper ohms
All grounds have been checked
MAP test good
Tried 2 ECM’s from running vehicles with no luck

Anybody got any ideas ??

 

Timing? Are the plug wires set to correct firing order?

 

10 degrees and 15426378

 

High pressure pump? is it a stock replacement or aftermarket?
Does the pump prime and shut off when you first turn on the key?

 

10° with the SPOUT removed? Fuel pressure checked with a mechanical gauge? How does opening the throttle not increase rpms?

 

The pump I’m calling high pressure is the one on the frame rail and yes. Fuel pressure is 36
36 psi. And that’s kinda what I’m trying to figure out

 

Even if you incorrectly installed the tps the engine speed would have to increase when the throttle is opened.

Put a vacuum gauge on it to check for restricted exhaust.

 

Im not sure how I could incorrectly install something that only goes on one way and has 2 screws in it, but I can assure you that the TPS voltage is perfect throughout the throttle swing, the truck has no cats or muffler and the pipe stops at the transfer case. I’m almost leaning towards the TFI module or the hall sender

 

Oh it has been done. There are two tabs that need to engage the tabs on the throttle shaft. It can be installed without that so when you move the throttle the TPS doesn’t do anything but you said you are getting different voltage as the throttle opens.

Is the timing advancing when you open the throttle? Does it look like the computer is controlling the timing at idle?

 

Is the timing advancing when you open the throttle? Does it look like the computer is controlling the timing at idle?[/QUOTE]

Yea, so the truck actually fired up today, I have the SPOUT removed and MAP unplugged... it’s still only running on 4 it sounds like, nothing obvious from the plugs, I even switched the firing order to a 351W/5.0HO and it ran in about the same way, I even flipped the wires 180* to see if some gremlins came in the middle of the night and moved my distributor..... I don’t freaking get it !!!!

 

Do you have an IR temp gun? The temp gun can help you determine which cylinders are firing and which ones not. With the engine running take the temps of the exhaust manifold where it exits the head and see which cylinders are hot and which are cold. Then you can get a spark tester, or use a timing light to find out if the plug wire is delivering power to the plug of non-firing cylinders. Get a NOID light and test to see if the dead cylinder injectors are getting a signal. That is assuming that there are dead and/or misfiring cylinders. Did you have the distributor out? Maybe it is a tooth out and can't get to proper time?

 

I had it sputtering long enough to verify 10* timing, the 5-8 are all roughly the same temperature but the odd thing is that 1-4 are roughly the same as each other, but 50* cooler than the other bank..makes no damn sense to me. I pulled a distributor from a running truck and I’m going to plug in and spin by hand to see if all the injectors are firing and at the right time, and I’m gonna throw a grounded plug in the coil wire to verify spark.

 

They will never all be the same temperature and if at operating temp, then 50* is not too great a variance. The injectors should be batch fire, so they fire simutaniously in groups of four. You just want to determine if they are getting a signal. I'm suggesting checking the spark with your timing light while the engine is running. Move the inductive pick up from wire to wire to see if each will trigger the light. Should be quick and easy. All that said, if you say all the exhaust ports are reading good temps, then they are all firing, so you would not be having a hard mis-fire, dead cylinder(s), just maybe an intermittent mis-fire. Intermittent mis-fire would seem to be electrical and either ignition or fuel injection. How are the bushings in the distributor? Maybe the shaft is moving around, out of tolerance, and is mucking up the rotor connections. What codes is the computer showing?

 

I’ve moved the timing light from wire to wire as you say, several days ago, and they all have spark, even threw on a spark tester to verify. It’s definitely not a hard misfire or dead cylinder as all the plugs are newer and they all “read” very consistent to each other. I cannot see an obvious skip in the flashing of the timing light but it’s very difficult to keep the engine running. No codes whatsoever

 

Get the codes.