Coil is new, resistor pack plug checked and cleaned, swapped out with known good ECU, vacuum advance working, cap/ rotor checked, mech advance springs back good, fuel flow out of surge tank good, plugs good a gapped, magma vote wires, all sparking, coil spark super hot/blue. Revs good P or N, idles like crap N or P, chugs in D or R. Same way it ran last March, though it was the CTS connector. Got a spare TPS, may swap that on.

 

Ok, swapped in another coil...same.
Put on another TPS....same
Mounted another spare ECU....same
Cleaned FI harness ground and multi plug....same
Cleaned resistor pack plug again...same
I've already swapped out ignition AMP...same
Vacuum connection to ECU is good.

Need to get a sample of gas from the tank bottom to see if it's contaminated with water. It ran like a top before doing the down pipe removal/replacement.

 

If you're getting good spark, then you may be running out of fuel. Maybe you inadvertently pinched the fuel line while jacking up the car? I think the vacuum line to the ECU is in the same vicinity. This could cause a similar problem. If it was running nice before the project and isn't now, I'd think you should focus your efforts in the area you were working first and make sure everything is good before widening the search. However, there is a small chance this is coincidental.

 

I appreciate the advice but I've already retraced my steps three times over any work I did to include, vacuum hoses, fuel lines, electrical connectors etc. I'm going to drain some fuel out of the tank and check it today or tomorrow for any water contamination.

 

Pulled out 2 quarts of fuel from the surge tank to the pump, nice light Amber color, no water, no contamination, just fuel and very heavy/fast flow out of the surge tank.

 

Changed to a new ATS and pig tail tonight, still the same, backfiring out of exhaust at idle and no power/stumbling in drive or reverse.

 

Ive been following this thread with interest. Doug gave a good extensive list of item to check. Sometimes it's easier said then done. It's seem likely fuel related since you have good spark. My procedure at this point is to get a small squirt bottle and put some gas in it. Remove the air filter and while it is running squirt some gas into the throttle body. If it smoothes out and rpm increases that bank is likely running lean. If it causes it to stall or idle worse it is probably not lean and could be rich. If you believe it may be rich open a vacuum port to add air. See if the idle increases and becomes smoother. It's not an absolute diagnosis but may give a direction to look. Careful to have a fire extinguisher handy.

 

Hmmmm, idle changed some when I pulled the "B" bank FPR last night and I didn't like the looseness of the vacuum elbow on it. I went out today to change the elbow and try a few other things on the car and the elbow was full of fuel, so I do know that Fuel Pressure Reg is bad and could be the culprit or a contributing factor.

 

If the FPR is full of fuel it is shot. No fuel pressure = no proper fuelling. Replacing it will probably sort your difficulty, or at least sort some of it.
Greg

 

Take a few days to get one for it, I'll report back with the good/bad results!

 

Replaced the FPR and no change, YaY! The joys of V-12 ownership, I guess it ran too good for too long! Time to pay the V-12 Gods.

 

What a sod. On my post number 20 above, can you tick off what you have done and let is see what is left? Either fuel or spark is breaking down at higher revs, just got to eliminate possible causes one by one and find out which and why. Courage as my French mates say!
Greg

 

Replaced ignition AMP
replaced coil
Checked all amp/coil connections
Replaced ECU
replaced TPS
Replaced CTS and plug
Replaced ATS and plug
Replaced fuel filter
All injectors clicking as it idles
Good fuel flow out of surge tank, pulled gallon of fuel out, no water or debris
Checked all vacuum connections.
New O2 sensors
Cleaned FI resistor plug/connections, checked FI harness/ground
Checked AMP coaxial

Problem isn't high RPM break down, it's idle, back fire popping and stumbling in D or R. In N or P if I run the RPM's up it runs fine. If I pull the vacuum from the left FPR it seems to smooth out, increase idle some.


Going to pull the distributor cap today.

 

So will it actually run Ok in drive once the revs are up, or will it refuse to pull at all above idle when in gear?
Greg

 

Greg, once it's under load it's runs like crap, it only runs smooth in higher revs in P or N. Letting it warm up makes no difference.

 

Of my Post no. 20 list it seems you have done/not done as follows:

1. Checked/replaced dizzy cap and centre graphite electrode NOT done
2. Replaced HT leads and plugs (correctly gapped to 25 thou) NOT done
3. Checked dizzy spindle is not jammed and springs back when turned NOT done
4. Checked/replaced dizzy internal pickup, starwheel condition, and condition of twin wires from dizzy bottom to the amplifier side plug NOT done
5. Checked vac capsule is functioning as it should NOT done
6. Checked connectors and wires to coil + and - (wires can fracture within the OEM connector rubber covers) Done ?
7. Checked for a big powerful blue spark at the plug end of the HT leads NOT done
8. Checked ignition timing? If so how exactly did you do it? NOT done
9. Checked and cleaned injector resistor pack plug and socket Done
10. Checked loom to coolant temp sensor on B bank thermostat casting NOT done
11. Tried replacement CTS. Done
12. Checked that CTS and air temp sensor plugs not accidentally swapped NOT done
13. Checked the first foot or so of the shielded wire from amp that leads to the ECU. That is strip and ensure the inner wire is NOT earthing to the shield. Check that the shield is earthed to the loom at the amp end of the wire. Done ?
14. Check you have not put a screw through the firewall low down (eg to secure the US passenger side front wheel baffle). This can hit the loom to the ECU which is the other side. Done ?
15. Checked injectors are pulsing and flowing the correct amount of fuel when fitted to the car NOT done
16. Checked the injector pulses are quickening when the car is revved Done
17. Checked fuel pressure in the fuel rail NOT done
18. Have you verified the vac line from the tapping at the centre of the cross pipe across the rear of the motor that balances the two intakes and ends up at the ECU will hold vacuum? NOT done
19. If you remove a vac pipe that goes into the inlet manifolds (eg gearbox modulator, crankcase breather sprung thingy on B bank air box, or any other capped off inlet manifold spigot) does the car rev up? NOT done

Is this correct as I have marked up? As you are about to look at the dizzy, that will be a start. The symptoms sound like spark breakdown as soon as load is applied, but could just as easily be fuel pressure falling off under the same conditions, or timing.
Greg

 

Nothing happening today, migraine today.

 

Fixed it! Turned out to be the distributor cap, popped a new one on and Bobs your Uncle! Runs like a top. Adult beverages all around!🍻

 

Great news. Congratulations.
Greg

 

Turned out to be a SIMPLE fix....