Help! I'm Stymied!, Only firing on #3 and # 4 Options

[DipShit]

1.7 D-Jet

Engine was running just great until about two weeks ago, sigh. Now only fires on # 3 and # 4.

I have cleaned every connection including all grounds. And I mean cleaned them good! The elecrical appears to be just fine. I get a good noid light at both # 1 and # 2. The injectors have tested just fine as well (I'm getting about 7cc in 15 seconds). I have 40lbs of pressure the 1,2 rail. The spark plugs are getting juice and fire.

I have installed new points, cleaned the triggers (which shouldn't have mattered because of the sequence) and set the dwell. I'm a tad under at 44 degrees, but again shouldn't keep # 1 and # 2 from firing.

The timing has to be close as it runs really smooth for just two cylinders.

If I pull the power to injector 3 or 4, I get a real good drop and she will die. If I pull 1 or 2 - no change.

If I add propane to the intake, I get a good response in higher rpm.

I had originally traced to the Temp II sensor and it failed, so I replaced it. A new one seemed to be the fix, but only for a moment.

I have good fuel, spark and air -

(IMG:style_emoticons/default/WTF.gif)

I'm STYMIED (or just a REAL DIPSHIT)

[r_towle]

Ohm out the wiring harness from the ECU to the FI plugs and FI trigger points..

Most of the really wierd issues go back the old brittle wiring that finally broke.

Rich

[ghuff]

Ohm out the wiring harness from the ECU to the FI plugs and FI trigger points..

Most of the really wierd issues go back the old brittle wiring that finally broke.

Rich

This.

I just had a crank sensor die on my 01 GTi and it was causing intermittent running problems.

This was an 8 year old bosch sensor, not some 35+ year old wiring.

If I wiggled the wire while running a certain way it would die. The vibrations from starting out in 1st with my super heavy engine mounts would cause it to vibrate and fuck up the timing signal causing misfires and other nonsense.

It had been causing intermittent running issues for a while.

The second half of my problem was a weak coil that would mis at idle and changing loads, this is a 4 cyl coil on plug setup.

Swapped in my spare 4 coils, car runs better than ever.


Intermittent wiring/electrical problems are hard to detect.

Start wiggling wiring around and such while running.

Cold = contract
heat = expand