Q45 Sudden Injector Death... maybe not?

[JedCoop]

My 94 Q45 with 130K miles has been running beautifully. And this Friday it ran excellent at noon, but then, suddenly, next time I started it to go home it ran horribly.... shuddering intensely at 1500-2500 RPM when going up an incline, and bump-bump-bumping at idle like a spark plug was disconnected, and generally not smooth.

I have diagnosed the problem to be injector #3 - it measures infinite resistance. It happened so suddenly, but maybe not...

In March '05 I changed injector #7... At that time I noted that injector #3 ohmed was inconsistently... that when cold it measured 12.0 ohms resistance, but when hot its resistance increased to 13.7 ohms. I was thinking maybe I should change #3, too, but it was still in spec, and it costs $140 for an OEM replacement.(see post zerothread?id=106668 )

Now I really wish I changed it a year and a half ago. It may be a general indicator of eventual failure... that if injector resistance increases between cold and hot conditions, you should think of changing it when convenient instead of getting stuck later. I won't drive the car as is. So now I am off to remove my plenum and wait for parts!

[I am still really surprised at how significantly it shuddered at 2300 RPM up hills, and how engine problems can cause all-around vibrations!]

[maxnix]

What you should have done is move it to one of the readily accessible locations. Now you will have to remove the plenum.

[Q45tech]

A little resistance increase cold to hot is normal. check the conductivity of copper. They should all go up the exact same percentage.

[Magnum PI]

I just had the same problem and had to replace one of the injectors to correct the situation. Of course it was located in the worst possible position under the plenum.

[Q45tech]

The other problems are changes in the resistance measuring circuit in VOM with temperature and the unit's Batteries.

Reading low resistances consumes the MOST JUICE from batteries so marginal batteries show up fast on low resistance scales.