low rpm bucking

[mikey]

Need some help gentlemen...on my '70, d-jetted 1.7 liter. Just recently it seems to be running on three cylinders, with the fourth cutting in and out. But only under 2,500 hundred rpm, and either warm or cold. Also, when sitting at idle, if I punch the throttle, there is a little delay before the engine responds. I already checked the injector electical connectors, and ignition connectors and they are fine. hmmmmmmm.

Mike

[Joe Bob]

TPS...throttle positioning sensor...on the side of the throttle body...

Leaks on the intake manifolds.....

Leaks on the injector gaskets.....

Those are ones I have dealt with, with those symptoms...

[oredith]

how old are the plugs?.. one of the plugs might be gapped wrong if you recently replaced them.. although that symptom usually occures at high rpm rather than low.. it's worth looking into though.. if one plug's color is distinctly different from the others, at least you know which cyl. it's from..

another thing, how thuroughly did you check the sparkwires?.. one of my friend's integra had a similar problem.. checked the plugs and wires, cap and rotor.. couldn't figure it out.. turned out that one of the plugwire's connector was broken, but was hidden by the insulating boot, so you couldn't tell. it arced at random intervals. had to spend 120 bucks at a shop before it was fixed..

good luck..

Jeff

[mikey]

I think I found the problem. While the engine was running, I pulled out the plug wires one at a time and found that three of them, at the plastic risers, had little cracks where the spark leaked out to ground once in a while. Also, when I held the wires themselves, I was feeling a little juice through leeking out through my hand. The guy at the shop said that when wires start to go bad, the shielding wears out. Does that sound right????

Mike

[John Rogers]

Since these engines produce a lot of heat, the neopreme/rubber parts will wear quickly, including plug wires. Several times a year I run both our 914s at night with no lights and you can easily see voltage leaks. I would recommend some 8.5mm sylicone wires with the softer boots, although the purists will say you need to stay with the stock wires. If you get a set of "universal big block V8" wires you will get enough for two sets. Good luck.