Question1982 Volvo 240(245)Wagon, 4cyl, Gas, No turbo, standard trans W/ electric overdrive: took car in for tune-up, distributer was frozen couldn't be adjusted, it was replaced along w/ plugs,wires, points etc..car ran fine for a week then engine began to surge, not idle hunting, jerking up & down. Repair shop couldn't find any vacume leak. I found electric connection going to fuel distributer(2prong) broken. held connector & engine smoothed out, cleaned & lock wired connection. engine continues to jerk, seems more so when speeding up to shift. At idle surging continues. Tach bounces up & down. Not sure if problem is electrical or fuel regulation, maybe combination. where do I look and what for. closes Dealer is 2 hours away. Thanks.
AnswerThe surging is usually a fuel problem, and usually means you're running a bit rich. The frequency valve under the injection manifold controls the duty cycle of the engine (rate and timing of air and gas mixture), which is responsible for how rich or lean the engine runs. Check for a pinging sound usually heard in the cabin on the right side coming from the engine under heavy acceleration. If that exists, check the emission system, mostly notably the oxygen sensor. This sensor has some control over how the frequency valve operates, and thus how the mixture is created. Also, if there is pinging, check the timing. If it is at 10 or higher, retard it to 8 or below and see if that fixes the problem.
Beyond those two things, a thorough check of the vacuum system is warranted if you haven't already had it done. A leak somewhere could also cause issues of this nature.
