Pontiac Repair: Follow up questions, fuel pressure regulator, crank shaft

Question
QUESTION: Hi Todd,

I have a 2000 Pontiac Bonneville with about 220k miles.  For the last several months the engine would sporadically stumble and sometimes the tach would drop to zero.  While searching for a solution I came across your suggestion that the problem might be related to a spark plug wire being too close to the oxygen sensor and speed sensor wires.  I had replaced my wires about six months ago and one of the rear wires was a bit long and actually had drooped down and touched the exhaust manifold and burned a bit of the insulation.  I had looped it up on top of the tie-down point for those two sensor wires.  After removing it from there and using a tie strap to keep it up, the problem has almost completely disappeared.  I think I need to check if any other wires might be shorting out as the problem seems to be worse in damp weather.  At any rate, can I send you some money to help compensate you for your time?  You certainly have saved me money!

Thanks.

-- Richard

ANSWER: Hi Richard:

well with that many miles it could be just about anything. but a few other things to check are a leaking fuel pressure regulator with the engine running pull the vacuum line off the top of it and check for any raw fuel comming out. check all the ground connections including the one on the frame rain on the left side of the enngine compartment to make sure it's clean and tight. only other issue could be a crank shaft position sesnor that at times cuts out. ther is no way to check it it's just good or bad especially with an intermittant and the fact that it starts right back up. that would be MY LAST GUESS to try.


---------- FOLLOW-UP ----------

QUESTION: A couple other questions, Todd.  The check engine light came on with a P0420 code which I take it means the catalytic converter needs replacement.  Could it be something else?  Since the car has such high mileage, I don't want to spend a lot on this.  A local shop said they could put in a universal one for $300.  Does that sound reasonable?  Any other options?

Second question.  Does the crank shaft position sensor control the tach in any way?  Since rerouting the ignition wires, the engine cough seems to have abated but every few days, the tach will still drop to 0.  Stopping and restarting the engine always restores it.  Could it be a bad instrument cluster?  The fuel gauge no longer works and the oil pressure always reads 120 when the engine is on.

Answer
Well a "fits" all converter "may" work and then again it may not. the engine computer is the only one that knows for sure if the converter will be big enough to process all the exhaust gases or not. The factory one if the ONLY correct way to fix it.

Yes the crank sensor is a direct input to the tach sort of. the crank sensor sends a signal to the ignition module and the module sensd sthe tach reading out from there. so it can be the sensor of the ignition module. As for the guases not working you could have a ground wire issue of just the cluster has gone bad. theer are ground wires all over the place on that car.  on both fender wells on the engine block by the starter and on the back of the engine behind and under the power steering pump. and ther is a BIG splice pack under the left front sill plate under the carpet if that goes bad all kinds of electrical stuff quits working like the fuel pump and power windows etc you may want to look at that as well.