Stalling at stop, hesitation at 4k

So I took my Monte in to a garage and had them do the lower and upper intake manifold gaskets. Cost me $625, but I figure if I contact GM and put up enough fuss I might be able to get a situational recall reimbursement. Anyway, after getting the car back, I was told by the mechanic to do a tune-up including spark plugs, wires, filters, etc... I assumed they changed the oil filter, though it doesn't look new. I changed the plugs and wires, went with Bosch 7mm wires and Platinum plugs. Car runs great, when it's being fed gas.

At most stop lights the idle is sporadic, needle fluctuating between 500 and 1500 RPM's. It usually stalls. I checked a rev today and it also bogs down like it's about to stall when revved above 4k RPM's. I ordered a Haynes manual today and plan to get the CEL code read soon. The garage thought that becuase it's stalling it might need the timing checked also.

Any advice on what to look at? Like I said, I'll get the code soon, maybe tomorrow, from Autozone. I may look at a timing light while I'm there, and pick up a fuel filter too. I'm beginning to hate GM cars.

Here's the codes pulled from the reader:

PO134
PO171
PO341

I haven't had a chance to look them up yet, but I talked to a mechanic friend of mine and he said it sounds like a possible vacuum leak. The guy at Autozone that did the CEL reading said one of the codes is "too lean", one is "camshaft position off", and the last one he wasn't sure of, possible misfire or something maybe.

Any advice on how to proceed? I was told to get a flammable spray to check for vacuum leaks, something not too explosive but that would affect engine idle significantly, like carb cleaner or starter fluid.

the codes are as follows
p0134- oxygen sensor circuit no activity
p0171- system too lean
p0341- cam position sensor circuit range/performance

Since the first two are both related to the oxygen sensor, I'd check to be sure it got plugged back in.
The cam sensor is in the front of the engine, just forward of the intake manifold. I would again check to be sure that it is plugged in and the wires didn't get pinched when the intake was re-installed.
Another possibility is the upper engine wiring harness connector (near the alternator) may not be plugged back in fully if he disconnected it there while doning the work. The injector harness, oxygen sensor, and cam postion sensors all feed off this main junction, so it's something else to check.

Have you had any luck with this problem? I received a letter from GM a few months back, stating that some of the engines in the 02 Monte have faulty cat converters. I took it in, and it was bad, so they replaced it. It was still running crappy so the guy said I may need the injector system flushed. I argued with them that they should pay for it...I won and they did.

Now...I keep stalling out. I have 68k miles and my spark plugs are WAY gunked up/burned. Took it to AutoZone and had them read the codes. It came up with an O2 sensor problem, running too rich.

So, I'm thinking that because the cat convertor was bad, it set off a chain reaction of things that contributed to 'GUNKING UP' everything else.

I'm planning to call GM and see if they will do anything about it.

Let me know if you found anything different with your issue.

Thanks!!

Actually, I did figure out the problem as to why my engine was stalling. Turns out the garage mechanics are complete idiots because I had my car back in to the same garage arguing that the cause of my stalling was something they did- and I was right. They disconnected the battery when they did the gasket change... AND FORGOT TO RECONNECT THE NEGATIVE! The negative terminal screw was simply sitting in the hole.

As to your problem, if the spark plugs are gunked up, I'd have one of them checked out by a mechanic. More than likely if you're running too rich then it's because your air system isn't providing enough air or your fuel system isn't being properly regulated. Could also be a reburn issue. I'm getting O2 sensor issues as well, and my camshaft sensor might be going. Both sensors are in the $80 range, but replacing them could improve fuel economy and performance. Just waiting to see when I might have the time to do this work, and I'm taking my car back to the same garage- for one reason- I plan on bringing up the BBB when I discuss my oil being overly dirty. They should have flushed the oil and changed the filter. I have reason to believe they did neither. I'm not happy, and this is one business I'm not going to get screwed by.

Also check the Air flow valve and the Throttle position sensor.

So, funny how i havent been around this site for awhile and when my 96 monte z34 starts acting up, someone has a post w/ similar problems. I know a tune up is in need for my car,which will be happening soon. When i turned my car off the night before,as i put it in park, it stalled. Now today, as i came to a stop light, my car decided to stall once again. Start it up, rev it, along w/ hesitation (misfires from bad plugs/wires) and off i went..for about 4 blocks,then it happened again. After completely turnin the car off and waitin about 5 min,it started right up and ran like nothing was wrong. Now, im really hopin its just a sensor or something minor, i know its nothin to do w/ the battery cables cause i already checked. Im wonderin if maybe cause of the bad plugs/wires this is happening?? or if it is a sensor problem of some sort... Other than this small mishap and my wonderful oil leak, i cant complain about this car, at 138,800 miles,she still running great!

One of the problems I was having was that my spark plug wires were also too close to my timing sensor wires, which run along the front top edge of the engine. Check to make sure your spark plug wires aren't too close to this, and that they are insulated from jumping a spark to the engine or nearby wires/metal surfaces. Other than that, CEL codes should give you a clue as to the possible causes. I'm far from an expert, but between conversations with mechanics and reading here, I've found a considerable amount of info on this particular problem.