Stalling at Idle..motor shakes as if running on 5

[JoeMechanic]

Cylinders.I replaced the 3100 motor with a good 3100 M motor from a 1996 buick Skylark(bone yard).The vehicle is a 1995 Grand Am GT 2 door that had a broken camshaft,pushrod,exhaust valve and 1 spring.I did an awesome job on my neighbors vehicle and the motor is tight and looks like new.I test drove it on the highway and it gets up to 70 mph in about 15 seconds or so and runs great at highway speed and speeds over 35 mph.The problem is that it shakes at idle and stalls out when I come to a red light or stop sign.I double and triple checked my wiring it has new plugs and it seems that the problem is either a clogged injector or the wires are bad.I didn't replace the wires with new wires..I just used the wires that the old engine had which were replaced by the owner about 2 years ago and they looked good and I tested them with engine running with water(spray bottle)to see if they leaked spark.Also I noticed that when I gun the engine while in park it cuts out at about 2500-3000 rpm.(like someone is in car turning key on and off) like a rev limiter type of cut out.I don't know if this engine has a rev limiter or not but it only happens when i punch it all the way down.Does anyone know how to make the ECM relearn the Idle as per a suggestion I recieved on another post.I am going to just replace all the wires with brand new ones and adjust this relean idle and cross my fricken fingers.I charged about $450 labor and recieved $100..I am due $350 and I can't collect until I finish this 2 month long project(seems like it took this long)thanks for any suggestions,Joe.

[IsaacHayes]

Rev limiter in park/neutral is 4k. Don't adjust any throttle screw. It's a stop not an adjustment.

What brand plugs?
Try swapping wires with some other old ones. Maybe swap the old injectors back in. Try tapping the injectors that are in there now with a screwdriver maybe one is stuck. The EGR valve isn't stuck open is it? Take it off and look at it.

[JoeMechanic]

Plugs are ACDelco

EGR valve will be my last thing to look at.I cleaned the intake when I had it off and the egr valve as well..I don't think its that.The wires or Injectors is where I am leaning towards.I also forgot to mention that the engine doesn't fire as easily as I would have thought.It takes about 5 seconds if counting 1-1000 2-1000 etc.With wires costing around $30 from my wholesale supplier I am going to just change them all with new and eliminate that.That and I am going to do a top end cleaner job with sea foam and do the intake while its running with throttle body and injection cleaner.I'll let you know if that worked..I will try tapping the injectors after I am done if the problem still persists.I am so close to collecting my labor $$..I want to finish this pig once and for all...thanks for your suggestions,Joe.

[bszopi]

How long has it been since the fuel filter has been replaced?

[JoeMechanic]

about 100-200 miles ago.

I checked underneath and its new..owner said he changed it prior to engine failure.I have the car in my yard and have been driving it for 2 day's now.It hesitates like hell now but the weather is 30 degrees compared to over 40 when it ran better. just purchased some sea foam and throttle body finjection cleaner spray and going to my supplier for a new set of wires tomorrow.I purchased the engine at a local bone yard with a 100 day warranty and it runs strong once it gets going but man it hesitates so bad now and smells like its running very very rich(out the tailpipe).There is nothing wrong with the motor as far as I can tell...no knocking,ticking or rattling..it is smooth running over 1500 rpm..its under 1500 where the problems are.I have almost 30 years experience messing with cars,lawnmowers,washing machines anything mechanical..but these 60 degree engines I have little experience with thats why I am here.I was checking some parts sites and found an idle air solenoid thats mounted to the Throttle body..perhaps this is bad?.No Service Engine Soon light so I assume there aren't any codes..I only have an OBD2 scan tool..I guess I will borrow or purchase an OBD 1.5 scan tool if everything I try tomorrow leaves me back at square one..let you all know what works,Joe.

[IsaacHayes]

I'm not sure the IAC solenoid would cause the bad running, but you could change out between the original and new one and see what happens.

Perhaps the oxygen sensor is bad???

At low RPM the 24x timing sensor is used for smoothness, but I'm not sure it would cause the car to run THIS bad if it was bad.

Also the Cam position sensor controls fueling for the SFI part, but it will run without it just in mpfi mode... It really shouldn't make it THAT rough either I don't think but maybe it's something to look into as well.

Yeah if you could scan it and read the sensor data you could post that and we could see if it's in range...

[Azrael]

I had a similar problem after driving for an hour a few weeks ago shortly after changing the O2 sensor. Had to shift to neutral at the lights to keep it from stalling. My vacuum gauge was also showing 10" of mercury at idle instead of the usual 18-19. It never happened since so maybe it is just the PCM relearning the idle.

[JoeMechanic]

Well I installed the new wires and it still shakes

I cleaned out the engine with sea foam and smoked the whole neighborhood..cleaned out throttle body with cleaner.The engine doesn't hesitate as badly nor does it stall out as badly as before after a test drive.Engine still shakes as if running on 5..I am suspecting a burnt valve..next step is to do a compression test.For some reason the starter sounds as if its working too hard to start this engine..I think I got a bogus engine from the bone yard.After compression test I will post results and then I will post what I did to the wrecking yard person that sold me the motor.I am going to hang him by his testicles with the forklift..I expect a full refund plus $50 for new intake gasket's..and they can pull it out.I hope its not one dead cylinder because I did such an awesome job on it and it does run nicely when getting up to 35-40 mph,Joe.

[JoeMechanic]

Found Problem..Weak fuel Pump and 2 clogged non working injectors.

[Coyote_Rage]

So all good now? I've been wondering how it was coming.