2000 3.4 l v-6 3 codes/ HARD SHIFT

[charliemwood]

okay new question.... i have a 2000 3.4 l v-6 grand am that i recently replaced heads , head gaskets, plugs, wires, coolant resovior, & serpintine ( ?) belt.... after running hot and water in the oil . After many "trial and error" sessions of putting motor back together ( wrong rod and rocker arm placements) still had rough idle and bad noises , posted a ? about and discovered i had bent the intake valve when i put the rocker arms and rods in wrong earlier ( thanks again for the great answer on earlier post) well the car is finally running somewhat of her old self but the rpms are surging now when i crank it up and noticed VERY HARD shift which never happened before this repair. so i drove it up to auto zone and had it scanned maf, iac valve sensor, and front o2 sensor wtf? ya know never had a problem outta this car before this and going bankrupt after the head being machined, new gasket set, new bolts, the belt, plugs,wires, rocker arm ( that broke) resovior, so i would like to narrow down the main fix of these symtoms the surging and the hard shift the iac was the cheapiest of the 3 so we went ahead and bought it no change. also car wont start and idle if the maf sensor is plugged up auto zone priced the o2 sensor at 63.99 and the maf at 103.99 also i have checked the wiring harnesses to each of them and they appear fine and i can hear a vaccum leak i think is coming from the heater bypass hose( gotta get an o ring for it) would this cause the scanner to come up with ne of these codes? thanks for ne help

[3100]

I would concentrate on IAC idle air control valve since you can start without maf and o2 sensor. It is possible that you damaged IAC valve connector pins or its wiring when you were working on your engine. Hard shift is probably because of the high idle. If your idle is ie. 2000 rpm and you try to shift from P to D you will have hard shift, unless you are talking about hard shifts while driving. So do visual check of your iac connector and wires. Also see that the transmission connector (round connector) is plugged in. Also see that the throttle plate is closed completely with engine off.

[charliemwood]

thanks for reply ! we replaced the iac valve sensor and no change. he took the throttle body off and cleaned it so now the car is shifting normal but the idle is still really low when u first start it up and at stop lights and signs. could a weak alternator cause the rough and low idle? how can i check at home if it is the alternator? the car idles now with maf sensor plugged up he said he checked all the wiring harnesses and connectors on the sensors going to check throttle body plate........

[3100]

check map sensor's vacuum connection it is the small balck box on top of the engine (top right hand side corner of the engine) this sensor uses "T" shape vacuum fitting one side goes to plenum one to sensor and the other to small plastic tube that connects to fuel pressure regulator. Also follow the pcv plastic hose it goes behind the engine and connects to evap solenoid make sure that the other end is connected to something. When you find the other side of that plastic hose plug it with your finger while engine is running and you will see that this was the problem. 100% your pcv vacuum line between the engine and firewall is disconnected.

[xeroinfinity]

IAC's typicaly dont just go out unless thier messed with, carbon build up in the port is most common issue.

Your surging and low idle sounds more like a vavuum leak still somewhere.

Might double check the PCV tubing, which runs on top of the TB and to the rear valve cover, it sometimes doesnt want to stay plugged in .
Thier is also a vacum line to the O2 harness connector back there which can pop off or leak from cracked plastic tubing.

[charliemwood]

ok the car is running now but it has a hard time starting after its been sitting a while but after you get it warmed up it does fine as far as cranking it does still have a small rough idle issue but that is only when it is in gear when u put it in park it idles fine i have replaced the iac valve and triple checked all vaccum lines they are ok.

[xeroinfinity]

Do you have over 100k miles on this GA charliemwood ?

If so you're past due for a trans fluid & filter change.

And by hard time shifting you mean it feels like it slips?
Or it just shifts hard(slams into gear) when it shifts ?