MikeS

I've been struggling with rough idle and terrible part throttle drivability for a little while now with my 87 LB9. Searches haven't covered it for me this time.

Idle quality is on par with firing on only 7 cylinders, and part throttle drivability is both low on power and rough running....to the point of causing bucking and shuddering through the driveline at times. I'm at a bit of a loss, but it sticks out to me that performance at wide open throttle seems great. I'm not sure what happens at WOT that would bypass (or mask) the problem I have elsewhere.

FYI, a fair number of new parts have been installed recently, although all of them after this problem began. New parts:
distributor w/cap and rotor
ignition coil
spark plugs
battery
cleaned throttle body
coolant temp sensor

I'm not sure where to go next. I'll probably replace the TPS over the weekend. I won't have access to an analog multimeter to check it with until then regardless. Any thoughts? The car is almost stock (headers w/out air injection).

ATX-Iroc

Check for vacuum leaks. The way I do it is to tape off the throttle body so no air can get in or out and then blow cigarette smoke in through a vacuum hose. Wherever smoke comes out is where the leak is.

NY87Iroc

iTrader: (1)

Did you replace with plug wires? I went through two brand new sets of 8mm napa wires. I opened the hood one night in the dark and it looked like a fireworks show under the hood. I installed MSD 8.5mm wires and a new MSD distributer all she runs perfect now. I was chasing a misfire for 2 years before that!!

MikeS

I have done a check for vac leaks recently. Not using a smoke method, but while running using starting fluid. Basically spray toward suspect locations and listen for a change in idle speed. None found though, so it was either a confirmation of no leaks or a failed check.

Plug wires, on the other hand, have not been replaced recently. They do kind of stick out as the only thing remaining in order to get the ignition system up to snuff. Not sure why old/bad wires would cause problems at idle and part throttle but be ok at WOT. Stranger things have happened though......so I should look into them.

ATX-Iroc

most of the time you cant feel misfires at high rpms you just notice the power loss

MikeS

Replaced the wires with a new set of Taylors over the weekend. No improvement. Also checked the TPS sensor, which checked out ok.