91 240 stock - vibration on starting

[daotoad]

occasionally when starting the engine, it vibrates fairly violently for the first 30 - 90 seconds. I can get it to stop vibrating by racing the engine to about 2500 to 3500 rpms 2 or 3 times usually. I have new spark plugs, wires, distributor, rotor and cap, new 300zx fuel filter, stock replacement fuel pump, new O2 sensor, and the ECU says everything is OK. Most of the time I have noticed this problem on days when conditions were not the best, i.e., extreme temperatures, high humidity, or when the engine has not been ran for at least 2 or 3 days. Injector problems? If so, should I replace with stock injectors, or would larger ones help this situation? Thanks.

Also, I have an overheating issue. I searched for the solution, and I have not had much luck. My 240 will overheat fairly randomly, but usually it is when she sits for a while idling. I have replaced the radiator, the thermostat, the fan clutch, and the water temp sensor. I have flushed the cooling system, and I have repeatedly blead the system to try to get the air out. Should I just continue to try and get the rest of the air to bleed out of the sys. or is there something I am forgetting?

[NISTECH]

hows the water pump? is it circulating good?

[daotoad]

as far as I can tell with the radiator cap off I can see good flow from the passenger side to the driver side through the radiator. I didn't notice any obvious problems when I had the pump off about a year ago.

[NISTECH]

It looks as though you have replaced damn near the whole cooling system. So know you need to determine if the parts you installed are on correctly and the correct parts for the car. First easy test is fan air flow. Which way is the fan pushoing air back toward the engine or toward the front of the car. Have seen it installed back wards before and cause this problem. Also make sure you dont have any debris against the front of the condensor behind the bumper. The other thing is your T-stat. Is it factory? did it have a bleeder hole in its outer edge of the plate? did you position that hole in the up position?

[180fan]

i suspect injector plugs for the shaking

[daotoad]

The thermostat is not factory, it is aftermarket. I did not align the bleeder hole to the top of the unit. The fan is blowing towards the engine. The radiator was purchased from a parts yard when I replaced the stock one, which was leaking from the bottom of the shell/casing, so I don't know if the rad I bought performs as well as a new unit would, or if it is partially disfunctional (?). As far as the thermostat problem, I have had similar overheating with another thermostat which I replaced with the current one, and still the same results. I think I will try repositioning the thermo, and seeing if that solves the prob. I am trying to learn as much as I can about this KA engine and make a decision if I want to go KA-T or not. If I replace my injectors, would it be detrimental to go larger with stock fuel sys.?

[NISTECH]

If you go larger injectors you need to be able to supply them and be able to control them, meaning FMC. As far as your cooling system goes, yes the thermostat is a problem. BUT initially I was going to suggest possible plugged radiator. You said you had replaced it so I assumed it was new. IF the Tstat doesnt resolve the over heat after a GOOD bleeding of the system I would take a look at having that radiator flow checked. Either by the judgemental running a garden hose through it and see if flow looks about even. Or take it to a radiator shop and have them do it. They probably dont charge much for the test.

[HashiriyaS14]

I realize this is a pretty old thread, but it's the only one I could find that referenced the specific problem I'm having.

I am having EXACTLY the same issue that daotoad here is having, but it's the first one, the vibration (NOT the cooling system problem).

Injector plugs were mentioned, that is part of the wiring harness? Anything else I should look into?

The car in question is a '97 S14 SE Auto.

[HashiriyaS14]

Bump.

Bueller?

[Bwana]

The injector plugs are part of the wiring harness. What you'll want to check is the plugs themselves, right on top of the injectors. They clip on to the top of the injectors. You'll probably be wanting to check and see if they're tight and also if they're clean. Have you done your plugs ect. too?

[eds13]

would it be motor mounts? by chance?