GasBuggy

I've noticed my 94 doing this when I'm on a flat stretch of highway. It's a faint pulsing that shows up only when you're using just enough throttle to maintain a good speed, like 55-70. A little more throttle and it stops, a little less and stops. My girlfriend doesn't notice it, but it's starting to get on my nerves. I know it's the engine and not a tire balance issue.

wnyjazz

I get that too in my '94.

My ecu was really bad, so I had it repaired, but in my case it didn't cure the issue.

Yamae

What happens when you shift the gear to the 3rd manually?
If it changes the pulsing speed, there's a possibility to have a worn transmission mount.

python

iTrader: (4)

yes..have ur mounts checked...all of them as well as the drive shaft damper

KJG92

Had a very similar issue with our 92. Sent off the computer but that didn't fix it. Then went thru and replaced the fuel filter, cleaned the IAC and the throttle body. Did a oil change and drained out what fluid I could out of the trans and refilled. Car has been fine since I did all that.

GasBuggy

I will check the trans mount and driveshaft, but you would have to feel this.

Shifting to third gear stops it, but so does applying a little more gas or a little less. It seems to exist only when the car is warmed up, ie, when in closed loop.

GasBuggy

Mounts are fine.

sshhlexus

I have been having the same problem lately. LS400 1993 150,000 kms. Happens when the rpm goes to just below 2000 rpm no matter what speed. Outside of that rpm range, runs fine. When it happens it's almost like a jerking motion and only after the car has warmed up. ECU was upgraded a couple of years ago.

GasBuggy

I did a long drive at night recently, it was oddly cool so my AC was off, it just hit me that it didn't happen with AC off.... since this car is new to me, almost all my driving time has been with the AC on. AC changes some engine parameters, adds load. Try shutting it off when you feel it, I will report my results.

GasBuggy

Ok, narrowed it down. The car has be really heat soaked to pulse. It's noticeable after driving in 90+ degree weather for 15 minutes or so, or after sitting traffic for a while. It doesn't do it on cooler nights. My temp gauge doesn't work, and though I have no reason to believe it is running warm, I better get it fixed so I know this isn't the car running warm and misbehaving.

sshhlexus

In my case it did not matter whether the A/C was on or off. I tried changing the brand of gasoline and it seemed to help quite a bit. Although not eliminating the problem entirely. Still happens, but far less. I hope I don't violate any forum rules by mentioning the before and after gasoline brands. But we are here to help each other. I live in Florida so it may be different where one lives. In both cases it was 93 octane.

That gas that caused the problems was Costco gas, I don't know how much crap ethanol they put in there. The much better gas was the Shell V-power, again 93 octane. And that is what I've been using since the last couple of fills.

I have a local station that sells ethanol free gas, but it is only 90 octane. I may try that and report here...

dicer

Do your test with the cruise control on and let it run the accelerator and report back. Are any of these cars equipped with Trac?

YODAONE

The fuel line runs up the inside fenderwell about 1/2" from the exhaust manifold shield. The fuel rail and fuel pipes run atop a hot intake manifold.

Try using appropriate fuel line insulation sleeving to reduce fuel line temperature.

Also, consider employing heat reflecting insulation material on underside of the fresh air intake that spans across top of the hot radiator...

Wrap the intake tube as well.

Check out DEI in Ohio for materials.
and write-up on this site

wnyjazz

Thanks for that.

The hotter it gets the worse ours sputters, misses etc. a/c on or off it doesn't matter. Low idle issues all temps. The ECU was repaired properly. After a rain the car really struggles within the 1st ten minutes of driving. In dry weather, it happens a lot of times after the car comes to a stop.

Skip

YODAONE

After a Rain?...

Check moonroof drain tubes for blockage and whether water is exiting below car.

If water accumulates around moonroof drain trays it will spill over onto the headliner and can drip down on critical electronics or connectors.

Verify the condition of your moonroof's rubber seal..it may be dry and require conditioning with Shin Etsu grease.

Sounds like a connector or ground somewhere requires time to dry off.

Do you have plastic undercover in place?

Are you experiencing humidity inside cabin after rainfall?