Slight Miss While Driving On Hwy.

[BlackLex]

I have an engine miss while cruising on hwy. I only notice it when the car is not fully warmed up and I am at a steady hwy. speed from 50-70 not increasing or decreasing speed.

the car starts great and idles perfect. I have tried sea foam with no results. gas milage seems ok

is there a sensor going out like oxygen or map?????

[NIALS400]

I’ve noticed the same thing with my 91’ and usually on black top roads. I don’t know if it’s frost heaves, in the frozen north as we both are, or the reaction of the suspension or something else. Did you figure yours out?

[TexasLexus94]

I had a similar problem at cruising speed, and found out that changing the plugs and plug wires corrected the hesitation. While this may not be your specific problem, I'd suggest doing this first-It's a cheap $100 possible solution. Worked for me....

[NIALS400]

The car did it before I changed the timing belt, W.P., plugs, wires, caps and rotors. It almost feels like the TRAC kicks in for a split second but it will do it with it on or off. Tried it in overdrive or out of O.D. The tach doesn’t move, its weird. I do have blizzaks on at 35psi. There a hard tire so next I’ll try dropping down to 30psi.

[NIALS400]

I'm still looking for the problem. One thing I did notice is that my fuel cap is a Stant, I can only assume the OEM is not made by Stant. Could improper fuel tank pressure be the culprit? Where is a good place to get a replacement OEM at a fair price since my nearest dealer is 2 hours away?

[nc211]

Have you guys checked your tranny fluid lately? I say this becuase the engine and tranny talk to eachother via computer. To me, problems during warming up lead me to believe it's fluid related. Maybe your engine is fine, but your tranny might be slipping ever-so-slightly until the fluids can warm up and help the clutch grab. Are you guys familiar with the "drain n' fill" proceedure for the tranny fluid? If not, run a search for drain and fill and you should see some threads on how it's done. It's easier than changing your own oil. Just one bolt, 2 quarts drain out, put bolt back on "get new crush washer", pour in 2 quarts through the tranny dipstick hole. Use toyota fluid only. Do this about 3 or 4 times over the course of next 6k miles, and you'll have effectively flushed your tranny completely, then just do it about once every 7,500 miles, and you'll keep that tranny in perfect condition. Remember, 2 quarts drains out automatically, 2 quarts go in. If it drains more than 2 quarts, then you've had too much in there, drains too little, well, you've been running with too little. You can buy a case of the fluid from the Toyota dealer "cheaper than Lexus dealer" for like $50 bucks, and it'll last you for quite a long time.

PS: Nails, a friendly suggestion; go into your profile and add the year of your LS for others to see, instead of just "LS400", put like "1993 LS400". ;)

[NIALS400]

I've done the trans drain and fill a couple of times, with help from this board, thanks to all, but to no avail. When I do, do the drain and fill though I put in 2 qts. and it barely touches the dipstick when cold, usually I have to put in 2.5 qts. to get it to the middle of the cold mark. I'll drain and fill again and only put in 2 qts. to see if that makes a difference. Maybe over filled tranny?

I did drive around for about an hour today messing with tire pressures, not difference. After I went to fill up and noticed there is a lot of vacuum in the tank, is that normal?

[BlackLex]

I will try tightening gas cap more.

superlube might have toppped off tranny fluid with other than toyota

I will try replacing plugs/wires/rotor when weather warms up.

thanks everybody I will keep you informed.

[VBdenny]

I am pretty sure that if the gas cap isn't closed properly, the check engine light comes on. I have had it happen on several different vehicles. Seem to happen more often in New Jersey since they put the gas in there and half of them haven't a clue.

[NIALS400]

BlackLex, how long has yours done this? Did it do it in warm weather? Since I'm in Iowa maybe its the cold?? I just bought mine so it’s been cold here since ownership. I drove it yesterday when it was -5F and it didn’t act up that I could tell, this morning at 10F it did only once. My next step is to add some weight to the rear, tube sand, and see if maybe it the suspension? I did change the trans again and filled with only 2 qts. but haven’t drove it more than a couple of days in which it acted up once, maybe it will take a little bit to purge? I'll turn the TRAC off again and to the POWER trans setting to see if it makes a difference.

[BlackLex]

It's done it for about 4-5 mo's I just wonder why it idles and accelerates so well . when it is at very light load it acts up . I seem to notice it in the high gear more between 40-55 mph.

[NIALS400]

Mine's the same way. It never does it under load, uphill or coasting. I called a bunch of dealers, Maplewood, Wayzata, Betts and some in California. All said it would need to be looked at by a technician. Sounds like a canned answer.

I did notice that I do not have a Lexus brand fuel cap and it isn’t for a vacuum only system. I bought a replacement at a parts store to see what happens and I'll order a new Lexus one on Monday to see if that helps.