Stumble At Light Throttle

[OldSkool]

To start things, Nice board you guys have here. Never knew that there were that many people into Lexus'. But now I know why. I just bought a '90 LS400 with 113k miles and it's a dream of a car. Couldn't be happier with it. I do have one problem with it though. When I'm driving it at a steady speed, let's say down the freeway, at a very light throttle, basically touching the throttle enough to maintain speed but not accelerate, it seems to just fall on itself for a splitsecond. Almost like the engine quits and gets going again.

I've looked for similar posts and found some where people have problems with the car speeding up on them unintentionally, but I have the exact opposite problem. Has anyone had this happen to their car or does someone know a cure? I'm open to suggestions on this one.

I'm used to much older and simpler cars and trucks like my '64 Chevy longbed I'm restoring.

Thanks guys and keep up the good work.

[silvermate]

sounds to me like you have a bad plug.........

do you have the mantenence records for her??? if not you might as well take a weekend and give her a full tune up, its do anyway

plugs

wires

dist.cap

rotors

PCV valve

air filter

clean throttle body, ect........

after that she'll be running like brand new ;)

good luck

[SKperformance]

change the rotor and cap first

it is probably a damaged rotor changing the timing when flexed

[OldSkool]

Thanks guys!! Will do as soon as I get a day off which isn't anytime soon.

Thinking about a roadtrip to Nebraska next month and I want her to run perfect.

One more thing. I need to replace the Belt, which I already have, but I also need to replace the Valvecover gaskets. They have a slight leak and the smell of the oil hitting the headers is driving me nutts. They look to be a bit of a pain to do. Any pointers from anyone that's done them? In Case you can't tell..I'm all about DIY :D

[jkmk75]

Did the distributor and rotor fix the problem? I have a 94 LS400 that does the same thing. Cruising along at any speed over 50 the engine cuts out for a second intermittently, then returns to speed. This does not happen when I use my cruise control; it keep maintains speed. Only happens when not using cruise control.

Any ideas?

[sweetls]

Go to Lexls.com for some great DIY service tips and instructions to save yourself a bundle. I think the spark plug change guide will include the valve cover removal for you.

[akewlguy]

Abrupt change in the smoothest ride.

Today my car was mis firing at idle and every speed above 0. So I looked at records and realized that the cap has not been changed in 112000 miles. So it is at the shop awaiting some LEXUS parts. Suspect this is why I have had a decrease in mileage over the past year. So I am so excited to see this puppy at full power! I orders plugs and rotor. Plugs were last changed 45k, so you think I need them or did right?

[swordfish]

hey oldschool

yeah i did the cam cover gaskets a while back. Took me about 6 hours. Getting the covers off around all the injector wiring and lines is the slow part. Sealastic has to be put on the part of the cover goes up over the camshaft indentation, you need to get the shop manual guide on it, i had trouble finding any one who had done it. The gaskets come with seals to go around the plug holes. I made an installer out of the neck of a plastic bottle the same diameter to knock the new ones in. Just screw driver the old ones out. The trick is the seals around the cam cover hold down screws, the screws are only tightened very lightly, some one probably created the leaks by over-tightening them. Worked out fine, all the oily smells stopped. You might also check the big rubber seal strip goes across rear of engine bay and gets compressed when the engine hood is closed- mine was missing, and this allows engine fumes and smells to get sucked into air vents.

cheers