My car idles high and accelerates by itself! HELP!

(Forgive the Honda cross-post, but you guys seem to know a lot... I own a
Honda too!)

My mechanic completely screwed up my car (95 Nissan 200SX SE-R with the
SR20DE engine), and I was hoping someone out there might know how, since he
doesn't. I took it in for an oil change and he recommended doing a throttle
body cleaning and a fuel injector cleaning. I said what the hell, okay.
The result? First, I noticed my car now has a high idle -- about 950 RPM at
rest in Drive and 1100-1200 RPM at rest in Neutral -- so it always feels
like the engine's cold. It also goes faster when I just let the idle take
me along in the parking lot. I took it back to him, he fooled around with
it some more but couldn't figure out what's wrong.
So it still has those problems, but now (and possibly before) it ACCELERATES
ON ITS OWN. If I leave it in Drive without pressing any pedal, it will
slowly accelerate all the way up through THIRD gear and at least 22 MPH,
possibly higher if I hadn't run out of residential driveway. Scary stuff.

WHAT'S GOING ON??? Thanks for any reply.

In the meantime, don't visit All Tune & Lube in Mountain View (Middlefield
Road). Please.

 

sounds like a helluva vacuum leak somewhere.

 

He probably didn't get all the sensor wires & hoses connected back correctly
when he reinstalled the air box to the intake. It sounds like the car
thinks it's cold and the cold start mechanism (or whatever they call the
choke/fast idle cam these days) is on. Hopefully he didn't destroy any of
the sensors taking it apart or cramming it back together.

 

what's not so funny is I just got this problem yesterday on my '99 V6
Accord. I just did a total detail of the car (wash, wax) and of course
degreased the engine. It then sat in the garage for 3 days before I started
it. Not sure if the degreaser did something or not. Just thought I'd fill
in all possible data.

Luckily for me, I have a huge maintenance visit coming up next week and I
can let it sit until I get there. But the (very reputable) garage told me
to check the coolant in the radiator, not just in the reservoir tank. (all
good there... make sure the engine is COLD) Then next suggested looking at
all of the vacuum hoses. He said that they don't clamp down, so they can
become loose or the case of old hoses, can lose their "grip" and hence the
vacuum leak. I couldn't see anything, but not a lot of room around the
engine to get a good look.

Was told while driving (mine is an automatic) to the garage, and sitting in
traffic, drop it into neutral and save on the brake system. Sure you'll be
rev-happy at the light but saving the strain on the brakes and tranny. I
don't care so much about the brakes, but a transmission is like gold.

Keith

 

This happened to my 85 200sx once, my cruise cable was
stuck. I disconnected it, no more acceleration probs.

t

 

If it dates from the degreasing, a likely culprit is water/degreaser has
gotten into one or more of the wiring connectors. Pop apart the more
obvious ones and dry off any wet contacts you find. A long drive that heats
the engine compartment might dry it up as well. For future reference, you
always want to drive it around long enough to dry out the engine compartment
immediately after washing the engine.

 

Go somewhere else and have them adjust the idle. It's a screw, if I recall
(I owned a 200sx SE) that adjusts the amount of air getting into the
throttle body at idle. When all the gunk is cleaned out of the TB, it needs
to be put back to factory idle because it's no longer being restricted by
all that carbon.

Nick

 

Nick, thou art wiser than my mechanic. He took my car to a mechanic friend
of his and that's exactly what he did: adjust that stupid little screw.
Tah-dah: idle's back at 800. What a relief. Still, what the hell was up
with that random revving up to 1,700 that took me for a ride through 3rd
gear and 25 MPH (and probably beyond)? And how often is a TB cleaning
recommended?

His theory was that the previous owner of my car messed with the screw in
the first place to compensate for a low idle. Does that mean if you just
let your throttle body get dirtier and dirtier, your idle speed will
gradually drop?

On another note, can I reduce the idle further to save gas? I noticed that
all Hondas are engineered to have really weak idle, though I don't know if
that's the same thing.