Throttle Body problem?

[1993CivicVX]

I recently became the happy new owner of a gas sipping 1993 Honda Civic VX (49 state version) It has a 1.5 liter VTEC-E engine and 5 speed manual transmission. The speedo/odometer don't work all the time so it has *at least* 175,000 miles.....

There's quite a few problems with the car so far but the biggest issue is with how it drives. A few things regarding this.

First,

when shifting at lower speeds (mainly going from first gear to second and second gear to third) the tach does not drop down to 1000RPMs immediately *like it should when the clutch is depressed between shifts*. I'm at 2000RPMs, I put in the clutch, but the tach just hangs out at 2000RPM for a second or three before slowly dropping down to 1000. I usually shift at around 1800-2000RPM when in first or second gear, and 1400-1600 rpm from 3rd to 4th, and 4th to 5th. This car likes to operate at low RPMs. The problem does not go away when the car is warmed up. The problem doesn't seem as noticeable going to 4th and 5th gear (but that could just be because I shift at lower RPMs for these gears)

Second,

When cruising at highway speed (60-65mph, I'm trying to get a bazillion miles per gallon here), and the gas pedal is depressed at a steady constant to maintain a constant speed, there will be a sudden, but subtle, loss of power, and the car will start slowing down, then there will be a sudden, but subtle, surge of power and the car will start accelerating again or at least maintaining speed--the power surge and power loss are very subtle. It actually happens at just about all speeds except maybe below 25mph. It's almost as if it is slacking on the job, and then realizes it and tries to correct itself. The person who sold me the car said that that was the car entering into the lean burn mode. But I am skeptical. Especially when you consider the third part of this problem of which all three parts I'm assuming are related.

Third,

When accelerating at lower speeds, especially at low RPMs (say 1200, no really, the car likes low RPMs!) sometimes in addition to lagging, it stutters, and for a brief moment, sometimes, I think the car is going to die on me. But then it pulls itself together and pulls forward. It doesn't always do this so I don't think it is a lugging problem. When a car lugs, it makes an unhappy but fairly even noise that screams 'Up shift! Up shift! For Godsakes Up shift!". There is no noise out of the ordinary, and it seems to me the jerky stutter is too erratic to be a traditional lugging of the engine.

Might there be something wrong with the lean burn aspect of the VTEC-E engine?

Here are some of the things I've been told might correct the problem, or that I thought in my own limited understanding of cars might correct the problem: (these are quotes from car forums)

"VX and CX engines are both finely tuned engines and require valve adjustments every 15,000 miles I believe."

"the varrying throttle in my expearince is the o2 sensor, but going thru and doing a tune up might make it go away as well, make sure your EGR valve is working properly too, as I was told by the dealer mecanice that if that is not working right that it can sometimes have the same affect, to check that simply pull the vaccum hose off the EGR valve and plug it with a pencel." [sic]--dyslexia maybe, or English not his native tongue

I'm car-DIY-aphobic so I haven't messed with anything on the engine myself. I've left that to my friend who works at Jiffy Lube (who was the one to do the tune up). Oh, the guy who sold me the car said the rising RPM problem could be fixed with a throttle body cleaning? or something with the throttle body--not exactly sure, the car lingo kinda goes in one ear and then gets stuck on some ear wax before it ever gets a chance to actually penetrate any gray matter let alone make its way over to my other ear.

It did have some other throttle issues, but they *were* mostly improved by tune up. For example it stalled once on the 45 mile drive home from where I bought it but hasn't stalled since the tune up. But the engine still rises to 2000RPMs sometimes inexplicably when I put the shifter in neutral (the temperature gauge indicates the engine is warm, but this will continue to happen up to ten minutes after the temp gauge has stopped rising-or even after a long drive [not all the time, but sometimes, when it feels like it. Sometimes it'll stay motionless at 1000RPM like a good tach, and other times it will bob up and down between 500 and 1100-but then sometimes it'll sorta just wander up to 2000 and hang out there. This seems to happen more while putting along in congested traffic in town])

Just so I'm really clear. What I *want* the car to do is to idle normally . That is stay at 1000RPM at all times when not in gear (I don't really mind the bouncing tach at low RPM). If it wants to warm the engine up at 2000RPM, then it should do it for the first five minutes, not at random intervals throughout the day. And I want it to have even and smooth acceleration and to maintain even throttle response when I have the throttle depressed at an even, constant pressure.

[GasSavers_TomO]

One thing I forgot to mention that would help with the surging idle is cleaning the IACV (Intake Air Control Valve). It is on the backside of the intake manifold. It's an easy DIY.

CLICK HERE for a How-To to help you along.

[bfg9000d]

I had a problem similar to this. I thought it was one thing it seem to fix the problem then it came back. A few things the ignition module, fuel filter, fuel pump, engine computer, spark plugs, distributor, Compressor lock up, to name a few can cause the resuting problems. With mine I had to replace just about everything for it to finally fix roughly the same problem you had. Try running the car with the A/C turn off. See if that improves the situation My car was a 94. I highly recommend before you do anything. Find a repair shop or some place that will run the codes for the car.

[1993CivicVX]

Try running the car with the A/C off!? Wait, do you think this is like, the Gassavers forum or something? Hah!! I'm just kidding. I haven't used the A/C since I've owned it. It goes into the shop on Thursday, and I will give the mechanic a piece of paper with all the advice I've received on what might be the causes. Oh boy, he's just gonna love me.

[GasSavers_StanleyD]

[QUOTE=1993CivicVX;69793].... I haven't used the A/C since I've owned it...QUOTE]

Welcome home buddy, you're right where you belong.

On another note make sure they check the timing belt. I had a car that would stall on me on the highway. No problem: just put the auto car in neutral while driving, restart the car and pop back in to drive an keep going. But it would keep doing it. Sometimes while gassing, it would just completely lose power (as if the fuel pump went) and sometimes it would die (hence, neutral and restart). Thought it was spark plugs or feul pump intul the car just died and would not restart. Luckily I was driving fast enough to coast to the next exit and roll into a sweet parking spot (LUCKY !!!)
Turned out to be the timimg belt. Auto store had one for less than $20 and a coworker install for next to nothing. Job took less than an hour. Was an older Toyota, so it was an EASY job. If you dont know how long its been since changed, you might as well install a new one if you are going to be doing ANY engine work. Plus on a 90's Honda, Im guessing its an easy and cheap job. Mechanics love working on older cars. so much faster and easier

[brucepick]

I've noticed newer cars (mine is an '89 which I consider "newer") don't drop rpms as fast as the older ones did. I think it's the computer maintaining rpms and letting them drop gradually to avoid driveability issues and maybe to reduce emissions. In the carburetor days, they added an idle-drop limiter of some kind so the idle would reduce slowly when you took your foot off the gas.

Anyway, do look around for intake leaks. That's hoses of course. Also if you have a corrugated air intake hose downstream from the air mass meter (aka MAF), remove the hose and check for holes everywhere. Nearly impossible to see the underside of those hoses when installed.

[bfg9000d]

yeah the timing belt is something to look into. The engine computer can cause problems like this as well. Its something that will fustrate even the mechanic believe me. I even thought at one point it was the throttle position sensor or whatever they call it. I almost made myself believe that the 10% ethnaol mixture made it stall because it couldnt handle the new mixture. Which wasnt true. I wish you the best of luck.

[1993CivicVX]

Thanks guys. Well, it only stalled once, and that was after 50 minutes of driving. But I haven't done a long trip since. But It hasn't idling real low like it used to ever since I did the tune up and the exhaust clean. I think those things really helped! A friend just installed the CD player and connected the speakers. So now I finally have something other than the rattle to listen to while driving! Actually, hardly notice it anymore--the music drowns it out nicely. Anyway, thanks guys, and I'll let you know how it goes on Thursday!

[GasSavers_Ryland]

Check your throttle possition sensor for a dead spot in it's rotation, if it's good then I highly suspect that it's your O2 sensor, you can check all that other stuff on your list, but the O2 sensor on the civic vx seems to have a life span of about 15 years, some people exspect an errer code from the computer, but most of the time it will not have one, but if you replace the O2 sensor your problem will most likely go away, and if it's a choice of paying someone $300 to figure out the problem, or pay $300 to have the sensor replaced, then I say get it replaced.

[Sigifrith]

There's no need to pay $300 for an O2 sensor. eBay for about 1/2 that price.
Check TomO's links, I think he has the info there.