JT89

I've searched the website and couldn't find an answer to my problem. Currently my 1999 integra gsr has a problem with the RPM dropping. It would drive normally for a couple miles and then suddenly the RPM would drop by itself when my foot is still on the peddle. If I leave my foot on the gas it would pick back up by itself in about 3-4 seconds. I could also correct it by letting go and accelerating again but it only corrects it for a couple seconds and drops back down again. It happens for a while and then go back to normal for a couple miles and then happens again. The car only has a megan header and comptech intake. I've replaced the distributor cap and rotor, spark plugs, all the belts, and oil. Car idles fine and doesn't die out when this happens. So if someone can chime in with what they think could be the problem then that would be great.

PatrickGSR94

iTrader: (1)

Does it only look like RPM drops (on the tach) or do you actually hear/feel the engine speed drop? If the former, there's an electrical problem, possibly with the distributor.

If the latter, your clutch is slipping, and sounds like pretty bad. If you're driving a constant speed in gear, the only way for engine speed to change is for the clutch to slip.

2LEM1

iTrader: (1)

IF his clutch was really that bad I would think he would assume the RPMs were going up, not down.

OP - if you're driving at around 4-5k RPMs and you floor it, what happens? It would bury the tach if your clutch was slipping that bad.

JT89

I actually see it on the tach dropping and feel my speed dropping so I don't believe the clutch is slipping.

That's the weird thing if I floor it it would accelerate just fine and hit vtec with no problem, its just when I cruise is the problem... so that might rule out the fuel problems? Also it happens in any gear.

2LEM1

iTrader: (1)

Possible bent valve??? Or sticking valve? I'm not sure honestly. When the RPMs start dropping, and you give it more gas, does it continue to decelerate?

PatrickGSR94

iTrader: (1)

Is the RPM drop on the tach like a sudden drop or does it drop gradually along with speed?

If the tach is reading correctly, there is NO WAY the engine could suddenly drop in RPM without the speed also dropping suddenly, which would feel like your car has hit a wall.

94 ls-r

It must either slowly drop with spped since the trans and motor move as one when in gear or his tach broke.

2LEM1

iTrader: (1)

pretty much this ^

JT89

so it pretty much feels like me taking the foot off the pedal.. the tach slowly drops in rpms like im decelerating. so my car DOES slow down exactly like I'm letting go of the gas. If i let go and press the gas again it goes again but to no avail it will slow down again. yes it does feel like i've hit a wall when this happens.

Also I've tested it just sitting in traffic in neutral, if i hold the rpm's it will drop by itself and pick back up just like if im cruising.

2LEM1

iTrader: (1)

Sounds like it's losing compresion... from what idk. A leakdown test would be my next step.

koss1229

I'm pretty sure its your O2 sensor

2LEM1

iTrader: (1)

Not even close....

The only other possibility besides a loss of compression would be a TPS sensor, but it doesn't really sound like that to me.

turboskratch

I've had this happen to me a few times before, but not constantly.. I was in need of a tune on my chipped computer though, and I'm running a built motor. That problem has stopped happening, but every now and then my engine won't stay on right after startup, and I have to keep on the gas for a bit before it will stay on.. seems like I'm having fuel system issues of some type.

koss1229

I'm sorry, but I had this same problem - RPMs would stay where they should, no fluctuation, nothing. Once you start pushing the throttle gently and it goes to 2500rpm, it would drop down to 500 and catch up. Same while driving - it goes up and down all the time making a huge loss of power and jump forward when catches up. Does not happen at WOT!
Only after I replaced the whole engine that came with new TB/IM/ECU and the problem remained, I found out the o2 sensor was the only thing left.
My car runs perfectly now, so I'm talking from my own experience

2LEM1

iTrader: (1)

An o2 sensor can trim fuel, but not enough to make your car decelerate. Same with any "limp mode" it might possibly throw you into. The car would still accelerate. You would also get a CEL with an o2 malfunction... which the OP never mentioned.

Not trying to start a fight, but what you are describing doesn't sound AT ALL like an o2 sensor problem. TPS maybe, or possible ECU problem, but I fail to see how a sensor to check smog emissions is causing your car to fluctuate engine speeds.

JT89

So the car did throw an cel o2 code but i just replaced that and it still does the samething... no more cel...leads me to believe either a TPS or distributor... and koss1229 which o2 did you replace the one on the cat or on the header?

koss1229

Mine only has one, its an OBD1. I believe, the secondary O2 sensor has nothing to do with fuel management at all.

wunfstgsr

what about the map sensor?..

JT89

Changed that also...

So besides the when the rpm is dying it also idles low around 500 and makes the car shake a bit and then after about 15-20 seconds it will compensate and raise it to 1900 momentarily and idle back down normally to around 800 and when that happens the car will run normally again for a bit.. and go back to the same routine of rpm dying

wunfstgsr

dude i bet you $5 you have a simmple vacume leak! also check the ait sensor.

2LEM1

iTrader: (1)

Vacuum leak cause a car to decelerate when the throttle is open? Unlikely methinks...

JT89

Update: Replaced the TPS and the car runs perfect now. Thanks for all the input you guys gave.