KivikinPieces

Hey y'all.

I've got a 1998 Civic EX with a D16Y7 engine. Earlier tonight while going out for a little drive with the vehicle behaving fine.
After about five miles I came to a stop at a four way intersection where I proceeded to turn left and was instantly met with an engine that bogged down incredibly hard, almost to the point of stalling. It was then that I made an immediate reversal and started the short journey back home. The vehicle behaved the same way until I got back home, where I found a few more symptoms.

The vehicle will not idle normally anymore. Whereas before it used to idle normally at 800rpm, it now rests and fluctuates between 1,100 and 1,500. Up and down, up and down.
When giving it a light or medium amount of throttle, the engine will bog down very badly. I say very badly, but it still never died on me, it just refused to move and felt like it was a hair away from dying. Granted, when it bogged down like that I either let off the gas, letting it return to the oddly high idle, or gave it some more gas. Which leads me to my next point.
When giving it above a medium amount of throttle, the engine is responsive and immediately delivers power.
When at speed, say around 40-50mph, giving it a low to medium amount of throttle doesn't make the engine bog down, but I'm not getting any additional power and gain no speed, so it's as if I'm not doing anything with the pedal at all.
When at speed, the only way to maintain speed is to keep the gas at slightly above medium throttle, where the engine is responsive.
The transmission made some weird downshifts which resulted in some strange slight jerks, but I'm assuming that it's only doing so because of the idle being forced at the slightly higher 1,500, therefore I don't think it's a problem with the tranny.

I'd greatly appreciate whatever input you guys have at all, so that I'll have at least somewhere to start tomorrow when I get to wrenching on it.

Thanks!

KivikinPieces

The two engine codes that the OBDII gives me are P0108 and P1259.

I suspect the first one is because I removed a vacuum tube near the fuel injectors and started the engine to check for a vacuum leak, so the code might not have been there prior to that.

The second code is for a non-functioning VTEC, which makes sense because this engine has no VTEC, haha.

ezone

P0108 is a MAP sensor code. Can't tell if it is a cause or result of idle surge. Erase code and see if it returns. Make sure it's plugged in.

Idle surge: idle too high: vacuum leaks, low coolant, sticking IAC valve, inaccurate ECT, etc.


P1259 VTEC, but not equipped?......engine has been swapped? Did it EVER run right above 4000 RPM or wherever its ceiling is now?
Did you buy this car like yesterday?

KivikinPieces

I've had the car for around almost two years now, I erased both codes and they keep coming back.
It's always ran fine and true until last night, throttle was always responsive and the engine ran great. One thing that did puzzle me is that the rev-limiter kicks in at around 5,000RPM and not the 6,800-7,200 value that most websites give for the D16Y7, but I've never goosed the throttle to 5,000 anyway. I drive it very softly and get around 42mpg.

I'll check the sensors in the morning.

KivikinPieces

Small update.

I decided to finally start working on the vehicle two days ago and, due to my laziness with taking off the air intake and disassembling the IACV to see if that was the issue, I decided to first test the MAP sensor and see if the voltages varied with how much throttle was applied. I also lazily tested for a vacuum leak by blocking the air intake from the filter side and the car immediately died, so no leaks.

I stuck the meter test leads into the correct wires and got a very strange voltage that never varied no matter how much gas was given, so there it was.

Bought an 8 dollar replacement sensor off ebay, new gasket, screwed it all in and plugged it back up and now she runs like a top again. I cleared the DTC codes and the P0108 one never came back.