negcamber

Looking for suggestions on where to start in resolving some problems I've been having following a Hondata Gasket install and couple other items (Mugen thermostat & fan switch and oem NGK spark plugs). These mods were done 6 days ago. Here are the symptoms:

On the test drive after the 2nd VTEC the car stumbled and ran extremely rough at idle. Turned for home and idle was fine on the way back. The next time the car was started, the RPMs hunted up and down between 1k-2k at idle. Shut car off, looked under hood for loose vacuum line...all looked OK. Restarted car, idle was fine. The car feels normal when driving out of VTEC...in VTEC the car is not as strong as it was before...by quite a bit if the butt dyno is correct. Gas mileage has dropped dramatically...was getting 31mpg hwy/24 city, now 26hwy/19city (not driving any differently and not noticing any leakage or gas smell). No codes are being thrown at anytime.

Here is what I know was right:
- plugs were properly gapped
- new fuel rail crush washers were used
- manifold bolts were torqued correctly (will re-torque again this weekend)
- O-rings were lubed

One mistake I know I made: When installing the plugs I disconnected the sensor on the far back passenger side of the cam cover opposite the oil cap. I forgot to plug it back in when I started the car. The car only idled and was throwing a solid CEL so I shut down and found/corrected my mistake.

Other mods if relevent: VAFC tuned; header; test pipe, exhaust, cai.

Any thoughts?

l8brakr

On your VAFC go to the monitor mode and check what your MAP is reading while the car is off (aka intake manifold pressure). It should be 0.0 psi. Now start the car and let us know what kind of vacuum it is showing while idling.

Wisconsin S2k

The Hondata IMG cuts off coolant flow to the TB which can cause a longer than normal warmup and an erratic idle. This is common when that type of modification is done, particularly on an engine like this.

xviper

Problem ........................

Answer ..........................
Ding, ding, ding, we have a winner.

negcamber

That is a good thought...unfortunately, prior to the test drive the car had been sitting in the driveway idling for 20 minutes to open the thermostat to make sure the coolant level was OK and to watch for any coolant leaks that might then pop-up. At the test drive the car had long been at 3 bars.

Plus, I'm not sure how that causes the fuel mileage to drop so significantly...especially on a 100 mile drive where the car certainly was up to temp on a 95F day in Florida. Is it possible for it to still be running rich in start-up mode after running that long just from the gasket?

l8braker...I'll go check that and come back.

Thanks for the input all...

Wisconsin S2k

It can cause an erratic idle or rpm fluctuation regardless of how long you have or haven't been idling the car.

xviper

You're missing the whole point. It doesn't matter if you have "52 bars" on the temp gauge. It doesn't matter if your thermostat has opened or not. The Hondata gasket shuts off coolant flow to the throttle body AND to the Idle Air Control circuit. It also insulates the intake manifold from getting hot. That's the whole reason why you put that thing on there.
If the IAC circuit gets no coolant, it will stay "cool" for an inordinate amount of time. It will continue to attempt to set a "cold" idle speed long after your engine no longer needs a cold idle speed. You have two different systems working against each other. The IAC system needs to have HOT coolant running through it's hoses in order for it to stop doing what it was put there to do. That's just one of the things you "put up with" when you have this mod.
If all that gasket did was to keep the heat out for 20 minutes (the time you let it "warm up"), that would be a pretty useless mod, wouldn't it?

negcamber

DOH! Got it... I'm awake now.

OK...so that explains the odd idle.

How about why the car is not feeling as quick in VTEC.

And, would the fuel consumption increase that much too from being in start-up mode? Certainly the intake was hot on a 100mi trip...but the fuel consumption at the end of the trip was 26mpg, which is 5mpg off what I had been averaging on the highway before.

l8brakr...here are the numbers from the MAP:

Off = -6 mm-Hg (not quite 0, but probably close enough)
Idle (810rpm) = -526
2000rpm = -580
4000rpm = -570
5000rpm = -410
6000rpm = -480
7000rpm = -540
8000rpm = -570

Hard accel out of VTEC would see -10 to -15. Hard accel in VTEC would see low -100s.

xviper

[QUOTE=negcamber,May 26 2006, 05:14 PM] How about why the car is not feeling as quick in VTEC.

And, would the fuel consumption increase that much too from being in start-up mode?

negcamber

BTW...something that I noticed while doing this mod is that the air pump valve is attached to the intake manifold. Hot exhaust gases are passing through the head and into a port on the intake manifold that leads to the air pump valve. That does not seem like a good thing for heat soak.