crisskro

EDIT: - updated
With the car out of gear, keeping the throttle at a constant RPM, the engine works normal for 3-4 seconds, then starts misfiring slightly and the rpms drop by as much as 2000 rpm. I've seen it drop from 4000 rpm to 800 rpm, then up-down 800>1500>800>1500 > 4000.

It's not the coils, the sparkplugs, stock airbox with new air filter, the IACV, the TPS, the crank position sensor near the alternator, valve adjustment, EVAP/Charcoal canisters, the cams align properly and show no significant wear, I've run redline fuel system cleaner, the vacuum seems ok.

I am missing the little screw that goes in the fuel pulsation damper.

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ye old post
Hello, I could really use some help here. Sorry about the long read btw
I've bought a my00 and I'm trying to fix some problems that were neglected so far. For this one, I am completely stumped.

Symtoms:
As the title says, I am having problems maintain constant RPMs. This is getting annoying as I can feel whenever the car will lose RPMs / gain RPMs when cruising, without me altering the throttle pedal.

What I have done so far:
The car accelerates with no problem up to 9000, has no hesitation during vtec and getting no CEL related to misfires - and that's why I think the MAP sensor is OK.
I've asked a friend to check the TPS with a multimeter, and the voltages were OK, there was nothing wrong with the readings (matching what I've found on the forum)
I've changed the first O2 sensor just today because the fuel consumption was really bad and you could smell it was running rich. I have not made the idle learn just yet, but the car runs fine except the variable rpm at partial throttle.

Mods that can be related:
Invidia test pipe with cel fix - hope I can get the cat back in the future but for now it will do.
Walbro fuel pump


PS: I cannot clean the IAC valve because one bolt was over-torqued and I am afraid it will break. I have not checked the spark plugs but I have a set and will change them in the near future (using the 1-1.1 mm gap).
I do not have much experience with fixing cars but I am mechanically oriented and I'm not afraid to get my hands dirty. Also, I like to search for what others did, and this forum is a freaking gold mine (for me at least)

If you have any advice, please tell me because I a really annoyed by this. Thanks a lot

T-Smac

If you have that volt meter at your disposal still, test the MAP sensor.

Here's what to do:
Back probe the connector going into the map sensor. (slide t-pins or sewing pins into the back of the connector, where the wires enter)
Make sure the pins don't touch each other.
Check voltage between the left wire on the connector (if you are standing at the front of the car), should be a yellow wire with a red stripe, and the negative battery post. Voltage should be around 5.0 volts.

With the car on and warmed up, at idle (800-1k) check voltage drop between the middle wire (green with white stripe?) and the right wire (green with red stripe?). Voltage should be around .8-1.0 volts


Also, try getting a vacuum gauge hooked up. should be 17-21 in Hg at idle.

crisskro

I will test the voltage this weekend (my electrician/friend is hard to get a hold of). From what I've read, the MAP is used only when you punch it, for idle/partial throttle/constant speed - the O2 sensor is used - and that's where I am having the problem. I doubt it's the culprit, but I will test it nonetheless.

For the vacuum part, I'll have to make some calls, but I will test it. Do you think it may be a vacuum leak or this thingy?
http://image.hondatuningmagazine.com...noid_Valve.jpg
I will check the vacuum hoses and I will search for a way to test the air control solenoid valve(?) as well.

Thanks for the ideas : )

T-Smac

MAP sensor is used at all loads

crisskro

"Check voltage between the left wire on the connector (if you are standing at the front of the car), should be a yellow wire with a red stripe, and the negative battery post. Voltage should be around 5.0 volts."
Done. It was 4.99 something.

"With the car on and warmed up, at idle (800-1k) check voltage drop between the middle wire (green with white stripe?) and the right wire (green with red stripe?). Voltage should be around .8-1.0 volts"
Done. It was 0.92 something.

Did not have access to a vacuum gauge.
In the meantime, while I try and get my hands on one, is there anything else that could be the culprit? Apart from the vacuum.

barrett4bama

I wonder if the fuel filter woould be the culprit. Although, I think on this engine, its in the tank.

crisskro

I was just thinking that today, but I know the filter was changed along with the Walbro fuel pump so it should be relatively clean.
However, I've tried to keep the throttle position at 4000 rpms and after 3-4 seconds, it dropped to 800 rpms and sounded like it was about to stall.


Later edit: http://www.us3s.org/freeforum/archiv...hp/t-6313.html I will get the car to a shop and try to take the IAC off to clean it. Fingers crossed they don't break the screw. But better them than me.

crisskro

Cleaned the IAC, throttle body and changed spark plugs. Did the MAP whack. The shop had no way of testing the vacuum.
Still no luck.

I'll try borrowing a MAP sensor tomorrow.

Dirty IAC and old plugs:
http://imgur.com/3i2Sq
http://imgur.com/STpWu

Billman250

Sounds like a massive vac leak or fuel starvation.

Be sure the o-ring under the map is in good condition (no cracks, not dried out, and not over-compressed. It must stick up a little so when the MAP is bolted down it is in a compressed state.

After that I would try a MAP of another s2k.

crisskro

Hello, thanks for your help.
The MAP o-ring is ok, I've checked it a month ago and I've added a very small touch of oil on it so it isn't dry. Checked it today, didn't see any cracks, it seems to be ok.

I wonder if the walbro fuel pump is doing its job as it's supposed - or it's indeed fuel starvation.
I'll post once I've tried another MAP.