K20 VTC/VTEC Issue

[munkaii]

Hi all,

Hoping the CITR community is able to help out here so those technically minded people, have a listen!

I've noticed over the last few days, there seems to be a lack of torque at low RPM, like trying to move the car in 4th gear at 40km/h. The revs will climb, but nowhere near as quickly.
At ~ 5000 rpm, the RPM accelerates to 8000 fairly quickly and it doesn't feel as though the car is out of breath (like you would trying to climb to high RPM without vtec enabled at all), however it isn't as aggressive as I'm used to.

As a note, this is on the road, not on the track and these symptoms are popping up in second gear. First gear is very short so it's hard to distinguish, and third gear would see me over the speed limits here in Melbourne.

Any ideas? I'll have a read later to see whether or not the VTEC Solenoid is hydraulically actuated? I did change oils recently so I will re-check the dipstick, however no warning lights are on. I will probably check with a diagnostic scanner as well just to see if any error codes pop up.

Do people have any idea what it could be?

Cheers
Kevin

[fr4n]

K20 VTC/VTEC Issue

Are you sure its the vtc sustem causing it? Check air filter, fuel filter, spark plugs

I'm no mechanic but anyone of those fouled or dirty can cause power loss.

[munkaii]

It's probably worth checking. The air filter hasn't been replaced for a while, though the power loss is quite noticable. Spark plugs are good. Fuel filter will need to be inspected so I will get onto those this weekend.

It seems very unusual though - the drop off in power has come from nowhere.

[T-BaGGeR]

K20 VTC/VTEC Issue

Check your cat/exhaust. If there is a blockage in the exhaust system, you will lose power

[munkaii]

I will report findings over the weekend as I have a look at it.

Having driven it this morning, the power drop off is in the mid-range. It almost drives like a B-series, however power drops off more just prior to VTEC engaging at higher RPM. To redline, it seems OK.

Over the weekend, I will inspect all components. Having said that, exhaust has been installed on the car for ~ 3 months and without hitch (Powergetter).

[mugsee]

Happy to use my kpro to help you diagnose (datalog) if you need. I won't be back in Melbourne until next Wednesday though.

[munkaii]

Hey Michael,

Thanks for the heads up mate. I have an OBD2 scanner which I may use first to check for codes, but the kpro may really help in giving me a torque curve to look at.

Will keep in touch!

[T-BaGGeR]

K20 VTC/VTEC Issue

Most probably, if your power loss is exhaust related, there won't be a problem with our new cat back but it's probably the cat has collapsed inside so check that part in particular

[munkaii]

I'll start by checking the items which I can access easily first. VTC Solenoid and Fuel Filter. I will take off the CAT and give it a shake to see if there are any deposits within it.

Then perhaps I can get a road-based dyno chart (say in 3rd gear) and from there look if the power loss is occurring at certain RPMs or if it is a consistent power loss across the graph.

[munkaii]

Loose IAT sensor plug was the culprit. My thinking is that because it was disconnected, the ECU's safety measure was to run the motor with more retard to reduce likelihood of knock related incidences.

[fatboyz39]

I would of thought it would throw a cel light..

[T-BaGGeR]

K20 VTC/VTEC Issue

Good job finding the issue. So the car was running in limp mode?

[munkaii]

The car wasn't limping, however the power delivery was not smoothn. The way the car was losing power only around 3500-5000 rpm seems to me as though that because the IAT wasn't plugged in, the ECU would prevent VTC solenoid was actuating, therefore not advancing the timing of the intake cam so it would just drop off in torque. VTEC would then actuate and push the car to redline, however it still felt slightly under powered.

I suppose it is a good note for those people running CAI and SRI, to have the IAT sensor placed somewhere in the intake flow and to not ignore it's purpose.