lancercool

So I have an 98 ls with a 98 gsr engine, vtec was connected using conversion harness, where you connect wires directly from the sensors to the ecu.

My car doesn't have a cat, nor a downstream O2 sensor, so I wasn't surprised to see the CEL just after the swap, at this time I didn't have the vtec conversion harness yet.

Then I put the vtec harness in, the car ran well for a few days, like I could bring it up to 8000 rpm and back, then up to 8000 again back and forth, I could hear the engine sound change at 4400 rpm then feel the vtec at 5700. Still no downstream O2 sensor on an OBD2 ecu, but no CEL, I was really happy, thought the car could just run like this.

I forgot how long exactly it was but one day I found out that my car had a check engine light after getting off from a high way. It scared the crap out of me, so I went to a friend who had a scanner, he plugged the scanner into the car but it said "could not communicate", at the same time I found that my CEL was gone, so I drove away.

But on my way home I was going onto the high way, on the ramp I was trying to speed up brought the car to 5000 rpm in third gear, felt the engine shook a little bit and a little powerless, CEL came on, I tried to keep stepping on the gas, at 5700 rpm I could still feel the vtec engagement.

I took the car to my scanner friend while the CEL is on, still cant communicate, then I went to another friend, couldn't communicate. Turned off the engine, turn back on, CEL gone.

Later on I found that my car can only rev to around 7000 when CEL in on, sometimes considerably lower that 7000.

So to sum it up my car has the following problems:
1. CEL when/around when vtec engages
2. Lower rev limit
3. CEL goes away after restart
4. Can't communicate with a scanner

I use a stock OBD2A P72 so that I don't have to use a conversion harness on the ecu end, which is supposed to have an O2 sensor connected to, that I don't. So I thought it might be the O2 sensor that's missing causing the CEL.

A friend of mine took my car and plugged an OBD1 P72 ecu to it, CEL still came on. So I'm guessing it's not the O2 sensor that's causing the problem.

I've been driving the car very carefully since then, I rarely go over 3000 rpm now, today before sitting down and posting this thread I tried to bring the rpm up again and it seems like the rev limit is even lower, tried once and limiter kicked in at ~6200 and the CEL came up earlier ~4400/4500, tried again CEL came up at 5000 when I pressed the clutch.

Sooo... Help guys.

If you see the same post on clubintegra.. it's the same person, thanks.

B serious

iTrader: (1)

VTEC is at 4400RPM or so with a stock P72. The IAB opens at 5700.

O2 sensors are ignored by the ECU when you floor it. They can set a CEL if they become unplugged, though. But they'd have to then plug tthemselves back in. So...likely not your O2 sensor.

Pull the codes. There's no way to answer this without pulling codes. US scanners will only communicate with USDM OBD2 ECU's. You can pull codes with a paperclip via the instructions on pulling a CEL on this forum.

LSracing94

vtec solenoid

lancercool

yes it was exactly the vtec solenoid!

I did the paperclip thing aaannnd I really didn't know it was so easy... if I knew it were this easy I wouldn't even have posted this thread.

the CEL codes I got were 1 and 21, or 22, couldn't remember,

1 is the main (upstream) O2 sensor, I have no idea why is this one on, maybe this light comes on when either one of the O2 sensors are bad? or I just have a bad upstream O2 sensor.

21/22 this is the one related to the Vtec solenoid, I figured that it must be the subharness wiring going wrong since the car ran good for a few days, so I pulled the pins out, one of them appeared to be broken, replaced and and plugged them back in, problem solved.