Misfire after Vtec cranks?

[::90AccordEx::]

I'm getting a big misfire after vtec cranks and its nasty!! Was wondering what it could be? My brother says its the dizzy but I just want other opinions. Thanks in advance!!

[::90AccordEx::]

By the way Merry Christmas to everyone!!! And Happy Holidays however you celebrate them!!

[deevergote]

You need to give us more information if you want any help. We know nothing about your car, your engine, or your modifications.

What do you mean by "after vtec cranks"?
What vtec engine do you have in your car?
What other modifications have you done to the engine?
Have you done anything to alter the vtec crossover point?
Is your ignition timing set correctly?
Is your valve timing set correctly?
Are all of your ignition components in good condition?

[::90AccordEx::]

Yea your right, sorry! I Have an H22 JDM swap, no mods done to engine. My timing is right and my ignition components are all in good condition. It just started doing it the other day. And what Is happening is after vtec engages It breaks up and I get a misfire. Vtec still hits hard but it just wont stay smooth.

[deevergote]

Is your CEL on, or does it come on when you're driving?

[::90AccordEx::]

Well its funny that you asked that because last night I got a chipped p28 and there is no CEL, and my car runs a 100 times better! But that's besides the point, but before, I had a p13 and the CEL was on for O2 sensor and traction control, it just recently started doing it, so im lost

[deevergote]

That chipped P28 shouldn't be used unless it's tuned for YOUR engine. If you don't know how it's tuned, you don't know what it's looking for, or what it's doing. Put the P13 back in until you can 1) get your car running properly, and 2) you find someone to tune that P28 for your setup.


The P13 was giving you an o2 sensor error code (which is what i was looking for when I asked about your CEL.) Chances are, that's where the problem is. The map in the P28 is probably super rich, which is hiding the faulty o2 sensor issue... but not eliminating it. The VTEC crossover is essentially running another cam profile... so that P28 most likely isn't programmed to do it properly, especially with faulty o2 readings.

Replace that o2 sensor with a brand new Denso or NTK/NGK unit (Rockauto.com has Denso for cheap, and there's a discount code in the Beginner Off Topic section for 5% off)
The TCS code that you're getting is meaningless. TCS is not functional on your car, and it has no adverse effects on performance. It is a "soft code", and won't turn the CEL on. It will only appear when you jump the service connector. The CEL that you were experiencing with the P13 was ONLY for the o2 sensor.



Let me guess... with the P13, you were experiencing a major power loss at times... you'd have to floor it for a few seconds just to get the car to move forward. At highway speeds, like 50mph+, the CEL would pop on. Right?

[::90AccordEx::]

That's exactly what was happening with the p13, and the cel always stayed on. At times I would notice that power loss, and it would also start idling like crazy after only a few minutes after driving it. Sometimes on start ups it would slowly bog down and cut off. With the p28 it does run better overall, I'm just having this one issue with the misfire now, but I'll get the Denso O2 sensor and see how that goes. Thanks for your help, I appreciate it!!

[deevergote]

Yeah, that's almost 100% to be an o2 sensor issue. Replace that sensor, make sure your wiring is in good shape, and put that P13 back in.

This is one thing that I actually DO know from experience. I've had the same thing happen... even down to running a richer map (that wasn't made for my engine) to bypass the problem.
The misfire is very likely due to the map being made for a different engine. It often won't matter that much (mine doesn't give me any trouble, aside from about 4mpg less than my custom tune) but since it's unlikely that you know exactly what that map was tuned for, it's the most probable cause.

[cb7resurrector]

could this same problem occur to a non vtec motor? im having a very similar issue. power loss at times. runs extremely rich. except mine has a cel for the map sensor. (code 3 i believe?)

edit - i have replaced the map sensor a few times and hasnt changed anything.

[deevergote]

Yes, VTEC has nothing to do with it, really.

Replace the o2 sensor with Denso or NGK/NTK, reset the ECU, and see if it fixes the problem. If it's still throwing the MAP code, check your wiring to make sure it's not damaged (and therefore giving an incorrect signal.) If everything checks out, try running a new ECU.
Where are you getting your replacement MAP sesors? That's one of the things I would get directly from Honda. Our cars are weird, and some aftermarket replacement sensors just don't work properly (such as a Bosch o2 sensor... they NEVER work properly!)

[cb7resurrector]

honestly the o2 sensors and map sensors i have tried have all been junkyard replacements. im just out of high school and i dont have the 200+ bucks that napa wants for a new map sensor. i know i have wiring issues. i just gotta find the ecu pin out that i had before and trace my map and o2 sensor wires.


also ive noticed (gotten worse since it got damn cold up here in pa) that under 2k rpms it runs like crap. almost sounds like its missfiring. and occasionally backfires threw the intake. i have checked and replaced all my vaccum lines so i know that isnt a problem. is all this shit revolving around the damn map/o2 sensors?

[deevergote]

That could be related to those. It could also be related to the distributor, or other ignition components, as well as your ignition timing, or even your injector function.

Address one thing at a time, wear items first (sensors and ignition components). Eventually you'll fix it!