My car had the engine light on and misfires P0301- p0302 - p0304. Nothing too noticeable only symtpom was it would almost stall after starting from warm. Car was generally ok but I wanted to try the MAP whack technique and reset the light.

I did the MAP Whack tecnique in the tutorial on here posted by XViper and since doing it the car randomly stalls when I put the clutch in and come to a stop (eg at the lights) It seemed to recover after a few miles but now has a much rougher idle and trys to stall when the revs drop.

Just wondering if anyone has heard of this before? and whether this indicates what the problem might be? Could it be that the MAP sensor is a bit dodgy and tapping it has made it worse?

Engine light just comes after 9 miles when ever I reset it.

Many thanks guys

 

Hitting the MAP is not something I would ever advise.

Why it was titled "whack" and not "tap" I will never know.

Whacking the sensor that has such an important function just seems nuts - its quite a delicate instrument.

Is it behaving on the move and in VTEC?

It may well be that you have damaged it, as it has a major input into the fuelling.

Lots of things can cause poor idle though.

Id check for vac leaks in the engine bay, and then an ECU reset, let the idle learn and see what you get after that.

 

Most of the misfire codes can be fixed with new injectors.

 

Thanks for the replies guys.

I did just gently tap it.

The low idle tends to happen when coming to a stop at a junction or the lights. However, it isnt consistent. Today I drove it and it was fine, no problems at all. (light is still on though). Whereas the day before that, she was wanting to stall everytime I stopped. Seems to have good and bad days.

There's nothing noticeable other than this symptom and the light coming on whenever I reset it. When i rev, and vtec everything is perfect.

Any ideas? What would be a logical (cost effective) route with diagnosing this problem. baring in mind it's not under warranty.

Thanks so much guys!

 

Also would i hear anything if there were vacuum leaks? When I have turned her off after a journey I can hear like a breathing noise as she cools down. Like a person gently exhailling intermittently.

Would that be anything?

 

I recently had an identical issue. I cleaned out the Idle Air Control valve and throttle body, and the MAP while I was in that area. Engine runs wonderful now.

 

Cleaning things out can work wonders.

The noise you hear when you switch off would be the fuel pump shutting down. Its like a whine / hum.

You might not hear a vac leak at all, over the engine noise. Just check around and push all the hoses to make sure they are tight.

Also check your throttle cable.

The link in my sig is a useful tool for diagnosing faults too!

 

I'm thinking that the sound that he hears when he shuts the engine off is the vacuum pulling air in through the shut throttle body...sort of inhaling the air until the vacuum becomes balanced with the atmospheric air on the other side of the throttle body.

And good way to hunt for a vacuum leak is to take brake parts cleaner and spray it at different areas. If you spray near a leak, you will cause the engine's idle to change either higher in RPM or sometimes lower, but it will be obvious either way.

 

I recently got an cel for secondary air intake something, anyway, that valve next to the fuel rail cover has a hose that goes to th MAFS and was off. After I fixed it and cleared teh code, no CEL since, however right after the car would die when I came to a stop and had a horrible idle. However, after about 5 minutes and triple checking everything with no CELs, the car eventually corrected itself. What I should've done after I fixed it was lit the car sit on for a bit to let the ECU relearn the new settings.
Anywho, 80 miles later no CEL, no near dying, just the usual bits of rough idle hear and there.
So yeah, check all your hoses, make sure all your connections are tight, check your airfilter, and don't correct the car when it's about to die (have to let the ecu relearn).

 

uhm, if you had those codes. my very first things to check would be, how old are your spark plugs? and then, id say pull the valve cover and do a retainer check. make sure your valve clearances are in spec. then id say, clear the light, and let it idle for a while or till the light returns, then rescan and see which cyl is misfiring. prob have a bad injector. lates