Misfire/ Revving by itself and fail starting

Revving by itself/ misfires and trouble starting

Hi could anyone please help me I have tried to fix this issue without resolve. My car is a Honda Jazz 2005 GD1 1.3 IDSI Petrol, which I got from a relative. The issues I am having with the car is that on startup the car revvs all the way up to 4k rpms by itself, and then drops to revving 2k rpms by itself. I have replaced the intake gasket and the MAP sensor, with the same fault happening. Check engine light is on. The car is getting quite hot both in the engine and on the inside, seems abnormal.

In addition, when I put the key in ignition to turn it on, the car fails to start. The only way it does start is if I put the key in and gas at same time. I noticed the mechanic put lubricant on one of the intake seals so could there be a reason for this? Also, I noticed that one of the coil packs were cracked. Could this create the symptoms I have listed above?

I have also noticed some other factors: sometimes if I remove the MAP sensor the revving goes back to only 1k RPMs, but it most definitely is not a faulty MAP sensor as its brand new.

I have the following diagnostic codes: P0113, P0108, P0444.

Please if anyone could help it’d be appreciated.

The p0113 means there’s problem with either the O2 sensor or it’s connection to the car’s computer. The p0108 means the MAP isn’t working correctly. If this code occurred after you disconnected the MAP (per your test above), that code is to be expected, probably normal. The p0444 means there’s a problem w/the evap purge control valve.

hmmm …You have multiple symptoms, so pretty good chance you have multiple parts problems.
So where to start? hmmm … if the evap system purge valve is open when it shouldn’t be that could cause the engine to rev, so I’m thinking that’s where your mechanic should start, figure out what’s causing that code and fix it. Ask you shop if it might be possible to temporarily block off the purge line as a test to prove/disprove the theory that the purge valve problem is causing the over-rev’ing at idle. If one of the coils has a visible crack, it may or may not be causing the misfires, but it is going to have to be replaced, so might as well do that as part of the first step. Suggest to defer on the MAP & O2 sensor codes until the first two are diagnosed and properly fixed.

I expect you already know that if the engine is overheating, car should not be driven.

Full dislosure, I’m just a driveway diy’er w/no experience at all on your particular car. Just offering up some ideas.

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oops, good catch by Tester. I must have made a typo, was checking p0133 which is for the O2 sensor. The IAT code may just be the sensor is disconnected from the harness.

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It is code P0113 for ‘Intake Air Temperature Circuit High’.

I’m doubtful the major symptoms you are reporting are related to that sensor problem. IAT sensor problems are pretty uncommon by reports here, presumably b/c there’s no moving parts in that sensor. Likely will be an easy shop fix. The intake air temperature is used by the computer to determine the proper air/fuel mixture, but if the IAT sensor isn’t working the computer probably makes a guess at the ambient temperature. If it is guessing 78 degrees and it is actually 88 degrees, not going to be much of a difference. If it is actually 108 degrees, or 48 degrees, then the IAT sensor problem might show up as a symptom.

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Hi thanks again. I agree with what you have said. Are you able to give me any more possibility as to what the issue could be? Please have a look at the original post.

You say the only way you can get the engine to start is to hold the gas pedal down first, that’s consistent with the purge valve problem. Another common cause for an idle rev speed problem by reports here is a problematic idle air control function. On your car there’s probably an electric motor that does that, and it may be sticking or the throttle valve itself could be sticking inside the throttle body b/c of accumulated carbon deposits. I own an older Corolla, and some years ago had an idle rpm problem when the idle air control gadget failed.

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So you think the purge valve and the IAT sensor could be one of the possible issues?

Yes for the purge valve, no for the IAT sensor.

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I just want to be sure before getting a new purge valve - do any of the other issues I am facing related to the purge? Thanks!

Suggest to re-read my posts above. Suggest to ask your shop to test the purge valve before simply replacing it as the code does not necessarily mean the valve itself has failed.

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Sounds great, I will look into it and update the thread if I resolve it.

If anyone else has any input I’d appreciate it. Thanks