Code P0455, rough idle/loss of power

SKOOZMAT

MEMBER
1999 JEEP WRANGLER
4.0L
6 CYL
4WD
MANUAL
177,000 MILES

Hello, this is a new to me project vehicle that I bought with the expectation of it needing work, but it seems like every day there is something else going wrong! The latest malfunctions is as follows: It was a pretty cold day, around 15-20 oF, so I let it warm up for about 5 minutes. Then I could hear the car’s engine speed dropping and struggle to not stall out, then it would wake itself up and the rpm's would bounce back to a normal range (judging by the sounds of it) so I hopped in and took it around the block. Noticed severe drop in power and super rough idle. Could barely get it back to my house even on level streets. My engine light is on (has been, I thought I fixed it but it came back) I’m getting p0455, with is the same code I was getting before noticing these problems. I feel this may be unrelated to my current issue. Also, not sure if I ran the car long enough for it to trigger any other error codes. Some other probably unrelated issues; the switch for the headlights randomly fails, and sometimes the speedometer and tachometer will drop to 0 while driving, then come back, and the airbag light will also randomly pop on. Only mention these just on the off chance that a professional might see a correlation where my untrained eye had figured they are unrelated. Thanks!

3 Replies

CJ MEDEVAC

MECHANIC
11,004 POSTS

Usually the code you are experiencing is a large leak in the EVAP system has been detected. This might usually be gas cap related.

Hearing your symptoms, I'd be more focused on searching for a big vacuum leak, it could be just about anywhere on your rig.

Start with the ideas in this link:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

Another way to search is with an "un-lit" (No flame!) plumber's type propane bottle handheld torch. Move it up and down "suspect" leaks around hoses/ fittings/ etc. and listen for the engine RPM to improve (as it is now receiving substitute fuel through the leak).

Many times you or your pals might hear the leak hissing.

A trick for doing that with a noisy vehicle is to use a long, but not restrictive pipe on the exhaust to divert the exhaust racket away. The last time I did this we used a 20 foot stick of 4 inch PVC pipe. We slid it over the exhaust pipe 6 inches or so and crammed some shop rags around the pipe to seal it to the PVC.

Maybe you are having multiple issues?

Removing the IAC and cleaning it and it's hole with throttle body cleaner might fix your idle problem. It might also be that it is at the end of the trail. The cleaning is a lot cheaper than replacement, one must always also weigh out how long it has been faithful and will not last forever!

If you are thrifty, coupons and promo codes found on the net can really knock the cost of parts down! (older example with pic 2 it worked well)

I'm about done!

One more article from our site, the opening page:

https://www.2carpros.com/articles/engine-idles-too-high

Let us know what you find!

The Medic

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