No power at start-up! Any ideas?

[jknappster]

I never thought I'd be making a post like this. I pretty good at fiquring things out but at start-up on my 04, there is absolutly no power until warm. It has happened twice now and only when the engine is cold. It will idle normal but under load will rev slowly and will rabbit surge sometimes, not all. Mostly just loss of power like half the plug wires are missing. No mods on the car with approx 25,000 miles and battery is one year old. Thanks all and happy fourth.

 

[Black Moon]

Fuel filter maybe? Got to start somewhere. Will it rev normally with no load?

 

[jknappster]

No it will not rev normally. Just idle normally.

 

[Martin]

Kind of weird for sure. Did you check the O2 sensors? Any codes stored?

With something like this, the first thing I'd usually do to troubleshoot is try to isolate whether the problem is related to the closed loop logic of the PCM. Unfortunately, I woudn't advise doing that when the engine is cold... What you'd have to do is do a WOT run to see if power comes on when the engine controller goes into open loop. In open loop, the engine pretty much disregards most of the signals coming from the sensors and just maps fuel and timing according to RPMs. If it seems to run OK in open loop, you can figure on it probably being your O2 sensors.

There are all kinds of sensors that could be starting to go bad that might cause this - sometimes they'll only misbehave when they're cold and then they behave when they warm up. A code reader should point you in the right direction.

 

[jknappster]

Thanks Martin. I was leaning on the O2 sensors also but wouldn't the PCM disregard these as well until running temp?

 

[ViperGTS]

PLUGGED CATS.

Get some HF cats.

 

[Martin]

Thanks Martin. I was leaning on the O2 sensors also but wouldn't the PCM disregard these as well until running temp?

That's a good question, and I don't know for sure. On some older cars that's the case, but I believe somewhere around eight to ten years ago car manufacturers had to start keeping the O2 sensors in the loop during warm up. Some car makers went with a heated O2 sensor, and some started using sensors that were effective really quick (and were more prone to crapping out early).

ViperGTS is correct that you could have a cat issue going on - but that is probably also related to the O2 sensors going bad. Once the sensor goes, if you don't fix it quick, the cat is going to be toast pretty soon thereafter. The good news is that it's a good excuse to replace all of it. You'll have to have the side sills off anyhow, so why not just do new sensors, hi-flows, and perhaps a Corsa track exhaust while you're at it You'll like the car a whole lot more - much cooler feeling and sounding. If the Corsa track exhaust is too loud, you could go with a Gen IV take-off exhaust - probably the same performance gains, sounds a lot better than the Gen III, and they're cheap.

 

[jknappster]

I like it! Never let a good crisis go to waste, right! I should let Dodge look at it since it's still under warranty. Wouldn't I get a check engine light for a O2 / cat issue?

 

[Martin]

You might not get a check engine light, but you should have some saved codes. You didn't mention it was under warranty - in that case, the best bet is to have them troubleshoot and fix things They'll be able to tell you right away what's up, and if it is the cats and sensors, they'll install a new assembly. If you still want to do a high-flow exhaust, it'll be a piece of cake after the new stuff is installed - the hardest part of installing a high-flow exhaust on a car with 25k miles on it is that sometimes things are really hard to remove. After they go through it, everything will be fresh and clean.

 

[Guy]

Sorry to revive this thread.. but just was wondering what it was in the end?

I have a weird problem where my '05 idles fine and drives fine up to about 2500-3000rpm and then starts to sound more "high pitched" than usual, almost like I lost a few cylinders, and has a significant drop in power when I step on it.

No smoke, backfiring, misfiring whatsoever. Aside from the noise and the loss in power, it all seems normal; very strange. I have a 100% stock engine and exhaust setup.

Any help appreciated. I will try to check for codes with my Craftsman scanner, hopefully it'll show something.

A couple of fouled plugs would have black smoke coming out the exhaust, right?

 

[tomob1]

glad to see this post!
been having a cold front last 3 days.
my 2004 has a significant power loss first thing in the morning.
the highway is 1/2 mile from the house on a dirt road. 20 mph max to the highway.
when accelerating onto the highway, power in 1st gear is tapped at 3000-3500 rpm. 2 gear goes to 4000 rpm and then bogs.
i'm in town after 3 miles, and cant do more than 30 mph. but 1st gear is still weak.
4 hours later, i go to lunch. ambient temp is up 15-20 degrees, and the car runs fine, full power.
i thought the viper would run better in colder temps.
has me worried, should i put the 160 degree stat in for the summer?
thanks
tom