"I have a 1998 dodge dakota 4 cylinder 5 speed. The engine is new with 40 miles on it. The head is totally rebuilt new valves, guides, springs etc., new pistons, new cam, lifters, pushrods, rocker arms, new injectors, new crank sensor, new distributor, new cap, new rotor button, new plug wires, new ignition coil, new timing chain, new timing chain tensioner, This engine is new except for the crank and rods... This engine still does not have any more power then it had before it was rebuilt? I'm lucky if I get 15 miles a gallon! It still cuts out or kinda of like a surge or something when you give it gas to get going? The check engine light works but it is not on! Any ideas what the problem could be? Could it be the oxygen sensors or what?

 

Why was it rebuilt?

The 4 cylinder only had ~140 HP if even that much.

 

I moved your post into the Dakota forum.

It does sound like you have a fuel problem if it's cutting out or surging. O2 sensors can get "lazy" and slow to respond. How's the exhaust, any restrictions? How's the cat?

 

Everything checked out fine fuel pressure, exhaust, cat. Converter, sensors everything! Gonna pull the front cover its possible I may have gotten the cam a notch out

 

http://www.allpar.com/mopar/amc-25.html

Did you over size the pistons you should have its worth the extra Hp?

The 2.5 is not a pusher engine its a curser engine even though my 2.5 is faster off the line than most cars the way its geared.

The way its geared its a great freeway flyer at 85 to 95 also... she loves 95 in 5th gear.


http://www.shop.505performance.com/c...?categoryId=40

 

Yes the engine was bored .030 regardless this engine still has a miss to it....a code keeps coming up that says catalyst is bad but I had that checked out there's no restrictions

 

That would mean your cat may be bad or even plugged up/old

It could be an O2 problem also or even MAP sensor

Pull the air temp sensor and clean it... it may need replacing they get covered in oil at times.

Just testing sensors doesn't mean everything is ok sensors get lazy and show up as good all the time I say replace all your sensors at the 120 to 150K mark even if still running good

If your cat is not welded in just clamped in take it off and take it for a drive see what happens you may get a dash warning but if it runs way better its the cat

Don't forget to reset the PCM so it starts blank

Also taking it off gives you a chance to inspect it you may find its plugged up good if you cant see inside give it a few good whacks with a hammer then shake it if you hear things rattling inside its toast

 

The exhaust was tested they don't think it's stopped up because it blows real hard out the exhaust tail pipe.... I had the cat off a few months ago it looked brand new I could see thru every pin hole. The computer is throwing code for a bad cat I just can't see the cat being bad considering how good it flows. I replaced the upstream oxygen sensor but not the down stream I was told the down stream didn't control the engine it was there to tell when the cat was bad

 

Then I would jump on the down stream O2 $35 I think NTK is best I have Bosch and have no problems but everyone says they are bad but so far my Bosch have been ok for me I think the V8 and V6 don't like the Bosch

 

Have you replaced the air temp sensor yet they are cheap $15 to $30 I think or just pull it and clean it inspect it.

KEEP all your old sensors they may come in handy at some time label the old ones so you know what they are