Moody 90 Daytona, 4 cyl, 2.5L, automatic... help?

[Christimin]

Let me start off by saying I am FAR from being a "car chick," and practically poor. With that said, here's the run-down... I'm hoping someone out there has a few suggestions!

My poor little 1990 Dodge Daytona has been nothing but trouble since I got it. If it's not one thing, it's another.
The previous owner blew up the engine (quite literally, so I'm told!) so the whole thing was rebuilt in the summer of 2002. It sat in the lot of the repair shop all winter long until I bought it, and it seemed almost perfectly fine for a month or two.

First thing that's still a problem... the darn thing shakes and rattles like a Bumble Ball while accelerating, it starts around 20mph and continues until about 35mph (all the while staying below 3,000rpm.)

Second thing... My tempermental vehicle dislikes being started several times in one day. I can usually start it once with no problems, but then I have to wait about 2 hours before I can start it again with no problems.
The problems I run into from frequent short-trips are:
At start-up, the engine revs itself up to 2,000rpms while in park, and stays that way for at least 10 minutes, sometimes never coming down.
It revs up by itself while at stop-lights.
It revs up to 2,000rpms when I put it back in Park.

Third thing (MUCH more recent)... car revs up on it's own then drops down (nearly stalling) whenever the mood strikes it to do so. Usually when I'm alone and far from home, just to spite me

Today the "check engine" light came on, for what seems like no reason at all. Sputtering and revving flared up, like hiccupping, after about 5 more minutes the temperature gauge started to rise to the exact middle... I blasted the heat (and rolled down the windows!) and it started to drop, but the symptoms never faded, and that darn little red light refused to go away. I got home, let it sit for an hour or so, then started it up just to see.... seemed to be idling fine, but that evil little light stayed on. This happened once before... I let it sit for 24 hours, and it ran ABSOLUTELY PERFECTLY for a full month (except the whole frequent starting thing, of course!)

Some days are more problematic than others, and sometimes I'll get all of these things in one day, and then the next day it'll be totally perfect!

A few people have told me to check the thermostat, which I plan on doing tomorrow afternoon/early evening. The only theories I've heard about the revving/hiccupping is 1) Bad Gasoline, and 2) Gummy Throttle. I have no idea how to fix a Gummy Throttle... and Bad Gas just needs to be burned off. I've thought about picking up a thing of Dry Gas, and topping of the tank with Premium to see if that makes a difference (was going to do it today actually, then the car got moody!)

No fluids are leaking, all fluid levels are normal...

Any suggestions?

[Christimin]

Quick update (eventhough no one has replied to this yet )

I changed the thermostat yesterday, heat works fine, but the darn thing stalled on me while we were testing it... and that evil little Check Engine light is still on. I'm too scared to drive my evil possessed car.

I'll probably be picking up some dry gas today or tomorrow, we'll see if that makes a difference.

Still, any ideas would be much appreciated!

[wannabespeed]

My only thought would be the computer has gone haywire...My last car had the bad idling up on starting problem. You could run a diagonistic or just replace it.

[pimp_squeak]

PCV valve or BCM (body control unit) check those two out, and see if you can get any engine error codes, ask around and see if any friends ahve a reader to get those off the vehicle. I hope that helps you

[Christimin]

Thanks guys!

I know for a fact I don't know anyone with a reader, so I have a feeling I'm gonna be begging for coins on the street so I can afford to take my car to a shop.

[slantsixness]

you can retract the codes from the SMEC, without a reader.
Look for the diagnostic codes on the web and you'll find what you need.

the basic procedure is turn the ignition on-off-on-off-on and leave on, then count the engine light blinks..

You probably have a bad idle air control valve, or throttle position sensor.

Don't rule out a weak fuel pump or clogged catalytic converter.

Slantsixness

[Christimin]

Originally Posted by slantsixness

you can retract the codes from the SMEC, without a reader.
Look for the diagnostic codes on the web and you'll find what you need.

the basic procedure is turn the ignition on-off-on-off-on and leave on, then count the engine light blinks..

You probably have a bad idle air control valve, or throttle position sensor.

Don't rule out a weak fuel pump or clogged catalytic converter.

Slantsixness

SMEC? Huh?

I tried a Google search for SMEC and got a bunch of Marine sites, and for Diagnostic Codes I got a bunch of Mental Disorders.

[ironman502]

The SMEC is the engine computer. I don't know exactly what the acrostic stands for. If you do what slantsixness said about clycling the ignition 3 times, you will see your check engine light blinking (eg. "blink" pause "blink blink" would be twelve). 55 usually indicates the end of the test. If you post the codes you find on here, one of us can translate them for you. I have a repair manual with all the codes, and I'm sure I'm not the only one.

[Christimin]

Hmm... I decided to give up on it and take it to the shop down the street on Monday morning. They're close enough that I can walk home from there and they'll tell me what's wrong with it.

However, I will try that on-off-on-off-on thing tomorrow when I get home from work tomorrow.

[slantsixness]

SMEC- Single Module Engine Control
or "the Computer" for short. It is not a computer though, a common misconception.

It's the big black box with the wires behind your battery and those fuses "hidden" in the left fender.

Read off your codes, start the car and let idle for 5 minutes. Stop the car; read the codes again. post your blinks and we'll get back to you with a reply as soon as possible.

One note:
some computers on the 2.5L motors come up with a code that means "low overall battery voltage" It's a defect in the way the codes are extracted, not a problem with your battery. Don't let your service shop pull your leg.

check the web for "chrysler or dodge or mopar engine diagnostic codes" "SMEC" won't help you there... sorry I work for the Army, where everything is an acronym!

good luck,

Slantsixness

[Christimin]

I took it to the shop and they replaced the throttle sensor (or something like that... I wasn't listening to him all that well on the technical crap)

Seems all is well now... Thanks bunches guys!