I have a 1997 Dodge Ram Van with 90,000 on it. It has a 3.9 V6 motor. I have replaced cap, plugs, rotor, wires, air filter. The van has a very intermittent miss. When it is cold, it has a very intermittent miss. Somedays it misses 10 times, sometimes once, sometimes not at all. It does not miss after it has been driven 15 or 20 miles, and seems to miss less when there is more gas in the tank. It has not kicked the check engine light. Any suggestions as to what might cause this?
Thank you,
Connie
Dream Weaver
08-09-2005, 07:17 PM
BTW, when you first start it in the morning, you can smell gas, and the indication is that it is running rich because inside the tail pipe is black.
Thanks,
Connie
Dodgevanman
08-09-2005, 08:36 PM
It sound like a possible injector problem causing the miss. And a rich condition may be caused by the O2 sensor(s).
Dream Weaver
08-09-2005, 08:40 PM
Thanks for the information.
We have a throttle body injector, not single fuel injectors.
Dodgevanman
08-09-2005, 08:58 PM
You did say a '97 right? That means you should have Multi-Port Fuel Injection (MPFI). You have six injectors, one for each cylinder. The thottle body does nothing more than regulate the air flow into the engine...not like the old Thottle Body Injection (TBI) design that used two injectors mounted on the throttle body that shot fuel down into the engine similar to a carburetor. If one of your six injectors isn't pulsing correctly it can cause a miss in the engine.
Do you smell gas all the time or just at start-up?
Dream Weaver
08-09-2005, 09:05 PM
Just at startup.
How can you tell which is bad? Is there a way to test them? Is this a do-it-yourself repair, or something I should take somewhere? Is this an expensive repair?
Thanks!
Dodgevanman
08-09-2005, 09:33 PM
Yes there is a way...using what is called a "Mechanic's Stethlescope" You can listen to each injector pulsing. A weak or clogged injector will have a different sound than the clean ones.
There is also a tool called a "Noid (yes Noid) Light" It plugs into the injector connector and will pulse in conjuction with the PCM's signal to the injector. If there isn't a pulse at the Noid Light, then there is a wire problem or a PCM problem.
Also, sometimes injectors can be cleaned. If not they must be replace, which can be expensive because fuel injectors aren't cheap.
Dream Weaver
08-09-2005, 09:40 PM
Thank you so much. You have been helpful. Can you clean these yourself or do you have to have them cleaned?
Sorry to be so ignorant. Do you work on these a lot? Have you seen this happen before?
Thank you,
Connie
Dodgevanman
08-10-2005, 06:49 AM
I used to be a auto tech./mechanic/grease monkey about 4 years ago. I had to get out and do something else. But to answer your questions, I wouldn't try cleaning them yourself. There's a product I used at the shop that would hook into the vehicle's fuel system and run the engine off of a chemical that cleaned the injectors and the entire fuel system....it worked extremely well. I just can't remember the name of the chemical. Gosh.
Actually I've seen a few instances where clogged or dirty injectors were a problem, but this service generally did the trick. Unless the injector itself had a mechanical problem and had to be replaced.
