hi all im new to this forum , i bought a 1997 ram van last year 5.2l with 158k on clock , the first few months it ran fine , one day it missed fired 2 times and has got worse , it seems to be at 45mph at its worst , if you drive carefully you can nearly drive thro the missfire , however i wonder whether any body has , had this problem before ,, i have tried the followimg
new dizzy cap/ rotor arm
removed all plugs, look a nice running brown colour /
had code reader, put on . no codes present
fitted new leads/
checked fuel rail pressure , is 3.2bar all thro rev range
checked wiring , no bare wires
could anybody tell me whether the sensor on intake manifold , is any thing to do with fuel inj, the other sensor near front of intake is i guess water temp , for guage , also what part does the lamba sensor in exhaust play in the running of engine , sorry for so many questions im getting a desperate now , to solve problem , thanks for reading , julian

 

(For those that don't know, 3.2 BAR is 46.4 PSI)

Have you checked for trouble codes yet? It would be easiest if you have access to a code scanner. If not, without starting the engine, turn the key on, off, on, off, on and leave it on. Pace the key turns at a moderate speed. If you did it correctly the digital odometer will start displaying trouble codes (if any exist). Report the results back here.

 

The 45 mph thing kind of remindes me of a torque converter clutch chatter I experienced when I was unknowingly using the incorrect transmission fluid. These transmissions seem to be incapable of handling anything but ATF +3 or ATF +4 for any duration.


How are you determining that the engine is missing?

Can you replicate the conditions with the overdrive off button engaged?


I have never heard on O2 sensor called a lambda sensor, thanks for different perspective. It tells the engine computer how rich or lean or neither the exhaust is. Generally they will set a code, but not always. Bosch 02 sensor replacements are known not to work well in the magnum series engines. Use NTK or denso.

http://www.aa1car.com/library/o2sensor.htm



Whenever one experiences weird electrical issues with these vans, poor grounds/ earths must be eliminated as possible culprits. Check the battery to engine, the battery to firewall, and engine to frame ground cable/strap/wires. Don't just look and declare them good, but remove, wire brush or file them shiny and retighten them.

After this, then you can throw more parts at it if you wish.

There are 2 sensors on the intake manifold. The 2 wire sensor is the coolant temp sensor for the computer. It will directly affect the ignition timing. The connection to this sensor must be removed when one is checking the timing with a timing light, at least on my '89 LA 318.

The one wire temp sensor is for the gauge only.



Do as alloro suggests and do let us know what you find.
Good luck

 

The 96 and 97 van will flash the "Check Engine" lamp for displaying the codes since they have the analog odometers. The 98 - 03 will display the codes on the digital odometer.

All codes on the flashing lamp after doing the key dance will be two digits. Example would be say code 12 which is normal to see: the lamp will flash once with a short pause then two flashes, then a long pause and the next code will start: say code 55 which means "End of messages" you will have 5 flashes, short pause and 5 more flashes. There will be a long pause between each set of codes. If you miss one or mess up just turn off the key and wait a few seconds and repeat the key dance.

 

hi guys , thanks for the replies and advice, today i have checked the earth cables on the back of the engine block , replaced with new braided earth cable and cleaned up etc , i have had snap on code reader attached from a local garage and there are no codes present , i have tried the key dance and nothing ,,, could anybody tell me the resistance of the 2 wire sensor on the intake manifold please , i have a noticed that when i start van and run it up the road from cold it runs fine no miss fire , pulls well and cleanly , but soon as temp gets to normal on temp guage it misses and spits back thro air filter , thanks for help , i hope to get to the bottom of it this week as im missing the days out with local club , cheerrs julian

 

sorry forgot to mention missfire is still ther with over drive button in or out

 

My gut says this is a ignition, timing, spark issue. I don't know where to start on trouble shooting that but that's that road I'd head down. I know there's some different position sensors. Maybe one of those is shot?

 

hi guys ive been spending a few hours on van before work each day , yesterday , i thought the fault had gone i dide a good 10 miles at normal operating temp and there wasnt one missfire , went home picked the wife up for the school run up to 45 mph missfire , back , , however i have noticed i now have a water leak on inlet manifold at rear , any body shed any light as maybe water getting into inlet manifold internally , hence only missfires when hot ,,,
i have ordered intake charge sensor , my resistance reading between 2 terminals when plug removed is 10.49ohm? i think it should be higher when cold so the haynes manual says ,
also ordered another set of leads ,
all earths removed and cleaned and exra earths fitted to engine ,
want to test the 02 sensor , what should i be looking for in readins please
thanks for the help julian

 

Umm, I think you might have wasted your money on this. Your meter might've shown 10.49 but if it's like most meters it's displaying Kilo Ohms. In other words, you multiply the meter display by 1,000. If I'm correct, then you got a reading of 10.49K ohms. The sensor when cold should be between 17.9K and 10.8K, which your's is.

 

Can you see you see the actual place where it's leaking? It's possible the 2-wire coolant temperature sensor is cracked and leaking. The fan would push the coolant towards the back of the engine. A bad 2-wire CTS would also cause misfiring when the engine is hot.

I see that landyacht318 suggested the 2-wire CTS up in post #3, but I don't see anywhere you saying that you checked it out. It's in the intake manifold, right behind the t-stat housing.