My 1999 Dodge Durango 5.2l 4x4, 100k miles last night, is having a bit of a power/mileage problem lately... BUT...

Mileage is down to 10MPG all the time...
Power loss is mainly on wet/rainy days... Happens part throttle and full...

The mileage decrease has been going down hill for about the past two months now... I used to get 15-17 with mostly freeway driving and a bit around town...

Now I am getting a whopping 10 MPG on ALL freeway...

Almost sounds like a cat problem to me as I have been smelling the hot rubber burning smell that I said a few days ago in another thread... The exhaust may be getting hot and burning something rubber around it... I haven't been underneath yet as the weather has been crappy...

Since I drive almost 1500-2000 miles a month, this is starting to take a major toll on my gas funds...

I have tried different gas.

Should I change the o2 sensor? I don't have codes... Other sensors I have tested with a DVM and they all turn out to be okay, such as IAT, coolant temp sensor, etc...

Don't notice any oil in the intake... I do have the death flash that was also mentioned to me a while back, but shouldn't cause a sudden drop in mileage like that...

Any idears?

 

Neo pull your plugs. You may just need a tune up.

 

Had a tune up not even 8k miles ago... New plugs, wires, cap and rotor, all mopar... Brass contacts on cap...

 

How soon after tune up was done, when the problem started? Could have the wrong spark plugs. Also the shop that did the tune up did they move the dist, and if so did they ck the sink timing with a scanner? Sink timing is zero to five BTDC.

 

what kind of plugs did they use, if they used the platinums go change them last week!!!!!! these engines HATE those plugs for some reason, just put in plain old champion copper core like it had stock, they workt he best in these motors

 

I did the work myself... I cannot afford or trust shops to do any work... I used Champion coppers... The exact plug that comes OEM according to Napa... It was quite a while after the tune up, that the problem started... I actually did the tune up because I felt this problem, only not as bad... I guess I can try to index the distributor and go from there... I don't have the scanner to do it, but I hear you can do it with a DVM... I will then check it with the timing light...

I think I will also check for oil consumption and maybe do a Seafoam treatment... I do burn about 1 quart of oil over 4000 miles... Then again, this is my 4th 5.XL motor and they all burned about that much...

Also, coming soon, compression test! I don't have my manual with me, anyone know the "normal" range for compression? Procedure? Just pull fuse for ECU and fuel pump, pull ALL plugs and get to cranking?

 

Oh yeah, and checking timing, you go off the #1 cylinder right?

 

It could be the CAT clogging up. Take your D to a reputable exhaust shop to do a quick test of your CAT. I had a old nissan that one day, just lost all power and gas mileage plummeted. It was a brand new replacment cat when I failed inspection. This new cat caused alot of problems since day one. Took it back to the shop to warranty the replacement CAT and all power and mileage came back to normal.

Burning rubber smell, you may want to check all the wiring under the hood to make sure it is not making contact with hot surfaces such as your plug wires near the exhaust, etc.

 

Yeah timing is off of #1. I would still pull those plugs to see what happened over the last 8K miles. If they are looking nasty pull the o2's and clean them up.

 

1. Crankshaft Sensor? It's under the distributor cap.

2. What is your range of voltage on the TPS at sit with the key on.

3. You can take the truck t a muffler shop and have them do a back pressure check on the CAT. Most shops will do this for free. Anything over about 3 lbs change the CAT.

4. Trany service can do that if the filter is plugged or installed wrong.