I have to monitor my husband every second he starts working on my 1998 318 Durango w 138,000 miles -especially now that I have read most all the posts in this forum.

Got the vehicle 1 1/2 years ago and was getting 15-16 in town in the mountains - now Im getting 10.

We knew the previous owner was a bonehead, and we did all the maintenance we could think of including all fluids, filters, ball joints, shocks,brakes,tires,etc.

It wasnt until after my hubby put Bosch Platinum plugs in that I noticed a big drop in gas mileage -and a sucking noise.

Well, I discovered he messed with the intake manifold and instead of buying a new gasket, he used blue rtv. Today I saw the plugs and they are blacker than black.

After reading the forums - I gave him a list.
New Autolite plugs 3923S
New Rotor and Cap
New Manifold Gasket
Check vaccum lines for leaks


....and now Im looking at CAI and I think the Volant is the best true CAI but Im wondering this....

If I buy a CAI without a box, it wont fit inside the stock box -will it ?

Ive got a couple of other issues to resolve :
low pitch engine thumping noise all the time - have to check the manifold studs and check for exhaust manifold leaks-

Vaccum problem with heater vents - hubby says he has to take the whole dash out ??? - just to check the hoses ?

Ok - here he comes - Please get back to me ASAP before he screws something else up !

 

hahahahahaha well personally myself get rid of the cold air system, mine dropped my mileage just made an impressive sucking noise if you call that impressive. The rest I don't have an opiniion I only have 46500 km so not needing plugs yet.

 

Welcome to the forums Veronica,

I think most importantly, get rid of the bosch platinmum plugs. The 318 and 360 engine design weren't made for them. If you cannot get ahold of the autolite 3923's, just go with the OEM recommended Champion plugs. Champion makes a plug design for SUV and they have them in irdium type for really good spark and hard to foul up. I am using them myself and problaby won't need a plug change for a very long time.

RTV silicone, it works if installed properly.

Thumping noise, cannot speculate much on that unless you kinda know more specific where it may be coming from.

Vacuum hoses, it may be possible to remove the dash to check some of the hoses. Are you having problems with heating in general or airflow problem when selecting where you want the air to blow at? If you have heat issues, you may need to check the heater core. You can check the two heater hoses going into the firewall, if one is hot, and one is cold, the heater core is clogged and you may want to try a reverse flush on the core to clean it out. Also, a clogged core could be a indication that your cooling system needs a serious looking into. You may want to check your radiator as well to see if it has signs of clogging.

As far as the cold air intake, to get a slightly better MPG improvement for not too much of a cost, get a OEM filter replacement K&N filter. K&N filter lets air passes thru much easier than paper filters and uses existing oem stock box. What you can do is build a ram air tube that I have posted on how to build it for a few bucks in parts from home depot. MPG is the same or slightly better but you will notice a power increase on the hwy. The link to build a ram air tube is located in the common questions and answers faq thread at top of this section.

 

a sudden drop in milage like that and black plugs could be the result of a vacuum leak. the computer is no longer correctly metering the airflow and is addign extra fuel. the CAI may not hurt the milage if you replace the gasket and seal it up right.

 

Greetings to Banner Elk, NC
near one of my favorite rivers.

I did two hundred mile MPG tests with Bosch Super+4 sparkplugs
and found no gain on a 1995 Magnum 5.9V8
Consumer's Reports magazine did careful MPG tests on a Honda with stock and Bosch+4 sparkplugs and also found no gain.

If the heater vents are switching when the accelerator pedal is heavily pressed
that is the well known problem 'Wild Vents'
and the vacuum leak needs to be tracked down and perhaps a little replacement
valve and reservoir needs to be added.
See post #4 here:

https://dodgeforum.com/m_868975/tm.htm

Black & oily sparkplug tips,
especially on cylinders 7 & 8 (the back-most ones)
may be a sign of a bad Plenum gasket blow out,
which can indeed cause
bad MPG and poor engine response.

There is a lot of incorrect info about how air cleaners affect MPG.
CAI's have never been shown to improve MPG in a 'real test'
and recently both Consumer's Reports and Hot Rod magazine
tech guru Marlan Davis have correctly reported that even dirty air filters don't reduce
MPG until the filter is super-clogged.

https://dodgeforum.com/m_1165921/tm.htm

For detail repair info for your Durango
another helpful Dodgefourm member posted
this EBSCO online repair database:

http://search.ebscohost.com/login.as...ile=autorefctr

and told us that it could be accessed by:
ID = greatfalls
Passwd = publiclibrary

For more 'no bull' ways to really improve MPG
there is a very long but informative read here:

https://dodgeforum.com/m_447500/tm.htm

 

I installed a volant CAI with the box and I only lost maybe .5 mpg and did effect my acceleration at free way speeds. It seemed to be much smoother. Getting one with the box is better becuase it does prevent heat from the engine from getting sucked back in. Cooler air = more HP, but less MPG...hotter air = less HP and probably less MPG. It is a little tough to take out the stock box though. You have get under the fender cover to access the bolt head so as to prevent it from spinning around. I learned the hard way because I didn't have a manual with me and took a good 30 - 40 min to know what I was doing wrong. you have to take out the stock box whether you get an aftermarket intake whether it's CAI or just has a heatshield like the K&N filter.

MoparMan99