its done this since i got the truck back in july and doesnt really seem to have any destructive symptoms as it seems to run smooth and has never thrown an engine code just evap codes. the reason im conserned about it now is obviously gas prices since 12 mpg and 3.59 per gallon is runnin pretty costly. it doesnt even seem to get better mpg on the highway just stays at about 12-13 mpg and was wondering if fixing this could help. i put a new exhaust system on but still does it and it still seems underpowered. i was having trans problems and took it a mechanic buddy of mine and we took it for a test drive. he told me it feels underpowered he actually thought at first it wasnt goin into first but it is. no trans codes ever apeared and he checked the cable and linkage which were all okay. since then ive replaced the tps and it does **** a little better but still does it but now i can use my cruise without it unlocking the converter. anyone know what could be causing this.

 

If you can smell gas in the engine compartment

Haynes manual says: Your evap system needs checked. Check hoses & canister.

Jeff

 

I wish it was 3.59 Im payin 3.99 for mid grade. double check your hoses in the evap stuff

 

ive had problems with that stuff before and i tested it all came down i had a split hose on the canisters below the bed and a bad gas cap(the hose trew the code and autozone gave me the wrong cap so when i fixed the hose i still had a leak at the cap until i figured that out to) but in a nutshell ive checked em before and i dont smell it in the compartment but more outside my truck or if i start my truck with my door open.

but 3.99 sucks we need to do somethin about this i think ima run for president haha jk

 

+1 on checking the evap system. Get yourself a repair manual and use it as a guide to troubleshooting for that smell. Also, have you checked your fuel rail and injectors for leaks? I recently did some work on my truck and after putting everything back together, I discovered a fuel leak from an injector. I'm not saying that it's for sure your injector that's leaking. I'm just pointing out that there's a possibility thus could be inspected. Before I ever did anything to my injectors there was no serious leak, however, I always did notice a small ring of moisture around the base of some of them implying that a small leak had existed. If your truck is anything like mine, maybe that is where the problem exists.

About your mileage; Have you replaced your O2 sensors? If the truck has lots of miles you may have some O2 sensors that have been fouled. That could be a reason for bad mileage.

For the lack of power, if your plenum is leaking your going to have a large vaccum issue right there which will foul things up. Under the intake manifold is a valley where the cam and lifters sit. That area has lots of oil circulating through it and with a leaking plenum gasket, oil can be sucked out of that valley and into the intake manifold. When that happens you can expect heavy amounts of carbon deposits to develop, moderate to major amounts of oil being burned, fouled plugs, and quite possibly over time your O2 sensors and catalytic converter going out. This is something that your should definately check out. Pull off your air cleaner assembly, open up the throttle valves in your throttle body and stick a flashlight into the throttle body. If you see a pool of oil inside the intake manifold, bingo. You've got a bad plenum. $20 at autozone will get the gaskets to fix this, however there will be a few hours of labor involved just to patch things up.

On the bright side of this, if your up for the challenge, this would be a good time to do a few things to tune that sucker up. Clean that throttle body, index your plugs for a few extra horsepower, check your cap and rotor and replace if necessary, upgrade to some lower resistance spark plug cables, check your air filter and replace if necessary, change your oil in the differential to a high quality synthetic, and build a homebrew cold air intake if you like.

Knock all that stuff out and your sure to get good gains in both power and efficiency.

 

wouldnt o2 sensors throw a code if they arent working right?
i looked in my tb earlier and i didnt see oil but i do lose about half a quart every 3k miles but the plugs look good i replaced the wires today and soon the coil

thanks for the info

 

my plenum was bad, my spark plugs were good, and I lost about 2 quarts of oil every 3000 miles before I fixed the plenum.

Spark plugs showed no signs of oil because they were the correct heat range thus they burned anything that settled upon them.

The O2 sensors don't have to throw a code if they are getting fouled. They will just struggle to give your PCM a accurate signal due to the buildup of deposits upon them. If they stop working all together, which is very rare, then you'll get a code for sure. Otherwise, they'll just give inaccurate readings to the PCM causing performance and mileage to suffer.

If you didn't see any oil in the intake manifold it is possible you just missed it. Try taking a small piece of cloth taped to the end of a thick metal wire, from a coat hanger or something similar, and use that as a swab to check the plenum area for oil. Sometimes the oil isn't very visible unless you remove the entire throttle body, so if you don't want to remove the entire throttle body to check, just use the swab test. Check in the low spots towards the firewall first. That's where the oil generally will pool up. Although many people have reported that their plenum gaskets gave up and got ripped apart all over the place allowing for oil to enter and fill the plenum from pretty much any which way so just be sure to check around.

Edit; Oh yeah, don't forget to check the distributor cap and rotor. I replaced mine less then 15,000 miles ago and it's already looking pretty bad. Be sure not to overlook those if you've already gotten new plug cables.

By the way, have you found the source of that smell yet>?

 

yea its comin from the exhaust but mainly when it starts and until it warms up
i got my cat looked at and they said it was good

ima look at my cap tonight i think if i have time if else tomorrow and come to think of it i looked through the tb on my driveway which is at a steep angle and the manifold looked pretty dirty in there. is there any way to clean the o2 sensors or do you just replace em i havent priced em yet but theyre expensive right?

how did you fix ur plenum did you just replace the gasket or buy a new belly pan?