Many issues: Input/advice : discussion?

[Myco]

I have several issues I'm experiencing with my Mark. It is a 97 Mark VIII LSC. The ECU has been flashed to the 98 ECU. The car has 180k on the body and 100k on the engine.

Couple of things: First: Gas Milage.

Right now in the city I get 13.5mpg. On the highway I get 27-28mpg. i drive mostly in the city and the city mpg worries me. On my first mark in the city I got 18mpg generally if I wasn't romping on the pedal all the time. On my present mark I have new tires, have cleaned the maf, replaced the IAC, put in fuel injector cleaner, changed the spark plugs, used that stuff that throws white smoke out your exhaust (i forgot the name).

I can't think of anything else to do other than pull the engine apart which is NOT what I am going to do.

Second thing: transmission leakage.

I replaced the fluid in my transmission. After dropping the pan/replacing the filter I put the new gasket on there that came with the filter. I did not overtorque the screws and then filled the tranny up with what I was told would be 6 quarts. After I did this the transmission started leaking. After about .. ohh I'd quess.. half a quart leaked out it stopped leaking. I check the fluid level both hot or cold and the dipstick shows full. I'd be ok with this but I'm worried that there is not enouph fluid in the pan because on turns (usually longer than normal) I get no power out of the car. I am aware of the turning problem with our transmissions though. Just a thought.

third thing: rough idle.

The car runs at idle roughly but when I put it in drive it runs smooth. Like I've said. I've replaced the IAC and the spark plugs so I'm not sure

 

[wood_e]

Fuel mileage - Replace your upstream (before cat converter) Oxygen sensors and your engine coolant temp sensor (2 wire).

Transmission - If the dipstick says full then you're probably good. I would drop the pan to make sure the filter is still attached.

Rough idle - Check your vacuum lines and replace any that are cracked or broken.

 

[Lux]

i get around 13-14 mpg on my 97 as well, alot of short trips with the heat blasting, romping on it, in cold weather.

all of my maintence i did as soon as i bought the car so thats up to par, new plugs, fuel filter, k & n, pcv, coil boot springs, (boots were like new), etc

It is what is is man.

 

[Lux]

ive thought about changing my o2's as well to see if that would make a difference. good advice.

 

[98CobraStarLSC]

mine gets crappy fuel milage and idles high as well as, it throws the IAC code !!! Almost the same problems as yours. i replaced my iac, and the code keeps coming back, ive been told i probably have a vacuum leak, but i cant seem to find it.

Ill let you know what i find.

 

[Roadboss]

Trans Leakadge: is probably the "O" ring at the dip stick tube is dried out and cracked so that when you filled the tranny again it leaked out to where it is slightly below the "O" ring. Easy fix, you just need a long set of extensions to reach the bolt on the back of the head that holds the tube in place. Once you remove it you can pull the tube out of the tranny and replace the "O"ring and reassemble.

IDLE & MILAGE: can be your O2 sensors as well as some vacum leaks.

 

[Rich88LSC]

I have to agree with the O2s/vacuum leaks being the most likely to cause your mileage issue. I geta little better mileage around town then you with 4.10 and 3500 stall converter.

 

[Myco]

ok..the vacume leak theory sounds like the first hurdle. to the poster above. i had the problem you have and the hoses sitting on top of the engine were causing the vacume leak. replacing those right angle tobes fixed the problem. 5$ brake line hoses from autozone.

as far as my problem is concerned. where else do vacume leaks occur? im assuming its so/ewhere that would effect my idle.

 

[XLRVIII]

yea those two hoses were pretty bad.

It'd be a safe bet that you should go over all the vacuum lines with a fine tooth comb.

there are alot of connections, pcv to intake..intake to brake booster..THE brake booster itself...(which is almost impossible to test)

 

[XLRVIII]

Trans Leakadge: is probably the "O" ring at the dip stick tube is dried out and cracked so that when you filled the tranny again it leaked out to where it is slightly below the "O" ring. .

That leaked on my 95 and tiffs 93 and it wasn't too bad to replace.

by the time the level gets low enough to stop leaking you are about a quart low on fluid.

when you turn the engine off the fluid level rises in the pan, well above that oring.

 

[k9t8m]

Replacing the stock trans pan gasket with the junk cork gasket was not a good idea. The stock gasket is designed to be reused. If it were damaged i would have replaced with oem.

Other than that i agree with everything else these guys are tellin ya....

 

[Myco]

That leaked on my 95 and tiffs 93 and it wasn't too bad to replace.

by the time the level gets low enough to stop leaking you are about a quart low on fluid.

when you turn the engine off the fluid level rises in the pan, well above that oring.

the situation is right now that whether it's hot or cold the fluid shows full. dunno what to make of it.

 

[Myco]

Replacing the stock trans pan gasket with the junk cork gasket was not a good idea. The stock gasket is designed to be reused. If it were damaged i would have replaced with oem.

Other than that i agree with everything else these guys are tellin ya....

I know. The stock gasket has a slight fold in it. In a black and white world it is 'damaged'.

 

[mafioso]

seeking vaccum leaks is easy with throttle body cleaner or carb cleaner, with the car at idle spray the hoses and listen to the engine any variation in RPM and you found a vaccum leak.