manche Posted September 21, 2008 Author Posted September 21, 2008 i hope now I'm reasonable with the size now we can talk mpg
BLHTAZ Posted September 21, 2008 Posted September 21, 2008 A 235 is a 29" tall tire so it is throwing off your calculation a little, but probalby not much more than 1 or 1.5 MPG.
BLHTAZ Posted September 21, 2008 Posted September 21, 2008 You should be getting better MPG than what you are calculating as the larger tires are registering fewer miles than you are really traveling.
Pete M Posted September 21, 2008 Posted September 21, 2008 My 88 should have been capable of decent mileage (back when it was still just 2wd), but I never got anything over about 12-13mpg. Something to do with my driving style I'm sure. :roll: Terrain can affect mileage too. Did you change your fuel filter yet?
manche Posted September 21, 2008 Author Posted September 21, 2008 thats next on my list btw i hooked a tach up and it says at idle I'm running 1500 rpm is this normal at idle? any suggestions
Pete M Posted September 21, 2008 Posted September 21, 2008 Idle should be around 750 I think. 1500 seems high enough that it should "sound" high without needing a tach. What tach did you use?
BLHTAZ Posted September 21, 2008 Posted September 21, 2008 Idle should be around 750 I think. Yep...mine idles at 700 - 750 according to the stock tach.
Pete M Posted September 21, 2008 Posted September 21, 2008 sunpro 2 tach  Well, if it's tuned to the right number of cylinders, then that might be a problem. High idles could be caused by things like a vacuum leak or a faulty IAC or TPS.
Eagle Posted September 21, 2008 Posted September 21, 2008 sunpro 2 tach There's a switch inside that tach to set it for 4-cyl, 6-cyl or 8-cyl. Did you set the switch in the right place? 1500 RPM is too high for idle speed.
SoloCamo Posted September 21, 2008 Posted September 21, 2008 My 88 should have been capable of decent mileage (back when it was still just 2wd), but I never got anything over about 12-13mpg. Something to do with my driving style I'm sure. :roll: Terrain can affect mileage too. Did you change your fuel filter yet? Â Must be my style too...I can't seem to pass the magical 14mpg mark in mixed city/highway. Â On an all highway trip I managed an awesome 17mpg...Go 4.0L! :brows:
aemsee Posted September 22, 2008 Posted September 22, 2008 If you are truely idling at 1500 due to a vacuum leak, that would also affect your MAP sensor causing an overly rich mixture. My 87 2.5, 4x4, AW4 with 4.56 gears averages around 22 mpg. That includes my wife using it as a lawn and garden hauling device. ( Her way of telling me to fix her wheelbarrow tire :D ). Of course that auto keeps me from hammering on it, cause it just gets louder with no faster acceleration. I also don't drive over 55 with it.
manche Posted September 22, 2008 Author Posted September 22, 2008 could it possibly be the thermostat
Dave88 Posted September 22, 2008 Posted September 22, 2008 i had a high idle problem a while back.. i made my own vaccum leak test too 8) . unhook the intake tube from your filter box, then put your hand over the hose, tr to cover the entire hose. it should suck the $#!& out of your hand but keep going. lower the idle to about where you think it should be and put the hose back in the filter box. if the rpm slowly rises you have a vaccum leak. if that happens just check your hoses make sure there all there etc..if there is a vaccum leak it will be pretty obvious. good luck
project88mj Posted September 22, 2008 Posted September 22, 2008 also check how you wired the tach i had that same one befor i got a new cluster and that same problem happened thought it was wrong looked at the wires and they were wrong. it was toolong ago to rember what wire was in the wrong place but there was a wrong on for sure do a good look over and  check the ground wire  i can't tell you how many problems i have fixed by finding a better ground
500-comanche Posted September 22, 2008 Posted September 22, 2008 Nothing mentioned so far would account for a 6+ mpg loss, except for the brakes. You mentioned that you replaced the 02 sensor. That would have been my 1st guess. Are u sure it wasn't cracked during installation? Possibly, you got the wrong 1? Are there any other factors? How does the engine run overall? Does it have normal power? Check ur O2 sensor again. I'm not sure if ur engine is L-EFI controlled or not (L-EFI is FI with airflow meter that checks the amount of air flowing through the intake manifold). The meter might need to be replaced.
project88mj Posted September 22, 2008 Posted September 22, 2008 also grease your certs on the u-joints and a lighter gear lube might help
manche Posted September 22, 2008 Author Posted September 22, 2008 is the gm iron duke amc style 2.5l tbi
Pete M Posted September 22, 2008 Posted September 22, 2008 The iron duke and the AMC engines are very different, they just happen to have similar displacement numbers. (and even then, only if you round off to liters. In cubic inches they are different).
project88mj Posted September 22, 2008 Posted September 22, 2008 alot like oh i don't know ... black and white up and down left and right in and out amc and gm
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now