well, I have read several things on this subject, but I would like to post this, since mileage isn't the only conern....

The car is a 94 LS, w/ 98 LS motor, converted to OBD-1, testpipe, 2.5" piping and ES Oval muffler...otherwise stock... (btw, I just got this car)...the car *had* a turbo on it, but was just taken off for me...the motor is new, ~9k miles at beginning of drive...

I drove home (2300 miles), basically 85-90mph most of the way, it runs obviously...(doesn't *seem* to be in limp mode...but maybe?)

1. problem is that it only gets 17.68 miles/gallon, and that is 99% highway

2. also, at random times during acceleration, or crusing, it kind of sputters (almost like it isn't getting gas...feels the same if you ran out of gas, but less...). Giving it a bit more gas typically takes care of it, or letting off may get rid of it...(side note: seems to do less now, the last 800 miles or so of drive...maybe fuel injectors were cleaned out due to constant driving? or my imagination take this with a grain of salt)

3. last, just noticed that it backfired a couple of times (at around 5-10 mph)...not real loud, but I am pretty sure that is what it was...I use 91 octane, and towards the east coast (and the previous owner) used 93 octane.

Things it might be???
1. fuel injectors?
2. fuel filter?
3. needs tune up?
4. O2 sensor? other sensors?

Notes:
1. I have bought fuel injector cleaner (Chevron type) and will use it...
2. I tried to read the code, but my paper clip didn't work for me (reconmendations?)
3. The check engine light, and maint required lights are on...(could be emission stuff though)

sounds like and O2 sensor to me...

get that code!

Does the ECU have a chip or something increasing fuel dilevery for the turbo?

Why wouldn't the paper clip work? Were you in the right connector? From there it should just flash the codes at you

I have a large safety pin that I have cut both ends off evenly. It works great for getting my codes. Just make sure you have what ever you use for a jump wire going in the right openings, make sure it is in all the way and I always put my pin in with the key all the way off and then once in place i turn the key all the way on with out starting the car. with that you should be able to have the check ingine light flash codes at you. good luck.

thanks everyone...I'll try and get those codes asap.

ok...I have 5 codes!

Codes 3, 8, 15, 16, and 41...

now click on the search button to find out waht they mean....

yeah, I am on c-speedracing and I got the meanings...just a matter of figuring out if they are unplugged or I need new stuff....

ok, just code 3 remains...the MAP sensor....

"MAP Sensor (Manifold Absolute Pressure) defective circuit or unplugged / defective sensor"

where exactly is this? I looked at a bunch of posts, but didn't find anything...thanks for the help.

it is a small black box witha vacuum tube runing to it and a three pin plug...

it should be either on the fire wall or on top of the throttle body (no vacuum tube)

yeah, thanks...I found it right above the TB. Anyway, it was plugged in, and the wires were secure (3 of them)...therefore, I don't know what to think, other than it is bad...

any last resort reconmendations? thanks again.

first up, reset the ECU (check C-speed) and take it for a drive and then check for codes...

sometimes the MAP can throw a code and still be OK...

so take it for a drive and tehn see if the codes have gone...

if it is still there, remove the MAP sensor from the TB nad check if it is cloged...

teh way to properly test a MAP sensor is with a digital voltmeter - do you have one?

t..

i'll try that...I don't have that meter myself, but I'll give my dad a call and see if he does tomorrow. IF not, do you recommend I buy a meter? Autozone type place? MAybe an alternative route? Thanks again!

so you reset the ECU and took it for a test drive??? how did it go?

what codes did it show?

t..

I did that earlier (when it had 5 codes)....after the drive, it just had code 3....that is where I am at still (haven't done anything since)...

so I am going to take off the map sensor and see if it is gumed up...then drive, and check...

OK, cool, that is the way to do it.

then if it is still code 3 - try to find someone with hte same map sensor as yours to swap it over and see if that fixes it,

if it doesnt then you may have a broken wire in the harnes or the ECU plugs are loose or something,

if repalcing the sensor fixes it, tehn you need to by a new MAP sensor...

GL!

t..

backfire is usually caused by wrong timing or it's running lean

it is running rich...so it seems (I need to check the plugs)...but the fuel/exhaust smell is strong...

those screws are a bitch, so I will work on it tomorrow...


Modified by polyphony_digital at 11:47 PM 6/18/2003

cant you cut a slot in them with a hacksaw blade?

make sure it is the MAP not hte TPS sensor you are removing - the TPS is rounded and the MAP is square...

*sometimes* people have reversed the MAP and TPS plugs, try to make sure this has not happened either...

(ie reverse the plugs and see if it runs and what codes you get...)

t..

nah, it is the MAP....

I will try vicegrips first...otherwise a hacksaw might work, thanks...

I'll update you tomorrow.

vice grips work too (but can get messy!)

t..

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ITR632 &raquo;</TD></TR><TR><TD CLASS="quote">backfire is usually caused by wrong timing or it's running lean</TD></TR></TABLE>

is lean always the cause of backfiring? i read somewhere that backfiring during deccelaration means rich. any thoughts?

A back fire is from unburned gas molecules igniting in the exhaust from high temps. You hae to have a rich mixture to do that or a weak ignition system.

ok, took off the MAP sensor...looked ok, looked inside the IM and ok, but I got a q-tip anyway and cleaned it out a bit (just some black in there)...so I *guess* that is all I could have done to clean it?

anyway, started up the same, rough, then rights itself....still some backfire when letting off of the throttle...and the code was still there afterwards....

So am I to assume the MAP sensor is bad? the previous owner said that code was not there when he had the turbo, etc hooked up...does that mean anything to you guys? thanks again