squirrelybird

if i only get code 12s...(no problem codes) is it possible to have a bad MAP sensor??? or any other sensor (like TPS) for that matter??

i guess what i mean is: if you have a bad sensor, would it set off a problem code for sure???

what can be wrong that wouldnt cause a code???
(symptoms like a vacuum leak.......pulsing/fluttering RPMs, perhaps a rich gassy smell, sometimes seems that it revs more than the throttle i applied)

answer any question, i really would appreciate speedy replies...thanks:hail:

TomP

No, you don't always get a trouble code when something's wrong. 'Fact, sometimes a sensor is busted but won't tell the computer at all. That's why we do visual inspections of the MAF from time to time... the MAF can die but not set a code. Same with the ignition module. Same with the fuel pump, etc etc. 'Fact the GM service manual has a section dedicated to driveability problems, with diagnostic charts, giving every possible system to check if the car acts a certain way (like, no power, or stalling). TPS's can go bad and the computer never finds out, same with coolant temp sensors, air temp sensors, EGR valves, oxygen sensors, etc etc.

squirrelybird

cool thanks tom...:hail: ...how bout the map sensor? i am thinking i need either map sensor or tps, but dont want to just shoot in the dark...they are cheap, but it adds up you know?

Nixon1

Rich gassy smell..running rich? Bad O2 sensor? Anything that deals with intake and exhaust gases, temperatures, etc. can make the car run rich, lean, or generally off..but the O2 sensor is an easy and fairly common thing. I haven't heard very much about MAP sensors going out.. Now, as for fluttering rpms, what's their range? What's your approx. idle speed, and by how much does it fluctuate? Have you checked your timing? Maybe it's fluctuating... As for the rev thing..it's kinda funny that you mention that. Yours revs more than the gas you give it...well mine revs less! I was driving the other day and gave it 3/4 throttle but it only opened at about half throttle if that...I kept inching down the pedal with the car giving me no response until I hit bottom, and the car SNAPPED from 1/2 to WOT and hauled ***...I HATE that! If you ever figure out what the cause of YOUR problem is, let me know! Maybe mine's the same thing, just backwards...lol...

TomP

When's the last time the car had a major tuneup? Did you do the full major tuneup or just plugs and wires?

You can also read your plugs to determine problems... example, a wet plug that smells like gas means either your injector's stuck open or that cylinder isn't firing.

Nixon1, sounds like your spark might not be strong enough to ignite the extra fuel you give the car. How's the inside of the distributor cap, are the terminals gunked up with crap? How are the plug gaps, did they open up? Resistance of the wires? Put the meter on ohms, take a plug wire off, one probe to each end of the plug wire, write the resistance down. Mark the plug wire (or just go according to cylinder #) and repeat for the other 6 wires (6 cylinders and one coil-to-cap wire). Then look at your chart. If one wire is WAY out of spec than the rest, the wire's bad.

confucius101

i'm still a newbee and the "SEARCH" button up there was little to no help

where are you guy's getting these codes from
do i have to go into a GM shop and pay a fee or something

Nixon1

No, there's a port by the fuse box, I think it's called the ALDL, something like that..it's a diagnostics port. You can take a paperclick and use it to connect two of the pins together and it'll kick the comp into diagnostic mode. I forget which two..I was an idiot and bought the $25 code scanner. :P Tom..interesting theory. Havent checked under the cap or the rotor, or the plugs..I've got new wires on and I have all new Bosch Platinum plugs and a Blue Streak cap and rotor just waiting to go in..I gotta buy/borrow an inductive timing light and a pair of extra long needle nose plyers, thats all.

squirrelybird

i already changed the o2 sensor, so that aint it. tom, no i havent got the time to go through your awesome tune up....i did change the cap and rotor, so that aint it, i returned the wires i bought so i could order some 8mm accels, but my wires arent really bad (didnt test resistance, but they dont arc in the dark, and the are not hard or brittle) '

the fluttery rpms i speak of are hard to describe clearly....my idle is not all over the place or anything.......and it doesnt always happen, but when it does, and its not only at idle, the rpms "jump rapidly" over and over almost like the needle is "vibrating" not jumping much...i would say not more than 100 rpms, and yes, i can "feel/hear" it, not just on the gauge.

Nixon1

Still sounds ignition-ish to me....maybe he's firing funny on a cylinder or two, whaddya think Tom?