ugh just today (as i needed the damn thing) my pos decides to run like CRAP. it's an 88 tbi 454 auto.
at first i thought the injector wires where givin me shit like normal. but fuel is flowing freely. it idles extremely high, over 1 to 1.2k and will idle back and forth from like 1k to 1.5k. it will also pull me at traffic lights when i come to a complete stop, the idle will pull me foward. it dosn't seem to miss or anything. what could cause this? it's not throwing a code or anything. throttle position sensor? map sensor? (im pretty sure this pile has a map sensor), or maybe a vaccume leak??? ideas anyone???? i hear someotherguy is on a roll for information. haha.

bump!!! common people help a brotha out!

sounds like a definate vacuum leak to me. the only other thing it could be is the tps on the fritz. try tapping on the tps while it is running and see if it clears up. spray some wd-40 around the base of the tbi and around vacuum lines. if it hits the leak she will rev up bro. just a couple of things to look for. keep us posted. later, brian

I'd be checking for vacuum leaks, sure. Don't overlook the IAC since it's just a computer-controlled vacuum leak. Could have a big chunk of carbon or crud not letting it seat.

Nothing binding up in your throttle cable?

Richard

pardon my newbness here, but wtf is an IAC? i have no idea what that is! lol. the throttle body it's self has 2 sensors on it, one is the TPS and behind that is some black box thingy that i donno wtf it does, then feeding off the back is the map sensor, and in the front is the egr valve and some kinda vaccume control unit. i unplugged that and replaced the map sensor and it seems to be running ok.

IAC = idle air control motor, it adds or removes air as needed to adjust the idle. It's that sucker sticking out of the side of the TBI that takes a huge wrench to remove it, 4 pin square connector on the end.

The part you're talking about with the EGR is almost surely the EGR solenoid, it should have 1 hose nipple on the front where it gets vacuum from the TBI, then what looks like 2 hose nipples on the back, people do get them mixed up or hook stuff up to them, but only 1 is actually a hose nipple - the one with barbs on it - is the hose to the EGR valve. The other one, with no barbs, should be left open, it's the vent.

Richard

^^^Tee-hee...he said, "nipple".^^^

it was nippular.

anyhow thanks for all the help. at leaste i can start lookin around and throwing sensors at this thing till it runs right i guess?

does it want to down shift when your driving

if your not finding any vacume leaks and your just going to go buy sensors start with the coolant temp sensor its the one under your thermostat it acts like a choke and its one of the cheepest

ur thinking of the blazer! my coolant temp sensor is on the side of the block, and i have a scanner that works on odb1 shit, i'll check tomarrow to make sure it goes into open loop mode. (or closed loop mode, i forget what one is good haha the book tells you) it's not throwing a code fyi

on the side of the block is the switch for the fan that out in front of your radiator and the other one is for your gauge you should have a small sensor that screws in below your thermostat just to the left

humm i'll have to look again.

What pig said, the coolant temperature sensor (CTS) is gonna be on the intake next to the thermostat. That's the one that the computer uses to adjust the fuel mixture. When they start going bad they usually read colder than the coolant actually is, mixture gets richer, if they go really bad they can read as low as -40F and it'll flood your engine so bad it will stall (this actually happened to me on my old '92, drove me nuts trying to figure it out because it would run for a little while then stall and not want to restart.) Unless of course you live somewhere that it gets -40F and in that case I say move the hell outta there..

You can test your CTS with an ohmmeter. What I do is use an IR temp gun, with the truck fully warmed up, and shoot all around the thermostat housing until I get the hottest reading I can get. With the correct thermostat in there (195F) should be close to 195-200F. Then unplug the CTS and put the ohmmeter leads across the two pins on the sensor. Here's the readings, thanks to Chevytech on chevytalk.com:

Coolant sensor approximate resistance specifications:
177 ohms @ 212 deg. F. or 100 deg. C.
241 ohms @ 194 deg. F. or 90 deg. C.
332 ohms @ 176 deg. F. or 80 deg. C.
467 ohms @ 158 deg. F. or 70 deg. C.
667 ohms @ 140 deg. F. or 60 deg. C.
973 ohms @ 122 deg. F. or 50 deg. C.
1188 ohms @ 113 deg. F. or45 deg. C.
1459 ohms @ 104 deg. F. or 40 deg. C.
1802 ohms @ 95 deg. F. or 35 deg. C.
2238 ohms @ 86 deg. F. or 30 deg. C.
2796 ohms @ 77 deg. F. or 25 deg. C.
3520 ohms @ 68 deg. F. or 20 deg. C.
4450 ohms @ 59 deg. F. or 15 deg. C.
5670 ohms @ 50 deg. F. or 10 deg. C.
7280 ohms @ 41 deg. F. or 5 deg. C.
9420 ohms @ 32 deg. F. or 0 deg. C.
12300 ohms @ 23 deg. F. or -5 deg. C.
16180 ohms @ 14 deg. F. or -10 deg. C.
21450 ohms @ 5 deg. F. or -15 deg. C.
28680 ohms @ -4 deg. F. or -20 deg. C.
52700 ohms @ -22 deg. F. or -30 deg. C.
100700 ohms @ -40 deg. F. or - 40 deg. C.

Richard

sweet, very helpfull! but i think i found the answer. the oldschool scanner i have does indeed display the temp it's sending back to the comp. the internal (dash) gauge would read 215 (ish) wile the computer was getting 190 to 195. do you think i need to replace the CTS? wile driving today (with the scanner) plugged in the truck started it's shit again. i went though and noticed that the TPS was reading a voltage of .98 at no throttle when just 15 minutes ago i set it at .40 - .43, so i thought maybe the sensor moved, so i proceeded to get back home and during the drive back home it came back down to .40 it would never do that in the driveway when i idle tested it. or when i tested it with the truck not running but turned on. the little shit only seems to act up when i am moving, therefore making it impossible to figure out, if i didn't have the programmer it would have taken me forever to figure this out!!! glad i didn't have to pay someone for this!!! so i'm guessing it's time to throw a new TPS at this beast.

If it's only happening while moving might be a bad/loose connection somewhere screwing everything up. That kind of stuff can be a real PITA to track down, too.

As far as the discrepancy between what the gauge is reading and what the CTS is telling the computer, I wouldn't replace the CTS just yet, 50/50 it's wrong or the dash temp gauge sender is wrong. That's why I compare with the readings from the IR temp gun.

Richard