need to pick some brains... 99 blazer...i can't figure it out

[oleshifty]

Friends sister has a 99 blazer with 4.3. No check engine light. i hooked up my laptop, all sensors are sending signals (didnt know values one everything, but seems like they were changing atleast somewhat)

Truck has fairly recent plugs/wires/dist cap/rotor/ maf


At idle seems to have a little bit of a shake to it, normally i'd say misfire.

Revving in park, it seems fine

Flooring it, it slowly accelerates til about 3k rpm, sits there for a while, shifts, stumbles, etc

Tops out at about 55. Manually shifting, it'll hit about 3k rpm and just sit there until shifting.

Buddy thought it was EGR, unplugged it, car got a little better. Not much, but revs up smoother, and will go about 70

I unplugged the TPS and nothing seemed to change, i would GUESS it's bad. But wouldn't that throw a code? She just bought a MAF cuz someone told her that was the problem, don't want to just throw parts at it. I'm not sure why unplugging the egr made it slightly better. If egr was bad, that should have fixed it completely correct? If it egr was good, unplugging shouldn't have changed anything.

[Ray@NP]

a bad egr could act like a big vacuum leak, also sounds like you might have restricted catalytic converters

[lil green]

a bad egr could act like a big vacuum leak, also sounds like you might have restricted catalytic converters

^^^+1 My truck did the same exact thing, so i unbolted the exhaust (after manifolds) and then unbolted the flange between the muffler and cat, then shined my mag light in there and could see the block.... unfotunatley it was about 300 for a new y with a cat. So i did the best thing i could think of. i stuck a 1.5" steel pipe in the cat and bashed the hell out of it with a sledge. (i pulled it out to let the chunks move around) then repeated till it was empty. bolted it all back up and runs like a top now. a few weeks later my buddy's truck had the same problem on his 350, but he had the room to put a new cat in on his pipe. didn't mean to thread jack

[oleshifty]

I sprayed carb cleaner around it...nothing changed. Pulled vacuum line, noticed change. I don't think there is a vacuum problem. It idles fairly decent. Slight shake, but could be bad motor mount for all I know, not noticeable unless you're really looking for it.


Never had a vehicle with restricted cats, not sure how that feels, but this definitely feels like the computer is saying 'nope, not accelerating, not going faster' more then a mechanical problem.

[tanz45]

x3, sounds like a sick kitten. Could also just pull out the front 02's to see if it revs out quicker.

[beingblueeyes]

x3, sounds like a sick kitten. Could also just pull out the front 02's to see if it revs out quicker.

+1
you could also just hook up a vac gauge, start it and hold it @ a certain rpm (lets say 2k) constant and see if over time (1 min) the vac starts to decrease. That would mean plugged cat. Just a stupid question, when replacing cap/rotor or doing any of the other work the dizzy wasn’t taken out was it?

[oleshifty]

I'm gonna try the tps and see if it helps...if not i'll unbolt the cat and see how she does.



Thanks!

[oleshifty]

I owe everyone in here a beer. TPS was bad, truck got a lot better, cut off cat, its back to normal. I'm assuming the tps was bad and extra fuel over time caused cat to clog. It was a dog a few months ago, and has just got worse. I just found out about it yesterday. Sad part is, 4 guys who 'know alot about cars' looked at truck over the last 2 months, no one could figure it out. cap/rotor/plugs/wires/maf later, truck did same thing.

[96/chevy/pu]

If they couldn't figure out the cat was stopped up I don't think I would look for there advise in the future! DUU

[oleshifty]

ya...most of the guys out here still argue carbs are better then fuel injection.


Thing runs great now though. I've never seen a car with clogged cat before, had no idea the symptoms.