98z71 No Power!

Sammit · September 8, 2011

I have a 98Z71 with a new 305 motor. Now it has NO POWER! I know 305s aren't like the 350s but it use to burn rubber now it has no acceleration what so ever. It sounds fine while idling and when I rev the engine but it just does not go, even with the pedal all the way to the floor. Had a front seal leak but that is fixed now and cleaned censors, cut off the cad-converter. I don't know what to do, it's sad to see it just sitting there. Please help me..

chris189 · October 2, 2011

I have a 98Z71 with a new 305 motor. Now it has NO POWER! I know 305s aren't like the 350s but it use to burn rubber now it has no acceleration what so ever. It sounds fine while idling and when I rev the engine but it just does not go, even with the pedal all the way to the floor. Had a front seal leak but that is fixed now and cleaned censors, cut off the cad-converter. I don't know what to do, it's sad to see it just sitting there. Please help me..

Hey before doing anything else you need to replace plugs, wires, cap and rotor. Get a cap with brass terminals also!

92rado · October 2, 2011

Sounds like you could have transmission problem. Could be starting off in 2nd gear.

GMstrong · October 2, 2011

One way to dianose that put in 1 on the gear selector.Do compression test,fuel pressure test.Does it fall on its face or did just lose power.

1997SierraSLT · October 13, 2011

I had an 87 El Camino with the 305ci engine years ago that experienced the same problem. No diagnostic codes popped up and the drivetrain was in good shape. Turned out to be a plugged up catalytic converter. Fortunately, there was only (1) and it was relatively an inexpensive fix. To have this issue on a 98 K1500 could be a hell of an expense since there are (4) cats.

takkotime · October 21, 2011

I had an 87 El Camino with the 305ci engine years ago that experienced the same problem. No diagnostic codes popped up and the drivetrain was in good shape. Turned out to be a plugged up catalytic converter. Fortunately, there was only (1) and it was relatively an inexpensive fix. To have this issue on a 98 K1500 could be a hell of an expense since there are (4) cats.

4 Cats? There should be only 2. Go find a friend at an exhaust shop / normal shop if you can't clean em out .. torch em or break the insides out. If that's not allowed there they aren't that expensive to replace.

Duelin · October 22, 2011

I had an 87 El Camino with the 305ci engine years ago that experienced the same problem. No diagnostic codes popped up and the drivetrain was in good shape. Turned out to be a plugged up catalytic converter. Fortunately, there was only (1) and it was relatively an inexpensive fix. To have this issue on a 98 K1500 could be a hell of an expense since there are (4) cats.

4 Cats? There should be only 2. Go find a friend at an exhaust shop / normal shop if you can't clean em out .. torch em or break the insides out. If that's not allowed there they aren't that expensive to replace.

I think he said that he cut off the CAT so that shouldn't be the problem if he did.

Cool Zr2 · October 22, 2011

I bought a rebuilt 305 vortec once, it was a Gopher rebuild and it was a huge piece of shit. Not sure what was wrong with it but at 14k I pulled it and put it away.

Was the motor a GM goodwrench? Most aftermarket rebuild shops can't get it right it seems.

Cool Zr2 · October 22, 2011

I noticed that you say your truck is a Z71. To the best of my knowledge you could not get a Z71 package if you didn't have a 350. You need to check your glovebox for the RPO Z71 and check your vin to see what motor your truck should have. Someone might have screwed up and put the wrong motor in your truck........

Your truck won't run right with 350 programming..... I know, been there......

takkotime · October 22, 2011

I had an 87 El Camino with the 305ci engine years ago that experienced the same problem. No diagnostic codes popped up and the drivetrain was in good shape. Turned out to be a plugged up catalytic converter. Fortunately, there was only (1) and it was relatively an inexpensive fix. To have this issue on a 98 K1500 could be a hell of an expense since there are (4) cats.

4 Cats? There should be only 2. Go find a friend at an exhaust shop / normal shop if you can't clean em out .. torch em or break the insides out. If that's not allowed there they aren't that expensive to replace.

I think he said that he cut off the CAT so that shouldn't be the problem if he did.

Whoops my bad (thats what too much whiskey at the computer will do) but if he did and depending on how that could also be a problem. I removed my exhaust on my 98 350, cut out the cats and welded flanges into the new (bigger) pipe for the o2 sensors.. kept throwing codes / not enough backpressure. Just a thought, ran like crap like that too.

-Takko

TJay74 · November 7, 2011

I had an 87 El Camino with the 305ci engine years ago that experienced the same problem. No diagnostic codes popped up and the drivetrain was in good shape. Turned out to be a plugged up catalytic converter. Fortunately, there was only (1) and it was relatively an inexpensive fix. To have this issue on a 98 K1500 could be a hell of an expense since there are (4) cats.

4 Cats? There should be only 2. Go find a friend at an exhaust shop / normal shop if you can't clean em out .. torch em or break the insides out. If that's not allowed there they aren't that expensive to replace.

I think he said that he cut off the CAT so that shouldn't be the problem if he did.

Whoops my bad (thats what too much whiskey at the computer will do) but if he did and depending on how that could also be a problem. I removed my exhaust on my 98 350, cut out the cats and welded flanges into the new (bigger) pipe for the o2 sensors.. kept throwing codes / not enough backpressure. Just a thought, ran like crap like that too.

-Takko

Your codes had nothing to do with back pressure, they were caused from removing the cats and not turning off the codes related to the cats in the ECM.