Manager Forum

I got a 2000 olds bravada that runs bad and is getting like on mpg; i know they don't get great but we are talking like 10mpg or less.

Check out and all looks good untill i get to cam retried it is at -13 and should be 0 but u cant adjust them. Idles good it is just when u are trying to get up to speed has no power. Fuel psi is 50psi plus sprak plugs and wires and newer and cap and rotor are new. When driving at higher speeds find then it feels like it has a miss every once in a while like 2 times in a mile but if u push down on it to go faster it dont do that. in the past year the plugs wires cap rotor mass meter and crank sensor fuel pump has been put in it. looked at miss fire and found all but cyl 1 and 6 have some none over 700.

so i'm assuming that there are no codes, correct. what is the fuel trim. if the 02's are trashed you may be washing the cylinders and causing this issue. if there is no code than i would look at the 02's.

Check exhaust backpressure. Could have a plugged cat.

great point on the cat. makes the most sense now that you've pointed that out.

checked cat it is great and i will get lean codes. Has anyone ever had a bad pump that had good psi

What are the fuel trims? Have you checked maf

fuel trim is about 128 and the maf reads great

Unplug mass air and try. And I show fuel pressure should be 60-63 psi.

how did you check the cat's? did you do a pressure test or drop the front pipe? it's been my experience that if you have a partially plugged cat it only acts up when the vehicle has been running a while. another point is you say it's running retarded, have you looked into the knock sensor? if there is a crack in the flywheel and it's rattling the sensor will tank the timing. now since i've got a few minutes here what about the timing. i've seen distributes dropped in incorrectly that will throw a balance code. another point here. i believe that the cam crank balance has to be manually reset. what is the history on this. what have you done to it as well as other shops. an example would be if it started after it was tuned the plugs could be gapped incorrectly. this is (i believe) a fairly low compression engine. i've seen cross plug wires screw things up and you can't even feel the skip. i'm still stuck on the code thing. if i were to scan this and there were no codes i'd look at the timing with the knock sensor connected and disconnected. if it appears to be functioning un plug the maf while it's running and see if it throws a code. again, another point i just thought of is check all grounds. i also check fuses when i have a head banger like this. sometimes the fuse description shakes dust loose and i'm off on the correct track.

with the scanor on it the knock sensor is ready nothing i can try to unplug. I have done a intake gasket on this about two years ago and right before that i had to do a fuel pump and then about a year ago the fuel pump would not hold psi and was hard to start in the morning. Both times i put a feul filter on it. If i unplug the maf it will set maf codes i did that already and when it was unpluged it ran alot better that is why i put a maf on it. Plug and wires are about year and half hold cap and rotor a few mouths ago. This is my truck i have been the only one working on it for the past five years. i dont get why the cam is reading -13 and u cant adjust it. Just had a 99 s10 in here at work with a 4.3 and it was at -10. When u take off it has no power and hard to do above like 50 and does not get any thing for mph. I checked the back psi with a gauge in the o2 hole in the front

Have you checked for slack in the timing chain? I have heard of people making a "modifacation" to the dist and adjust it to get the reading that is expected (o).

liljoe wrote:Have you checked for slack in the timing chain? I have heard of people making a "modifacation" to the dist and adjust it to get the reading that is expected (o).

Well, I thought of the timing chain as well, but there is a slight adjustment that can be made to the distributor. The -13 degrees is enough to give it some issues and not set a code. I would try to back that to 0 degrees plus or minus 2 degrees and see what that does. I also thought of a vacuum leak as well but that would not make a -13 degrees timing offset.

when you unplug the maf what happens to the timing. does it advance? un plugging the maf could be throwing it into "limp". meaning no disrespect but i'm not sure what you mean when you say you can't unplug the knock.

And dont forget the fuel pressure is not sufficent. 50 psi does not = 60 psi. Could have multiple issues

It also could be the fuel injector metering assembly more commonly called the spider assembly is at fault. We have seen more than enough of these cause various driveability issues.

possibly, lets not forget the egr plugging issue.

steven kiser wrote:possibly, lets not forget the egr plugging issue.

I clean fergot about that problem.