98 burban, 5.3., TBI. came in for an intake gasket. tried to leave...but owner and we (the shop) feel it has a lack of power (drive) after we touched it. we have re-done the intake 3 TIMES...3rd time we did it by the book. have replaced new sparks, spark wires, cap, rotor. We tried a new EGR solenoid valve...no change. New MAP sensor... to no avail. New O2 sensor. ALL connections (sensors, wiring harness) are connected. Timing is correct (0 degrees) and is advancing properly (10 degrees + with RPM). once, a sulphur smell came from tailpipe...went away. also in park, or under heavy load, SOME black smoke comes from Tailpipe. Drilled "speedholes" (shop joke) in tailpipe before cat. conv...gave a very slight increase in power. We thought that cat. conv. is choked. Now it's thought that the EGR valve is bad. Oil is clean, and it could use a slight amt of ATF. NOT THROWING CODE
I personally (as well as the shop) would very much appreciate a viable solution to get this POS out of our bay.
Answers & Comments
Verified answer
If you will try the timing chain you may see that there is a lot of slack in it,,what this does is cause the timing to always,s be retarded,,you can adjust it by moving it up a little but this wont fix the fact that the chain and gear,s are worn out,simply put,,the piston,s and valve,s aren,t opening,,and closing when they should,,and the spark,,is not occurring when ,,everything is in line,,and this situation wont improve it,s self by simply advancing the timing up some,,it may seem like it run,s a little better,but your not helping the situation,by simply advancing it up,,you wont get any trouble code,s on this situation either,,it,s an internal problem,,that must be dealt with,,good luck with it. i recently answered a similar question like this,,with a similar problem.
Use the PCM to your advantage. It's an OBDII vehicle, so you can scan all of the things that you mentioned (except the cat) while it's running with a Tech2 (GM Dealer tool) or a tool like ATAP (about $150 to purchase it). This would have told you that the MAP and O2's are good prior to replacing them - it pays for itself very fast.
Try resetting the PCM (not reflashing). I'm not sure on that particular model, but on the 98 F bodies you pull the PCM ignition and PCM batt fuses and then wait about 5 minutes. They are located in the engine bay.
Another culprit could be adjustment of the throttle cable. It's possible that it's not opening up. Have someone floor it (with the engine off) and check if it's actually opening up.
Is the vehicle actually going into first gear? It's possible that it's taking off in second which will make it seem like it's gutless - if it's an automatic.
Also, I believe the harmonic balancer those engines doesn't have a keyway. I know the LS1's of the same year don't. It's possible that the balancer has moved, so although you think the timing is correct - it's off.
Its probably your fuel pressure regulator. If it is not supplying enough pressure to the injectors it will not have power. This can cause it to smoke also. Hope I have been helpful.
this eng has to be retimed through the (ECM)once the eng has been disembled. Take it to a good dealer for the reprogram.I hope this helps you