Bravada Running Bad!

grose67 · January 6, 2011

I have a 98 Bravada with the 4.3 vortec. Vehicle was runnin fine, then all of a sudden started losing power. It idles smooth as a kitten, but as soon as its under a load it falls on its face. I found a mouse nest in the air box so I took it apart and cleaned it and replaced the air filter. I cleaned the MAF sensor which was fairly dirty. I cleaned the throttle body the best I could. I removed the egr valve and it was nasty but not doesnt appear to be sticking. Plunger moves fine when I push on it. I cleaned it out real well. None of this seems to have helped. I havent had the chance to check fuel pressure, but figure since it's starting ok it must be getting fuel. It did throw a code for all 3 oxygen sensors being lean this morning. I Sea Foamed it last night as well. Any suggestions?

grose67 · January 6, 2011

Nobody even has a guess?

jdubub · January 6, 2011

Beats me..... maybe a bad coil, boot or plug?

grose67 · January 7, 2011

Update:

Checked fuel pressure last night, holding 60 plus pounds. Iam running out of ideas.

233monte · January 8, 2011

Tough to fix cars nowadays without some scan data.

PastorKramer · January 18, 2011

from past experience -- 93 Jimmy fuel pressure tested OK sitting, but on the road -- with a pressure gage attached & fasten against windshield (under wiper) -- discovered that the pressure dropped as the engine warmed up -- actually the fuel pump was warming up and not pumping enough (and not enough fuel in the tank to keep it cool) -- on the road at highway speeds... even died -- replaced fuel pump & all was fine. (NEVER let the fuel go below 1/4 tank if possible -- tank pumps rely on fuel to keep them cool!) All that said, I doubt that is your problem. HOWEVER, it could be on the other end of the fuel line... did you check to see if the fuel pressure holds after you shut it off? It should hold for a while. If not, especially if it immediately bleeds down, chances are the fuel injector spider assembly's regulator is leaking! I'm not sure of the newer ones -- 98 -- mine (Jimmy & Bravada) are 93s. I've replaced the spiders (and nut kits) on both of them. Also, a clogged fuel filter can cause problems. How many miles -- did I miss that? Any chance the converter is clogged? (or a collapsed exhaust pipe). You said you cleaned the O2 sensor... so you've had it out. Try taking it out -- leave lead(s) attached and grounded with a jumper (if possible); AND then take the truck on the road and see if it runs better. The O2 opening should allow enough relief -- if the converter is clogged -- to see if it runs better. (It may set a code with the O2 out, but easily cleared.) I "assume" you've checked vacuum lines -- you might also run a remote gage to be able to check vacuum "on the road". I doubt it's the coil -- normally works or doesn't, AND you'd know if the coil was cutting out b/c it would be stumbling / running rough. Now all that said, have you checked the timing? Can't imagine that's the problem unless you, for whatever reason, had the distributor lose... Good luck -- let us know what the problem(s) ended up being