Hi, I was reading some articles on the 95-99 4.3's with CPFI, is it true that all them have problems with fuel lines leaking and the intakes cracking? Just courious because I have a 99 GMC Jimmy with a 4.3 and I keep getting a misfire code on cylinder 4 and I cant find and problems, should I maybe lift off the upper cover and take a look?
Also is CPFI the type that looks like TBI after removing the air cleaner assembly?
Thanks
Don't know about "all" but a large percentage do. FWIW, the CPFI dates back to 92. The failure list reads something like; Broken/leaking intake manifold gaskets. Plugged heater cores (relates to above gasket failure). Plugged injector poppets. Leaking fuel pressure regulators. Cracked/leaking fuel inlet tubes (nut kit). Fuel pump failures. Fuel pulsator failures. Carbon chunks blocking the EGR valve open.
(god, I love these trucks and the people who buy 'em)
Your 99 would be a CSFI which complicates things a tad because the injectors are fired sequentially and as such, makes for a bigger parts bill. Odds are if the ignition system is up to snuff, your #4 injector has become plugged. Easy enough to spot with a scan tool. Dunno what cover you're gonna lift and what you think you'll see...
The CPI looks nothing like a TBI, the CSFI has a throttle body mounted atop the plastic upper plenum, so yeah, it looks sort of like a TBI. Your 99 is a CSFI (central sequential fuel injection)
So, how would I remove the upper plenum to check the #4 Injector
You forgot the remote oil lines leaking and the front "silly putty" idler arms....
Actually, the system that debuted in late 1992 was replaced after the
95 model year. The 1992-1995 system was the CPI system and is the one that was most subject to the fuel issues described below, mainly the regulator, nut kit and poppet nozzles. The 96-present system is similar but the "spider body" is only a fuel rail, the hoses that come from it have the electronics of the injector at the end, maybe the 4.3 has the "injector" at the body end, but there's a seperate one for each cylinder.1992-1995 was just called CPI, Central Port Injection, it had an intake that looked like a spider and a TB that pointed to the front of the truck.
1996 and up have CSFI, though the system changed slightly >So, how would I remove the upper plenum to check the #4 Injector
Move all the crap out of the way, un-do the bolts and lift the upper plenum off.
But, I'm not sure what it is you think you'll find once it's apart. You'd have to pull the poppet out to where you can see the spray and then crank the engine. Atomized fuel spray is extremely hazardous, I sure as hell wouldn't want to try it.
The torque values for the upper plenum bolts are extremely low, you'll need an inch-pound torque wrench for re-assembly.
MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.