I have a 4 dr 2000 blazer 4x4 4.3l with CSMFI assembly and i am absolutely stumped about this problem i keep having. I noticed this problem when i replaced the intake gasket. It seems that when i try to accelerate hard my Blazer wants to bog down and hesitate and jerk back and forth like its not getting gas or power. This is beginning to be a huge problem and i am totally clueless as to which way to go now. Since i noticed this problem i have replaced fuel filter, plugs, wires, dist cap, MAP sensor, MAF sensor, and o2 sensors. The spider injectors look ok and dont leak. I replaced fuel pump couple yrs ago with an ac delco and it seems to be working fine. Could someone please help and steer me in what direction to go next. I also replaced the fuel pressure reg. Could i have a leak in a gasket in upper plenum? Would this cause this bogging and hesitation problem? Also saw could be TPS? Have not had any codes pop up lately either. Any help or advise on what to do or look for now would greatly be appreciated. I love my Blazer, but not much longer if it keeps this up. Please help.

 

If the problem started right after replacing the intake gasket, then the problem is most likely related. Maybe something wasn't plugged back in? Not to say that there couldn't be a coincidence. Mine acted like that when the fuel pump was dying out. It acted exactly like how you described. Replaced the pump, and no more problems! The old pump was a Delphi and only a few years old, which surprised me. Anyways, just something to ponder.

 

Unless the check engine light comes on, there are DTC's in memory, and following the diagnostc flow chart specifically instructs you to replace a sensor, the sensors are ok... save your money. DTC's NEVER tell you to replace a part. They tell you what circuit malfunctioned, or is/was out of range, and it needs to be diagnosed.

Correct fuel delivery system operation is absolutely critical on CMFI and CSFI systems. First step is to get your hands on a fuel pressure tester. Most auto parts stores rent/loan or sell them. Let us know when you have one and we can walk you through the diagnosis.

 

I'll second what captain hook said about checking the fuel pressure. Be weary of renting one, I had two bad ones in a row, and MacGuyver'd the two to make one working one.

Also, you didn't mention if you had a check engine light on. If you do, can you please read or have the codes read and post back the results if any with your fuel pressure results.

 

Like the others said start with fuel pressure, then i would look into the catalytic converter being plugged. You can remove the upstream o2 sensor and drive for a short time to see if it helps. If it does then the cat is bad.

 

Thanks so much for the quick replies. Now I have a slight other problem. I was reassembling the upper plenum and during that while tightening the fuel line clamp down i stripped out the nut and stud that the fuel line hold down clamp goes to for the 2 fuel lines into the fuel meter body. the stud came out of the fuel meter body and now i can get the nut off the stud. Does anyone know what the thread size is for the blot stud and nut size so i can replace it, or would i have to get a whole new csefi assembly? I hope i explained that clearly. Could i get that stud bolt and nut at a hardware store? The other stud and nut seem not to be stripped only the one side. I dont even know how to ask for that at a parts store or salvage yard. Is it called a fuel meter bolt stud? Please help i very much appreciate it. If i can fix this then i gonna do a pressure test but now i am stuck.

 

Pretty sure it's M6x1.0 stainless steel. Take the old stud with you to a good hardware store and match the threads up, (definitely metric). Might be able to use a cap screw, (bolt) instead of the stud & nut, but make sure it's stainless steel.

 

Ok so the size of the stud bolt that is attached to the fuel meter body is m6 x 1.0? Do you also know the size of the nut that goes on that stud bolt to hold the clamp down to the fuel meter body? What happened is i stripped the bottom part where the stud goes into the fuel meter body itself, the nut wont tighten cause the bolt spins now think the plastic body thread is stripped. I was gonna try jb weld to reattach the stud into the fm body so it wont keep spinning as i tighten down the nut on hold down clamp. Would appreciate any suggestions or comments. Thanks again.

 

JB Weld is worth a try, that stuff is pretty amazing. After it cures, you can drill & tap new threads into it. If it doesn't work, you'll need a new injector assembly.

 

Thanks cptn hook. Having a problem now with getting the timing correct with my distributor. I read and followed the diy tech article about how to do it for EDI. I turned the crank to line up the two notches at the correct position but the problem is that when i put the distributor in it does not sit flush and cant figure out why. I aligned the white paint mark up with the two dimple holes on the dist shaft and inserted but wont sit flush. I read to take a long screwdriver to adjust the oil pump but not sure how to do that or what to feel for down there. The rotor is by the #6 but not exactly. any ideas of what i am doing wrong here. it seem fairly simple but i cant get it to seat flush to screw the bolt back in. Any ideas or suggestions of what i am doing wrong? Thanks for all the info so far.