Blazer has had some intermittent issues. I have replaced the fuel pump, filter, and injectors a few thousand miles ago. My average mileage was usually around 15 city, and 20 highway.

I was driving a 300 mile trip, it was running fine, then I stopped at 150 miles to get a bite to eat. Upon returning to the car it would turn over and fire, but only run while in the start position, as soon as the key went to on it died. After several tries I got it to start but it ran like **** and sounded like only a few cylinders were firing, the whole truck was shaking. I got it on the road and it appeared to be fine but was getting really hot. I have a scan tool in the truck because its a POS and can't go anywhere without a full mechanics chest and a scantool. So I hooked it up. My LTFT were +25 and the STFT + 20 to 30. I had error codes saying it was running lean. and she was hot scantool says 236F (95 outside) so I got the heat on and windows down.

I got it to my destination and of course it would not stay running again. The next day it started fine, but had a rough idle again shaking the cab. I get it in the minor road and its jerking, i give it gas but the rpm doesn't change and it spits and sputters. Then it takes off...My foots not on the gas the whole time and the pedal was not stuck. It then accelerate to 30MPH by itself and tries to go into a major road. I jam on the breaks...still accelerating...pop into neurtral...revs up to 3k...pop into D and drive off...got her turned around and she parked fine....Basicly been repeat since then...Also I get black smoke which means im running rich...the computer says lean...

Anybody got a guess? Vacuum, TPS, IAC, IAT, and MAP sensors are all good. no error codes but bank1 and bank2 lean, She runs a little hot, and I have black smoke in the exaust. O2 sensors are around 3k miles old and seem to be working according to the scan tool.

 

Just went and bought a compression tester and fuel pressure tester to add to the on the road tool kit to keep this chevy running. Compression is around 170 for all cylinders. The fuel pressure is 20 to 25 psi. I have the aftermarket injectors not the CSMFI screw up. So they can still "function" at 20 psi I have found out...just not well. It appears my 3 month old 2k mile "quality" AC Delco pump has once again failed me...fortunately its got a year warranty this time.

 

20psi for the fuel? Never heard of a 2000 Blazer being able to function at that low pressure. What 'aftermarket' injectors did you install and why? Have you started by working completely through 96+ Fuel System Diagnosis?

 

Its an aftermarket kit that uses a real electronic injector and not poppets with tubes. The fuel is pressurized all the way up to the end of the injector so it can function under the 42psi CSMFI limit. I installed them because the current design looks like GM stole it from a tractor design in India or something, it was a joke. I have work through the fuel diagnosis already 3 months ago when I ended up replacing a fuel pump that burned up, and injectors that were leaking fuel into the rear cylinders. my mileage went from (city/hwy) 16/12 to 15/20..and that 16/12 is correct. The cheesy pump just must have lost a pole or something. I have 20psi output even before the filter.

 

New Pump in, and I am happy to be back on the road. Also according to my MAF I am getting better mileage then I was before. If anybody is interested I can post after my fill up.

 

Please do.

 

Results are in!!! 302 miles for 13.44 gallons which comes to 22.47 mpg which is outstanding. Driving conditions 30% town 70% highway 50-60mph. Acceleration habits are 1st and 2nd to 2500rpm, 3rd hold at ~2000 rpm and the cruise that OD.

Fuel trims are between -10 and 0 most of the time. that's probably due to the aftermarket injectors and free flowing exhaust. I have a feeling my previous pump was putting out low pressure from day 1.

 

Excellent; best I've ever seen with my '96 was 21 m.p.g.