First off, this is my first post. Hello everyone. Now down to business. I've seen several posts close to my problem but not quite there. I just bought my late grandpa's 97 Blazer, who was a career mechanic, but it hadn't run in 4 years until I touched it. New fuel pump and filter and she cranked right up and ran good. Unfortunately I broke the return line connection on the pump reinstalling it. So I drilled the top right through the "R" and attached a 1/8 x 1/4 brass elbow and ran 1/4 inch fuel line to the steel line to get past the unusable quick disconnect. I mention this because it may be my problem. Now for the problem.

It ran perfectly until I put my foot in it. After that she started bogging down and wouldn't accelerate well with the rpms bouncing. The next day she drove fine with moderate acceleration. It bogged a little going over bridges but returned back to normal. Then it did it after about 10 minutes of driving a few days later. So basically it's progressive. The hotter it is outside the worse it gets. It finally threw a p0151 this past Wednesday and I was told it was o2 sensor 1 on bank 1 and 2 so I replaced both of them but keep the same issue. P0151 is the only code I have. I cleaned the MAF and the code disappeared for half a day then came back but the problem never left. Throttle body looked really clean. My gas mileage is good but every time I hit 15-25 mph (depends on temperature outside) she just jumps rpms up and down like she's having the fuel taken away. With a very light touch I can get it to behave a little but there's practically no acceleration. And no response at WOT. Could my 1/8 fitting in the return line be the cause or is it something to do with the o2 sensor? If I turn the truck off for a minute and restart it it'll run just fine for about 2 minutes then act up again.

 

Welcome to the forum from Wyoming - plugged cat ? hows your exhaust flow
edit - while twisting wrenches for a living years ago i also ran into something you wouldn't expect - on a vehicle that had sat for a few years came in with about the same problems you have - pulled the pre cat O2 sensor and it ran way better, reinstalled it and pulled the post cat O2 sensor to double check and hmm it ran better with it pulled - upon further inspection mice had made a nest from he// - packed tight all the way inside the tail pipe and inside the muffler - you would think running the car would have blown it out but nope the lil buggers do a good job of playing house when they want too..... food for thot

 

P0151 is indicating a problem with B2S1 oxygen sensor, (passenger side upstream sensor). This DTC does not necessarily mean the sensor is bad. DTC's NEVER tell you to replace a part. They tell you that a problem was detected in a certain circuit, and you need to diagnose it before replacing any parts. Following the steps in this flow chart will take you to the problem: https://blazerforum.com/forum/diagno...plained-30417/


As for the driveability issue: Correct fuel pressure and leakdown is critical on this engine. They are not directly monitored by the PCM, so it can not set a DTC if there's a problem. The use of aftermarket fuel pump modules is strongly discouraged due to their inability to provide sufficient fuel pressure, and hold it. Use AC Delco or Delphi pumps only. Following the tests outlined in this link will check the fuel delivery system. If your fuel return line repair is causing an issue, it will show up in the results. Post all 4 readings and we can analyze them for you. https://blazerforum.com/forum/2nd-ge...eakdown-88305/

 

Thanks for the quick replies. I will check those when I get back home from work. My user name actually came from the truck being red and wasps loved making nests under the hood, in the doors, and even in the fuel filler door. So I don't doubt something made a nest in the exhaust system. I get debris coming from the a/c vents too. The CEL disappeared this morning too as I just replaced the fuel filter yesterday after work (forgot to buy one with the new pump). I still have the same issue though.

 

Rough drive home. The CEL came back on and I got it scanned again. P0151, p0141, p0102, p0108, p0300, and p0110. I have a print out of the descriptions. She kept shutting off on the way home and the CEL disappeared even though I could feel the misfire and it kept shutting off. Any main culprits that cause this before I rip it apart and start replacing? Well... I'll go ahead and start ripping things apart and check back for any answers.

 

Yup, https://blazerforum.com/forum/2nd-ge...eakdown-88305/

 

That looks simple and pain free. I suspect the fuel pump since it is a Precision pump rather than AC Delco/Delphi or possibly a leaking fuel regulator. I didn't get a chance to do any tests today but tomorrow I will. Can I rent a fuel pressure gauge from an auto parts store? I'm very limited on money at the moment so I can't buy it just yet.

 

most auto parts stores have a loaner program - most you put down refundable deposit and get it back upon return of the tool - most Oreillys do and several others

 

Loaner tool program is cool. The tester will connect directly to the service port near the distributor. However, you will need to build the adapter to check pressure and leakdown at the fuel filter outlet. Testing at the service port alone will not give us the information necessary to make an accurate diagnosis.

 

Well, no testing today. I hate AutoZone. None of the fittings were in the kit and O'Reilly had the test kit rented already. Yes other stores had them but there's no way the wasp would've made it to them. The problem just gets worse and worse.