Well brief rundown: I got a 1998 blazer on trade, and the check engine light came on. Said upstream o2 sensors. I replaced fuel pressure regulator, rebuilt spider, fixed fuel line kink, replaced cap, rotor, sparkplugs, wires, fuel filter, did oil change and radiator flush. Runs like a champ!...for about 5 minutes. then the thing gets really hesitant, doesn't want to get over 10 mph without flooring it, and backfires excessively. After a few minutes of this the check engine light came on again. This time it was saying the downstream o2 sensor and one of the upstreams has low voltage. p01141,p01131,&p01151 are the 3 codes I remember off the top of my head. Thank god I finally got past p01133 and p01153, they are not showing up anymore. The mechanic I took it to test drove it a time or two and had issues even getting the symptoms to start. after keeping it for a bit and doing some basic diagnostics, he claims it is the fuel pump. I took it back and now the check engine light is off and it drives a little sluggishly, and only seems to get short bursts of speed. I have looked through this forum and others, and do not see a fuel pump causing these symptoms, but at this point I am worried the kinked line could have damaged it. Any thoughts, suggestions, jokes at my expense? PLEASE!

 

more like a throttle body backfire than an exhaust backfire.

 

If the fuel return line is kinked, it will not damage the fuel pump, but it could destroy the fuel pressure regulator if fuel pressure got up to 75psi or higher, (the regulator diaphragm can rupture if pressure exceeds 75psi).

Fuel pressure and leakdown are critical on this engine and can cause all sorts of different symptoms if it's too high or too low. Very quick and easy to check it. Most auto parts stores sell and/or rent fuel pressure testers. Key ON, engine OFF, fuel pump running: Pressure must be 60psi to 66psi and must remain above 55psi for 10 minutes after the pump shuts off.

 

Fuel Pressure Has been checked. Only ran a few miles on new regulator before realizing the line was kinked, so I don't think I toasted it, was holding good pressure once line was replaced. I think the line totally killed the one I replaced for sure. One thing, I bought a pressure tester from sears, but when I wanted to see if it would hold pressure, I needed to kink the 6foot release line for the tester, then the pressure holds, otherwise it seems to leak pressure from the gauge. Am I supposed to have to do that? I figured it was because I bought the $40 tester instead of the $200 tester.

 

Shouldn't have to kink the line, must be something wrong with it.

This tester is pretty decent: Buy Actron Fuel Pressure Tester Kit CP7818 at Advance Auto Parts_____

 

wrong with the tester or the regulator? I assumed tester, but my assumptions have been turning me into more of an *** lately than usual.

 

haha my internet firewall at work won't let me go to the link you posted....stupid firewalls.

 

Problem: High fuel pressure.
Solution: New Fuel Pressure Regulator

Problem: High Fuel Pressure.
Solution: replace kinked fuel return line

Problem: misfiring 5&6.
Solution: Rebuild spider

CURRENT Problem: Backfire, hesitation, sluggish intermittently with spurts of great power.

Solution: UNKNOWN

Not changing the fuel pump (at least I can watch the thing burning through $4/gallon gas now with the working fuel gauge!)

Vacuum Reading at 15. I know it should be 17-22. When throttle is put up Vacuum acts appropriately (according tfm) and steadies at 15. very steady. I cannot find a vacuum leak. I have unplugged pressure sensor, but that dropped vacuum significantly so I think that is okay. Fuel Pressure is about 60 and drops to 55 on engine start, seems to hold well.

I thought I was done last week

 

EGR {?}
Backfiring once can wreak havoc
-also, not sure it applies but-
Exhaust popping on decel is classic lean missfire condition

 

popping is on acceleration, only in low speeds, intermittently, and then the sluggishness is replaced by extreme amounts of power and no more popping when going faster. I think I turned over the fuel line grommet into the spider, so fuel lines aren't in quite all the way (about a 1/4 inch). I will correct this and pray it is the problem.