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Service engine light flashing on my 4.3L v6, 96 Chevy blazer?! Code P0175

Having some trouble diagnosing this problem. Showing a P0175 : System too rich @ Bank 1. I’ve checked for vacuum leaks with no luck finding one. Service engine light started flashing at idle and now is on again. Any suggestions would be great. Some one told me to start with the Fuel pressure regulator. Would this be the way to go? Thanks guys!

Check the spark plugs on that bank (it will be the driver side of the engine) to make sure they’re OK. Make sure the mass airflow sensor is clean. Fuel pressure is a good thing to check, but if the person who told you to start with the FPR meant to just replace it, I’d hold off until you have evidence that it’s faulty.

A bad fuel pressure regulator could cause it to go rich, I would think it would be both sides. Start with a tune up, new spark plugs won’t hurt. Clean your MAF with actual MAFcleaner not just carb cleaner. If you have a vacuum leak bad enough to cause it to go rich you’d probably know it from other problems. What other problems does it have? Does it idle rough? Check your vacuum with a gauge if you can. If you know your o2 sensors are good and you know your MAF is clean and the vacuum seems to be steady, the pressure regulator would be a good next place to go. Check your fuel pressure and see if it’s too high. How long has it been flashing? when was the last time you changed your air filter?

Thanks for the reply! This is the first time I have seem a flashing check engine light. It flashed for about 60 secs the stayed on. I notice the idle was rough just before it light started to flash. But I have had long crank times for about two weeks. Normally it would start within 2-3 secs now it’s seems to be an 8sec crank time when warm. And if I turn it off to pump gas, run into the store for 5mins, it will start immediately with the starter. Air filter is new. Less the 90 days sense I put it on.

A flashing check engine light is caused by a severe misfire, bad enough to potentially damage the catalytic converter

With all due respect, don’t bother looking for vacuum leaks

Vacuum leaks lead to lean codes

You’ve got a rich code, so you need to determine why that is

As far as fuel goes . . . do you own a fuel pressure gauge?

Your engine has a test port, and if you posted some readings, it would tell us a lot.

The fuel pressure regulator actually isn’t that easy to replace on this engine, because it’s underneath the plastic plenum. I wouldn’t go there, until/unless you know that’s indeed the problem

Any fuel smells?

any problems starting?

Check MAP/MAF operation. Your engine may only use an MAP, not sure. Check the air intake system for any obvious problems, torn boots etc. Air intake duct, air filter, IAC esp if having any idle problems, gunk blocked throttle body/IAC ports, throttle position sensor. After that fuel pressure check. Injector balance test. Check for silicone contaminated heated O2 sensor. Check EVAP system.

Fuel pressure is a constant 50 psi and drops slightly if felther the throttle. Sells of excessive emotions from the exhaust no and raw fuel smells though.

Would you clarify that please.

Maybe like a burn oil smell. Best I could come up with to describe this smell is like the smell of a two stroke dirt bike exhaust.

That is too low by a few pounds. In my opinion, your fuel injection system is currently not in good shape

Here are my next questions

What is your fuel pressure key on engine off? Cycle the key a few times, ending in the on position, and post a reading, please

Does it hold, or does it drop?

What other special tools do you have access to?

Any scan tool which will allow an injector balance test?

Any tools which will show you misfire history on specific cylinders?

The fuel pressure climbs to about 45 and then slowly drops. I don’t have access to many special tools. I don’t have a scanner at this point.

You’ve got significant problems with your fuel injection system

Are you able to connect a gauge directly to the pump, so that you can deadhead it . . . or can your gauge only hook up to the test port?

Absent that information, though, my gut feeling . . . at this point, based on your findings and the fault code . . . is that all of your problems may lie with the entire fuel injector assembly, which is comprised of the central injector, nylons lines, poppets and regulator


The pump is bran new from factory gym. I put it in about 4,000 miles ago after the last one suddenly went out. If that helps. I was hoping I wouldn’t have to take this route due to cost and time but i make sure to update my findings to the forum. I appreciate everyone’s help.

I’ll certainly defer to your expertise. My thinking was a leak could introduce too much air, which would make it read lean, and cause the ECU to dump too much fuel in, which would make it run rich, but I’m sure my reasoning was flawed.

ah, the GM CPI system? with the spider manifold? there just arent that many blazers of that vintage left in mn now. rust has taken its toll

The fuel pressure should raise a little when you bump the throttle, not drop. You may have a faulty fuel pump or a fuel flow restriction somewhere between the pump and the fuel rail.

You’re correct about that, assuming you mean some kind of a vacuum leak?

And the result would be a lean code, say P0171 and/or P0174

The pcm would attempt to compensate by dumping in extra fuel, but that extra fuel wouldn’t result in a rich code

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