1995 4.3l V6 Vortec SPUTTERING/MISFIRE on acceleration
 

About a week ago I was driving my car when it suddenly started sputtering and driving almost like it was out of gas this stopped and I left it alone. The next day the same thing happened, and to overcome the sputtering I accelerated faster and it was no longer noticeable. (This is mainly happening once the engine heats up) Now it is terrible, I cant drive a half mile without it bucking with acceleration and dying at a low idle while in drive at a stop sign. I have been driving it to test things that I have fixed which have not fixed the problem yet.

I have replaced these things:
Spark Plugs, Spark Plug Wires, Distributor Cap, Distributor Rotor, Throttle Position Sensor, MAP Sensor and the Fuel Filter. I have cleaned/checked the EGR valve, Idle air valve, vacuum lines electrical connections, fluids, and inside the intake plenum where it seems clean (no broken/leaking lines).

I feel like I have done everything possible, but I know there are a couple more sensors I could change, and possibly change the fuel injector/pressure regulator.

Whats next? Has anybody had something similar happen?

Thanks

before you do ANYTHING else check fuel pressure. it must be above 59ish at key on and hold above 55 for 10 min. if its low replace pump,if its good then slowly drops its probably the spider.

If you replace the pump,ONLY buy ac delco. these blazers are so picky on pumps. dont chance it like me,and 40000000 others did. We ended up doing it again.

Actually if inside the plenum is clean it means something is leaking. Either the fuel pressure reg is leaking or the injectors are leaking. Its normal for the plenum to be black and sooty looking.

Sorry, I should have specified more. It is clean as in there is no pooling of fuel, and it is not abnormally filthy or clogged up. I cleaned it several months ago too and put a new gasket on.

I am new to the site AND SIGNED UP BECAUSE im having this SAME issue.

for the both of you. A bad area in these are the fuel systems aka pump and spider injection. Whenever they start to go out,you will get all kinds of hard starts,flooding,rough idles,sputtering etc. A simple pressure test will tell you if you have a fuel issue. You can go to autozone and borrow a pressure tester for free,but you have to leave a deposit in case you dont return it. You get every penny back when you take it back.

How much they charge you for deposit? I am working part-time so I don't make much.

Fuel Pressure Tester
 

I'll be doing that today. I'm guessing autozone will charge $50 for the tester... thats how much one costs new and thats how they price.

I THINK it was like 100 bucks. I dont remember. They usually charge more since the parts are usually a higher commercial quality since they are being loaned out. call and ask..

Alright, today I got the fuel pressure testing gauge. I followed all of the directions that were included and got the running test, acceleration test, and battery (system priming pressure) test. The pressure range that my Jimmy is supposed to stay at is 56-66... That seems like a large range.

So I turned the ignition on, but not the engine and the fuel pressure jumped up to 64, but then instantly dropped. It took it about a minute to reach 20. After that I turned the ignition on and off to pressurize it more and it did the same thing... it just couldnt hold pressure.

I then turned the engine on and the pressure jumped up to 56/57 and stayed steady for the most part. If I pulled on the throttle it would jump up about 1 and as soon as I let off it would drop down to 52/54. I tried the same in neutral and it was just a bit more extreme, but not too much different. (The car sputters while in neutral, but not park)

So what it seems to me is that my fuel pressure is low, and it does not hold pressure while the engine is off (which it is supposed to I guess). So what now, can anybody think of any other ways to test it, or different things I could try before I return the pressure tester?

Thanks... let me know

Sounds like you got it covered. Its either the fuel pressure regulator or you have a leaking injectors. With that much of a drop I would suspect the regulator. Time to pull the plenum. It should be black and sooty, it its clean you know something is leaking. At that time you can test the regulator to determine if its the reg or injectors.

Is the regulator part of the spider? If I buy a new one would I just get the whole setup? Do you think that the fuel pump has anything to do with it?

The reg. Is a different part from the spider. From the numbers the fuel pump is ok. If you want to change both the reg and spider I would reccommend getting a delphi MFI conversion from rockauto, they are less prone to failure.

The reg. Is a different part from the spider. From the numbers the fuel pump is ok. If you want to change both the reg and spider I would reccommend getting a delphi MFI conversion from rockauto, they are less prone to failure.

so the problem is most likely that? Anything else that could be wrong?

Sorry about the double post, damn android phone lol. Your key on pressure is good so its not the pump. You have fast leakdown and that usally points to the regulator. Look down the throttle body, if the passenger side is very clean or shows signs of washing then that confirms it.

i looked into the engine and both sides seem the same. it does look pretty clean though... like silver splotches

Take the plenum off so you can pinpoint the leak, but that's definetly where the leak is coming from.

I was trying out a few things today with the fuel pressure gauge, and it has gotten very severe with acceleration. My fuel pressure however stays consistent, until the engine dies and the key is still in the ON position, then the pressure bleeds out pretty quick. When I was driving it the engine seemed to be gasping right before it died, or when the RPM would drop super low like 500 then jump back up to 1500 (this is while idling in drive). Like a said before the inside of the intake manifold looks pretty clean, and it was more moist than before. I think I'll just replace the injector and pressure regulator. Anybody know what MFI conversion would work with the 1995 GMC jimmy 4.3l vortec v6 engine?

I saw this after I posted, I'll do that and make sure that it is there.

Go to rockauto.com they have everything you need for the conversion

If its got silver blotches inside the plenum its the injection system for sure.

Inside the engine
 

Okay, so I pulled it all apart and there is a slight difference in the passenger side from the driver side. There was also some pooling of what seemed to be oil! The wiring for the injector is starting to fall apart, and some of the poppet clips are cracking, so I will be replacing that stuff.

More Information for AIRTEX / WELLS 4G1887
AIRTEX / WELLS Part # 4G1887 {#12568332, 19210688, M1045}

Would that work with my engine?

Avoid airtex like the plague! It will fail on you again probably within a month. Stick with delphi, it costs more but at least you know when you finish the job you won't have to do it again. There should be a discount code floatin around somewhere to. The "oil" was more likely gas that has been turned black from the carbon on the intake.

More Information for DELPHI FJ10565
DELPHI Part # FJ10565 More Info
Actual OE Part; SCPI to MFI Conversion - Complete Assembly

Yup, that's what you need. There is also a new bracket that you need for the upgraded spider. I don't have the part number for you though.
Edit: don't remember if the bracket comes with it, contact customer serive, they will get back to you asap. After looking closer I'm kinda shocked that delphi is cheaper than airtex lol. Stick with oem.

DO NOT order that part! You cannot convert the older CPI system over to the newer setup. The MFI upgrade only applies to the 96 thru mid-02 SCFI trucks, not to the 95 and older CPI engines.

Thats what I was wondering. I have the generation 2, but I guess it still wouldnt work. So Just stick with a Delco with the poppets still?

Unfortunately, you only have the 2nd gen body. The engine is still the old CPI engine used in the later 1st gens. So yes, you have to stay with the older CPI spider.

When you are ordering parts, do not forget the 'nut kit' (internal lines). These are notorious for leaking after being disturbed. Another item worth replacing is the electrical connector to the cpi spider injector (also called the 'maxi-injector'). It's cheap enough and has caused a few members to pull their hair out and toss countless dollars into other parts after they were sure that the fuel system was good. The part number for the connector has been posted before and a search for "cpi+injector+connector+part+number" (without the quotes) should turn it up.

Wow, thanks for catching that. Sorry about the bad input

Unfortunately I don't have a lot of time to help out so I try call out those things that jump out at me when I'm browsing through the new posts when I do have a chance to jump on.

Thanks for catching that! And thanks for all of your help everybody. I'll keep my fingers crossed that this all works out! If I buy the full injector assembly on rockauto do I need to buy the seal kit to, or will it already have that?
Right now I am planning on replacing the fuel injector (spider), pressure regulator, injector fuel lines, injector electrical connector, and possibly the seals.

This is my cart

The new spider will have a regulator. The line kit will include the o-rings necessary. You will need the plenum gasket, but other than that and the connector, that should be it.

Do I have a problem if there is a little bit of oil in the intake manifold? I'm almost positive that it is oil.

Hello team,
New user here with a 98 jimmy having sputtering issues.Fuel pressure is good at 61 to 65.we just replaced the fuel pump and the ignition module.catalic converter is emptied out cause we thought it was clogged.now we are debating weather to install it or keep it out.here in FL we dont need it.please help.is it necessary to keep the converter?

I don't know enough about catalytic converters to answer that, but my problem was the fuel pressure regulator/injector unit. Can you give some more details of how the sputtering was, and how it was driving?

The Solution
 

So I just realized that I never posted how the fix went, and all of that.
Anyway I ended up replacing the Fuel Injector/Regulator Spider, Fuel in/out line, Intake Plenum Gasket, Fuel Filter, and a few other small things. The real problem was the fuel injector unit. That fixed it, and increased my Fuel efficiency by 3mpg.
So if you have sputtering, and very jerky driving and inconsistent rpm's/idle then it is the fuel injector/regulator unit. When you replace that you should also replace the fuel lines in the intake manifold, and possibly the wiring. Both of those were very brittle and about to break in my engine.

I have had the same problem on my 93 s10blazer. Do you have a vortex engine because if you do then it is the tubing that leads to the spider injection its not sitting right and leaking fuel or its the spider injecter itself. I just had it all worked on back in February. They do not sell the tubing you will need if that's the problem you will need to go to a junk yard and get the whole upper intake manifold or go online to eBay or something to find the part. But i had the same problem and i had the fuel pump and filters changed and i change the coil pack and the pick up coil. If the tubing is not seated right or the spider is bad you will not get a accurate reading when you check the fuel pressure. I went through that with the auto shop when they told me it was the fuel pump and it still did the studdering and dieing on me. Until I took it to another shop to get it fixed.