Hello. New member here. I bought a 2001 Blazer LT 4wd 120000 miles loaded in excellent shape last weekfor what I think was a good deal at $3800. So far I love it except I'm having sluggish engine problems andservice engine soon lightissues. At times it runs great but then the SES comes on it gets sluggish and idles rough when I stop. The light usually doesn't come at start up but comes on after warming up then it gets to the point that the light will start flashing. It begins flashing when my speed gets to about 25-30 mph and above and returns to a solid light when the speed drops down below 25-30 mph. I had the codes checked at local auto parts store and found DTC codes P0171, P0174, P0200 and P0304. It showed DTC pending codes of P0200 and P0304. I have my own code reader and got the same codes when I checked it. The guy who checked the codes at the store believed the problem is with the #4 cyclinder injector(poppet)? I do some basicwork on my own vehicles oil changes, air condition recharge, plugs and wires etc. I have dropped the tank and replaced the fuel pump on my 1991 Jimmy (which will be up for sell soon with the Blazer as its replacement) but I'm not sure how involved changing out the injector would be. I wanted to see if anyone here also believed changing the injector was a good idea or if anybody had their own diagnosis or recommendations. I have been scanning the threads for a few days and they are full of a lot usefull information from some very helpful members. I found a service receipt in the glove box from the previous owner showing the intake manifold gasket was replaced just last November. Would the replacing of the gasket be related to this problem? Otherwise I'm not sure why it would have been replaced. I just hope replacing the gasket didn't solve the previous owners problems and more repair work would be too expensive and decided to unload the truck. Any thoughts or recommendations would be greatly appreciated.

 

Here is the explaination for your present codes:
P0171 - Fuel Trim System Lean Bank 1
P0174 - Fuel Trim System Lean Bank 2
P0200 - Injector Control Circuit Voltage
P0304 - Cylinder 4 Misfire Detected

I too would suspect a faulty fuel injector, but the B1/B2 lean codes seem to suggest that there are further problems. With the cost of a single injector being in the realm of $90 and the imbalance that can occur if only one injector is replaced while the other 5 have 120,000 miles on them, I would recommend you install the updated MFI injection spider.

The installation is fairly straight forward. The biggest headache is removing the fuel lines on top of the intake. You will need a good set of metric stubby wrenches and/or metric liner wrenches to get the job done. IIRC, most metric stubby wrench sets do not include 16mm and I believe this is the one that I needed, [:@]. Once the lines are off, all that is left is to unbolt the components that are assembled to the upper plenum, then unbolt the plenum. The seal to the injector pack may require some force to remove. A spray of WD40 around the parimeter of this seal will help during removal. When reassembling the unit, use some clean motor oil to lube all of the seals including those in the injector pack.

 

Can you explain what an "updated" MFI injection spider is and is it completely interchangeable with what is installed now or is there any other components that would need to be changed? Do you happen to know the part number of the updated one so I'm sure I'm purchasing the correct unit and not an old style unit? Also can you tell me what a metric liner wrench is and what does the acronym "IIRC" mean? Thanks for the info.

 

IIRC == If I Remember Correctly

Yes, the MFI spider is a direct replacement with nothing else necessary to complete the swap. I did this on my 2000 Bravada with no complications.

Search term 'MFI'... Or CLICK HERE

 

I searched the forums and found that thread. It was very helpful. Do you think its a good move to go ahead and do the MFI replacement or do you think I should have an analysis on engine done first do be sure? I called dealer and they want $90 to do analysis. Also can you tell me what the metric liner wrenches are? Thanks.

 

With the codes that are present... Well, I would say that it is probably a safe bet that the dealership will tell you that the spider is shot or atleast that one injector is shot. Knowing that and not having access to the tools that I have, I would say your next step would be to replace the spider with the updated MFI spider.

Check around as far as prices go. $300 should be the maximum that you pay (Lindertech.com) with the minimum being the price from GMPartsDirect.com. But be aware that the shipping from GMPD.com has been lack-luster in my experiences with them. Print off the price page from GMPD.com and take it to your local dealer parts counter and ask them what their best price would be. Use the price from GMPD as leverage. If you get a price you like, take it. My experience with the local dealer parts guys has been great. I don't even have to bring in the slip anymore as they give me their best price every time now. It pays to be informed!.

 

I think changing the spider is probablymy best bet.I cleared the codes and put in new air filter, cleaned MAF sensor, cleaned EGR valve, ran about a half a tank of gas with sea foam through. I took it out for test ride and SES light came on and was flashing after about 15 miles. The engine did not seem to be as sluggish as before with light on and the light would go off when speed dropped below about 25 mph like before. Read the codes after test drive and got P0200 and P0304 again but no P0171 or P0174 this time. What do you mean that GMPD shipping is lack-luster? Do you mean shipping time? shipping price? I would probably get the spider from them because of price of $206 compared to Lindertech price of $300. Too bad Lindertech isnt cheaper because I live in Indianapolis where they are located and could pick it up. Also IIRC in one of your post you said the new bracket and seals are not necessary. Is that correct?

 

For the newer trucks, the bracket should be the same. My 2000 Bravada did not require a bracket change.

I think I bought the spider from my local dealer for $240 or somewhere there abouts. Use the GMPD price and see what they can do. Nice part about the local dealer was that I had the part in my hands the next day. With GMPD, I got raped on the S&H and didn't get the part for 5 weeks! That was on 2 separate occasions and I haven't gone back.

The fuel line o-rings come preinstalled. The seals for the upper plenum should be reusable, but check them for nicks/tears just to be sure.