Long winded here, sorry.

Got a 91 4.3L TBI, just bought it. Replaced the following:

Spark Plugs(Gapped Properly)
Wireset
Rotor
Cap
PCV
TPS
Exhaust from the cat back(Replaced muffler with cherrybomb turbo. Original configuration on the pipe, just upgraded the 2 1/4 pipe to 2 1/2 pipe)
Serp. Belt
All fuses

And when i got it inspected it didn't want to pass, the guy passed it tho, but it looks like maybe my o2 sensor is bad. In general the car runs good, except when at idle, it currently idles at under 600rpm according to the inspection stations computer. Is very rough, but any gas and it runs smoothly. Does seem to be lacking power, of course I haven't had it fixed yet to know for sure, just a feeling.

Trying to stop pouring cash into this for a while so I can enjoy finally enjoy owning a blazer but I need your help. Any ideas where I should go next? I've thought about cleaning the map, maf, and egr but don't know how, found some tutorials but t5hey are for much newer trucks, I will try anyway tomorrow on my day off to make any adjustments to get it done. Any other ideas?

The exhaust repair was to fix holes, only one leak was found before the muffler and that was patched by the muffler shop, it was from the hanger breaking the weld. No other leaks were detected in the system. I would think that the straight through cherrybomb turbo is causing too much of a drop in back pressure, but it idled low and rough before too.

Thanks.

 

how did ur spark plugs look when u did them and when u did ur blazer idle rough when u did the spark plug change? also do u notice worse gas milage and a strong smell of sulfer coming from the exhaust?

 

No worries on the exhaust. At idle, you don't have an issue from that.

You don't have a MAF sensor.

How does the fuel spray at idle look? Does it form droplets or does it stay in a nice spray pattern?

 

Nice to know about the maf sensor, the fuel spray I haven't looked at that closely but I do remember it being more like a drip than a spray, seemed odd to me.

I don't remember on the plugs, besides the description would suck anyway, so I'll get them out tomorrow, I saved and marked them, and I'll upload a pic of each one and you can tell me. There was nothing deformed about them, just an off color that I don't know about, not white though.

I'm assuming you're gonna say the injectors are dirty/clogged, so how do I cleam them? Can't replace them for a couple of weeks so I hope they can be cleaned. I also did run a bottle of stp injector cleaner through the tank last week, and I have burned through that whole tank already. As for mileage, I haven't driven it steady enough to check mileage, but it's definately under 20 in any kind of driving. Though I did a very corroded exhaust system, couldn't hardly get any air out of the tail pipe, let alone enough to smell, but I'll check that too just to be thorough.

Oh forgot one thing,when I changed the plugs, found two plugs that were far less than handtight, one of those had a wire just hanging on the tip, not actually clipped on, and one of the other wires was a full half inch off it's seated position on the cap. I'll include pics of the cap and rotor contacts as well. It idled better after the plug change, but just as well as it does right now, I've only had the truck for two weeks.

Thanks.

 

ok ya rough idle can be caused from a couple of things like the injectors being bad, the fuel lines in the plenum r bad, or the egr valve is clogged (might be a few other problems i dont remember). but ya if ur spark plugs were fouled out on one side or at all then it would be a fuel related problem.

 

They weren't fouled out really, I mean the engine wasn't missing at any point before I changed them, just rough, but then again I've never had or heard of a car or truck idling at 530rpm in park, drive maybe but not in park. Everything seems to be about original on this truck, so I've got some work to do with things like clogged egr valves and injectors etc.

I'll have to get my manual out and see if I can find anything that'll help me with my first egr cleaning. But the plugs were just brownish in color, almost like rust, they were also gapped out to like 60 or higher while my manual says the 220 tbi on the 4.3 should be at 35, though I did leave the plugs at a 40 gap as they came, I just made sure each one was gapped the same at 40.

 

As far as cleaning the injectors, I would use two bottles (18 gallon treatment size) of Chevron Techron Concentrate Plus in one tank of fuel. Dump the bottles in before you fill up. See if that helps. You also might want to replace your fuel filter.

TBI engines do not have internal fuel lines.

 

Okay, good tip on the filter, it's after market but dunno how old, thanks, and here are the pics. First is a referrence to how I lay out the plugs, left my book at work so no firing order or anything.
http://www.brokesanity.com/blazer/ref001.jpg

Here is the rotor.
http://www.brokesanity.com/blazer/rotor.jpg

The cap.
http://www.brokesanity.com/blazer/cap001.jpg

And this one shows the one that the wire was barely on.
http://www.brokesanity.com/blazer/cap002.jpg

Here is the best I could get of the spray pattern.
http://www.brokesanity.com/blazer/pic005.jpg

And a couple more shots trying to catch it.
http://www.brokesanity.com/blazer/pic002.jpg
http://www.brokesanity.com/blazer/pic003.jpg
http://www.brokesanity.com/blazer/pic004.jpg

Okay, here are the plugs, all labeled.
http://www.brokesanity.com/blazer/all.jpg
http://www.brokesanity.com/blazer/d1.jpg
http://www.brokesanity.com/blazer/d2.jpg
http://www.brokesanity.com/blazer/d3.jpg
http://www.brokesanity.com/blazer/p1.jpg
http://www.brokesanity.com/blazer/p2.jpg
http://www.brokesanity.com/blazer/p3.jpg

And the PCV valve.
http://www.brokesanity.com/blazer/pcv.jpg

The exhaust seems to smell very slightly rich of fuel, also the pattern of the exhaust pulses i more like a miss some where, though the engine doesn't seem to be missing. Today it's messing with me and idling pretty good in park, but in drive while stopped it sucks ***!!! It's an automatic by the way.

Thanks.

 

The spray looks ok from what I can tell. The cap and rotor have definitely seen better days.

With the older ignition systems, I definitely would not exceed the recommended spark plug gaps. These systems need a shorter gap due to the lower voltage level used.

Have you checked for a vacuum leak? The TBI base gaskets have problems as they age.

 

About the most that I'm equipped to do as far as vacuum testing is to find a bad line and replace it. I've spent hours checking them all and haven't found any with significant cracking, though I have found one that was not connected and cut too short to reach anything, it's by the master cylender and it has no pressure on it at all. I also found a fitting the right size for that hose in front of the proportioning setup for the brakes, but I think it goes to the windshield washer system and it too has no vacuum on it at all.

Aside from that everything there seems fine. Looks like I'm at a stale mate until I can replace the fuel filter and the o2 sensor. When I first bought it it was showing two codes on ses, 13 and 22 I believe, it was one for the tps and the other for the o2 sensor, changed the tps and it went off for several days, but this weekend it started coming back on for a few seconds at a time.