A leak external to the engine would also not result in a vacuum leak. The if the poppet nozzles were not receiving the proper pressure, they would stay closed, sealing off the fuel system from the intake vacuum.

 

I have had all of these symptoms before and it was pretty confounding, esp with the codes that have seemingly no purpose. Here was my experience, with 2 '95 blazers that had almost the exact same problems, coincidentally or not, around the same milage.

P0172 - Fuel Trim System Rich Bank 1
If you haven't changed the FPR, get ready to

P0137 - HO2S Circuit Low Voltage Bank 1 Sensor 2
caused because your O2 sensors are covered in soot - you can try cleaning them with o2 safe cleaner (check to make sure it is), but you might have to replace them as well. I changed mine, both pre and post cat. This is b/c of incomplete combustion b/c FPR is giving too much fuel to drivers side and correct amount to pass, probably. You can tell if you take off the plenum and the drivers side is extremely sooty and the other side much cleaner (esp if there's washing).

P0401 - Exhaust Gas Recirculation Flow Insufficient Detected
This is from a large amount of solidified soot inside the EGR passageways. I ended up removing alot of it by repeated seafoaming one of my blazers then cleaning out the associated passageways with the plenum off. This worked pretty well on one. On the other I had to replace the lower manifold gaskets so I cleaned out ALL of the passageways really well then. You may be able to get it fixed using a screened EGR gasket, but the problem is that so much/many pellets will keep clogging it up you'll have to take that EGR off (kinda a pain on this model) and clean/blow out the pellets so frequently you might as well address the problem more directly. I think this model makes alot of carbon deposits too because of poor valve stem seals too, but I'm not totally positive about that. The FPR problem is more probably the cause if you haven't had it go out already.

P1442 - EVAP Can. Purge Valve Diagnostic Switch or EVAP Vacuum Switch Circuit
This one mystified me for quite awhile til I checked all of the connections on the evap pieces located to the drivers side of the plenum. Make sure everything is nice and tight and all the wires/tubes are not damaged. Probably one of the tubes is loose. I'm pretty sure they can test it at autozone if you still can't get it figured out, and if it's bad, I happen to have a whole new unit I picked up from a junkyard while I was under the hood that I can sell you if you need it. I'm just guessing that it still works ok, but it's more than likely fine.

P0700 - Transmission Control System (MIL Request)
strangely enough, when I got the evap thing fixed, this went away

P1100 - No matches...
ditto for the mystery evap problem

Will update with more information when I get a chance with my other references.

I would be concerned about that rich bank 1 code. This can be caused by a fuel leak on the driver side of the lower intake manifold.
>>Your bank 1 is probably rich because your other side is running lean due to the FPR or fuel lines leaking. Check under the plenum for washing; you can also check my DIY article on here for instructions/help. On 1 of my blazers have this problem for a while and the FPR was not visibly leaking, so I didn't replace it. The problem kept getting worse until the FPR did start weeping, then I replaced it and voila. Problem solved. The other was much worse and I changed both FPR's on my blazer within only a couple of thousand miles on the odometer of each other. Hah! Talk about reliable. If you have the CFI engine, this is probably the problem, just my opinion. Make sure to check and diagnose correctly though, obviously.


It is possible that the EGR code is being triggered due to the screen being plugged up with carbon deposits.

Yes, definitely.


I have been meaning to repost my complete instructions on how to do all of this stuff (sorry about that swartlkk), complete with pics! hehe. Well I'll try to find that file and send it along today or tomorrow if you'd like some instructions.

Good luck. Once I got all of this stuff done is was like a different truck.

 

i replaced the spider last summer with a reman 2 year 24,00 mile warranty and a new nut kit so ill get a new one of those. i removed the sensor in the intake and it looked washed on the passengers side. i also cleaned out the EGR valve last summer and put in the screen gasket while it was off. today i changed the dist cap and rotor and was checking all the vacuum lines to the EVAP and all looked good and were connected. i want to change the cat because im afraid of it being bad and O2 sensors as well.

 

howcome no one knows what P1100 code is on these 95 trucks???

 

It doesn't even come up as a valid code in the '95 FSM... Sounds like an erroneous code from the code reader.

 

is this true with the P700 code too? because i can't find P700 either? what gives?