1994 S10 Blazer 4.3 W code
Ok, this might be a little long winded but I want to clear up everything I have checked or replaced already before people start spurting out resolutions. On the way home from work the other morning, I had noticed that hitting the gas from a stop there was sort of a delay and then the powerband kicked it. About the time I got home the truck was running extremely rough (only 3 miles), and was running hot (about 250 or so on the gauges), and I almost ran into my garage door backing my truck up because it had no brakes at all.

It's been three days of fighting this truck and this is what has been replaced.

Idle air control valve (warranty)
TPS
MAP Sensor
Ignition Module
Cap and Rotor
AC Delco plugs + accel wires
MSD blaster coil
Oxygen sensor

Now I had a few problems with the laggy starts off red lights a day or two before it finally died, and had intermittent SES lights coming on, but they were never hard codes so my obd1 scanner did not pick anything up. I pulled the round valve (some kind of recirculator) off the top of the motor and cleaned it up. I took the EGR valve off and it appeared to be jammed up with carbon, I cleaned it out but HAVE NOT installed it back yet. I also messed with the timing at the distributor w/ECU hooked up and not hooked up, doesn't seem to make any difference.

What is the round piece on the top of the motor? Is there anyway to test it? The parts store has no idea what it is or how to replace it. I doubt cleaning the EGR is going to help and I dont want to spend $220 on one and have the truck still not want to run right, I am running out of cash this paycheck ugh.

I saw a few posts about the CPI and injector/regulator/nut kit, but mostly I see the problem on 1995's W codes, is it similar with a 1994 W code?

Somebody please give me some advice, I am out of patience and out of money. Thanks!

 

forgot to mention truck has NO catalytic converter so this is not part of the problem

 

The EGR valve being all carbon'd up could be the reason for the issues you have been having. If you have gotten it cleaned up and verified that there are no vacuum leaks in the diaphragm on the valve itself (I can't remember if its vacuum controlled or electronic like the newer ones), slap a new gasket on it and reinstall it. See how things go.

And all CPI motors are equally susceptible to internal fuel leaks. Some get lucky and never see the problem. Before coming to the conclusion that the spider or fpr is at fault, a fuel pressure and leak down test must be performed. If you determine that there is a leak somewhere in the fuel system, the next thing would be to remove the 'round piece on the top of the motor' (I know the name of the part, but I cannot for the life of me remember it right now). Look down into the plenum and see if there is a pool of fuel on the passenger side of the motor. If there is, then you have an internal fuel leak. Pull off the upper plenum and pressurize the fuel system again. Inspect for the exact location of the leak.

Let us know how those checks go and we can advise further.

 

Ok, so I cleaned out the EGR really well, it had a little rock of carbon keeping it stuck back ( I guess open), after playing with it it seems to open and close fully, not sure how long this will last though. As far as a vacuum leak, it's electronic on my motor. I found a pinched spark plug wire and replaced all of the wires with accel as well as the cap/rotor.

It's running a lot better but still something is wrong. When it idles it sort of runs a little rougher than normal and sorta spits and sputters, almost like a misfire or backfire...it's strange I can't tell what it is. I have checked over all the plugs and everything I could see for anything thats wrong.

I took it out on the road and drove it, it seems ok, throttle response could be better, but then it shifts from 1st to 2nd and sorta bogs down, not transmission but the motor actually drops rpm and almost dies, then comes back to life but still runs like crap...at this point it pretty much runs like **** until you let it idle for a minute.

I let it idle outside for 45 minutes or so, it would get rough and I would hit the gas for a minute or two and it would clear up.

My friend had said to check the distributor and advance the timing a little but I don't know if this is good advice..? I am going to check in that whole right now to see if I see any fuel leaks.

Thanks!

 

When was the last time you ran some fuel system cleaner through it... I run a large bottle of Chevron w/ Techron through all of my vehicles at every oil change just to keep things cleaned up.

I suppose it is also possible that you have some water in the tank. A red can of Iso Heat will fix that problem.

Both of the above suggestions aren't 'break the bank' items, however, they may not do a thing for your problem aside from rule out those two possibilities.

 

I put a bottle of this in it last week http://www.autobarn.net/ch05063.html

The problems did not start until a full tank of cheap gas at (wawa)...after half a tank of that (87), I filled it up with 92 since it was running bad. 16 miles later I am coming home from work at it reaches the climax of it's messing up.

I checked inside the (imtv?), aka "round thing on top", and I see no clean spots or any signs of a leak, just lots of carbon everywhere. I will try some of that stuff and some fuel additive and see if its the gas, I just went over everything in the motor again and I still cannot find anything astray.

I tried unplugging the imtv and egr and starting it, no difference. Do you think my egr could actually be broken and cleaning it didnt help anything?

 

Oh and where can I get iso heat at?

 

Ah yes, that is what it's called! IMTV == Intake Manifold Tuning Valve. Here's some info on the IMTV:
Anyway, Iso Heat is available at pretty much any autoparts store and your friendly neighborhood Walmart among many other retailers.

It is possible that the EGR valve is causing all of these issues. If the EGR valve is remaining open, it will result in poor idle quality and depending on how 'open' it is, it can cause a vehicle to stall.

 

I stand corrected. I was reading a post on another site about spider injector replacement on a 1998 and he said the first step was to unplug the two wire harness and remove the round cylinder which is the imtv...I don't even know what it stands for just was assuming thats what it was, I understand my fuel system is totally different..

I will try the iso heat, about to run down to the store and try it. I guess what I need to do is buy an EGR, I just avoiding it because it's freakin' expensive [:@]

Anyway, after cleaning it and putting it back on the truck ran good, at which time I noticed is was missing, and it was the broken wire. After replacing it, it ran perfect, drove it away from the house and as soon as it shifted to 2nd gear it started messing up.

 

this is where I saw it
http://www.automotiveforums.com/vbulletin/t584122.html

2nd response