My 1994 chevy blazer keeps shutting off in drive and reverse. only when i am at a complete stop most of the time. it starts to idle rough and dip down in rpms , simultaneously the oil pressure begins to drop below 40, soon there after the engine shuts down, ive replaced the throttle position senor and the coolant temp senors aswell. any help would be greatly appreciated.

 

TBI? More info on the truck would be great. You could try cleaning the TB if it has one in sure it's covered in carbon and can cause low idle stalls. My wife's 06' mustang had that issue where it would die grabbed a can of TB cleaner whey to town and it's ran perfect ever since!

 

IVe cleaned out all the injectors, it doesnt seem to be any type of dirt, but im no truck expert, im not sure what type of info youd be looking for but when it is idling is goes up and down never a steady idle

 

Does it have a throttle body or is it carbureted? What about the idle air control valve?

 

It defiantly has got a carburetor

 

Is the motor original to the truck? You said you cleaned the injectors what did you mean by that because a carbereted motor doesn't have injectors. Also if the motor is original it would be TBI (throttle body injected) which looks very similar to a carberator but is not a carberator. What I am talking about cleaning is the throttle body blade. Easy way to see if it needs cleaning is to just remove the intake bonnet and flip the throttle open. If the underside is layed with black carbon build up I would remove the TB and get yourself some TB cleaner and go to town. Don't do it without first removing the entire TB from the motor so you don't get debris in your motor. The other two things that come to mind are the EGR and MAP sensor. First is the EGR valve. pull it and see if there is a piece of carbon stuck in the pindle seat not allowing the valve to close. if there is, pry it out of there and make sure the pindle closes firmly. if it doesnt, replace the EGR
the second item may be the map sensor, which tells the computor at what elavation you are at. when these fail its gives the computor a false reading which the computor would adjust the injector spray, too rich or too lean

 

Well if it looks like a carb. the first thing i did before changing senors was make sure it was clean.

 

Ok well have you checked the EGR and MAP sensor yet?

 

I'm having a similar problem. Mine is a 94, 350 TBI with Accel distributor, cap, rotor, ign module, coil and plugs. I have Pacesetter shorty bolt in headers, Magnaflow "bolt in" cat, new Delphi egr and temp sensor. Replaced intake gasket, added tbi spacer when I rebuilt the tbi assy and new fuel filter, tps and iac and map. Also has K&N FIPK intake system.I think that covers it.....Anyway, the truck fires up nice and idles well but after a few minutes it will slightly buck every minute or two. It does this but will idle all day if I let it. The big problem I am having is after it idles for 10 min or so and I put it in drive or reverse it dies, quick and to the point-no stumbles-just dies. Then it starts right up just fine. The other problem (I'm sure is related) is in heavy stop and go traffic it idles fine for about 3 to 5 minutes then stumbles and dies, same when I stop at a light. The idle shows 250 to 300 rpm when in gear and at operating temp (if the stock rpm gauge is correct) and about 400 when at idle. Is that idle too low? I'm thinkin so, and I smell fuel after I shut the engine off either after idle or fresh off the road. The strange thing about the problem is that it has tons of power and gets 16/16.5 mpg highway (80 mile roundtrip commute) with 217,xxxmi. No knocks, no timing chain slap. Could it have the wrong fuel pump, too much pressure? Bad injectors? Lazy o2 sensor? No codes at all except when I double foot the brake and gas to keep idle up but thats normal due to confusing the ecm. Any ideas?

 

Well, I decided to go the cheap and easy route....I drilled out the plug covering the idle adjustment screw and manually adjusted the idle just a tic. It now idles at 400 while in gear and about 750/800 when in p or n. I initially adjusted it too high and was throwing a cel every so often but now I believe thats under control. We'll see where it goes from there.