I have a 92 Blazer 4.3l 4×4 TBI. When in park it will rev up just fine , but when in drive its almost like the gas wont catch, kind of a sputtering effect. I’ve replaced the plugs, wires, cap, fuel filter, injectors. The timing, I believe, is correct. I should also mention that this is a replaced motor and I havent had it running perfect as of yet. Any advice would be great. Or perhaps we have an IDA certified mechanic?? lol
Check the map sensor that might be whats wrong.
when it was timed was the distributor wire unhooked under the dash?? and hooked back up when timed ?? and aslo map sensor good place to start. Dont forget to check EGR valve too , carbon build up or just piece of carbone caught in it maybe
Dubble Dubble check your timing if that doesn’t work check the flowt in the carberater if it has one. The only other thing it could be is the otomatic chock is not working I have a truck that wont even move unless it is relly wearm. 
bad O2 sensor is my bet
Try checking the throttle position sensor, if its going out it will do just what your saying, it gives the wrong signals to the main brain and won’t rev right.
Let’s not jump to all the sensors. Very few will allow an engine to idle properly and not rev up. In the grand scheme of things GM used the MAP sensor as one of the main information inputs in those years, and yes they failed. This is one of the few sensors that can cause this symptom.
However all the computer controls in the world still only work right if the base engine is working right. In any internal combustion engine you MUST have three basic things for it to run. You must have a combustible fuel, good compression, and ignition. Missin any one of the three in various amounts will result in a running condition that cannot be masked by sensors.
So first off forget the thing even has electronics on it. Get yourself a compression gauge and check compression of this used engine. All spark plugs must be removed and the throttle open when performing this test. You must also disable the fuel and ignition during this test for obvious reasons. You should be within 15% from the strongest to weakest cylinders.
Because it is simpler to do you should check for fuel pressure. If memory serves me the GM’s are very fickle to this and will not run properly under 45 PSI. The injector (not plural) feeds a “spider” type series of tubes. There must be good pressure or it will not run very well.
If A and B both check out it is time to verify, not “believe”, the ignition is correct. I’m not a GM tech but I believe you’ll need at least a timing light for this. In 02 I didn’t think the 4.3 used a distributor cap. For that matter I thought all 4.3 were coil packs? Maybe that’s the Ford 4.0 I’m thinking of. Anyhow be CERTAIN you have ignition when you need it.
If all the basics are there then it is time to get more involved. If it comes to that save the shotgunning method of replacing parts and get yourself to a dealership and get it diagnosed.
I’d also install a vacuum gauge to a manifold cavuum source. At idle a good, strong engine should produce very close to 20 inches of vacuum. Less than say 17 and I’d be looking for exhaust restrictions and incorrect timing, along with a weak overall engine.
GM TBI fuel pumps run 12-14 psi I have seen a few with psi but not enough flow. it should be a pint in 30 seconds. A weak coil can cause this problem. double check your plug wire order. these are the best places to start.
I hear what your saying Riveratt. I’ve had a couple that the throttle position sensor was getting weak and they did this, hardly any excelleration or a missing and uneven run. I know theres big diffrences in years so i agree the best thing to do is put it on an analizer, saves alot of time by giving codes on what the problem is. A few of the auto parts stores give keys away with instructions on where to place this key in the receiver under the dash. When this is done it reads out a series of short and long flashes. It repeats itself once it goes through the complete series of flashes to see them again. Write down the flashes short and long and tell the person at the counter what the series of flashes is, they can then look it up and alot of parts stores will help you and watch the flashes with you. If this dosen’t solve the problem find a reasoanable service station or auto shop and put it on an analizer. Check and see if all the vacume lines are plugged in or are cracked, this will make the engine run unevenly too.
I’m not aware of any fuel injected engine that runs that low of pressure. The following is copied from the GM service diagnostic chart.
Quote:
Start the engine and observe fuel pressure reading. It should be 400-440 kPa (58-64 psi).
Quote:
I’m not aware of any fuel injected engine that runs that low of pressure. The following is copied from the GM service diagnostic chart.
Quote:
Start the engine and observe fuel pressure reading. It should be 400-440 kPa (58-64 psi).
Double check your specs for year and fuel injection style. GM TBI (Thottle body injection) uses low fuel psi. I have been a tech for over 10 Year and have worked on hundreds of GM TBI vehicles.
Plugged converter…. 
I appreciate all the help, did want to mention that this is a 92 not an 02. Whats the best way to check fuel pressure, is there a specific tool? I am gonna head out and double check the compression, but as far as I know it should be in good shape.
I would have to doubt that its a sensor. Cant say for sure but it revs just fine in park and will drive in idle, its just when you give it gas that it pauses and sputters.
If anyone in the immediate area feels like performing a magic trick and fixing it, I will give up my other truck. 88 Ranger
Yes you do need a special adapter fitting for your fuel psi gauge. The easiest place to check it is at the fuel filter. Watch the psi when you are driving it it should not drop.It may fluctuate a couple of psi, but never below 10-11psi.
The cat. converter is a good place to check also. an easy test is that the pipe should be hotter behind the converter if it is working properly, or at least the same temp if it is not plugged. It will usually be hotter in front of the converter if it is plugged. If you suspect the converter disconnect the exh before the converter and drive it if it clears up thats the problem.
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