Alright, so I have a 1995 Chevy blazer with the 4.3 vortec engine. A while back I had a problem come out of no where where I would get it around 1500rpms, then it would bog down to around 1000rpms very hard and quickly and it felt like a massive misfire. After a few months past of it sitting due to switching jobs, I have finally decided to dig back into this mess. I have done a lot of searching in this forum and around on google and have not yielded and cases that are the same as mine, or any cases that I can take a lot of applicable information out of. I just put in a new fuel pump today, thinking that had go be what it was. All was good and it was running, although pretty weak, until about two hours ago, when it started bogging down again. This time not only did it bog down, It also stalled as soon as I got it off the road. It fired right up after it stalled. But them started jumping up and down rpms by about 500 either way. I got to a parking lot and it was actually accelerating on its own and I wasn't able to stop it until I turned the key off. I happened to have a fuel pressure tester hooked up to it, and as It was bogging, I did not see much of an effect on the fuel pressure, so I ruled out fuel pump. In the pasg 6 months i have replaced the regulator, spark plugs, wires, cap, rotor, fuel pump, filter, tps, iac and the egr. I think there has been more, but that's all I can think of at this moment. I also have code P0441. Any ideas on what step I should make next would be very, very appreciated.
Thank you all,
Josh

 

Almost sounds like a vacuum leak. look and listen

 

I am pretty confident that it's not a vacuum leak, although I very easily may be wrong. I've sprayed every single in of the engine with starter fluid at one time or another and have done an at home smoke test on several occasions. And today I also just replaced the crankshaft position sensor, and it did not fix the problem.

 

I have been trying to find a vacuum leak on my 02 4x4, but can't find one. Last Night I noticed several bolts that secure the throttle body to the intake were pretty lose. I tightened them up and will see if they fixed my little problem. Mines not running near as poor as yours though. I wonder if it's your coil? I am not a mechanic at all, just butting in with some thinking outside of the box ideas. When you find your solution please post so we can learn from you.

 

I appreciate the input, at this point any ideas could help. I actually did put a new coil on it after getting it tested several times and it coming back a hair weak. I also had my icm tested at this time and it checked out pretty well. And trust me, I will be back with my solution and a celebratory post haha

 

Before you do anything else, you MUST have the crankshaft position sensor relearn performed with a capable scan tool. The el cheapo ones at the auto parts stores can not do it. If/when the crankshaft position sensor and or timing cover is moved, removed, replaced, or disturbed in any way, the relearn MUST be done. Without doing it, the engine will still start and run, but injector timing, ignition timing, and misfire data will not be correct.

1. Does the check engine light come on with the bulb check, and then go off?


2. Does the check engine light stay on or flash while the engine is running? If so, retrieve the DTC's and post them here in the order they are retrieved.


3. Check fuel pressure and leakdown at the service port, and at the fuel filter outlet, and post all 4 readings. This thread explains: https://blazerforum.com/forum/2nd-ge...eakdown-88305/


4. These engines are very fussy when it comes to spark plugs, distributor cap, rotor, & fuel pump, they need to be AC Delco. The spark plug wires need to be good quality, NOT a "store brand".


P0441 is indicating a problem was detected in the EVAP system. EVAP DTC's can be difficult to diagnose. This link offers a few suggestions: http://www.obd-codes.com/p0441 If this doesn't help, it might be best to have a pro look at it, (you can waste a lot of money guessing).

 

I appreciate that post very much, my fuel pressure when first turned over gets up to about 60 psi, then when running it's around 55psi. After I turn if off it does leak down fairly quickly. I just put in a new fuel pump on Friday due to its failure. I also just tested the map sensor today and it checked out well. I had the icm tested today at autozone, it came back bad but they had to use the test for the one with vertical towers, does anyone know if that will skew the test, or is that a pretty reliable test? I also took my fuel filter off and inspected it yesterday, there wasn't much resistance when I blew through it. But back to that leak down problem I have, I doubt that has anything to do with my current problem, as i have always had that problem and the current issue with how It runs started more recently. And the engine light that's on is only the evap light and it's constantly on no flashing. Let me know if I left any information out

 

Leakdown is a problem. On your 95 with CMFI, It must remain above 50psi for at least 10 minutes after the pump shuts off. 60psi at the service port, without knowing what pump max output pressure is, tells you very little. If 60psi is all the pump can build, you WILL have problems. The pressure reading at the service port only shows regulated pressure, or pump max output, whichever is lower. You need to test it at the fuel filter outlet as described in the link.

 

Okay, I haven't had a chance to look at that link quite yet, I'll get on tonight and see what it says about attaching at the fuel filter, which should be easy because I have it off right now, I just have to get the connector because mine is just the standard Schrader valve connector

 

There is a parts list to build the adapter at the end of the article.