I'm sure its not an issue of load on the motor . I can drive it very slowly and reach 28 or I can really get on it and go to 28 mph and the results will be the same . also ive driven it up to 55 mph and then coasted all the way down 28 and will only stop blinking when I cross that threshold . I will try that test tomorrow though.

I did notice when changing spark plugs for the second time (to 41-993's) the #5 plug which im having the issue with does seem to be firing ( when looking at it , it was all black except for a small area around where it fires was ,for the lack of a better term , whiteish ) . Maybe the spark isn't strong enough or its getting too much fuel in that cylinder ? Course I would've thought the fuel press test would've discredited that.

 

well I messed with it again today and might go back to it again later after engine cools off a bit . I tried putting a load on the motor to try and force the SES to start flashing , I revved it to 2000 rpm (wouldnt rev any higher )in drive but no luck. I also checked each injector for resistance at the pins , book calls for anything in between 11-14 ohms ,mine were 12.4 - 12.6 ohms .

I even ran a vacuum test . I know sometimes they are tough to decipher but I'm running out of tests to perform without a scan tool. The test was done after it had warmed up 5 min or so and the results were at idle it steadily fluctuated between 18.5 and 18. When i snapped the throttle to maybe 2500 -3500 rpm it dropped to 5 inches then climbed rapidly to 25 inches and when I dropped the throttle back to idle ( over the course of maybe 2-3 seconds) it dropped to 16.5 then settled back in to 18.5-18 inches.

In my limited experience diagnosing vehicles and the time spent reading other peoples posts and reading other tech articles I'm leaning more towards something to do with the injectors , either giving too much fuel or not enough . I could pull the valve covers and check the springs but I'm kinda thinking that's a waste of time.

 

Did you try checking exhaust backpressure at one of the front oxygen sensors? It's possible the converter or something in the exhaust system is restricted.

 

how do I do that ?

 

You can make a fitting out of an old spark plug or oxygen sensor, (or you can buy one). Knock out the insides and connect a pressure gauge to it. WOT acelleration should not go above 1.5 psi.

EDIT: The thread is 14mm and you might be able to find a fitting with a hose barb on it at a good hardware store.

 

I may have found the issue !! In my mind I kept thinking of all the posts I read and all the tests I performed that seemed to check out ok and the only thing I kept going back to was the fuel injectors . So I came home today and went back on the internet and found an article about testing injector wiring. It showed me how to make sure the injector was getting power , I used a test light ,and back stabbed the injector harness at the metering body (with the key on )I tested each injector . All was good .

Then I had also read on here about doing an injector balance test with a glass jar. I know I don't have the proper equipment to measure flow and volume but I really only needed to see if I could energize the injectors to see if there was fuel getting to the cylinders . I also figured that if there was a big enough difference in flow I would at least notice that. So off came the upper plenum for the third time and then I reconnected the fuel lines to the metering body and kept the harness unplugged . I did however take off the top half of the harness plug off so I could reference the positive and negative side of each injector . That may or not make a difference, but I kept it the same anyway . I would turn the key on to pressurize the fuel lines with the pump .I would also pull out the poppet from the manifold and put into a glass jar. Then I hooked up a lead from the battery to the positive side of the injector and I took another lead ,connected it to the other side of the injector and I would touch the end to a good ground (firewall to engine strap). And then repeated the steps for each injector .

What I found was the #5 poppet nozzle is stuck closed. I can hear the injector tick like its working but no fuel . This is also the cylinder that's misfiring , SURPRISE, SURPRISE .I know that you guys are probably going to tell me i'm way overdue for the upgrade to MPI anyway and that's probably what I will do but just for info sake , would I be able to clean just the poppet valve ? And how ? Is there anything else I would have to do ,to put the MPI system in ,for example tuning or recalibrate something or is it a true bolt in and go type of thing ?

 

Nice bit of diagnosis! There is an easier way to activate each injector, but you did just fine! As for cleaning or fixing the stuck poppet, don't waste your time. That's one of the reasons GM came out with the upgrade... it totally eliminates all of the poppet valves.

Besides the new injector assembly, you'll need the new style bracket that holds the housing in place. Some injector kits come with it, others don't, you'll have to check. Replace the plenum gasket and oil the O ring at the top before you install the plenum. The unit is truely plug & play, no muss, no fuss. Be very careful with the placement and routing of the new injectors and lines. Read the instructions!

 

delphi MPI unit is on the way !! I hope this is the end cause I'm flat broke now.

 

PROBLEM SOLVED !!!! THANK YOU Captain Hook and Leanne Bravada. The MPI unit went in easily , and it runs great . We have put on about 250 miles with no issues or service engine soon light . I didn't think that thing would ever go out. I will fill it back up this weekend and post my mpgs .

 

Great!