New Injectors and Distributor, Now Random Misfires

[CTX-SLPR]

I might suggest it to the shop but my house is in the actively on the market stage so yesterday's attempts were the last gasp of me doing anything for a few weeks. I tried the larger O-rings on the end but they pushed out into the intake and I threw them out.

 

[98K2500burban454]

I am having the same exact problem, I have the same rig and installed the same injectors this last weekend. I am now getting a bank 1 lean code and a rough idle with LTFT at 25. I did not replace my distributor/cap/rotor but mine are not very old and looked pretty good upon inspection, I know sometimes they have issues you cannot see but I do not expect them to be my problem. I also didnt initially replace the upper plenum gasket, I am considering that now. I also have recently replaced my MAP, IACV, EGR, TPS, Air Filter, Mass Airflow, PCV, upstream 02 sensors (CATs removed), Fuel Pump, Fuel Pressure Regulator, spark plug wires, fuel filter, and probably some other stuff I missed. I would like to pick up where this thread left off and try to solve this issue so when CTX-SLPR gets back maybe we can have an answer. I love this suburban and would love to get it back to running the way it should. I am going to take the plenum off again and see if I can tell which injectors may not be seated properly. Any advice would be much appreciated.

 

[98K2500burban454]

Let me know if I should start my own thread on this topic, I dont want to hijack CTX-SLPR's thread, we just seem to be having the exact same issue. Thanks!

UPDATE: Pulled the plenum off. Looks like all the injectors are seated evenly. The gasket looked to have some gasoline on both sides of it leading me to believe that it was leaking between each injector port. I am considering adding permatex motoseal to each side of a new gasket, any recommendations for or against that? I am hesitant to remove the injectors and add the second O ring because they look pretty well seated to me, it would be hard for me to believe that really any air at all would be passing those O rings. Pictures below show how all eight are installed on the fuel rail. Let me know if any other pictures would be helpful. Thanks.

 

[gwolf]

The upper intake manifold doesn't require huge torque on the bolts so I wouldn't think that would be that critical or likely to be a problem. I used AC Delco injectors from Rock Auto and they even came with the mysterious missing clips. I also double checked my Orings as the injectors didn't seem to seat like the originals but after checking there was really only one way for them to go. I also replaced everything under or behind that manifold with AC or Delphi stuff, and I mean everything. I have had grief with intermittent problems with made in China crap parts so no more. Now it runs like new and I have a baseline and spares to swap when diagnosing. I know it's a frustrating learning curve but once you have it all figured you'll have it dialed and memorized. In the end it was cheaper for me to figure it out and buy a Tech2 than send it to a mechanic. The mechanics don't seem to want to learn these trucks anyway and you really have to pay attention on that job, anything missed can cause a problem, something as simple as a leaky vacuum hose to the Fuel Pressure Regulator. Honestly I don't trust the mechanics, there always in a hurry. Keep your truck, once it's sorted you'll have it for a long time.

 

[CTX-SLPR]

My turn to come back around to my stuff.
The shop found I crossed 3 and 7 plug wires so there's a lot of the misfire issue (dumb on me) but the MAF was also bad. They also think they found my missing injector connector wire clip rattling in the CAT. I'll probably pull the pipe off and dump it out. So glad it didn't seem to do any damage on the way through.

I've not picked it up yet (been house hunting in TX) but there was a definite difference between having the O-rings installed with the retainer and the second O-ring so I'd say something needs to be different with the install instructions on the 5-0 Motorsports injectors.

 

[98K2500burban454]

Sounds like you may have found a solution. I am still fighting this one. I ended up pulling the plenum off and replacing the upper plenum gasket. Using a torque wrench to put it back together I found that originally I was probably over tightening the bolts, on mine the book calls for two passes in the correct order, first time around at about 6ft-lbs and final pass at 10ft-lbs. While I was in there I double checked my fuel pressure regulator, vacuum line, and injectors being seated properly. Upon re-assembly it seems to run well until I get into closed loop, then it wants to idle between 500 and 600 and sounds like it is about to stall. I was getting a Bank 1 lean code due to a small upstream exhaust leak (i think) so to rule that out as the source of a lean condition I unplugged the 02 sensors. The low idle issue remains with the 02 sensors unplugged, lean code has gone away. The problem really seems like a vacuum leak but I cant find one, I have hose clamps on everything and starter fluid does not cause any sort of increased RPM. The vehicle stalls periodically when shifting into reverse, or reverse to drive. This problem started when I got it back from the transmission shop. The first torque converter they installed failed almost immediately so they had to rebuild it again under warranty. I cant help but wonder if there is an issue with the new torque converter. Unfortunately, or fortunately depending on how you look at it, the problem with the low idle remains even in park and neutral so it leads me to think there is still an engine issue. I had adjusted the butterfly in the throttle body originally to make sure my IAC was within the adjustable range, maybe I need to crack it open a little bit more after all the sensor swaps and tune up.

 

[gwolf]

Did anybody check to see if the input vss on the transmission is reading and correctly providing the ECM the right data to adjust engine load when you go from park to reverse etc? There a lot of other sensors as well that send the ECM signals to adjust fuel based on load.

 

[CTX-SLPR]

Looks like I melted/damaged my drivers side (bank 1) cat in the process trying to hunt down the misfire (should have checked the wires more closely). CA specific cat is $1750 though a Federal cat is still $1150 so overall expensive.

 

[CTX-SLPR]

So it sucked the second O-ring off of the end of the injector on the way home last week and I took it to a shop and had them call 5-0 Motorsports. To 5-0's credit, they are super helpful after you're in the frying pan but don't give you the instructions to try to keep you out of it. They seem to have switched to the suggestion of putting the thicker O-rings on and either a very tight spacer or the "pintle caps" back on to hold it in place. Oh and I had also not torqued down the rotor to the distributor properly and it was starting to get a lot of run out. I think I need to reset the fuel trims to get the idle to smooth out but it's running without codes and cleaningly again.

 

[yevgenievich]

I found that alot of non factory injectors sit too low on the lower intake manifold. My current injectors actually have spacers on the bottom to keep them from falling down too far. It slightly obstructs spray pattern, but better than issues with sealing.