No they kept jumping around the numbers all seemed higher with the propane but I never saw any steady numbers

 

So what does that mean

I'm not sure what to do from here

 

It means the oxygen sensors are capable of responding to a "forced" rich mixture. It also means that the lean mixture that B1S1 is reporting, is likely causing the P0300, AND the backfire.

The low MAF reading, along with the results from the tests that you've done, indicates there is most likely air leaking into at least one cylinder, (and likely more due to the P0300), on bank 1, (driver side). When this happens, it is referred to as "air intrussive" meaning the engine is consuming air that is not passing through and being measured by the MAF sensor. Usually, but not always, air intrussive will set a DTC. I've had a couple of times where the leak is not large enough to meet the criteria necessary to set it.

There is either too much air, or not enough fuel, but only on bank 1. An injector balance test would confirm or eliminate a restricted injector as the cause, but that requires a high dollar scan tool. Unfortunately there is no practical "work around" for that test. So, you'll need to do a little "exploratory surgery". Very doubtful, but not impossible, that the throttle body gasket, or plenum gasket are the cause because they are not close enough to the intake ports in the lower intake manifold to affect only one bank, or one cylinder. I would suspect a leaky intake gasket on the underside, which will require very carefully removing the lower intake and inspecting the gasket. Felpro MS98002T is the gasket set that you'll need.

 

ok couple of questions

i replaced lim gasket (felpro ms98002t) and the injectors (delphi fj10565) in 2012 about 50,000 miles ago (checked amazon history for date and part numbers)

do you think it can go bad that fast?

could it be possible that the intake bolts have come loose and just need to be tightened?

would it be a good idea to pay someone to do the injector balance test before replacing the lim gasket again (which i don't really want to do)

 

Anything is possible, a piece of crud can clog an injector in a heartbeat. All it takes is something smaller than a grain of sand to get past the fuel filter.


When you did the LIM gasket, did you:
1. Chase the threads on the intake bolts.
2. Chase the threads in the heads.
3. Put sealer on the intake bolt threads.
4. Use the correct tightening sequence on the bolts, (3 steps).
5. Use the correct torque on the bolts, (132 inch pounds).


If you missed even one step, the bolts can loosen up and cause a vacuum and or coolant leak. If you have an accurate inch pound torque wrench, you can try tightening them. After 3+ years and 50K miles, the rubber is not real pliable. Not sure what kind of success you'd have, but it can't hurt to try. Make sure you tighten them in sequence.





Injector balance test takes roughly an hour and a half, so it depends what your local labor rate is. I'd say stop by the shop and I'll do it, but it's about a 3 hour ride

 

I don't post much as I'm a old school wrench twister that started around the time a SB 327 was Chevy's power house and I have too double check myself on the things I post on newer engines way too much so I don't mislead somebody. But in this case I can.

Back in the early to mid 80s I bought my now EX wife a mid sized Chevy car it had the 2.8. Months after I bought it the intake manifold gaskets went out. Being the 2.8 of that era it oozed oil out of every seam it had.

Pulled the engine and did a head, bearing, oil pump and gasket refresh on it. It ran like a champ for about 30 tho miles then cyl 2 & 4 plugs showed they went lean. As we never could figure it out 100% we just ran it with a slight miss and a little lower power.

Around 10 tho miles later the intake gaskets went again upon removal of the intake we noticed the front of the gasket had slipped just a bit when I had did the refresh, over time the lower part of the gasket around the intake ports had weakened and was sucking extra air.

new gaskets and she ran like a top with no miss for another 20 tho miles until my daughter and her boy friend at the time was T boned in Colorado and totaled the car

 

1. I could not find the correct tap so NO I did not chase the intake bolts
2. I don't remember removing any head bolts
3.I used red loctite on the bolts
4. Yes I used the correct sequence
5. I used the correct torque

So I think I will try to torque the intake bolts again
And I will see what my local shops will charge for a injector balance test since you won't come to Illinois for me lol

 

Head bolts would only apply to my post as I did a more or less total refresh and would have nothing to do with the intake gaskets leaking at the lower points.

Red lock tight is the maximum thread lock - usually it's used for bolts that you never want to move again - you may have hell budging them - Blue can be tough to move but it can be done.

In one of our old buggy's was the last time I used red and only did because I was in a bind and could not get blue in my home town at the time. It was on a old VW crank where the flywheel attaches.

When removing the large bolt the next time for a rebuild both the bolt and crank threads were peeled out. ruined the crank and torque bolt

 

5/16 x 18 thread, you'll need a tap, and a die. If you did not chase the intake bolt threads, or the threads in the heads, the old sealer that was left on the threads will cause the bolts to bind up when you install them and the actual torque that you applied was substantially less than spec. Loctite red 242 is a thread locker, and it won't do any good to try to re-torque the bolts now because there's too much crud on the threads, (you'll never get an accurate torque applied). Torque spec is 132 inch pounds, (11 foot pounds) which is very low torque to begin with. Some of the intake bolts go through the head and into the valley, (there's oil in there). The thread sealer keeps oil from travelling up the bolts. With such low torque, they can "walk" out from normal engine vibration, and the oil makes it easier.


It wouldn't surprise me a bit if the gaskets are leaking, and at this point, you have no choice but do the job correctly before it causes MORE problems. Tell the boys at the auto parts store that you need Loctite thread sealer, not thread locker.

 

Ok sorry for the confusion but it was blue loctite the color of the bottle is red (not sure why they would do that)

Also I forgot that I still have the old spider injector that I took out. I would assume I could swap them out to see if that's the problem instead of paying for a injector balance test