2500 RPM limit

Discussion in 'General Discussion' started by reboosted, Feb 2, 2019.

  1. reboosted

    reboosted Full Access Member

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    Looking to see if anyone has had this issue. I just finished installing new head gaskets and now the engine will not rev over 2500 RPM without popping and banging - This is with the accelerator floored. There are no knocks or ticks in the engine (other than the loud ass injectors) and it seems to idle OK. Here's what has been done to the engine:
    gutted front cats (this was done well before pulling the heads)
    heads milled .008
    LMS head gaskets
    New head bolts
    New pushrods (Jesel 3/8, 7.6, .080 wall chrome moly)
    New valve springs (Comp Cams LS style)
    New valve stem seals
    Screamin Demon coils
    JTSV Performance wires (in the correct order)
    Champion spark plugs

    While trying diagnose:
    No CEL or codes (checked with key and cluster procedure, just says done)
    new crankshaft position sensor (guessing with parts)
    new TPS (guessing with parts)
    reinstalled old coils to eliminate new one from being defective (acts exactly the same as with the demon coils)
    checked the spark plug wires are in correct order
    double checked the ground wire on the back of the passenger head
    Gently drove the truck to put new fuel in. Didn't help.

    Next steps:
    I can't get my code reader to communicate with the ECU. I am going to plug it in my other car to see if it has died. But it makes me suspect an ECU issue.

    Testing fuel pressure (gotta buy the tool).

    See if the exhaust has plugged up further downstream, neighbors probably won't like this test.

    Put the stock pushrods back in. Would the heads being milled make the pushrods too long, holding valves open, but letting the engine idle and rev to about 2500?

    The truck was running OK before pulling the heads but was using a lot of coolant. I did find a crack in the head and had it welded. And then they were milled.

    Are there any other grounds? I have checked the one on the back of the passenger head, the one on the block, fender, and frame going to the battery.

    Other than a Magnaflow cat-back exhaust the truck is stock.

    Any suggestion are welcomed as I'm running out of ideas.
     
  2. reboosted

    reboosted Full Access Member

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    Looks like I need a new code reader. Fuel pressure checks out good. Double checked the O2 sensors are plugged in.
     
  3. rottenronnie

    rottenronnie Active Member

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    Your stock pushrod length is 7.6" so the new ones should be just fine.
    Shaving .010" will do nothing to the rest of the valvetrain, in an adverse way as the stock hydraulic rollers have plenty of play to compensate.
    Unless someone has already milled them before you did but it would border on excessive!

    Whatever is miiled off of the block side of the head needs to come off of the intake face of the head.

    Did you install a new crank position sensor? (I didn't understand that part in your post)

    Based on your description, it sounds like a firing order issue.
     
    Last edited: Feb 2, 2019
  4. reboosted

    reboosted Full Access Member

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    I did install the crank position sensor and the TPS as they seem common issues that will not set a CEL or code. It does seem to have the same symptoms of a car with the distributor being installed 180 out - decent idle but no power. The towers on the coils are numbered as are the wires which are marked at both ends. I have arranged the plug wires as per the diagrams I have found here on the forum with #1 on the drivers side front of the head and #10 on the passenger side rear. I know they didn't machine the intake side of the heads. I'll hose the area down with some intake cleaner/carb spray while the engine is running to see if it reacts like a vacuum leak.
     
  5. rottenronnie

    rottenronnie Active Member

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    These things can take some time (been there MANY times).

    When you find the problem, it will likely be something simple.

    Best of luck.
     
  6. reboosted

    reboosted Full Access Member

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    Intake gaskets don't seem to be leaking. Next I'm going pull the exhaust and see if its plugged somewhere.
     
  7. Slitherbeast

    Slitherbeast Active Member Supporting Member

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    as difficult as it seems..... you need to check the firing order.....
     
  8. reboosted

    reboosted Full Access Member

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    Demon coils are back in. I'm posting pics to see if I'm not reading the diagram correctly. Wires 6 and 9 seem to have the same font so I used the logos to orient them. 2 can look like 7 if you cant see the whole number. Still runs the same. I did notice the some smoke coming from below the oil fill cap. There does seem to be oil being pushed past the cap. Ill clean it off and see if it comes back.
     

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  9. rottenronnie

    rottenronnie Active Member

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    8 & 10 on one side.
    5 & 9 on the other side of the (4-pack coil) is
    correct.

    Then 3,7 and 1 (one being towards the front of the engine), then
    2,4,& 6 as shown in your photos.

    Is there somewhere you could go to have the coils tested?

    Once they are proved to be OK, and the firing order is correct (looks like it is as far as the coils go), then you have to look at things controlling the coils.

    The "air-gap" on the cam position sensor is important, for example.

    Look for a pinched wiring harness at the back corner of the passenger head.

    I wouldn't be concerned with oil right now until all the cylinders are firing when (and like) they should.
     
    Last edited: Feb 5, 2019
  10. reboosted

    reboosted Full Access Member

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    I can check and see if A/Z still tests coils but I kind of doubt 2 separate sets of coils are having the same issue internally. I tried taking it on a short trip around the block to see if it would "relearn" something in drivability but the truck is soooo gutless. I have a small hump at the entrance of my garage, even with my foot to the floor, it couldn't make it into the garage. I had to pull forward and hit it with some momentum to get it back in.
     
  11. rottenronnie

    rottenronnie Active Member

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    If this is a second set of coils, no it's not likely.
    Did you check for a pinched harness on the Passenger head, rear??

    Could you pull a plug and do a quick compression test on one cylinder?
    I know it won't be accurate as the starter will be against 9 other plugs but, close enough for now.

    I've seen engines behave like that when a camshaft jumped the chain and went out of time. It wasn't a Viper engine though but something odd is going on here, that's for sure.

    Possible to post a quick video??
     
    Last edited: Feb 5, 2019
  12. reboosted

    reboosted Full Access Member

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    Ok, pulled the plugs to do a compression test and found this. All of these were installed new with the head gaskets. All of the dark ones are from the drivers side, all of the light from passenger. There is maybe 30 minutes to an hour of runtime on the whole set. Compression test will have to wait until at least tomorrow though, getting called in to work. My first guess is the O2 sensor on the drivers side. Second is a plugged convertor on the drivers side. The fronts are gutted but the rears are still there. I'm thinking about pulling the rear O2 sensors and seeing if the truck runs better by relieving exhaust pressure. Maybe even just the drivers side. Its just frustrating the this still thing will not throw a code/CEL.
     

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  13. Slitherbeast

    Slitherbeast Active Member Supporting Member

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    Is your truck an 06?
     
  14. reboosted

    reboosted Full Access Member

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    No its an 05.
     
  15. rottenronnie

    rottenronnie Active Member

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    Yes, one 1/2 of your engine's plugs look to be rather lazy and that could very well indicate plugged exhaust on that side.

    I have no way of knowing what kind of slope your garage entrance is on but even with 5 cylinders working, it should be enough to pull itself in. (?)

    Impress your neighbors and fire that thing up without an exhaust, go for a (short) drive and see if it springs back to life.

    Oil in the cap area (as you mentioned earlier) could be caused by a large increase in crankcase pressure.
     
    Last edited: Feb 7, 2019
  16. Kopack_05

    Kopack_05 Full Access Member

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    Has been a good read, and hope you solve the problem. Looks like Ronnie is getting you on the right path. After reading through all the posts, I have a few questions.

    You said a crack was repaired. How did you find the crack? by eye? or did an expert use dies for aluminum heads? Meaning, did an expert redo the heads. Have you checked for any bent valves?

    Basic question, have you checked the oil? is the crank case full of coolant?

    Seems unlikely two set of coils would be bad. But not out of the question is something else is wrong and shorting them out. Have you had them tested?

    It is easy enough to disconnect the exhaust and test and if that the problem, you should see immediate improvement.

    It sure doesn't seem like a lot of material to be removed from the head surface,, but it doesn't take a lot to cause the manifold to leak,, especial when you get into mixing and matching aftermarket gaskets. Did you use a factory thickness head gasket? I never had any luck with using carb cleaner for finding vacuum leaks. I prefer to use starting fluid.

    I'm curious to see how this turns out.
    You seem to be working your ass off trying to solve this.. so I'm just saying.. I don't know you, you don't know me, but there is no shame in having it toed to someone who knows these engines inside and out.
     
  17. reboosted

    reboosted Full Access Member

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    I compression tested #1 at 110 PSI (cold) but then my gauge quit holding pressure. Gonna have to see if its still under warranty. I bought a fresh set of plugs and put them in but I ran the battery low while compression testing. I have it on charge so it should be ready by the time I get home tonight. If it does the same thing I'll start on the exhaust. It ought to echo pretty good with the metal roof garage.
     
  18. rottenronnie

    rottenronnie Active Member

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    You should be in the 155-160 range but IF the tester is leaking and/or IF the battery is low, your results WILL vary.
     
  19. reboosted

    reboosted Full Access Member

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    I have a separate thread for the head issues: http://www.vtcoa.com/forums/f7/crack-68710/ with pictures showing the crack and work done. I never had coolant mix with oil or vice versa. It just used a lot of coolant and I could never find a leak either in the cooling system or compression/leak down testing. The truck did run fine before disassembly. I assumed coolant was going out the exhaust until I found the crack. I used a set of Fel-pro MLS gaskets, I believe they are stock thickness. Unfortunately the budget wont allow me to pay anyone to work on it.
     
  20. reboosted

    reboosted Full Access Member

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    I was hoping for more but between a suspect gauge, not being able to compare numbers from other cylinders (especially from the other bank) and possibly a restricted exhaust there's no telling. I'm eyeing cat-less mid-pipes if it turns out to be the rear convertor or an x-pipe and muffler delete if its the muffler. It would be nice if it was just a weird spark plug issue and its happy with the new ones but with my luck....