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Thread: Can’t figure out misfire/poor running new engine build

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    OldKota's Avatar
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    Default Can’t figure out misfire/poor running new engine build

    Fresh engine and new setup runs like crap and I’m lost..
    I really hope someone can give me some pointers, I’m at my wits end, sorry for how long this is going to be haha. Will not run right with fresh engine that I rebuilt. My truck is a 95 Dakota with 96 Dakota obd2 electronics that I installed years ago for custom tuning. It had a 408 already that was built before I obd2 swapped it so it had a small cam and was weak for its size But ran great for 23000 miles. In past years I’ve been upgrading brakes, suspension and driveline stuff to handle a supercharger, have averaged 2000 miles a year the last 4 summers up to the point of tear down and driven between modifications.

    This past winter I decided I had saved enough and this year was the year, in September of 18, I mocked up the Vortech centrifugal supercharger setup with front mount inter cooler and had everything running well but did not put the belt on the blower and only ran a few miles because it was just in mock-up and ran all summer fine and didn’t change anything electronic at that point. Then began tear down.

    My mopar performance r/t 2.02 heads got all new valves, springs, and hardware, along with a major porting job from reputable local company. I reused my stroker crank, rods, timing chain, oil pump and 2618 forged pistons. I installed a comp 236/242 114+4 lsa cam .579/.580 lift cam installed to 110 centerline per cam card (I hope well get to that later) my block machinist fit upgraded main caps and a girdle, studs and line honed and honed cylinders to akerly and child’s recomended grit, and installed new cam bearings freeze plugs etc. I assembled the engine with all new gaskets, lifters, gaskets etc. new pushrods measured and installed last and have a great pattern, new comp xd rockers. It is 9.1:1 compression with -+0.045 quench I did install a new flywheel (6spd viper trans has been in it for two driving seasons) but needed a better clutch to handle the upgrades, I got a twin disc manic clutch and the flywheel to match, the factory electronics run a crank pickup off gaps in the flywheel so the computer knows the engine position.

    Since the first startup it has not run quite right, I assembled engine and installed in truck, my ryan sent me a boost/start up tune for the new 2 bar map sensor, bigger injectors, and complete new setup. The truck started right up, I used break in oil and did not let the engine idle for the first 30 minutes, roller cam but wanted to ensure ring break it, once at base idlle it was obvious it had a very slight miss, I verified cam/crank sync with scan tool, and got an idle datalog off to my tuner, he made a revision and it idled great so time for first test drive, which it feels rough like an old farm truck, bad tip in response, engine feels shakey on acceleration but will pull up to 3,000rpm ok on light acceleration but feels shakey, ryan sent a new tune based off test drive from datalog and new tune feels better but still shakey/misfire feeling when accelerating, Ryan can’t see any issues based off datalogs, but I notice cylinder 2 plug black and sooty compared to the rest, I swapped fuel injectors, plugs, wires, cap, rotor, engine computer, verified valve adjustment, compression tested, cylinder leakage tested, running compression tested all 8 cylinders and find no issue, so I send him another datalog and he sends another tune which I upload think it’s gonna fix everything and it’s like I feel the tune change but the shakiness continues, I don’t believe I mixed up pistons to disturb engine balance and new flywheel is for neutral balanced engine, my compression tests came back 120 on all cylinders, (which I thought low but all even) leakage tests all only 5psi loss, running compression results same on all cylinders, I think I degreed the cam right but at this point anything is possible I guess. The one time I accelerated to half throttle and 3100? Rpm, trying to get 1 pound of boost it back fired out the intake hard enough that it turned on the check engine light for a throttle position sensor code. It was loud and not cool and ran terrible afterward untill it stalled, restarted fine and ran like nothing ever happened.

    I still get the sooty #2 plug, I’ve swapped cap, rotor, wires, injector twice, pcm, listened to injector with stethoscope, verified spark with hei tester, ran compression and cyl leakage, verified cam syn, verified valve adjustment, counted teeth on flywheel and find two cylinders MAYBE are off a tiny bit but have to assume slight error looking through starter hole and counting teeth watching the gaps, vacuum gauge reads a dead steady 8, if slowly increase rpm vacuum climb steadily up then spikes up further if let off throttle and on a quick blip it drops hard but comes right back to 8”. verified valve lift with dial indicator.. running out of ideas on what to check or where to look. I can feel the shakiness/miss but don’t really hear it out exhaust or anywhere blipping throttle in neutral, when driving it just feels shakey like a dead hole miss, if maintain higher engine speed it’s fine but throttle transition feels stumbly . The only thing electronic changed was srt4 map sensor which Ryan is aware of and the new gerko flywheel.. I was going to compare my new flywheel to my old flywheel to exactly compare crank pickup gaps but can’t remember if I actually did or just thought about doing it. Both flywheels made by same company.

    I did notice after doing leakage test and rotating engine by hand 100 times that there is some oil on top of the dished pistons, it doesn’t smoke and passes all tests, I get nothing but pure water in my catch can. The whole build has maybe 20 miles on it, after to backfire out the intake on one pound of boost at half throttle/3000rpm I’m scared but have retested everything again and have no ideas, feels like a dead miss when accelerating but fine at idle. I know the timing marks are different now then when I took it apart but assumed different cam degreed differently but now I’m wondering.. crank sprocket is 2 teeth clockwise compared to my old cam, I did degree it but wondering if I did it wrong

    World record post length here probably.. thanks for any ideas!!!!!
    1995 Dakota Club Cab, 408, 5spd, 8 3/4 rear end

  2. #2

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    The trouble I have with long posts is things getting lost but it's not you but me. Forgive me if I've missed something you've stated you've done.
    This could be a myriad of things and it seems you've checked for a bunch. A cylinder misfire would cause what you're feeling. Only reason it smooths out at higher rpms is because of a harmonic balance being achieved but the problem is still there as you've noticed. You.ve checked for vacuum leaks I can assume. Have you put a heat gun on each exhaust port to check for firing temp equilibrium? I believe you've said no valves were sticking.
    I'm going to assume your cam is put in correctly and all the piston rods are the same. A sooty number two can be a clue. That's where the heat gun would come in handy.
    .
    Your cam came with 4 degrees advanced and you put it at the recommended 110 center. You degreed the cam so its not upside down (don't laugh I've seen this happen when people have "mis-dotted" the dots without using a wheel or paid no attention as to where the distributor was) .
    I do know that if a cam is off by even one tooth, the vehicle will run pretty crappy as there are a ton of degrees either way with one tooth. It's rare but it can happen that the cam wheel is all wrong. You've synched the distributor and everything using no 1 cylinder as the marker?

    If it isn't air, fuel, timing or electrical, then all that's left is mechanical and unfortunately the only way to find it is tearing into the engine again.
    In the old days where I'm from, cams were not made of the strongest metals and would actually warp. We always had to check for this as a new cam was no guarantee of a straight one. You can imagine what made us crazy before we discovered this.
    Keep us posted. You'll find it.
    Last edited by arro222; 04-21-2019 at 11:56 PM.

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    OldKota's Avatar
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    Yea I agree long posts are hard to follow but I wanted to put in all the info, I did have a vacuum gauge on it and do not find any leaks.. vac gauge responds normally. I did put a infrared temp gun on each tube, cylinders 1&2 were about 250 all the rest were 350, cylinder 1&2 are closest to the front where the fan is and have the longest straightest tube before collector so assumed that was normal. I am also assuming that the cam is installed right, now definitely second guessing myself haha
    1995 Dakota Club Cab, 408, 5spd, 8 3/4 rear end

  4. #4

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    Quote Originally Posted by OldKota View Post
    Yea I agree long posts are hard to follow but I wanted to put in all the info, I did have a vacuum gauge on it and do not find any leaks.. vac gauge responds normally. I did put a infrared temp gun on each tube, cylinders 1&2 were about 250 all the rest were 350, cylinder 1&2 are closest to the front where the fan is and have the longest straightest tube before collector so assumed that was normal. I am also assuming that the cam is installed right, now definitely second guessing myself haha
    Two things. 1. Make sure the heat dot is at the back of the header outlet or take off the fan. Could be what you say but double check that they're cooler because they 're running rich.2. allowing that you used a correct timing procedure, did you happen to make sure you're cam points were correct by using a deck strap to check equal degrees at tdc at both sides on no 1? Did it all match the cam card after you were done?.

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    Duner's Avatar
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    I would double check the distributor position / cam sync. It sounds like it could be off, but that wouldn’t explain a sooty #2 plug.

    That sounds like the cam I am running, and with PCM I ran cam sync at +4* for best throttle response and idle manors and a whopping -9 for best horsepower.
    Duner
    4.7 Turbocharged CC in white - 12's
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    1999 Dodge Dakota R/T RC Turbo: 10.51 @ 130.13 MPH

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    OldKota's Avatar
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    There’s only one spot for the cam gear but 9 on the crank gear. When I was rebuilding the engine I installed it how I took it apart and then degreed cam and it showed a 114 centerline, rotated crank gear one and rechecked 112 center line, rotated one more and got to 110 per cam card, then checked each valve event at .050” and all lined up, not sure if the 114+4 threw me off or what, or maybe I degreed off the exhaust lobe instead of intake, not sure but all signs are pointing to cam timing off and I’d say that’s about how it runs, I’ve got some new gaskets ordered so that’s where I’m heading next, I’ll let you guys know what I find, thanks guys and I have tried multiple cam sync settings with drb3 and none make any difference.. I’ve tested everything on cylinder 2 and all cylinders pressure wise are the exact same..
    1995 Dakota Club Cab, 408, 5spd, 8 3/4 rear end

  7. #7

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    Quote Originally Posted by OldKota View Post
    There’s only one spot for the cam gear but 9 on the crank gear. When I was rebuilding the engine I installed it how I took it apart and then degreed cam and it showed a 114 centerline, rotated crank gear one and rechecked 112 center line, rotated one more and got to 110 per cam card, then checked each valve event at .050” and all lined up, not sure if the 114+4 threw me off or what, or maybe I degreed off the exhaust lobe instead of intake, not sure but all signs are pointing to cam timing off and I’d say that’s about how it runs, I’ve got some new gaskets ordered so that’s where I’m heading next, I’ll let you guys know what I find, thanks guys and I have tried multiple cam sync settings with drb3 and none make any difference.. I’ve tested everything on cylinder 2 and all cylinders pressure wise are the exact same..
    What size injectors are you running? Also, I've seen cam gears that were incorrect. The bigger the degree wheel the better but since you have the engine back in the truck you'd have to use a smaller one. Make sure you align on both sides of tdc. It does sound as if you have a pretty good miss that a faulty fuel sync could cause. I do know of a guy I met at Epping NH at N.E. Dragway this past summer who started off with 56lb injectors. Truck ran like crap. Cam not as long as yours at 220-236. I think he said he went to 32's and the truck cleared right up.

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    Duner's Avatar
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    Just another off-hand thought....
    if it’s a new build - how good are the grounds?
    Make sure there is no paint under the grounds, or it will have very weak spark, poor performance and not run under load for beans.
    Duner
    4.7 Turbocharged CC in white - 12's
    5.9 Turbocharged RC in black - 10's

    1999 Dodge Dakota R/T RC Turbo: 10.51 @ 130.13 MPH

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    OldKota's Avatar
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    Thanks guys, I have 60lb semans deka injectors per ryan and definitely have good grounds, I have additionals added and ground the block to bare metal and put dielectric grease on the ground points to prevent rust at time of assembly. Both solid points.

    I just realized I never added pictures of my before and after timing setup to the original post so am adding them now, I am quite sure that's my issue although idk what I did wrong. When I disassembled engine last fall, on tdc of the compression stroke the crank gear marks were at 12 oclock and the cam gear dot was at 6 oclock and the distributor rotor was point to the #1 mark on the cam pickup.

    When I reassembled the engine I installed it to the same marks I took it off in and degreed the cam, at those marks it showed a 114 centerline, I rotated the crank sprocket 1 notch clockwise and it then showed 112 centerline, and then rotated it one more turn clockwise to get the 110 centerline per cam card and then verified valve events @.050 because I thought I did it wrong and was strange I had to move slots over on cam gear.

    Last night I took timing cover off and noticed at #1 tdc compression stroke the cam gear and crank gear dots were at 12 oclock and the distributor rotor was pointing toward number 6? (180 off of number 1) which has me completely confused about how I did it because I didn't put it together that way I thought but from what I research that's actually correct?
    before dissassembly
    IMG_2629.jpg
    when reinstalling after degreeing
    IMG_2630.jpg
    taking apart last night
    IMG_2740.jpg
    1995 Dakota Club Cab, 408, 5spd, 8 3/4 rear end

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    OldKota's Avatar
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    any thoughts on this? I overthink everything and ive overthought myself into confusion at this point lol, I like to understand things not just throw it together, and if I make an error id really like to understand why, I know I can just rotate the dots back to straight up but idk what I did to get it off or how I degreed it wrong, I followed procedures I had printed off line very very closely using intake centerline method and then double checked at .050 cam timing is the only thing that could cause my low compression that's even on all cylidners at this point, I even loosened rocker arms 1 turn and rechecked compression with lifters fully pumped up and still showed 120psi on all cylinders, I should be at least 160 id think
    1995 Dakota Club Cab, 408, 5spd, 8 3/4 rear end

  11. #11

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    Quote Originally Posted by OldKota View Post
    any thoughts on this? I overthink everything and ive overthought myself into confusion at this point lol, I like to understand things not just throw it together, and if I make an error id really like to understand why, I know I can just rotate the dots back to straight up but idk what I did to get it off or how I degreed it wrong, I followed procedures I had printed off line very very closely using intake centerline method and then double checked at .050 cam timing is the only thing that could cause my low compression that's even on all cylidners at this point, I even loosened rocker arms 1 turn and rechecked compression with lifters fully pumped up and still showed 120psi on all cylinders, I should be at least 160 id think
    Certainly low compression can be caused by valves not quite closing or valve events that are off and happening too soon. As I previously stated, cam gears can be incorrect from the start.

    Based on your static cr any chance your cam is overlapping to the point of excessive bleed off? This would be mitigated with an lsa of 114 however. One way to check of course is to calculate your dynamic compression. Did you say how many degrees your intake closing angle is on your cam card? Just seeing if your DCR is inline with your SCR. Cylinder pressure is something entirely different and is always changing for a variety of reasons.

    You didn't rotate the cam independent of the crankshaft at any point right?
    As tough as double rollers are, I still would have used a brand new timing chain. If when dot to dot, your key should be at no place but 2 o'clock otherwise it's not indexed correctly. Also, did you slip in the distributor with the cam at 12 and the crank at 12 o'clock?
    Sorry, just throwing out ideas which just gets things more confused.

    I like to start at 6 and 12 for the cam and crank dots simply because its easier to align.
    Last edited by arro222; 04-24-2019 at 04:06 AM.

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    Soooo... last night I got to the gears, I set them dot to dot, installed checker springs for piston to valve etc and that was as far as I got. Tonight I threw on degree wheel and found true tdc with stopper and set up my wheel and dial indicator.. followed the same same procedure and came up with the same numbers I ENDED with last time I degreed it.. then it hit me.. the wheel must’ve slipped.. or maybe I degreed the exhaust lobe?? I did it with the heads off but obviously made an error somewhere... that’s the only thing I can think of anyway.. so I set up my rockers and checked compression.. 150 psi bone cold with throttle closed... ran the test 3 times on 2 cylinders., Haven’t driven it yet, but I reloaded my base tune which it idled poorly on originally and it idled great.. tomorrow I’ll set cam sync and get some datalogs recorded and sent to my tuner, but I think I’m gonna be good to go.. thanks everyone
    1995 Dakota Club Cab, 408, 5spd, 8 3/4 rear end

  13. #13

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    . I doubt you measured off the exhaust since its so much smaller but anything weird can happen when you're trying to think of everything. I'd believe your degree wheel rotated first. Glad you used some type of metric for tdc.
    I'd still of used a new chain. You can lose as many as 2* off cl and as many as 5* duration on an even mildly worn chain over a new one.

    I always thought this would be an easy fix once you delved into it a bit more. Good luck and let us know how she rips.

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    Well figured I’d update this, now that I’ve actually made some progress.. lol.. so turned out once I moved cam gears dot to dot a redegreed the cam it put my intake at 112 centerline but compression went up to 150 and seemed to idle better.. the better idle may have been placebo affect because the next day I drove the truck and it still ran like crap on acceleration.. rechecked compression and it was back to 120psi? Rented compression gauge from part store and went back and forth between the rented gauge and found out that my gauge was junk and stopped at 120 (well except for twice in a row right after I switched the gears dot to dot) the other gauge said 150 every time So at that point being determined i was dealing with a timing problem, I rotated the distributor drive gear one tooth and set sync with scanner again and that fixed my one plug that was getting sooty? Lol And fixed the poor running.., i put the distributor back in the exact spot I took it from, I engraved the distributor body to the block and took good pics during tear down, the only reason I can think of why it worked in the old spot was my old cam was two crank gear notches more retarded then where I was now?? Idk I didn’t build the last engine..

    I did go back in and installed a new timing chain and redreed the the cam and it ended up where I had it originally, I guess when I moved the cam timing and compression went up and it went to a 112 centerline I was thinking that retarding the cam would increase centerline but in reality advancing the cam does and to get to 110 centerline like the card says I had to advance it which put it back to where I started, guess I should’ve degreed it before moving it and getting excited by my compression gauge that worked three times in a row out of the blue..

    Anyway onto the next problem.. at this point it ran good, started good hot and cold and ran good up to 3,000rpm, if accelerating medium hard it would still pop out the intake hard at that point.. my tuner thought it was in the tune and was working with sct to hopefully get the to add a function to my 96 computer to allow him to change something with the tps and map sensor to correct it, but then I noticed when i hit 3,000 lightly it wouldn’t always pop out intake but almost felt like a rev limiter and after playing around with it noticed I couldn’t even free rev In neutral and get past 3,000, after some messing around trying to convince myself it actually was tune related I decided on a whim to raise my msd box rev limiter that was set at 6,300 to 9,300 and then could immediately for the first time on new build it revved up to 5,200, set down to 2500 and verified it worked there, then went to my original spot where it seems to be working fine now..

    Buuut after all that now it runs great except if I step on it too hard it will pop out the intake still, could happen anywhere between 3&4,000 rpm, but I do believe the rest will be tuned out when my tuner can get sct to add the function he needs and I’m just happy to be driving at least..hope to have fully dialed soon. thanks again for all the help everyone!!
    1995 Dakota Club Cab, 408, 5spd, 8 3/4 rear end

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    99dart's Avatar
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    Boy I feel your pain! Glad you got it running better! Nothing like having Bugs in a new build!
    99 DA CC R/T
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    Quote Originally Posted by 99dart View Post
    Boy I feel your pain! Glad you got it running better! Nothing like having Bugs in a new build!
    I expect to have some bugs on a build of this magnitude, hopefully this will be the last one. Its just dumb luck that I just so happened to have 3 separate problems all causing almost the same thing
    1995 Dakota Club Cab, 408, 5spd, 8 3/4 rear end

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    Corey's Avatar
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    it is solutions to issues like this that makes this place worth investing, year after year. Thank you for posting your results.
    DRTC #1176

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