Engine Only Running on 4 Cylinder

[HEMIDON]

I finally got my motor started after my most recient swap. It idles and revs good but sounded like a 4 cylinder motor. It seems to only be getting fuel on cyl 1,7,2 and 8. I unpluged the fuel injectors on 3,5,2 and 8 and got no change in the way it runs. If I unplug 1,7,2 or 8 the engine has a distinct miss. I pulled the plugs and they were dry so I figure it's not an ignition issue. I pulled the valve covers, there are no issues with all the rocker operations. I pulled the rockers, looking down the push rod holes I validated the MDS lifters (ones with snap ring) are in the proper holes. I checked all the grounds to the block and body. With a DVO meter, at the injectors, I checked for a ground and power.

Is there a sensor that can cause the problem? I hope it's not something with the PCM. Does anyone have any suggestions on what the cause could be.

[Redfox0099]

Why do you have MSD lifters in a 6.1L?

Posted via LXFMobile

[HEMIDON]

^^
MDS in 6.1...Why not ?... I did it more so because it could be done.

[Centurion]

6.1L blocks don't have the passages for MDS as far I know... But it only shows RT for his car so I don't know all the mods you have.

[Redfox0099]

^^
MDS in 6.1...Why not ?... I did it more so because it could be done.

Don I say this with all the love I can muster.....


With as much crap you have gone through with motors recently Why wouldn't you not just put one in normally and just let the damm thing be????

Posted via LXFMobile

[HEMIDON]

A 6.1 block does have the passages drilled and machined. From the factory,the holes have plugs in them rather than solenoids like the 5.7. If it was a MDS issue the miss would be on 1,7,4 and 6 , they are the ones that are firing

[RobAGD]

Don, if it idling then use a crayon on each header pipe and see if you are getting any heat at all from the cylinders.

Did you swap the cam ?

if you did what cam did you stuff in ?

I take it you are still using your 5.7 PCM and Harness ?

What injectors ?

-R

[Hemi31]

Is the MDS harness plugged in?Actually scratch that....the MDS cylinders are 1,7 on the left side and4,6 passanger side and you really can't screw up the lifters.I would try swapping an injector.I just recently saw a similar issue with 8(yes all 8) injectors plugged from sitting.

Posted via LXFMobile

[HEMIDON]

Rob, here's what I have....

Stock 6.1 except cam swap
Spartan Cam installed straight up
MDS lifters with Solenoids
Stock cam gears and chain
Crank and Cam sensors from 5.7
Yellow cap Injectors and fuel rails from my 5.7
Tune unchanged from 5.7 with SRT MAX cam

.I would try swapping an injector.I just recently saw a similar issue with 8(yes all 8) injectors plugged from sitting.

Tonight I'll try swapping out all the injectors for the ones from the 6.1. Once it's running I'll try to data log P/Ws. Last night the A/F was ~14.2. The A/F did not change when I unplugged the ignition on the mis-firing cyl's but did on the running ones. I'd like to see if the PCM is firing the injectors. I have an induction pick up tach, will the injector power feed have enough load to trigger it?

[MadCharger]

Don - Did you try disabling MDS and EGR when loading the tune, and see if the same occurs?

[HEMIDON]

I did not make any changes to the tune. The 5.7 was running with EGR off and MDS on. I figure the tune should be pretty close to right. It was scaled for 6.1 injectors and I was running a 6.1 intake manifold before. There is only 17 cube difference from what I had to a stock 6.1 and the compression ratio is the same. Stock 6.1 heads should flow close to the same as my ported 5.7's. I figure the exhaust should be close too since I now have stock 6.1 from heads to tails vs the smaller 5.7 with LT headers. Both exhaust systems do not have any cats. The only tune issue might be the 112CL on the Spartan vs the 115cl I had on the SRT MAX cam, durations are pretty close.

[MadCharger]

You may want to just try disabling MDS via the Predator to eliminate it as a suspect......

[HEMIDON]

I doubt disabling MDS will change anything. The cylinders with MDS are the ones that are running. If the motor was from a '06 or 07, for a test, I'd swap out the SRT PCM that I got with the motor but, it's a '08.

[MadCharger]

You're probably right - but for the 5 minutes to load the tune without it, it's worth trying IMO. It's the easiest thing to eliminate, even if it is the least likely.

[hemituner]

^^
MDS in 6.1...Why not ?... I did it more so because it could be done.

If You use MDS lifters in a 6.1 block all you need to do is just put the solenoids from the 5.7 in and even with them disconnected the engine will run normally. If you leave them out its in 4 cyl mode because it IS bleeding the lifter off.
Hope this helps
A.J.