RhinoAL

Ok, I would like to start off by saying I would greatly appreciate any help possible. I am really stuck and it is the most frustrating thing in the world. So I have recently rebuilt my 4.6 npi engine (first real engine build on my own) and in the process I had replaced the npi heads with pi heads, stage 1 trackmax cams, and long tube headers. When I finally had everything buttoned up and went to start the car. It fired up on the first try or 2 but seemed like it struggled to stay running. I turned it off and tried again, it turned it over and the same thing ran (fluctuating rpms) for like 20-30 seconds then died. From that point it would not start again. I had really weak fuel pressure so I got a new fuel pump. Fixed that problem. I had my car tune set up with the PATS system disabled, so I know it cant be that. I just replaced my crank position sensor today thinking that maybe thats causing it to not fire properly. So to continue the starter sounds sort of labored when I try to turn the engine over but I am not sure if thats because I have heavier duty cam springs installed. Also I notice a backfire-ish sound coming out of the headers. So I jumped the car off of my dads truck so I know that I for sure had enough juice to start the car. When I would hold the throttle half way down it would start to smooth out the starting sound but didnt seem like it was actually starting or running . I have also checked the plug wires multiple times to make sure that they are in their proper places. Im not sure if it is a timing issue or what. Im fairly certain that I had installed the cams properly and all that as well, but who knows. Im surely not saying that I couldnt have overlooked something. Ive read a fair amount as I have done lots of internet searches, but nothing really matching up to what I am experiencing. Again any help would be greatly appreciated.

98BlacknWhite

Backfiring-like sound and fluctuating RPM's on a rebuilt engine? I would say double check the plugs, wires, etc. Honestly, it sounds like a bad tune (so fiddle with the tuning a bit with/without the system again). We are also under the assumption you are without a doubt that the rebuild was done properly? The problem sounds electrical, BUT don't rule out the quality of the rebuild just yet unless you are positive the issue is not internal.

I am passing on giving a sure answer, but just my two cents from "similar" issues with my Stangs.

jwog666

get a scan tool and check for codes, then pull the plugs and check to see if they are fuel fouled (wet with gas), chances are since you replaced the cams, and didnt get it tuned, it will run like crap. start there

WJL

Sound like you could be a tooth off on the timing chain or chains

RhinoAL

Alright, I know it has been a while. I have been busy with a bunch of other stuff sadly but I have managed to reset the timing, put it all back together, and still nothing. No firing. No flashing theft light either. I am getting fuel to the rails as well. I just dont know where to look next. Any help would be appreciated.

jwog666

codes, check for codes, as stated before.

RhinoAL

There are no codes showing up as the battery had been off for a long time. So since I can't run it, there is no opportunity to throw any new ones, which is a huge part of the problem. It's an awful cycle.

Chromeshadow

No codes, so I'd go old school. Did you check the timing with an inductive pickup? If so, you can use it to make sure each plug is firing. I'd check compression on each cylinder and check the firing timing to make sure you compare #1 is firing at tdc on the compression stroke. I'd also check for vacuum leaks with a vac guage. Have you checked fuel pressure and volume? Is the firing order set correctly? All plug wires going to the correct plug?

jwog666

i hate to say it, but taking it in to someone with a good scan tool that can run the key on engine off self test might be the way to go, this will test certain componants and circuits and will throw codes if they fail. most cheap code readers will only pull codes that are history codes. so maybe tow it in and have them run the koeo, test and at minumin give u some codes to go off of. you could be testing things for days otherwise.

RhinoAL

Ok, so I have a scan tool and I did a koeo diagnostic. It came up with p0605 pcm code. I dont know if that is my problem as I dont know much about it, but I will start reading about it.