96 misfire under load, help please

[96twofiddy]

I have a 96 7.3 5 speed with 6 position switch and exhaust but otherwise stock as far as I know. Under a load probably most prevalent with the trailer at about 1500 rpm or so until about 2000 rpm or so the truck bucks pretty bad like it has a misfire. Truck has done it for awhile. I replaced low pressure lines, replaced hpop o rings, valve cover gaskets and connectors. Still no better. Also truck smokes pretty good on cold start, first diesel not sure if it is normal. Also passed buzz test. What could it be? IDM? Bad injectors? Thank you for any help.

 

[kanuck15]

How many miles are on it? it could be injectors going weak.

 

[96twofiddy]

It just rolled 304,000 Tuesday. I couldn't tell of they were new or original when I pulled the valve cover, everything looked really clean. Oh and I put in new glow plugs, don't think that would make a difference. Guess I should run a contribution test. But I kept getting an oil not up to temp code when I tried last time...

 

[Bugman]

In my book the first thing to do when running a chip when you have engine problems is to remove the chip and see if they persist. I have seen a lot of chips cause problems with the truck owners trying to fix everything else before they remove it.

 

[96twofiddy]

Well I will have to try that. I was wondering if that coulda been a problem. But I didn't know if that was common or not.

 

[Derek@Vision Diesel]

Have seen CPS cause a strange miss in the mid range. May try that as a cheap option. Definitely pull the chip first though.

The more expensive option is injectors, if they are weak they may not be able to maintain the expected pressure increase from hotter tunes. Who's tuning? What is desired ICP?

 

[Bugman]

It is just easier to eliminate the easy stuff before you start to dig into the rest of it.

 

[JCart]

Agree with ^^^ Bugman, pull the chip and see if it changes.

I have a '96 now parked for a parts truck and it had about the same miles when I finally parked it. Had a similar issue with it at WOT pulls it would miss/jerk over 2200 rpm, or if pulling really steep with a load, when I got on it hard. In the end what I found out was the CPS interface distance to the timing wheel would change when hot, which may have been caused by a bit of Cam shaft walk due to wear and or there was an error in front cover machining. The '95's had a problem with front cover machining iirc and international came out with a shim kit to address this. I think the newer versions of the CPS perhaps have a larger sweet spot to account for effective CPS/cam wheel distance. At any rate, I tried the shim kits made truck run very badly so what I ended up doing was to purchase a new ford CPS (when they where $250.00) and I put it in a lathe and turned down outside collar so it would fit deeper in the front cover, with the end result positioning it closer to the timing wheel. Worked and fixed the problem. Now to get me to that point I looked at a host of different things first. Start with unplugging the chip, (remember to leave keys out of ignition and unhook batteries when you pull/install chip) have you ever replaced the CPS?

jrc

 

[96twofiddy]

Don't know what tuning, chip was on the truck when I got it. Yea I replaced the cam sensor after having it give me a no start problem.

 

[Derek@Vision Diesel]

Don't know what tuning, chip was on the truck when I got it. Yea I replaced the cam sensor after having it give me a no start problem.

This doesn't mean that sensor hasn't gone bad again, trust me.

 

[96twofiddy]

How can you tell if is the cam walking forwards and backwards or the sensor? What kinda ohms should the sensor be? I didn't think it got better when I changed the sensor though but I will ohm it out to be sure.

 

[JCart]

Not sure if there is a way to tell cam end play while engine is running might show up via CPS error code. I sorta stumbled across my issue as I had checked all other avenues first and have never heard of someone else having same issue. That is to say too shallow seating depth of CPS. I was basically out of ideas at the time and thought WTH turned the CPS down tried it out and it worked. In my instance I learned that the CPS depth was critical on my engine as I tried the IH shim kit that shimmed the CPS further away from the timing wheel, I mean these shims where really really thin. So when I turned down the CPS in a lathe it was like 10,000th of an inch at a time. Don't recall what I eventually took off but in my case smartened it right up. I will check my files and see if I still have what I spun off...
You've checked your wiring harness for CPS, IPR and ICP?

jrc

 

[96twofiddy]

Haven't checked ipr and icp wiring very thoroughly, I had some bare wires on the cps, I heat shrinked and taped them up but I should really replace the pigtail. I will try to remember and check the other pigtails

 

[96twofiddy]

Alrighty, so today I ran a cylinder contribution test, with the chip I got injector cylinder 1-8 contribution/balance fault. Ran koeo test, got code p0605 with the chip and p0603 without it. Also did the oil cooler because oil was coming out of it pretty good. Running another cylinder contribution without the chip also. Found out chip is a ts performance, good? bad?

 

[earlybroncoboy]

Had the same issue as you mentioned. Tried everything u mentioned. Bought truck with 295k on it. Randomly misfired under load. Kept throwing cps in it. Took chip of replaced cover harnesses etc. Put a fresh set of 160/80 in swallah problem solved and so begin the road down the housing game.

That being said might want to do a comp check just to see if its worth throwing sticks in it. Might have bigger problems.

Sent from my SCH-I535 using Tapatalk

 

[96twofiddy]

disconnected chip, re connected and now it has 1,4,5,6,8 contribution/balance fault codes

 

[96twofiddy]

Had the same issue as you mentioned. Tried everything u mentioned. Bought truck with 295k on it. Randomly misfired under load. Kept throwing cps in it. Took chip of replaced cover harnesses etc. Put a fresh set of 160/80 in swallah problem solved and so begin the road down the housing game.

That being said might want to do a comp check just to see if its worth throwing sticks in it. Might have bigger problems.

Sent from my SCH-I535 using Tapatalk

Yea I kinda figured that could be an issue, but I am really hoping it isn't that lol. I will run a compression test at some point if it doesn't turn out to be an electrical issue.

 

[earlybroncoboy]

I was in the same boat. Didn't want to spend the coin but in the end wasted a lot of time till I made that leap. Good luck man hopefully it is something cheaper for your sake lol.

Sent from my SCH-I535 using Tapatalk

 

[96twofiddy]

Lol thanks. Well took out the chip and drove it. No codes on buzz test or cylinder contribution test. Koeo test good, koer test good. Icp voltage .9-1v at idle and ~600psi. No corrosion on pcm connector. So I'm thinking maybe mechanical problem with injectors maybe weak idm or a cylinder with low compression. But wouldn't compression make it run crappy and miss all the time? It should right?

 

[96twofiddy]

Also I replaces uvch on both sides but I used Dorman, truck had miss before and after. Maybe mis-shielded wires? Anyone had this problem?