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Random miss - can't figure it out

21K views 51 replies 11 participants last post by  TrailerHauler 
#1 ·
Early '99 Crew Cab 7.3PS 4X2 192K miles. All stock...

Originally started out what seemed to be a cold start issue....In the morning, it normally be a bit sluggish. 1 in 10 it would romp. Only died once in about 4 months since I had it. Sometimes it would be fine. As I got about 5 miles down the road...it would warm up and run fine.

Gene ran the codes for me along with a contribution and buzz test. No codes, buzz test was fine. Contribution showed low on 8 the first time....then low on 5 and 8 the second. Recommendation was a look at the IPR.

I pulled the IPR, looked fine....cleaned it anyway. Put it back, no change.

About a month ago, cold start, jumped on the highway for about 3 miles, went up an on-ramp and as the lockup disengaged the RPMs dropped right to zero. Waited 15 seconds, truck started up and no more problems.
Two days later I was driving up the highway and I head a distinct change in tone....it sounded like knock.

When I stopped, truck was missing badly...felt like a gasser with a HUGE Cam and a nasty lope. When I gave it throttle, it couldn't feel it.

I've replaced the oil, fuel filter (bowl was pretty nasty), GP relay, CPS (which resulted in a failure of the Tension assembly and Serpentine belt....now both new). GP's have all been ohmed and look good.....I haven't had it romp in quite some time....but it will idle crappy in warm or cold weather when I start it.

I've tried using an IR gun to see if one of the holes wasn't firing....but each runner seemed to be about the same temp (around 270deg).

Worst of all....problem is completely intermittent. I fired up the truck this afternoon after not running it for a couple weeks and it felt pretty smooth. No miss. No knock. WTF?

By the way....Why do Autozone and Kragen both tell me my serpentine should be a 1215 (121.5") instead of the 1223 (122.7") that actually fits? A little online research seems to indicate the 1215s were indeed for the 99 and 00 trucks....why does mine need a 1223?
 
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#35 ·
Tell them you want to see the "burst" line. Pick one up at the parts store, and replace it in their parking lot.
 
#36 ·
Bad news....

Took the intake off and noticed a tab had broken off.

Looked at the compressor - toasted. You can see grit/residue on the walls leading in to the wheel....



In addition the puffing out the filler neck is worse than before... its heading downhill fast.



Do I even need to bother with a compression test? I'm assuming the engine will continue to eat itself and destroy the cylinder walls if I keep driving it right? On the bright side....at least I get a chance to rebuild a diesel.....

Thanks for the help so far Dave....
Major bummer.....
 
#37 ·
ugh...

Sorry to hear, JD...

I swear to gawd...whichever Ford engineer designed the POS air boxes on the 1994-2003 trucks should be strung up by his 'nads.

I mean, at the end of the day...it's the owner/operators responsibility to maintain his/her vehicle...but 70% or more 7.3's we see have had near death experiences due to broken filter lids, cracked intake tubes, etc.

:mad:

Dave
 
#39 ·
yeah...

shoot me an email

dave@swampsdiesel.com

and I'll reply with a full quote...

pistons & rings, bearings, full eng gasket kit, new valves, etc..

of course you'll need to have the block machined (overbored, honed & decked)...and if you want to mess with the heads (deck, new valves) I would suggest thin bronze valve sleeves (prevents valve stem & seat wear).

take care~

Dave
 
#40 ·
What do you think of this air filter kit?
Motorcraft FA-1759 Ford 7.3 Power Stroke AIS Severe Duty Air Filter Kit

I may have to drive the truck a little before I can do any work....I'll clean all the piping, replace the filter assembly and do an oil change to help minimize further wear....
 
#42 ·
Alright...have some time this weekend....
Ordered a couple injector rings and a new Comp wheel from Swamps..hope they show up today or tomorrow.

Grabbed a WIX filter....should be here today.

I picked up/assembled a "Harbor-Depot" Compression tester for $35 and will give it a run this afternoon or tomorrow morning. Hoping for the best....

Also planning on swapping the injector in #5 with whichever cylinder is giving me my best compression hoping its a combination of injector issues and compression loss on that cylinder. Maybe I can at least reduce the miss a bit to make it a bit more driveable until I have time to tear it down....

I'll post results when I get 'em.
 
#43 ·
Having trouble with the compression test.....

I can't thread the nipple into the glow plug holes as the rocker arms seem to be in the way.....the angle isn't right and I certainly don't want to cross thread the thing....

Am I supposed to have to take the rocker arms off to do this?
 
#44 ·
Most compression test kits don't have the PSD adapter, only the IDI. I've never heard of a $35 kit for a psd. I'm assuming you have the correct (long) glowplug adapter. If it is correct, the fit is tight; I recall having to use the remote starter to rock the motor a little on some insertions to make sure the position was correct on the rocker arm for clearance.
 
#47 ·
The good news...finally manage to piece together a working compression tester ($67 total)....$30 Harbor Freight Diesel Comp Kit, $32 adapter (TU-15-22A) and a 3 dollar fitting from a local pipe and fittings shop.

The bad news....looks to be dusted.

Compression results on a 5 crank test - all gp's out
7 - 300 8 - 340
5 - 200 6 - 320
3 - 325 4 - 360
1 - 360 2 - 360


So I've got 4 "decent" cylinders.
Funny thing...since I've put in the KWIX and changed the oil to RotellaT it doesn't miss anymore when its warmed up.....and the last few days it started without a dead hole....can't quite figure that part out.

I am going to pull the injectors on 5 and 7 and replace the 0-rings, as well as pull the pushrods and make sure they aren't bent.....but I think at this point, I'm grasping for straws....
 
#52 ·
I kind knew, but confirmed my problem on the phone with swamps yesterday.

On any cold start no matter the temperature, until the oil warms up near or to operating temp I will get a lot of blue smoke out of the tail pipe and a slight miss.
Also in the winter the truck would NOT start unless it was plugged in for a couple of hours, then when it did decide to start it would have a slight-bad miss.

I figured I needed injectors, and Swamps said it sounds exactly like a common worn out Poppet valve on an injector, so its time to round up coin for baby swamps injectors and some of their tuning!
 
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