7.3 PS running rough, but only sometimes - Ford Powerstroke Diesel Forum
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Old 07-05-2011, 06:06 AM
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7.3 PS running rough, but only sometimes

I own a '96 Cal Spec 7.3, 4X4 E4OD; 4.11 finals. It has about 130k miles on it, original injectors, plus the Banks big downtube behind the turbo. That mod was done at about 118k miles, and it gave another ≈ 1.5 mpg but only at my specified 65 - 75 mph. When I do bury my foot in it, I'm estimating it's now got about +40 hp and +50 - 60 lb-ft, but the hp gains are probably all over 2500 rpm, who means it's not that useful. Do those OE two-stage Cal-spec low-volume injectors hamper or help that?

Of course, when you do let it run up, WOT, into the low- to mid-3000 rpm range, it' quite fun, running this big 7500 lb truck up over 100 mph territory quite quick and easy, and with a nifty low lion-like roar from that thinwalled uninsulated downtime over 2500 rpm, WOT. It is too bad, though,that Banks [who did the actual install at their AZUSA shop and still had problems with fit, vibration and noise] doesn't ovalize that tube so it had a bit more clearance (3/4" would easily do it!) to the firewall!

Anyhow, over the past 5k or so miles, I've noticed what, if this were a gasser, I'd call a light load misfire feeling, especially when going from a floating throttle to a light up-throttle. Not real bad, but still, not very smooth. Like it's a gas engine running with a lean surge. I end up popping it off of the OD just to spin it a bit faster. It feels like I have a few loose U-joints going from on- to off-throttle, in that it sort of bucks lightly when I increase or decrease the throttle. But had them all checked out and they are tight-tight!

My local independent truck shop, who used to be the local Ford Dlrship Service Mgr, says he can do an injector cleaning for about $150 and that will fix it all up! Also, someone else suggested there may be a bad wear spot on the "throttle converter" under my right foot.

So: Two questions: this has the Cal-spec dual shot injectors I believe. Is it possible they might be getting a bit rough? But then, why the fine performance under WOT? But if so, should I just go with those DIY Injectors? I'm really not looking for any sort of performance increases, unless it's in terms of smoothness or improved mileage. I'd just like to have a smooth running powertrain.

Two: is it possible this is just in the throttle body (whatever you call that analog to digital converter under the right foot...). This is the second one of those I've had, the first grinding to a halt at about 78k miles. (actually, the engine just goes to a mandatory idle...). This would possibly explain why it only runs rough at a certain throttle position, no?

Finally, I'm a good mechanic, but I now have arthritis, esp. in my back and neck, and I'm assuming that getting at those injectors is not really fun, esp. with the truck being a 4X4 and therefore a bit higher. I think I'd end up hanging near-upside down to get at them all. Yes? No?

If it would only take an experienced 7.3 mechanic about an hour or so to pull them all, and noter hour to get them bcd in, perhaps I should have someone like that do it? And I wonder then what the turn-around time from a good injector rebuild shop might be? And where is that DIY Injector shop; e-mail or website perhaps?

________________ Oh yeah; forgot to mention:

This truck also has a rebuilt, durability HD E4Od trans, with welded TC, and the Banks Trans-Go (I think they call it) trans shift kit as well. No apparent hift problems with it, and it only has about 20k miles, running Aimsoil Synth ATF. Engine also runs Amsoil Synth oil and yeah, I always notice a performance & smoothness improvement whenever I do an oil change. I know these injectors depend partly on the engine oil. I currently have about 10k on that Amsoil, and am going to change it out this next weekend.

Thanks in advance guys

Last edited by HiMyler; 07-05-2011 at 06:18 AM.
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