Keith Browning Posted April 13, 2007 Share Posted April 13, 2007 Okay, I am stumped! I have a truck that over all, runs well, doesn't smoke and has good acceleration. It is a 2003 F450 with a 7.3L. The problem is that it flutters off the line in a way that I can describe as letting off the accelerator and back on rapidly three or four times then smooths out and takes off and runs perfectly. It also displays a strange idle, not quite a miss and not what you might call rough... more like a flutter. You know, like a 1995 Explorer 4.0L engine does at idle. This comes and goes. Anybody see anything like this? No codes, passes all electrical tests, fuel pressure 62-PSI, IPR 11% and no reason to initially suspect a base engine concern. I looked at performance delta PIDS and it showed 4 or 5 five hit 5% and clear up then a different 4 o5 five... and so on. Whatever it is, it is affecting the overall engine. I am truly baffled! /forums/images/%%GRAEMLIN_URL%%/whattodo.gif Quote Link to comment Share on other sites More sharing options...
CERTIFIEDFORDTEC Posted April 13, 2007 Share Posted April 13, 2007 Maybe an under valve cover harness just starting to got bad..Also had a few Ipr wires chafe near the Ipr that gave no codes and a weird driveability problem... Quote Link to comment Share on other sites More sharing options...
DwayneGorniak Posted April 13, 2007 Share Posted April 13, 2007 Does it have an aftermarket air breather system or that damn little brass tube in the wastegate pressure hose? I have seen these cause that problem. Quote Link to comment Share on other sites More sharing options...
Keith Browning Posted April 14, 2007 Author Share Posted April 14, 2007 Well, a good night's sleep, a fresh look at it and a few new data recordings I discovered the IPR was doing some strange things. I guess I get mentally hammered by the afternoon as this was not too difficult to figure out. Thought I would share the graphs: The first is the abnormal ICP reading with a steady full throttle acceleration. Notice the RPM's and the IPR are smoothly increasing but the ICP shows some really erratic pressure control. The second graph was made under the same conditions after replacing the IPR. Sticking IPR valve operation Normal IPR valve operation Quote Link to comment Share on other sites More sharing options...
DwayneGorniak Posted April 14, 2007 Share Posted April 14, 2007 Neat. We all get days like that. Sometimes you just gotta walk away from a job and come back to it with a fresh coffee. Quote Link to comment Share on other sites More sharing options...
HGM Posted April 17, 2007 Share Posted April 17, 2007 Glad you got it... I've found that changing the scale makes a huge difference in some cases. In other words, changing that IPR 0-100% to 0-30% might have shown a little more movement.Might be worth a try on the next one you get.. Quote Link to comment Share on other sites More sharing options...
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