Idm problems?

ghohouston · Mar 31, 2015

My truck is 5 hours away from home right now, and acting up. Went and rescued it from truck stop where a buddy I let use it parked it. Told me it wouldn't run over 40 mph. Scanned it, had a cps code. Replaced with original black cps. Ran great till 4th gear. So we limp it to his place, truck won't go over 40. Way down on power as soon as you shift into 4th, and gets so bad in 5th you gain no speed. I tear the valve covers off after it buzz tested perfect. Found the uvch's would wiggle a bit on the vch's. So I ohmed out the uvch's and valve cover harnesses, all were under 3 ohms. I did some "rigging" with zip ties on the clips so it had no possibility of wiggling, in a hope it would make a difference. Got back together, and once again, runs perfect till 4th gear, same issue. So I get back from my 40 mph test drive. Inspect the engine harness above the drivers valve cover for chaffing, and didn't see any. I perform another buzz test, and get p1271-1278, except 1273... Sound wise, the buzz test is perfect, no difference in any of em. I'm thinking the idm is the culprit. I started the truck, with the idm unbolted from the fender, and shook it to see if it acted up, and nothing, did same with the engine harness, and nothing. Any other ideas?

old man dave · Apr 1, 2015

Check the fuel filter or possibility of bad fuel?

dangerdon · Apr 1, 2015

Did the IDM sound like it had water in it or any corrosion on the box or paint peeling anywhere on it?

Do you have a boost gauge? If so what was ur boost like?

Did it feel like it wasn't running on all cylinders?

Does it act like it isn't getting fuel? Might sputter like it's starving?

I had all these problems one day....wouldn't go over 40 either.... then died and wouldn't start.

Turned out to be the IDM. Went to a salvage yard bought a used one for $100 and fixed it.

If you have somebody with a 7.3 that's running just try their IDM out on yours..

ghohouston · Apr 1, 2015

old man dave said:
Check the fuel filter or possibility of bad fuel?

Filter has less than 5k on it. Bad fuel is always possible, but honestly don't think that's the issue, since it has every bit of power it has always had, until 4th gear.

ghohouston · Apr 1, 2015

dangerdon said:
Did the IDM sound like it had water in it or any corrosion on the box or paint peeling anywhere on it?

Do you have a boost gauge? If so what was ur boost like?

Did it feel like it wasn't running on all cylinders?

Does it act like it isn't getting fuel? Might sputter like it's starving?

I had all these problems one day....wouldn't go over 40 either.... then died and wouldn't start.

Turned out to be the IDM. Went to a salvage yard bought a used one for $100 and fixed it.

If you have somebody with a 7.3 that's running just try their IDM out on yours..

Idm has no water in it, that was one of my first thoughts, and no, no corrosion. It was replaced about 5 years ago along with 8 new injectors, and truck sat for 4 years after. Only has 5k miles or so on them. I'm buying a used idm, hell if it turns out it's not the problem, then at least I have a spare laying around.

Every time I've seen a 7.3 throw that many injector codes, it's been an idm issue. When I saw all but #3 code for high to low side open, yet it audibly buzz tested perfectly, it made me think idm.

dangerdon · Apr 1, 2015

That's what I did. I scanned the truck and I had a pcm communication error was all. After goin thru all the wiring and finding nothing I just bought a IDM and tried it and...popped right off...

Good luck. Hope you figure it out..

Keep us posted..

dangerdon · Apr 1, 2015

That's what I did. I scanned the truck and I had a pcm communication error was all. After goin thru all the wiring and finding nothing I just bought a IDM and tried it and...popped right off...

Good luck. Hope you figure it out..

Keep us posted..

old man dave · Apr 2, 2015

I would rather put your IDM into a good running truck. There's a chanch that there is a condition in your truck that affected your IDM and could ruin the test IDM.

ghohouston · Apr 3, 2015

I hear you Dave. The problem is the truck is hours away from home, and I'm going even further away from home and Austin for work, so i don't have the time, or another 7.3 in Austin to swap with. I've got one coming, and will go from there.

gnxtc2 · Apr 3, 2015

Did you take a fuel pressure reading?

A buzz test just tells you the electrical wiring is ok.

I would clear the codes and scan again.

Billy T.
[email protected]

ghohouston · Apr 3, 2015

gnxtc2 said:
Did you take a fuel pressure reading?

A buzz test just tells you the electrical wiring is ok.

I would clear the codes and scan again.

Billy T.
[email protected]

How is fuel pressure gonna cause injector high to low side open codes? I understand how this stuff works for the most part. I did clear the codes, before the last drive, then came back, and after what was probably the 4th or 5th buzz test, those codes popped up. I buzzed it before the first start of the day after sitting all night, and several times after test driving. Like I said, every time I've seen a 7 3 throw that many codes, the idm has been the problem.

gnxtc2 · Apr 3, 2015

I don't know all the codes off hand. I've seen fuel pressure cause some funky ****.

I'm not doubting its the IDM but something to check.

Billy T.
[email protected]

ghohouston · Apr 3, 2015

I hear you. If the idm doesn't fix it, that'll be my next item on the list to check. I'm gonna do whatever it takes to get this truck back on the road, and sell it. It's becoming more and more apparent I don't have the time I thought I had for a "project truck". So if anyone is interested, pm me for specifics. Not real sure on a price yet, but it'll be cheap ish.

ghohouston · Mar 24, 2016

Realized I never posted a fix for this. The tank selector valve had failed between positions, so the truck was starving for fuel.

gnxtc2 · Mar 27, 2016

So it wasn't the IDM after all

oke:

I know its hard but gotta use the KISS principle.

Billy T.
[email protected]

joe d · Mar 27, 2016

I balive that falls under. Gnxtc2 saying of fule cousing some funky sh it....

ghohouston · Mar 27, 2016

Haha yes, good call. It ran a few hundred miles after that, and died on me on the way to New Mexico for work, got towed to a coworkers house, and it's sat there since. All fuses check out, relays swapped around, buzz tests okay, cps swapped twice, tried unplugging icp sensor, no start, tried unplugging map, and ebp to see if they were shorted, etc, no start. thinking a piece of sending unit foot may be causing a blockage in a fuel line. I put a brand new electric pump on from riff raff, and pressure still seems odd, if I open the drain with the key on, finger over the port, it'll build pressure, only after several seconds. Let off, same thing again. High pressure oil looks good on scanner as well. Didn't make it this weekend to put gauges on the high pressure oil and fuel side of things.