Tech Tim
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The past couple years it has slowly got worse. But at 375K, that wasn't too surprising.
I figured with all the new stuff, it should be firing easier.
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OBS 7.3 Experts Please Step In - Rebuilt Fuel System - Rough Idle
The past couple years it has slowly got worse. But at 375K, that wasn't too surprising.
I figured with all the new stuff, it should be firing easier.
Tech Tim
Your AD Here....
Recap: Turn the key, it fires up and idles perfectly for first 5-10 seconds or so, then the idle drops and it idles like crap. Take it off idle and it runs good, let up on throttle and it drops back to crappy idle. Restart and it does it over again.
UPDATE -
Over the past couple weeks I've replaced :
Both the new genie FORD ICP and CPS sensors with new Ford ICP and CPS sensors - The take-outs will be carried as spares.
Full engine wiring harness
Fuel bowl wiring harness
Oil pressure switch
The data port dongle finally showed up and I ran the ForScan Lite app on it.
Testing
Ran it through the full battery of tests they have listed:
A couple of the tests don't work on the OBS, must be SD tests?
Results here:
DTC Codes I'm getting:
P1211 - ICP - Googling it, found multiple possible causes, including the IPR
P1284 - ICP failure - Could also be caused by bad IPR
P1298 - IDM failure - Fresh rebuilt IDM with the high voltage high current mod. Those mods will cause this code to pop up.
P0566 - Cruise Control OFF - Not sure why that popped up?
P1536 - Parking Brake Switch failure - parking brake works fine, not sure what switch would have to do with anything.
Live Data Video
Using the graph function (see video below) you can see the ICP is working then just drops off at the same time the IPR jumps. This coincides with the engine starting up, idling great for the first few seconds, then dropping to crap idle.
ICP:
I know people are screaming it's the ICP, but the new Ford ICP has been replaced with another new Ford ICP and now the engine wiring harness has also been replaced.
IDM:
I've emailed back and forth with the people at Diesel Tech of Chatanooga who did the rebuild and mod to the IDM. They confirmed that their HVHC mod to the IDM will cause the P1298 DTC. They also said they'd be happy to take it back and test it. Before I do that, I want to make sure it's not something else.
Fuel Pressure:
Grabbed a fuel pressure tester from Harbor Fraught. It is running right around 30psi, which would be low, it should be between 40-70psi. But now I'm second guessing whether the cheepo gauge is accurate or not.
IPR:
I did just get in a new Ford IPR, that will be the next part changed. About the only thing left.
Low Pressure Oil Pump:
Maybe this is something I need to start looking at?
UPDATE -
Over the past couple weeks I've replaced :
Both the new genie FORD ICP and CPS sensors with new Ford ICP and CPS sensors - The take-outs will be carried as spares.
Full engine wiring harness
Fuel bowl wiring harness
Oil pressure switch
The data port dongle finally showed up and I ran the ForScan Lite app on it.
Testing
Ran it through the full battery of tests they have listed:
A couple of the tests don't work on the OBS, must be SD tests?
Results here:
DTC Codes I'm getting:
P1211 - ICP - Googling it, found multiple possible causes, including the IPR
P1284 - ICP failure - Could also be caused by bad IPR
P1298 - IDM failure - Fresh rebuilt IDM with the high voltage high current mod. Those mods will cause this code to pop up.
P0566 - Cruise Control OFF - Not sure why that popped up?
P1536 - Parking Brake Switch failure - parking brake works fine, not sure what switch would have to do with anything.
Live Data Video
Using the graph function (see video below) you can see the ICP is working then just drops off at the same time the IPR jumps. This coincides with the engine starting up, idling great for the first few seconds, then dropping to crap idle.
ICP:
I know people are screaming it's the ICP, but the new Ford ICP has been replaced with another new Ford ICP and now the engine wiring harness has also been replaced.
IDM:
I've emailed back and forth with the people at Diesel Tech of Chatanooga who did the rebuild and mod to the IDM. They confirmed that their HVHC mod to the IDM will cause the P1298 DTC. They also said they'd be happy to take it back and test it. Before I do that, I want to make sure it's not something else.
Fuel Pressure:
Grabbed a fuel pressure tester from Harbor Fraught. It is running right around 30psi, which would be low, it should be between 40-70psi. But now I'm second guessing whether the cheepo gauge is accurate or not.
IPR:
I did just get in a new Ford IPR, that will be the next part changed. About the only thing left.
Low Pressure Oil Pump:
Maybe this is something I need to start looking at?
Last edited:
If the LPOP was struggling your HPOP pressure would be too. When my LPOP took a crap I couldn’t even get it to start. Wouldn’t create enough HPOP pressure to run.
If I was in your shoes I’d be chasing the fuel pressure first, then the IDM, then the LPOP.
Could you get a gauge on it to read while driving? That can be your tell tail sign if it runs good then not good.
Edit: is your HPOP pressure good? You can read that off the forscan app
If I was in your shoes I’d be chasing the fuel pressure first, then the IDM, then the LPOP.
Could you get a gauge on it to read while driving? That can be your tell tail sign if it runs good then not good.
Edit: is your HPOP pressure good? You can read that off the forscan app
Last edited:
reptillikus
ate lug
Since you have the IPR I'd swap it. I don't trust the aftermarket stuff. That said, I don't see anything wrong with that ICP vs IPR%. I like the idea of verifying fuel and oil pressure.
I've got one of their IDMs from back when he was still with Swamps, never had a problem with it, but that doesn't mean yours isn't faulty I suppose. I'm gonna have to hook up my laptop, I've never actually used Forscan on mine, but my regular cost reader never reports an IDM code.
I've got one of their IDMs from back when he was still with Swamps, never had a problem with it, but that doesn't mean yours isn't faulty I suppose. I'm gonna have to hook up my laptop, I've never actually used Forscan on mine, but my regular cost reader never reports an IDM code.
Tech Tim
Your AD Here....
The HPOP should be good, its new. I'm going to say should, but now I'm second guessing every part I've stuffed in it.
I didn't see the HPOP pressure as an option in ForScan, will look again.
Yep, will definitely be swapping in the new IPR.
I'm borrowing another fuel pressure tester to verify what mine is reading.
I found a few schematics of the fuel pump circuit online last night and read a bunch of people problems and solutions on the Ford forums. It looks like the fuel comes from the tank up through the fuel pump, into the bowl and then out past the schrader valve. So if my pressure is low at the schrader, there are 4 possibilities, yes?
1) The pickup screen in the tank is plugged - Need to blow it out with some air and see what happens.
2) The new fuel pump is bad.
3) The fuel bowl has some sort of blockage.
4) The fuel pressure spring is bad.
I'm ordering a new genie Ford fuel pump along with a high flow banjo bolt (what the hell, can't hurt).
Will be back blowing the fuel lines when I get the old pump out.
Just got a fuel bowl oring kit, gotta pull the bowl to replace the pump, so might as well give it a clean and rebuild while it's out.
Also ordering a new pressure spring, looks like the EightySixd is the one to go to.
Thanks again for all the input.
Cir20
Active member
Your ICP at idle should be around 500 psi. That starts out at over 3k and then faults out and flatlines at a default setting. Either your IPR is stuck closed, or you are getting bad readings. If the new IPR doesn't fix it, check/clean your grounding wires and straps. After that I'd start looking at having the PCM tested.
Cir20
Active member
Your ICP is your HPOP pressure.
reptillikus
ate lug
The fuel comes from the tank thru the pump to the bowl as low pressure, then returns to the pump where it bumps the pressure and outputs to the heads at high pressure. I dont recall where in the system the shrader valve is, i just always assumed it was on the high pressure side of the pump but maybe not? I have never checked that even once in the 20 years ive owned mine
Ive used just generic pumps on mine, first replacement pump lasted maybe 10 years before it cracked at the base and leaked fuel into the valley but it still ran fine 
I dont remember the mileage on yours but im ~215k on the original fuel pressure spring with no issues, altho now i might have to buy that upgraded one I was interpreting that as an engine stall, but i think i was wrong. If its idling like that with those values then i agree.
Tech Tim
Your AD Here....
New IPR will be going in next few days.
All grounds were checked and now it has a new engine harness.
PCM passes the ForScan tests.
CarterKraft
Red Skull Member
From scanning the latest posts it doesn't look like you are logging anfly pids, it also doesn't look like you are actually reading any pids live to see what effects of the various parameters are having during operation.
The tests don't do much IMO on this old of an engine.
Is the ivs in the pedal working?
What is the ipr in current/%/Ms while this is happening, same for icp in psi.
The tests don't do much IMO on this old of an engine.
Is the ivs in the pedal working?
What is the ipr in current/%/Ms while this is happening, same for icp in psi.
Tech Tim
Your AD Here....
I posted a video a few posts above, posted it again below.
ivs in the pedal?
See IPR % and ICP psi below
'84 Bronco II
El Chingón
The idle ICP pressure caught my eye as well. I would pull up the injector pulse width as well to see what that is doing. More pressure needs a shorter pulse width to deliver the same amount of fuel, and the start of injection would need to be later than a lower pressure and longer pulse width to not advance the timing. I don't remember off the top of my head where the duty cycle should be at idle.
I could fire my truck up and log these values for you if you want for comparison sake, but the HPOP and injectors on my truck (Superduty) are admittedly a bit tired (270K originals).
CarterKraft
Red Skull Member
I think that 3k psi at startup is the problem, it's then dropping to "limp" mode psi, same as unplugged icp sensor.
But the ipr duty cycle doesn't jive with that 3k pressure? Low % should be low pressure.
CarterKraft
Red Skull Member
Do you have a mechanical pressure gauge?
Something seems crazy, unless my memory of ipr % is off.
Tech Tim
Your AD Here....
Mechanical oil pressure gauge?
I don't. But I do have a 4K hydraulic pressure gauge, I can pick up the rest and build one.
IPR is getting replaced this weekend, along with the fuel pump (both genuine Ford) and a full fuel bowl rebuild. I'll also pump some air down through the fuel lines to blow off the screens too.
CarterKraft
Red Skull Member
Yeah 4k hydraulic pressure gauge is good, something seems weird with it making 3+k psi at idle with little to no ipr duty cycle, that means maybe the icp pressure is not accurate (sensor bad etc) or the pressure is that high in reality and it's switching to limp home settings for IPR and then the pressure is too low and it runs shitty.
CarterKraft
Red Skull Member
Can anyone confirm unplugged icp sensor yields that 750 psi output?
Levigarrett76
Zeus of the Sluice
Yup, correct right in that 7-800 range
CarterKraft
Red Skull Member
So pay attention Tim, that's not a actual 750 psi reading but a extrapolated number from "bad icp" symptom.
If the pressure was really at 3k maybe the IPR is stuck open?
Seems more likely the problem is in the sensor.
If the pressure was really at 3k maybe the IPR is stuck open?
Seems more likely the problem is in the sensor.
Tech Tim
Your AD Here....
Reading every single line in this thread very closely.
IPR is getting replaced this weekend.
ICP?
I can see if it was the first ICP sensor I put in, but I've already replaced it once with another genie Ford ICP sensor.
I guess it's possible to get two faulty Ford ICP sensors in a row.
-Homer luck
CarterKraft
Red Skull Member
Reading every single line in this thread very closely.
IPR is getting replaced this weekend.
ICP?
I can see if it was the first ICP sensor I put in, but I've already replaced it once with another genie Ford ICP sensor.
I guess it's possible to get two faulty Ford ICP sensors in a row.
Re-reading I hope you don't think that was talking down to you.
Let us know what happens.
Tech Tim
Your AD Here....
Re-reading I hope you don't think that was talking down to you.
No worries there. I've never messed with these things and the one thing I've learned over the years, is, if you don't know the subject, ask others!
reptillikus
ate lug
Maybe its not the ICP, but the pigtail for it? Pics of the conector? This engine is super susceptible to bad connections from questionable connectors.I guess it's possible to get two faulty Ford ICP sensors in a row.
CarterKraft
Red Skull Member
And maybe pull the seal out the back, back prove the connection live while it's running, check for power, ground and signal voltages.
Tech Tim
Your AD Here....
Brand new engine wiring harness. Nothing to worry on the electrical side.
Tech Tim
Your AD Here....
UPDATE*
The idle problem is fixed!!!
Today I replaced the IPR and Fuel pump with genie Ford parts, then spent an hour+ going through the fuel bowl. Cleaned out every nook and cranny, blew all the passage ways, just went through it top to bottom. New o-rings, cleaned the screens etc.
Now it runs better than it had in years, Lots of power, pulls hills beautifully, very little smoke and all the good stuff.
Best of all, now it idles perfectly.
What fixed it? The IPR? The fuel pump? Something gummed up in the fuel bowl? Who know, it was easier to do all 3 at once, then try to go through each step individually. All I can say is it's now fixed... Big sigh......
Thanks for everyone for the input and the help. It's nice to get all the tech help and ideas.
Cheers!!!
Will update this thread if needed.
The idle problem is fixed!!!
Today I replaced the IPR and Fuel pump with genie Ford parts, then spent an hour+ going through the fuel bowl. Cleaned out every nook and cranny, blew all the passage ways, just went through it top to bottom. New o-rings, cleaned the screens etc.
Now it runs better than it had in years, Lots of power, pulls hills beautifully, very little smoke and all the good stuff.
Best of all, now it idles perfectly.
What fixed it? The IPR? The fuel pump? Something gummed up in the fuel bowl? Who know, it was easier to do all 3 at once, then try to go through each step individually. All I can say is it's now fixed... Big sigh......
Thanks for everyone for the input and the help. It's nice to get all the tech help and ideas.
Cheers!!!
Will update this thread if needed.
CarterKraft
Red Skull Member
Awesome, do to the ICP pressure change id imagine the IPR was the solution.UPDATE*
The idle problem is fixed!!!
Today I replaced the IPR and Fuel pump with genie Ford parts, then spent an hour+ going through the fuel bowl. Cleaned out every nook and cranny, blew all the passage ways, just went through it top to bottom. New o-rings, cleaned the screens etc.
Now it runs better than it had in years, Lots of power, pulls hills beautifully, very little smoke and all the good stuff.
Best of all, now it idles perfectly.
What fixed it? The IPR? The fuel pump? Something gummed up in the fuel bowl? Who know, it was easier to do all 3 at once, then try to go through each step individually. All I can say is it's now fixed... Big sigh......
Thanks for everyone for the input and the help. It's nice to get all the tech help and ideas.
Cheers!!!
Will update this thread if needed.
The ecm has no fuel pressure feedback so fuel pressure issues are not readily noticed by the ecm.
Edit: now that it runs 💯 get familiar with various parameters and how they react while cold starting, hot starting, driving pulling etc. It will make it so much easier to troubleshoot in the future.
Tech Tim
Your AD Here....
I ended up getting all the genie Ford parts from our local Ford dealership (West Hills, Bremerton) and from Clay over at Riff Raff Diesel in Oregon.
Riff Raff had some parts the local dealer didn't have, like the full engine harness.
Riff Raff had some parts the local dealer didn't have, like the full engine harness.