North American Turbocoupe Organization



IRCM TROUBLESHOOTING
87TurboBird2.3 Offline
Junior Member
#1
Hey guys, I need some advice about the IRCM on my 87 Turbo Coupe. From what I understand this box contains relays that controls different things like the fan and fuel pump, etc....Another thing it controls is voltage to the ECU. So I have a couple questions. 

1) Would a bad IRCM cause a erratic and unstable idle so bad that the car won't stay running at idle, but fires right back up when it dies? Could a bad voltage issue from the IRCM to the ECU cause this?
2) How does a guy test the IRCM to see if it's bad? I need specifics on how to test this. 

Thanks for the help...
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JT Offline
Posting Freak
#2
What trouble codes do you have?

While a relay can fail and electronics can do odd things when there is circuit/power issue, an IRCM issue doesn't sound very likely in your case. Key On Engine Off and Key On Engine Running are the same relay state for the ECM. In other words, it's hard to believe an interrupt only occurs while the engine is running but not on a restart to result in a no start, per your description. Relays generally fail to energize, stick on, or possibly could result in high resistance if the contacts are bad.

You could monitor the output voltage to the ECM to ensure it's always getting vehicle power via the IRCM relay. Also, while not something to rely on, the ECM may set a code if it detects an interrupt in power as that is part of the logic. I would suspect your issue is elsewhere.
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87TurboBird2.3 Offline
Junior Member
#3
Well, this is kinda a long story and an even longer process of troubleshooting an idle problem I have been trying to resolve since May, 2021. But I'll try to give you the short, condensed version. The car will not stay running at idle. If I hold my foot on the throttle, it will run. But as soon as I let it idle, it dies. But it will fire right back up and the engine will run for about 3 -5 seconds and then dies. I have a code reader and the book that came with the code reader. These descriptions are from the book. The codes I've sporadically got are as follows:

14 = Continuous Memory = Profile Ignition Pickup (PIP) Failure 
41 = Continuous Memory = HEGO (O2) Sensor Voltage Low / System Lean
        Key On Engine Running = HEGO (O2) Sensor Out of Range / Always Lean
72 = Continuous Memory = System Power Circuit Fault / Message Center Control Assembly (MCCA) Circuit Failure
        Key On Engine Running = MAP, MAF, or BP Sensor Out of Range During Dynamic Response Test
81 = Key On Engine Off = Air Diverter Solenoid Fault, Intake Air Control Circuit Fault / Air Injection Diverter

As I've replace parts (See parts list below for new parts) I have cleared the codes off the computer and started over to see if the part I replaced solved the problem. As of today, my only code showing up is 41. I replaced the O2 sensor and the code 41 came back. So I returned it under warranty and replaced it with another new O2 sensor and I'm still having the problem. I even disconnected the exhaust pipe from the elbow coming off the turbo to make sure there's no exhaust leak, and there's no leak. I've checked for vacuum leaks and I even totally eliminated the vacuum leak as a possibility by disconnecting (and plugged) the vacuum line going from the intake to the vacuum tree and it still won't idle. In order to at least get the car to run without dying, I turned up the idle screw so the idle is about 1200 rpm. When I first did this a few days ago, the car would stay running but the idle was rough, erratic and fluctuated. But now when I try to let it idle, it dies even with the idle turned up. The car will fire right back up and then die again. If I hold my foot on the throttle the car will stay running. 

After all the parts I've replaced and all the things I've tried per suggestions of others, I'm stumped. I've replace all the ignition components and sensors I can think of and nothing is resolving the problem. At this point I'm just spit-balling. 

The reason I'm asking about the ICRM is because someone mentioned that he was having the same issues I was having and his problem was the ICRM. Someone else mentioned it sounded like an electrical problem. So here I am asking if this could be the problem before I throw more money at this car only to find out that wasn't the problem. Any ideas? 

I just put the car up for sale because I'm tired of messing with it. Maybe someone knows what the problem is and can fix it. 

The following is a complete list of all the NEW PARTS on this car that has absolutely ZERO MILES on them: 

·        Rebuilt Head (new valves, valve seats, guides, seals, surfaced)
·        Rebuilt World Class T5 Transmission (bearings, synchros, seals, 2nd gear)
·        Clutch Replace by Previous Owner Shortly Before I Bought the Car
·        Gillis Turbo Boost Valve Conversion
·        Fog light Relay Conversion (separates fog lights from the headlight system using relays)
·        Radiator Fan Control Relay Conversion Kit (not yet installed)
·        Power Vacuum Brake Booster & Master Cylinder Conversion (93 Mustang Cobra)
·        Lower Control Arms w/New Bushings & Ball Joints
·        Inner & Outer Tie Rods
·        Inner & Outer Wheel Bearings & Seals
·        Brake Calipers Rebuilt
·        Front Brake Hoses & Lines
·        Fuel Pump & Filter
·        Distributor
·        Cap & Rotor
·        Spark Plugs
·        Spark Plug Wires (Motorcraft 8mm)
·        Alternator
·        Battery
·        Custom Made Thick Battery & Starter Cables (1/0 gauge Welding Wire)
·        Oxygen Sensor
·        IAC Valve
·        Throttle Position Sensor
·        MAP Sensor
·        Fuel Pressure Regulator
·        Air Filter
·        Oil (Valvoline VR1 10w-30 w/high zinc)
·        Oil Filter
·        Ignition Switch & Plug/Connector
·        Wiper Blades (not yet installed)
·        Rebuilt Passenger Window Motor
·        Electric Antenna (not installed yet)
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JT Offline
Posting Freak
#4
While code 72 is the ECM code to indicate a possible power interrupt, you indicate it's currently not present. Additionally, that code can appear, occasionally, due to possible electrical noise from sources such as the ignition system. Your symptoms still don't tell me the IRCM is at fault for a constant an idle issue.

Code 41 type codes are an indicator of an issue that the o2 sensor is reporting and not necessarily because the sensor or circuit failure, though that is possible. The vacuum tree does not completely remove all possible vacuum leak sources. Throttle body, throttle body and intake gaskets as well as PCV failure are possible sources of vacuum leaks that can cause fuel trim to report lean since it's unmetered air that isn't matched with correct fuel. Code 41 could also be a low fuel delivery/pressure concern.

Note that vacuum leaks can "get better" with more throttle as the vacuum drops.
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87TurboBird2.3 Offline
Junior Member
#5
Intake gasket is brand new (replaced it when I rebuilt the head), but I haven't replaced the TB gasket or pcv valve, although I've never removed the TB from the intake. Those would be easy and cost effective enough to replace. I will replace those and see what happens. 

Regarding the fuel pressure concern....it has a new fuel pump, as the old one quit working. However, who knows how good it is. I did do a fuel pressure test before I replaced the fuel pressure regulator and the pressure was a tad low. If I remember correctly, I think it read 38 psi and it was supposed to be 43 or 45 or somewhere in that range (my memory is a little sketchy). It doesn't seem low enough to cause it not to idle.....correct? If it was a fuel pump/pressure issue, wouldn't it have issues when I revved the engine also?
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Kuch Offline
Senior Member
#6
Did you install a new TFI/PIP in the distributor? I do not see it on your list, a bad PIP will do strange things, an engine only needs 3 things to run, fuel, air, ignition. You have good air, fuel is there, this should be an ignition problem. When the car runs, does it run smooth or choppy and rough? I would replace the TFI and the PIP or a t least test them or swap them with a known good set. I have not seen a vacuum leak cause the issues your having,
1988 Turbo Coupe, Black/Black, 5 Speed, Moonroof,  T3/T4, ported E6, 255LPH, Kirban, Stinger Exhaust, MGW shifter, K&N, Gillis valve, BP1.5, PIMPx, Koni's
1964 Ford Galaxie 500XL, 390 6V, Big Solid cam, Headers,3.89's, 4 Speed, Vast and fast
1960 Ford Starliner, 292 Y Block, 312 4bbl intake, headers, 3 Speed, slow and low
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JT Offline
Posting Freak
#7
(10-18-2021, 11:28 AM)Kuch Wrote: an engine only needs 3 things to run, fuel, air, ignition. You have good air, fuel is there, this should be an ignition problem.

I have not seen a vacuum leak cause the issues your having,

That is true but this engine does in fact run, per the author, just not well at idle / low RPM. So all three are there for the engine to start and run...just not run well.

Fuel trim from fuel issues and/or vacuum leaks, EGR stuck open, ignition, etc., are all on the table for rough idle concerns. Code 41 and the rough idle would suggest a possible vacuum leak. Of course that is no guarantee. Vacuum leaks, generally, have the greatest impact at idle and cause lean conditions that can result in lean misfires. This is a 4 cylinder engine, so there's not a lot of overlap to cover. The computer is reporting a condition and knows more than we do from X miles away, so that's something to keep in mind when diagnosing an issue.

Code 14 was present, but the author indicates it's currently not present and hasn't been after secondary ignition parts changed. So code 14 and ignition concerns may or may not be a factor. Again, no guarantee there either.
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Jeff K Offline
Administrator
#8
I am betting on a vacuum leak. Every time I have had a lean code or codes on my EEC IV cars, the issue was always a vacuum leak. Same with my newer OBDII cars..... codes P0171 / P0174 were always caused by a vacuum leak. It doesnt take much of a vacuum leak to set a lean code.

Another possible cause of a lean code is low fuel pressure caused by a plugged fuel filter, failing fuel pump or filter sock on the fuel pump plugged with rust from the in the 32 year old fuel tank. I have personally seen all of these issues.

Have you checked fuel pressure and pump output (flow rate) to see if they are in spec?
Jeff Korn

88 Turbo Coupe: Intake and exhaust mods, T3 turbo at 24 psi, forced air IC, water injection, BPV, Ranger cam, subframes, etc., etc.
86 Tbird 5.0 (original owner): intake, exhaust, valvetrain mods, 100 HP N2O, ignition, gears, suspension, etc., etc.
05 Taurus SEL Duratec daily driver
04 Taurus Duratec (wifes car)
02 Pontiac Grand Prix GT
95 Taurus GL Vulcan winter beater
67 Honda 450 Super Sport - completely customized
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87TurboBird2.3 Offline
Junior Member
#9
KUCH,
I replaced the distributor, which came with a new PIP and TFI (in my original post, (it’s listed in the list of parts that I replaced). When I give it throttle to keep the car running, it runs smooth (no fluctuation), but I can hear it randomly missing.

JT,
you mentioned an EGR stuck open. That is one part I haven’t replaced. Would the EGR being stuck open throw a code 41? The description in the code book doesn’t mention anything about an EGR for any of the codes I’ve received.

JEFF,
during my testing, I completely disconnected the vacuum line to the vacuum tree, essentially eliminating a vacuum leak as a possibility. However, I haven’t replaced the pcv valve or TB gasket yet. That’s on my list to do.

The fuel pump and filter is brand new also, but the fuel pressure is a tad bit low, but not sure if it’s low enough to cause the issues I’m having. I did do a fuel pressure test before I replaced the fuel pressure regulator and if I remember correctly, I think it read 38 psi and it was supposed to be 43 or 45 or somewhere in that range, but I’m going off of memory so this may not be accurate; I did this test months ago. Do you know what the fuel psi is supposed to be on these cars?

So I just looked up the specs on the fuel pump I have, which is a Carter P90023 that I purchased from Rock Auto and it lists the minimum fuel pressure is 51 psi and the minimum free flow rate is 18 gp. Here’s the fuel pump I have if you want to look at the specs…  https://www.rockauto.com/en/moreinfo.php...183&jsn=16[/url]

Question….if the fuel pump was the issue, wouldn’t it die even when I revved the engine to keep it running?
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spittinfire Offline
Member
#10
If you have 38# of fuel pressure and you're supposed to have mid 40s I don't think you would ever see an issue until the engine was under load at high RPM. Revving it up wouldn't cause enough of a fuel demand to show an issue. To me it sounds like it's just having a hard time finding it's idle.
With your long list of replacement parts have you tried swapping any of the old parts back on to see it changes things? I've seen replacement IACs do weird things. Have you confirmed good clean connections at your sensors? It's easy to miss a burnt plug and these cars are 30+ years old.
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