97 Cobra Imrc Issues (please Help Thanks)

[ppartain]

I bought a 97 cobra a week ago with a few bolt on mods. It has been a garage queen with 48k original miles. 93 octane and mobile 1 synthetic its entire life. Now that being said I drove it a few days ago and it suddenly acted, sounded and ran like a V6. I thought I sprung an exhaust leak (sounded funny) so after driving it to the muffler shop and realizing it wasn't that it got its first CEL come on. Hooked a hand held up and realized it had a 303 & 305 misfire. I assumed coil pack being that it was on the same half. I bought new ones but figured out how to test them and realized they test like the new ones. I cleared those codes and realized I had a 1516 IMRC code. I ran fresh 93 through with NOS octane boost and lucas fuel treatment. I also sprayed a little seafoam through the TB. Still same issue. I carried it to my local oil change place and they had larger computers and said the IMRC was stuck closed. It is off and on or sometimes its for several miles. From what I gather its the plate sticking closed that's throwing the misfire codes. I also understand ford doesn't carry the IMRC controller if its the issue? Anybody with some thoughts or links on repairs please chime in. Ive heard of a delete kit but with 410 gears and 19mpg I hate to lose more gas mileage. I hate to remove the entire upper and lower and not have needed to. I guess ford can diagnose a little deeper im not sure. Does these open all the time? I thought they only opened at 3250? Also they didn't want to do a fuel system flush because neither vacuum line looked to atomize to all ports. thanks guys

 

[wmburns]

FWIIW, a stuck IRMC isn't going to cause a misfire. Always focus first on the misfire DTC codes before working on any other DTC codes.

If the IRMC is stuck closed, this will cause power loss at higher RPM.

If the IRMC is stuck OPEN, this will cause poor throttle response at low RPM's.

Also remember that a bad/clogged/stuck fuel injector can also cause a misfire. Use a "noid" style test light to confirm a firing "pulse" on the fuel injector.

My vote is a coil pack issues since for the V8, #3 and #5 share a coil pack circuit.

 

[ppartain]

well maybe its stuck open at times. it was idleing low/rough has no throttle response ar low rpm. just like a v6. I figured the ports acting up would cause a misfire. So does the IMRC stay 100% closed until 3250?

 

[ppartain]

sounds like a V6 with flowmasters when its acting up. Runs like it too.

 

[ppartain]

I tested the primary and secondary resistance on my factory packs. they were in spec and matched the new ones. I took them back thinking that wasn't the problem.

 

[trinity_gt]

I tested the primary and secondary resistance on my factory packs. they were in spec and matched the new ones. I took them back thinking that wasn't the problem.

Keep in mind that a resistance check with a standard VOM will only tell you part of the story. A coil with decent windings will show good resistances but a failure in the insulation that breaks down at 1kV or so will not be detected by this test.

At the very least swap coils left and right and see if the problem follows the coil or stays on those cylinders.

 

[ppartain]

MY LATEST UPDATE : I swapped coil packs and made no difference. I just removed the tower brace so I could get my hands on the IMRC linkage. Now I cranked the car and it was sounding/running like it was on 6 cylinders. I assumed IMRC problems but I opened them up by hand and I heard maybe a little more air flow but no change in running. Now im guessing the issue is something else. I may have a IMRC problem but its not whats causing the 303/305 misfire codes and the not running on all cylinders sound. The car has MSD digital ignition box. Could the box be an issue? I would think it would cause problems on all cylinders. Thoughts? Getting frustrated lol.

 

[wmburns]

Consider using a "noid" style test light to confirm a firing pulse on the coil primary. While you are at it, also confirm the firing pulse to the fuel injector.

Inspect the electrical connector on the primary coil side. Look for bent/pushed pins.

 

[ppartain]

took it to the dealership today and they hooked it up and found the IMRC controller to be bad. said it would cause misfires. now to delete or not?

 

[Clayton302]

I mod everything so I may not be the best to answer but I say delete them. The car will not loss much or even noticeable low end. We did it on my bothers car years ago and it ran better without. It's a restriction above 3000 or so RPM even if its working right. Although on a stock car the restriction is small.

Now with all that being said if it were me in your shoes and I could fix it without pulling all the manifold off and stuff I would fix the IMRCs and leave them on. Also you might want to check with a tuner to see if any adjustments are needed to air to fuel or with possible codes from the IMRCs being removed.
http://www.lethalperformance.com/96-98-svt-cobra/induction/imrc-delete-plates

 

[Zitro11]

Sorry to revive an old thread (should I start a new one) but I have noticed on my stock 98 Cobra (132k miles), I am not getting the "surge" so many have mentioned at 3200-ish rpm. In fact, the acceleration on the top end feels really sluggish up there. Really noticeable in 1st and 2nd trying to hustle to 60 (obdII tool read a 8.4 sec 0-60 time; I'm no pro driver, but something is wrong!).

I'm wondering if my IMRCs are stuck closed. My question is, what is the simplest way to test if they are functioning properly? No check engine lights present.

If it is not the IMRCs, what else could it be with no CEL on?

 

[Zitro11]

Ping to top Someone more familiar with this forum, please let me know if my question is better asked as a new thread. Thank you!

 

[wmburns]

My question is, what is the simplest way to test if they are functioning properly?

The simplest and easiest way is to use an ODB2 scanner to "command" the IMRC to a different position. Then either listen for a change in how the motor is running or visually verify that the IMRC linkage actually moves. Doing it this way quickly answers two questions.

• Does the IMRC controller respond to PCM commands?
• Does the PCM have control over the IMRC function?

Another "low tech" way is to disconnect the IMRC controller and see what happens. Even better. Use the ODB2 scanner to monitor LTFT's and STFT's before and after disconnecting the IMRC electrical connector. IF the IRMC is NOT responding the PCM commands then expect to see no change in how the LTFT/STFM behave.

ForScan ODB2 scanner w ELM327 USB​

ForScan ODB2 scanner w ELM327 USB

While working on your car have you ever wanted: to find an ODB2 operational PID value (say fuel pressure or MAF)? How about graph a PID value over time? Or compare multiple PID's over time? Access a bi-directional PCM control such as test a...

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