HELP, No more high RPM

Steve491 · Mar 19, 2010

I have a 1997 Cobra with a few engine mods. C&L inlet pipe, CAI, Flowmasters, high flow cats, that's about it. It ran great last year but this spring I have nothing over 5000. The hit is still there around 3500 (IMRC) but then it just peters out and sputters. Any suggestions? The engine has 120,000 miles and I don't think it's ever been apart. Maybe an IMRC clean? Fuel pump? Plugs and plug wires are new.
Thanks in advance, Steve

COBRA90GT · Mar 19, 2010

Did this start happening after your plug/wire change ?

Steve491 · Mar 20, 2010

No. It did it before the plug/wire change.

CMEFLY · Mar 25, 2010

Fuel pump or plugged fuel filter.

shoobs99svt · Mar 27, 2010

Im sure you would've mentioned this but, No CEL?

e8597cobra · Mar 28, 2010

i own a 97 cobra and i was wondering if you got a service light on or not. i lost my imrc's at 50,000. when that happened it did not sputter out on me it just ran like crap. at 3200 rpm the imrc's kick in and from what the other guy said earlier, i would go with the fuel issue. but i would not rule out he imrc's yet cause the kick will still be there due to the tune of the car, but if they are stuck closed it will not get the air it needs and it will dump a lot more fuel into the cylinders. the controller for the imrc's is only a little box with two cables run on a plastic gear. its a horrible design and you cant find them anywhere in the us. Ive tried and failed miserably.

Steve491 · Mar 31, 2010

No trouble codes.
I would rather change the fuel pump than tear off the intake and clean the IMRCs.

It certainly sounds like a fuel pump issue. Like I said in the initial post, it seems like the IMRCs kick in and then it falls over around 5000 and spits and sputters like it's out of fuel. I changed the fuel filter last year but I'm guessing the fuel pump is original, who knows.
Now my next question... According to my Ford manual the original 4.6 32v fuel pump flows 150 LPH @ 39psi. What I'm seeing available are 190 and 255 LPH. What's the best choice as far as brands? Also, Does this system have a pressure regulator and a return line? If so, could it be a regulator issue? Haven't even put the pressure guage on it yet.

Hey e8597cobra, You said "the kick will still be there due to the tune of the car". Are you saying the computer dumps more fuel @ 3200 RPM even if the IMRCs fail. I've never heard that and I kinda doubt that. I always assumed the air flow meter would adjust the fuel like it always does. I could be wrong. Who knows, maybe it gives it a small kick of fuel like a double pumper 4-barrel to compensate for the new rush of air.

Steve

jeremy canter · Mar 31, 2010

easyest way to tell if your IMRCs work or have failed is to find the end of the cable on the bracket > and turn it by hand if it tuns easy > then you'll know if they are easy to open and close > but I don't have any idea how to test the box to see if the controller is working ? > unless you feel brave and hold you head close to see the cable while the engine is running and slowly rev the motor to see if they move > not the smartest thing to do but hey it would work.

nckissfan · Apr 5, 2010

I guess there is no way of cleaning the imrc's without breaking into the motor? I am thinking I have the same problem. When I hit hard on the car, it bogs for a second.

shoobs99svt · Apr 8, 2010

Can anyone rule out a faulty/dirty MAF?

Steve491 · Apr 10, 2010

You can clean the top end with a product like Sea Foam but I doubt it will do much for the IMRCs. Plus, They say it's O2 sensor safe, but beware!

Shoob, I cleaned the MAF sensor a while back, installed a new K&N and buttoned everything up tight. Who knows.

I've ordered a new fuel pump so when I get time to drop the tank we'll see what happens. It's grass cutting season again and I fertilized my yard pretty good so I'll be cutting every other day, hence, not much play time.

Thanks for all the info.

Steve491 · Apr 16, 2010

My cars are falling apart.!
This morning my trusty truck had a flat tire. I mean flat on the rim flat so I decided to drive the Cobra to work. It runs fine under 5 grand so I figured it would be OK. After work I had to run some errands around town and after it heated up the voltage guage went down to the bottom (8 volts or less) and started running like crap. I reved it up a couple of times and the guage went back to normal but creeped back down to nothing and continued to run like crap. Obviosly something is wrong, probably alternator. Could this be associated with my high RPM problem? The alternator is a reman from NAPA and is still under replacement warranty but the battery is old.
It's always something. Any suggestions?
Thanks, Steve

COBRA90GT · Apr 16, 2010

Steve491 said:
...The alternator is a reman from NAPA and is still under replacement warranty but the battery is old.
It's always something. Any suggestions? ...

It's possible that the reman alternator is junk. However, I would first remove the battery and have it bench/load tested at the parts store since it is "old."

Steve491 · Apr 17, 2010

I agree about the remanufactured alternator. They replace the bearings but the voltage regulator, rectifier, and windings are probably not replaced unless they are bad. So that means that even though it's a 2 year old alternator, the electronics inside could be 10 years old.

Steve491 · Apr 24, 2010

Got a replacement alternator. Installed it and it seems to charge well.
I still need to put the strut brace back on to seal up the job.
Fuel pump is next.
-Steve-

Steve491 · May 11, 2010

FYI for 96-98 Cobra owners

Got my new fuel pump this week from Rock Auto. 255 LPH Carter, actually a Walbro. Came with everything, all seals etc. Might have time this weekend to install it BUT...
After nosing around a little bit under the hood I noticed the left IMRC cable had removed itself from the shaft. My fat hands can't fit in to reconnect it or check the other one. I'm guessing the right IMRC is working because I still have a change @ 3200. This would explain my performance problem. Looks like I'm going to tear off the intake and clean/rebuild the IMRC plates.
No codes were present so hopefully the IMRC actuator is still working.
AAAAHHHHH. It never ends with a Hot Rod.

Dannyb · May 21, 2010

NEED HELP!!! with my 97 Cobra

I own a 97 Cobra with lots of engine mods, some ie: 20 over and mild ported heads and matching intakes, IMRC plates completely removed, all bolts on, etc. The car seemed to run perfectly until I gave 2nd gear and at about 6500 rpm's the car sputtered and made a loud bang and a big cloud of black smoke. I put the car into neutral and coasted with the car idling at 950 rpm, when I stopped the car it shut off on it's own. When I tried to restart it, the car back fires in the intake, cranks over but doesn't start. Checked the fuel and spark, both were okay. Any suggestions on what this problem could be?

393strokervert · May 21, 2010

Steve491 said:
Shoob, I cleaned the MAF sensor a while back, installed a new K&N and buttoned everything up tight. Who knows.

I was told to never use a K&N on a mass air car. was told the oil would get on the mass air meter wires & foul it up...

Steve491 · Jun 14, 2010

K&N makes filters for thousands of cars... They do it right.!!

HELP, No more high RPM

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