Cold Air Intake = bad...?

[Thoroughbred]

I recently bought a JLT cold air kit for the fox. Put it on the car monday, she now runs like dog shit. Before I put the JLT on, the car ran great, idle fine, drove fine with a/c, i could drive the car anywhere with the a/c blastin no problem.
With the JLT on the idle is erratic, it doesnt surge but will idle at different rpm's anywhere from 600ish-1k. The past few nights the temps got down to the 40's outside and the car is now a bitch to start. (it did not do this pre JLT CAI) I have to start the car and hold it 2-3k rpms, let it warm for a bit and then it will eventually not die.
Now, when I go to drive the stang it feels to me like the car is wildly detonating at all rpms after the clutch is let out. The entire SOB shakes horribly. My high dollar TKO500 feels like it wants to join me inside the car. It will also backfire. :(

Next, my MAF is an infamous C&L that I have used going on 4yrs+ now and has worked flawlessly. I exchanged emails with JLT before putting the JLT CAI on and the owners specifically reminded me that "C&L's make your car run lean. Check ur A/F ratio." So I say ya okay my car runs fine with a C&L and go ahead and put the JLT CAI on. My stang now officially runs like crap.

Today I decide to fire up the mustang and after I go through the I dont want to start cold shit, I up the fuel pressure via my Kirban regulator from the stock 39psi to 50psi. Drove the car 4-5miles close to home and the detonating, shaking, earthquake feeling is almost completely gone. I then decide to give her about half throttle up to 3,500-4,000rpms and see what she would do. The power of the car has dropped massively. Ya I was only half throttling it but when I cruise the stang normally I baby the car alot, know it inside and out and Im sure the power is gone. The JLT CAI is H-U-G-E....4inch diameter. Alot more air is entering the motor now vs. the factory tubing that I was using before the JLT. Do you guys think that this could throw off how the car runs this badly? If the car was running excessively lean would it act like that? When I upped the fuel pressure it went almost 100% away.

For those that dont know this is in a 1993 GT. H/C/I/255 intank pump/24's/no tuning. I think perhaps it is time to buy a tweecer RT. I have the extra funds to do so now but wasnt planning on it.

One last thing, the JLT shuved the MAF deep inside the fender well. They claim somwhere on their website that this is how Ford designed the maf to be used?

[red95gts]

Well, obviously you were chasing a lean condition prior to raising the fuel pressure. The bad part is, the O2 sensors should end up seeing the extra fuel from the pressure increase and you'll very likely be back to square 1 after some more driving. It's just going to take some time for the EEC to pull out enough fuel to compensate for the extra pressure.

I looked on their website and didn't see any good pics of the kit. Is there a bend in front of the MAF? I've heard of people having problems with a bend right before the MAF. It creates a situation where the airflow through the MAF is not consistent and what the sampling tube is reading is not proportional to what's going through the rest of the meter. I've heard of people having good luck rotating the MAF (relative to the rest of the tubing) into different positions and trying it.

I would start simple:

- Return the fuel pressure to it's original value and make sure the problem returns.
- Make sure you don't have any vacuum leaks downstream from the MAF.
- If you had to extend the MAF harness, make sure all of your connections are correct and solid.
- Try rotating the MAF 180 degrees from where it is now. See if it drives any differently.

I don't know about Ford designing the MAF to go in the fender. Seems to me like it was probably designed to go right where Ford put it.

Good Luck!

[Thoroughbred]

There is no bend before the MAF. The MAF and airfilter are at a slight angle in the fenderwell, pointing diagonaly towards the front of the car. I angled it because it was too long to point straight down, it was hitting the fenderwell. The only bend is after the MAF when it comes into the engine bay.

I did not have to extend the MAF harness.

I will return the fuel pressure back to 39psi, rotate the MAF and post back later.

[Rusman]

I would actually go one step further: Put the C&L and other old parts back on and see if you still have a problem.

I've also heard of the turbulence issue, hopefullly rotating it will work. If not, maybe the MAF is bad? Can you put your C&L on this kit?

[Thoroughbred]

I put the fuel pressure back to 39psi today and rotated my C&L (which fits fine on the kit, if thats what you were asking Rusman) about 45 degrees, which was all I could turn it because I had no more wire to spare on the MAF harness. And the stang has now returned back to its former self! I took a few laps around the neighborhood and took it out on the highway and she runs completely normal. Driveability is back to where it used to be, the shakking, detonating is gone and she will start with no problems.

After the test cruise, I gave her about 1/2 throttle again and she seems like her former self 2,000-2,500rpms and below if not more responsive. Any RPM's above that she seems to want to pull harder but needs some more fuel perhaps? If I dont pick up a tweecer RT soon, I will atleast go to a local shop that has a mustang dyno and wideband to see whats going on with the A/F.

Atleast my driveability is back where it used to be! Thanks Darrel.

[maveRick]

Thanks Darrel.Bah. That was a lucky guess. :blah:



(j/k Bid D (like others here) has helped me on more than one occasion. :thumbsup: )


...and I have to take back something that I said about a certain low 4 second car driver/mechanic that once told me that rotating the MAF might solve my no-starting problem back when I was trying to get mine going. I looked at him like this :squint: , wished him well, and went on my way. :darkbeer:

[red95gts]

No problem! Glad it worked out for ya!