Engine 1989 Fox Gt - C&L 24lb Sample tube causing sporadic idle?

cab8183 · Aug 4, 2018

New to the group! Shoud have signed up ages ago lol. So I have a 1989 5.0 that has a pretty built motor that I bought about 4 months ago. Cleaned motor up and changed top end gaskets and all. Motor is stock bottom end with Brodix 5.0 heads, 1.6 RR, Trickflow Stage 1 cam, Track Heat intake with 1" spacer, Professional Products 75mm TB and EGR plate, 24lb injectors, Aeromotive fuel reg, black c&l 76mm pipe with a 76mm maf housing and 24lb sample tube. Was chasing a rough idle and bad backfire etc. Ended up replacing all of the ignition, tps sensor, maf sensor, new grounds to block. Car will start up sometimes ilding better then other times. On startup itll only idle up around 900 or so on a cold start. Idle doesnt sound bad but something still seems off and it doesnt seem mechanical, almost like bad readings from maf. Timing is set at 14 degrees and fuel pressure shows 38 with key on engine off and 40 at idle. Ive read a lot about how these C&L maf can fight you sometimes. Some say you can run a cone filter on the end (which is how I have it now) and some say that it has to have either the original air box or a cai through the fender to get it to run right. Has anyone had any prior experience with this before I order a cold air kit in hopes that it fixes it? Thanks in advanced!

General karthief · Aug 4, 2018

Welcome to stangnet
Now for the problem at hand, we have a technical/how to section on the 5.0 tech page, in that thread there is a list of stuff, look for the 'surging idle checklist ' toward the bottom, some of the things you have already replaced but you still do the list step by step, the results of one step leads to the next so don't skip around just because you have replaced that part.
I run a c&l meter on my car and had trouble with surging and bucking. I will say that my problems where not the meter.
Research and talking to the people at c&l (this was a long time ago) I found that it needs about 5 or 6" of straight flow into the meter and the air filter needs to be isolated from the engine heat so grab a cai or install the stock air box.

jrichker · Aug 4, 2018

You guys with idle/stall problems could save a lot of time chasing your tails if you would go through the Surging Idle Checklist. Over 50 different people contributed information to it. The first two posts have all the fixes, and steps through the how to find and fix your idle problems without spending a lot of time and money. It includes how to dump the computer codes quickly and simply as one of the first steps. I continue to update it as more people post fixes or ask questions. You can post questions to that sticky and have your name and idle problem recognized. The guys with original problems and fixes get their posts added to the main fix.

It's free, I don't get anything for the use of it except knowing I helped a fellow Mustang enthusiast with his car. At last check, it had more than 250,000 hits, which indicates it does help fix idle problems quickly and inexpensively.

deathb4dismount · Aug 4, 2018

cab8183 said:
New to the group! Shoud have signed up ages ago lol. So I have a 1989 5.0 that has a pretty built motor that I bought about 4 months ago. Cleaned motor up and changed top end gaskets and all. Motor is stock bottom end with Brodix 5.0 heads, 1.6 RR, Trickflow Stage 1 cam, Track Heat intake with 1" spacer, Professional Products 75mm TB and EGR plate, 24lb injectors, Aeromotive fuel reg, black c&l 76mm pipe with a 76mm maf housing and 24lb sample tube. Was chasing a rough idle and bad backfire etc. Ended up replacing all of the ignition, tps sensor, maf sensor, new grounds to block. Car will start up sometimes ilding better then other times. On startup itll only idle up around 900 or so on a cold start. Idle doesnt sound bad but something still seems off and it doesnt seem mechanical, almost like bad readings from maf. Timing is set at 14 degrees and fuel pressure shows 38 with key on engine off and 40 at idle. Ive read a lot about how these C&L maf can fight you sometimes. Some say you can run a cone filter on the end (which is how I have it now) and some say that it has to have either the original air box or a cai through the fender to get it to run right. Has anyone had any prior experience with this before I order a cold air kit in hopes that it fixes it? Thanks in advanced!

I would go through that checklist just to be sure, but CL meters are known to be finicky. It may need to be clocked to a certain angle and vibration and fanwash from that hot air intake you have could also be the culprit. I would use stock airbox with kn panel filter or some sort of CAI or power pipe

cab8183 · Aug 5, 2018

jrichker said:
You guys with idle/stall problems could save a lot of time chasing your tails if you would go through the Surging Idle Checklist. Over 50 different people contributed information to it. The first two posts have all the fixes, and steps through the how to find and fix your idle problems without spending a lot of time and money. It includes how to dump the computer codes quickly and simply as one of the first steps. I continue to update it as more people post fixes or ask questions. You can post questions to that sticky and have your name and idle problem recognized. The guys with original problems and fixes get their posts added to the main fix.

It's free, I don't get anything for the use of it except knowing I helped a fellow Mustang enthusiast with his car. At last check, it had more than 250,000 hits, which indicates it does help fix idle problems quickly and inexpensively.

Oh trust me been through the check list several times. Checked all the easy beginner stuff such as vac leaks dirty maf etc.... I also know how to clear computer codes quickly which would help except for my computer has 0 codes and according to it everything is looking and running A1. But on another note I believe ive isolated it to turbulence causing my MAF to give sporadic readings. This maf setup needs at least 6" of straight pipe in front of it to help straighten out the air going past the sensor. Appreciate the help and direction!

cab8183 · Aug 5, 2018

deathb4dismount said:
I would go through that checklist just to be sure, but CL meters are known to be finicky. It may need to be clocked to a certain angle and vibration and fanwash from that hot air intake you have could also be the culprit. I would use stock airbox with kn panel filter or some sort of CAI or power pipe

Your thinking along the same lines. Have gone through the checklist numerous times before spending money on sensors etc. Have done some research and come to the conclusion that its my maf giving incorrect readings. Found out I will need at least 6" of straight intake pipe in front of sensor instead of just a K&N cone filter on the end and may have to clock it a hair to get it straightened out. I think im definitely on the right direction with it and will be picking up a cai fender kit to hopefully resolve this.

cab8183 · Aug 5, 2018

General karthief said:
Welcome to stangnet
Now for the problem at hand, we have a technical/how to section on the 5.0 tech page, in that thread there is a list of stuff, look for the 'surging idle checklist ' toward the bottom, some of the things you have already replaced but you still do the list step by step, the results of one step leads to the next so don't skip around just because you have replaced that part.
I run a c&l meter on my car and had trouble with surging and bucking. I will say that my problems where not the meter.
Research and talking to the people at c&l (this was a long time ago) I found that it needs about 5 or 6" of straight flow into the meter and the air filter needs to be isolated from the engine heat so grab a cai or install the stock air box.

cab8183 · Aug 5, 2018

Really appreciate the response and after numerous hours of research I believe you are correct and will be getting that cone filter off the end and putting a fender cai on it.

General karthief · Aug 5, 2018

If you find that the maf is still erratic then do what deathb4dismount said and clock the maf housing one way and the other.

a91what · Aug 5, 2018

the stock airbox is actually a CAI itself.... it can also flow more than enough air to feed a 400+ hp engine... the design on it is actually very good.

deathb4dismount · Aug 5, 2018

General karthief said:
If you find that the maf is still erratic then do what deathb4dismount said and clock the maf housing one way and the other.

Or buy @deathb4dismount ’s Pro M chrome 75mm MAF that he cannot seem to give a way, haha.

Blown88GT · Aug 5, 2018

cab8183 said:
...Ive read a lot about how these C&L maf can fight you sometimes. Some say you can run a cone filter on the end (which is how I have it now) and some say that it has to have either the original air box or a cai through the fender to get it to run right. Has anyone had any prior experience with this before I order a cold air kit in hopes that it fixes it?..

Yes. I talked to C&L many times. (Cathy & Lee Bender).
The MAF housing was his invention before there was such a thing as tuning.
His flow bench was sophisticated enough for NASA use, I think he had worked there previously, both in same town, Huntsville, AL.
He retired & sold the company to MAC a few years ago.
His website is gone, but the remnants are archived.
I needed his expertise when I was still using the EEC-IV in a blow-thru supercharger intercooler configuration.
I got it working pretty well, then went Megasquirt but still use the same C&L MAF you have, 76mm with green tube. Megasquirt doesn't care about matched tubes, only the calibration curves which I have for all C&L configurations.

C&L's worked well if configured properly in one of 2 ways.
1. Cone filter attached directly to MAF
2. Factory airbox.

There were some other tricks & workarounds to achieving laminar airflow across the sensor.
1. MAF clocking.
2. 8-10 inches of straight pipe at the MAF inlet, i.e. no bends before the MAF.

Neither of these are applicable for your configuration.
Since you already have the cone filter attached directly to the MAF, start looking at something besides the MAF.

You can do a cold air kit only if it meets the laminar air flow requirements for the MAF. Even then, it might give you trouble. I would not recommend one unless you use the factory airbox.

Engine 1989 Fox Gt - C&L 24lb Sample tube causing sporadic idle?

cab8183

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General karthief

wonder how much it would cost to ship you a pair

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wonder how much it would cost to ship you a pair

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Engine 1989 Fox Gt - C&L 24lb Sample tube causing sporadic idle?

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