Aftermarket Cam idle woes

jetski247

jetski247

Member
This is a non lightning, f150 with the 5.8 and e4od. So there are many differences that may not be the same as the lightning. But you guys probably know this stuff better than the 4x4 forums. This truck has 1 ton axles with matching master cylinder and brake booster amongst a bunch of other mods.
Figured I'd start a new thread with my idle issues after an aftermarket cam swap. I've tried so many different ways running speed density as well as a maf system and still have similar idle issue problems. So far the closest I've gotten was to enlarge the small holes in the stock throttle body butterflies of the F-150 and got it to idle fairly smoothly with the idle stop screw completely backed out. The 351 with the maf system in the 112° lope separation cam does idle much more smoothly (then speed density) with the IAC and TPS disconnected in the idle stop screw completely backed out just idling on the enlarged holes through the twin throttle plates. This solved much of the engine dying when putting it in gear or sitting in traffic or any kind of idle issues not using the little IAC adjustment plate sold from LMR which was mentioned in a previous thread. So far after 2 days of testing have yet to have it die in traffic extended idle. For 20 to 30 minutes in gear out of gear AC on multiple things that I could think of it hasn't died yet the only tiny issue that I have found is the aftermarket cam seems to idle more like an aftermarket Cam and have a thump thump thump thump thump thump thump idle to it which it didn't do before, so what I believe is happening is it is either a little bit lean and it's causing it to idle lumpy like an aftermarket cam for some reason why I don't know, before I enlarge the holes in the throttle butterflies the idol was very smooth it would just fluctuate randomly on its own and sometimes hang and sometimes not and it was it was almost impossible to to trace and or diagnose but idol was very smooth and crisp it most times.
Going back to the stock twin throttle body so I can use it for testing purposes has severely choked the engine with the aftermarket heads and Cam and intake and all the other performance parts on the engine but the idle to 2500 rpm usable torque is much smoother and crisper with the smaller throttle body.
 
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Before you post about my fantastic wiring job know that it's just temporarily hooked up for testing purposes because I was switching from speed density to maf back to speed density to maf and anyway I got tired of putting everything exactly where it needed to go so it's just jumbled up sitting right there looks like crap. It's an original baumannator and A9P.
 
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what is the cam brand and part number? or complete cam specs or at least the duration at .050"? have you positively determined that you do not have any vacuum leaks in the hoses or anywhere else? more info on the engine build/specs would be helpful as well.
 
According to my vacuum Guage all is well.
Cam is a custom ground from cam research.20201010_113359.jpg
This was ground for speed density and collection of parts listed below, which ran pretty good minus the idle issues.
 
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Ported gt4os with 1.90 intake valves, ported on the intake to a felpro 1250, exh side raised and matched to the ford motorsports shorty headers, edelbrock upper lower, 76mm maf, 24# inj, dish pistons or other words stock compression. Shortys, high flow y and exh sys, timing set to 10 deg, verified multiple times. Checked for vacuum leaks several times, cleaned maf, swapped air filters, cam was ground for the 1.7s, which requied longer pushrod s due to smaller base circle.
Ive drove this truck like this for over 15k miles, long trips, etc. Speed density or maf had same issue at idle. It was random, it would just die at a light sometime s. Some days run great, some days die in gear. Ecm just had 3 capacitors replaced and took apart to verify work was lagit.

Something strange, when my key is on and im adj. Tps sensor, i can hear what sounds like an injector spraying? Something is making a slight hiss noise? But i haven't checked yet what it could be. It stops when the key is off.
 
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Oh and by the way, I've installed two other cams to see if idle issues would return among other things and there were zero issues with the stock cam or an 86 5.o cam. Speed density or maf, all the same parts were used except different length pushrods.
So I'm assuming this cam and the stock Ford fuel maps from the a9p or the jog1 used just don't idle great. Because weather the idle air slips past a cracked butterflies or a hole, shouldn't matter, just that more Air is needed.LOL I've owned this truck since 98
 
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I wouldn't think that cam would be any problem for MAF setup. many people run E303 cams and trickflow stage 1 cams (including myself years back) with stock A9L/P and MAF and that cam is slightly more mild in just about every way.
 
This is a long shot with roller rockers, but since you've got a reduced base circle cam with custom pushrods I'm going to ask. Are you sure the rockers aren't bottoming on the rocker studs before the valve closes all the way? I had this problem on my Cougar back in the day. The valve still closed because the stud would flex, but it acted like it had a much larger cam than it really had. I would have never figured it out except one of the studs finally broke.
 
They are pedestal mount, to the best of my knowledge they are fine. I had to shim most of them. Ive rotated the engine over by hand a thousand times to degree the cam and would have thought i might notice that.
 
your cam research cam has -13 deg overlap and 208 deg/213 deg duration @ .050, so that shouldn't be a problem with Speed Density, much less a problem with MAF. what is your idle rpm and vacuum (inHg) in drive? the hissing noise you hear when near the engine at idle is probably the air flowing by the throttle blade and thru the intake manifold. mine does the same thing with the stock gt40 intake. for refence: my cam is .484/.512 lift, 216 deg/228 deg and -2 or -3 deg overlap @ .050. idling in drive it has 15-16 inHg at stock 704 rpm. i have it idling Open Loop with C3P2 Speed Density.
 
Vacuum is at 16 in gear, 18 in park. Rpm is about 650. The hissing noise is with the engine off key on.
Again the problem is minor but random. Sometimes it will die when put in gear or at a traffic light. All other aspects seem great. I tried to post a video but it keeps saying error.

If I crack the butterflies open to bring rpm in gear up to say 700, 750 when I return to park it goes to 900, 1000 but won't die in gear. It's like high idle or die in gear?
 
i think i would try re-setting the the base idle throttle opening by going thru the specific throttle setting procedure by unhooking the battery cable and waiting the specified time, unplugging the Idle Air Control and then re-setting the throttle blade position. there's a very specific procedure to closely follow, sometimes it will help. been a long time since i did it and can't remember off-hand the details. do a search on this forum or perhaps someone will have the procedure info handy and will speak up.
 
Bobwhite I have the procedure and have done it several times. There was a member on here that sent it to me and all these years of owning this truck I was doing it wrong lol. It helped somewhat.

Fmos, Maf meter is a C&L and if I had one I would but this may help......

I have this stupid air adjuster which actually works but I know it's not the right way to go about it. It's from IST, it hooks between the maf meter and ECM and has an adjustment screw that you can change the signal from the MAF to the ECM. . making it run Lean or rich. As I adjust it, idle will smooth out perfectly and have no issues but I can hear deto at wot when I get idle right. If I richen where deto goes away, idle is too rich. I didn't need it with the stock cam, speed density or maf ran everything fine. Idk, I just got to live with it. But idle seems lean for sure, because as I dial it in, rpm increases several hundred rpm when I find the sweet spot and then have to back the throttle back down, then go through the whole TPS reset thing again. But it usually ends up lean at wot due to the coke bottle rattle coming from under the hood, I've even backed timing down to 8deg to rid deto at wot.
 
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Is there anyone I can send this video of what sounds like an injector spraying with key on engine off? You can hear what sounds like an injector spraying and hear that It sounds like it s coming from the intake? Unless an injector is supposed to at start up? I can't post it for some reason but it sounds just like I'm describing
 
jetski247 said:
Is there anyone I can send this video of what sounds like an injector spraying with key on engine off? You can hear what sounds like an injector spraying and hear that It sounds like it s coming from the intake? Unless an injector is supposed to at start up? I can't post it for some reason but it sounds just like I'm describing
Click to expand...
Because of storage costs I have videos locked down to "Supporting Members". PM me and I'll shoot you my email address and you can send the vid and I'll post it this once :)
 
As a single dad of many children as well as my handicapped mom, I don't have a ton of time to work on it so this helps me tremendously, and by the way, I build (use to) offshore endurance engines for jet skis.
 
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