Aftermarket Cam idle woes

Does the engine temperature stay consistent?
Is it possible that the egr or air pump are randomly adding air?
Bad O2 sensor?


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Engine temp is consistent.
Last time I had o2 issues it threw lean/rich bank 1 or 2 codes type stuff.
Air pump is gone and heads are non air with passageways blocked off.
Egr is def not 100%, it always throws code 31 seconds after start up. Ive replaced all parts with new but the sensor shaft is longer on the new sensor so i trimmed it with a dremmel to match the length of the old one but made no difference. It does not throw tvr which i believe controls it.
Honestly it acts like a cracked intake manifold type symptoms but i can tein can douse the engine with two whole cans of starting fluid when it acts up but has no effect. As soon as it stops raining and isnt 20 deg outside im going to swap out the maf and injectors
 
If it runs fine with the stock cam it's probably safe to say that the cam is the problem. IMO the cam is too big for speed density, but it should be OK with the MAF. Back in the day we said 50 degrees of overlap was the limit for stock SD, but as tuning has gotten better that may have crept up a few degrees. Your cam has 52 degrees of overlap at the seats, so it's borderline. There was a guy on here a few years ago that had a Comp 268 in his truck and it didn't idle right with 48 degrees of overlap.

FWIW, I have had a similar idle issue in my daily driver that I've been chasing for years and it's got a stock cam in it and I haven't modded anything to cause that problem. It just idles high for no apparent reason. Sometimes 1200 rpm, sometimes 2200 rpm, sometimes in between. I've thought a dozen times I had it fixed and it always comes back a few days or few weeks later. I've posted about it here before. I can tell that the computer is commanding the high idle, but nothing fixes it and none of the data looks abnormal. The closest I can get to a fix is to turn the truck off and back on after it warms up. And because of this I've got a Holley HP system to put on as soon as I get a few days with decent weather and nothing else to do.
 
jetski247 said:
Engine temp is consistent.
Last time I had o2 issues it threw lean/rich bank 1 or 2 codes type stuff.
Air pump is gone and heads are non air with passageways blocked off.
Egr is def not 100%, it always throws code 31 seconds after start up. Ive replaced all parts with new but the sensor shaft is longer on the new sensor so i trimmed it with a dremmel to match the length of the old one but made no difference. It does not throw tvr which i believe controls it.
Honestly it acts like a cracked intake manifold type symptoms but i can tein can douse the engine with two whole cans of starting fluid when it acts up but has no effect. As soon as it stops raining and isnt 20 deg outside im going to swap out the maf and injectors
Click to expand...

I agree that it acts like an intake leak but that shouldn’t happen randomly.

You have a weird noise with key on- engine off. I was just trying to think of any electrically controlled components that would allow a leak into the manifold.

Although they could be unrelated.
Just spit balling ideas.


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Have you checked or changed the pcv valve? If it hangs up sporadically, it will change the vacuum in the engine and cause idle changes.


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Well no go on the MAF meter, the connector is not egg shaped like my c&l unit so I couldn't swap it, so I'm going to have it recalibrated. Because I don't want to make another custom wire adapter harness......cuz I've got a lot of them.

The hissing noise came back, I turned key off this time and hissing continued. I unplugged all injectors and hissing continued. I pinched all vacuum lines and hissing continued so I'm assuming, the injectors are bleeding off pressure like they're stuck or at least one of them. I can't find my Guage to watch it when I turn key off but don't know if that would show me anything anyway? I assume it slowly bleeds off anyway?

So I removed the upper intake manifold to remove the passanger side fuel rail which can be done w/o removal but I have to feel my way around and had a phenolic 1" spacer anyway which what I'm about to tell you may spark a solution to what may be happening.

I really need to make a video to show you the difference of two things that I noticed. If I trim fuel system richness or leanness it changes idle vacuum drastically.

After putting everything back together starting it up to see if anything changed it didn't. The signal from the math meter to the computer can be richened and or leaned out due to the little device that I can change the voltage going to the computer. If I lean the mixture out vacuum will increase, if I rich in it too much it will decrease. If I unplug the ability to change the math signal and just plug directly to the math meter to the a9p vacuum will go back to about 17 and 1/2 but it sounds like it wants to die at any second. So I'll install the little doohickey that I can change the math meter voltage to the computer, the idle will be smooth and crisp vacuum will be back up to 17 and a half 18 instead of say 15 or 14 and things will seem fine until I come home put the truck in park and vacuum goes back to 15 and idle goes to 1100 RPM and I put it in gear and it dies and we go right back to the beginning of every other issue no matter what I change the symptom keeps coming back. But if I richen and or lean the system out it changes vacuum drastically a smooth clean crisp idle means that I'm approaching 18 lb of vacuum or inch pounds whatever the heck it reads I don't remember. And everything works phenomenally when vacuum gets to it or it's close to 18 this applied for the speed density and the math system I thought installing the math system will solve that problem which it had nothing to do with it. The only resolution I have is swapping the cam everything works flawless in fact the stock cam I ran this entire system with all these performance parts for 10 plus years with zero issues whatsoever. But all those years I was thinking man a custom cam would really dial in all these parts that I have to make it run even better but that's not the case. Well it did make it run better and faster because I know from a particular road that I drive all the time from a dead stop if I floor it there is a driveway that I can now get to 70 plus miles an hour which with the stock cam I'm not even close to 70 when I get to this driveway so I know it makes more power due to just the miles per hour by the time I get to this driveway the only problem is I have these random idle issues that usually leave me stranded in the middle of an intersection or a light with a bunch of people honking behind me because I'm having to restart the truck and feather the throttle to get it to idle to get out of the way.

So the only thing I can think of which isn't going to involve a whole bunch more money and get a custom Dyno tune is I'm going to install a set of known working 19 lb injectors that have no issues of problems and I'm going to get a stock math meter that I can put in there and see if these idle issues go away if the idol issue still have weird symptoms then the only other thing I can think of is that it must be the camshaft like mentioned above and there's just no way around it I can't use this camshaft with this particular setup sorry.
 
On the hissing sound, if you want to rule out the injectors just push in the Shraeder valve when it's making the noise and see if the noise goes away as the pressure drops off. I really don't feel like that's part of your problem.

Have you tried advancing the cam a few degrees? Ignition timing?

Do you have a wideband you can measure the AFR with? That may have been covered previously, but I'm not going to go back through the whole thread to check. If you have to change the mixture to get decent idle quality that's a good indicator that your problem lies there. When you turn the key on the computer takes a quick reading of the MAP sensor to see what the barometric pressure is. It then looks for an idle vacuum based on that number. If the vacuum it sees is lower than expected it interprets that as the engine being under load and richens the mixture. You would think the O2 sensor would catch the problem and it would fix it, but the PCM usually hits the mixture adjustment limit before you get there or it never goes into closed loop mode at all so it just sits there rich. Based on the vacuum readings you listed, I wouldn't expect this to be the issue. But the combination of the cam and a weak/incorrect MAP sensor could put it over the edge. Do you have another MAP sensor you could throw at it?
 
This map sensor is a piece I got from the company I got the kit from and is supposed to have a wider range than the stock one but I swapped the other 2 stock ones before with no difference in idle quality.

It sounds clumpy when the MAF is hooked direct like it's too rich or too lean and sounds like a big cam but when I mess with the maf voltage, it smooths out and idles clean and crisp. Granted it won't die idling clumpy but the smell is that of rich.

I'm going to try another MAF sensor and if that doesn't work stock cam is going in but leaves the next question.......
 
Do I use my stock cam or my 5.o cam?
Do I use 1.6 or 1.7s?
Do I advance the stock cam 4deg?
Are all these parts any better than stock with the stock cam? Because these ported gt40s with Chevy 1.90 intake valves didn't feel any better than stock e7s and manifolds honestly.

The only parts that I remember making a seat of the pants difference was the Edelbrock upper/lower and bbk throttle body, hi flow y pipe and exhaust.

Remember this is a heavy truck that shifts at 4500. I think tmoss wrote about the stock cam advanced was very good
 
My vote would be for 5.0 cam advanced either 2° or 4°with 1.7’s.

When it idles like it has a cam in it, it’s lean.


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I believe so, because vacuum drops from 17.5 down to 15.5, then when I Hook the adjuster up and richen it, vacuum goes back up to 17.5 which is about as hi as I've been able to get it. Too rich and it drops, too lean and it drops, the sweet spot is in the middle around .98v coming from the MAF sensor. Is there a way to test the sensor?

Anybody have an obd1 MAF sensor and housing for 19 pounders I can test?16445417962673867079001384944862.jpg
And like a dummy I didn't Mark which one was the 5.oho cam but the one on the right has wider lobes than the 98 e150 5.8 cam on the left. I ran the 5.o cam before just to test it but didn't feel any seat of the pants increase of any sorts. But tmoss I think advanced his 4 deg which would bring the power band slightly lower in rpm where it's needed in this big @$$ heavy truck, and vacuum was 20 just like the stocker, with SD or Maf, it didn't change like this custom ground one
 
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you can measure the cam lift with dial calipers or a mic. measure the dimension at the peak lift of the cam lobe minus the dimension across the the lobe 90 degrees from the peak lift. this gives you the lobe lift value. multiply it times 1.6 (rocker arm ratio) and you have the lift at the valve. 5.0 gt roller should be around .444" lift at the valve IIRC. you can also look for any numbers stamped in the ends of the cam or letter/number combos in cam between the lobes and cross-reference to id cam. don't know specifically how your cams will be id marked. this is the way ford did it in 60's, 70's and 80's. you can research how to id it online or someone on here may post the way they were marked for id.
 
Thank you Bob. I can do that.

So yest yesterday I was waving the stock camshaft cussing at the truck telling it if it didn't straighten out I was going to put this back in it and today it ran flawless and left me with a possible thought and maybe you guys can help me with this but it could explain why it's dying when I put it in gear.

One of the fault codes that always come up is code 67. When I look up code 67 it gives multiple symptoms for cars and trucks and engine sizes and whatnot. So one of the codes is the manual lever position sensor fault, what if the computer doesn't know that it's in gear and that's why it's dying. I don't remember if code 67 came up the last time I hooked up the baumannator but I would think that the truck wouldn't start if it didn't know that it was in park or neutral so I'm assuming some functions are still connected some may not be I don't know if that code pops up because it's an a9p that controlled an aode and it's not hooked up to anything so I don't know if that code is even relevant but what if that affected say the idle in the computer doesn't know that it's in gear to say kick up the idle to compensate for being in gear? Here's a couple snapshots of what the book says so you don't have to look it up.
IMG_20220211_075151553.jpg

IMG_20220211_075142792.jpg

So, if I fix the a/c, I can turn the a/c on before I put it in gear which should in turn, kick up the idle so that it won't die in gear.............the cost of performance.
There's 5 67's
1 is nps and would think doesn't apply
2 is clutch switch, so no
3 is truck only, no more truck pcm so no
4 is nds, possible, whatever that is
5 is mlp, so 2nd possibility
 
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Well I've got more mystery to the puzzle.

I got all check engine lights to go away so when I do a Cam swap I know all electrical is good and can't blame any issues on that. Drove the truck all speeds, about 12 miles, light never came on but symptoms remained as usual, but no light.

Hook my code reader up and still same 2 codes start Morse coding with no light? Then long pause and 11 twice for continuous memory, which is, all is well?

I've only had 11 when there is no light unless it was intermittent and light went away but stayed in non continuous memory?

I went pin by pin again, verifying pin location, cleaning pins on connector and pcm, ohming out circuits related to 34 and 67 which were fine? Except I didn't test a/c because it works.
And I have a suspicion that I may find out the issue when I've torn everything apart like an intake gasket misaligned somehow even though they are studded.

Short story long, no light, but same ol issues. I'm preparing for a cam swap, going through my modded Wal-Mart shopping cart, getting all my tools and gaskets ready etc. Like a doctor does before surgery because climbing in and out of this lifted truck sucks. Honestly I can swap the cam in a couple hours start to finish because I've done it so many times and know none of the bolts will give any issues because all have been heli coiled and replaced with stainless studs where applicable because this truck lives hunting and fishing and gets salt and Sand everywhere.

So unless somehow it works flawless again, and even if it does how do I know where to look to see what's changed I don't know but more than likely I'll be posting back the results of a 5.o HO cam advanced four degrees in the exact same setup.

And before I start a post about advancing a stock cam, is there some unforseen issues that I may encounter? I've advanced a LOT of cams but they were all double overhead cam engines where intake vacuum isn't as critical because these are all race engines.
 
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It was easy with the indexed crank sprocket from a good, reputable true rolling timing chain set. I ran a 4° advanced 5.0 with 1.72’s(may require shims) for years with great results. Lost a little torque down low(which caused it to spin less- so was a good thing)but pulled really good mid range through 5200, especially with better heads. In my case, back then I ran edelbrock performers. Really made a difference with those heads, the cam and full Bassani exhaust. These engines NEED bigger heads despite any other mod!


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Thanks asap, lol I needed shims after the cam and pushrods no doubt.

Forgive me for the long posts.

Well, as I'm getting my cart ready I get the meter out one more time to do a final test and things get wierd, and may have solved this case but it snowed earlier and was getting too dad gum cold outside as well as dark. Yes it snows in Texas. Am I beginning to sound like those women who share a recipe but you have to read they're whole life story to get to the recipe? I knew I shouldn't have taken those women's vitamins..........

I start jiggling wires while it's running around the iac and idle RPM jumps up and back down several times when I wiggle the wires?????

Again, check engine light went away, 34/67 remained but no light, unless the bulb just now burned out?

So I disconnected the negative battery cable, disconnect the 60 pin connector from the computer and disconnect the IAC.

Set my meter up to test resistance with audio so I can hear it beep and guess what. Of the 2 wires going to the IAC, first wire tests fine, second wire tests fine.......... until I look at where the second wire is going on the 60 pin, it's labeled inj 7. So I test inj 8 and it pings back to the IAC. In fact, all 8 injector grounds pinged back to the IAC? Btw I labeled a lot of wires going to the 60 pin.

Which is confusing....... The MAF kit has a separate independant harness for the injectors. One red wire and 8 black.
One red for soldering into 37/57.
8 black independent grounds for each cyl.
The only wire shared is the 12v run which shouldn't be ground?
Or does it ground when off? I'm confused.
And if it does ground, why didn't it ping back during any of the other sensor tests on the ground or hot side??????

I thought the IAC, EGR, TPS and purge shared the same ground? I'll need to look at the schematics.
I'll do further testing tomorrow if it warms up. It made sense for a second but as I thought about it, it should not be tied in with the IAC in any way, should it?

I put everything back together, fire it up, purs like a kitten, no check engine light, drive 15 miles very hard, no check engine light. Get home, put it in park, idle hangs at 1100 RPM. Here we go again, cam would be swapped but I did see things run flawless for several days with no air adjuster needed, no codes, just like day's of old, so I know it's possible.
 
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Short story long,
If I put my meter to ohms.
Unplug 60 pin but leave battery connected.
Put one lead on the red wire on the disconnected IAC connector.
Touch ground anywhere on the engine, I get 750 ohms as well as body, basically all grounds.
As I watch my meter, I start unplugging things one by one to see what happens.
If I unplug the MAF meter, ohms go up to 1500. Injectors....goes up to 2000.........unplug baumannator..........meter goes to open loop.

Plug everything back in but IAC, ohms 750. Unplug baumannator, ohms 1500, unplug MAF sensor 2000, injectors.........open loop.

Injectors, MAF sensor and baumannator are all soldered into 37 or 57 which are key on power for most obd1. So it seems they are all slightly grounded somehow or at least helping dispersed a 12v power to ground.

I completely disconnected the baumannator and ran the truck in park. Idle was still a little choppy without the air adjuster but it was 1200 rpm. Infact, I almost completely backed out the idle screw and was able to maintain a decent idle with just slight contact with the throttle screw just like a stock cam.

So, Short story long. Something is bleeding 12v power somehow, sending less ground/ more 12v throwing things out of whack, making me have to use this air adjuster to crank up sensor voltage, which tells the computer to send more @$$ down the line to make things run right.
 
I personally wouldn't tie the Baumannator power or ground into anything related to the EEC. I'd pick up KO power at either the relay box or cabin fuse box.

I had all kinds of nightmares using EEC power/grounds for anything. It seems it's very sensitive, especially on the clean ground circuit.
 
+1. thoroughly clean all of the grounds for the EEC, batt cable (-) to ground, others in engine compartment and apply quality conductive grease. reference the service manual schematic to be sure to locate them all. it certainly can't hurt to ensure everything is clean.
 
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