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Discussion Starter #1
Hi everyone,

Recently installed a new cam in the car, which has the 5.7 hemi. (comp cams hrt stage 2). I got the car tuned by Jay Greene.

Basically, when coming to a stop, the voltage fluctuates erratically, and the car dies. It will jump from high 13s/low 14s to the 11s, and then the car will die. It will then hesitate to start back up, and I have to blip the throttle or else it will die again...

If I start the car normally (basically, when it hadn't stalled) it fires right up, but after it stalls out, the thing wants to fight me...

When the car is cruising, it drives perfectly fine. In fact, I was able to drive it almost 80 miles last night on the highway, and the car seemed to drive beautifully, but when it comes to the stop and go, the darn thing wants to give out on me. Oddly enough, when I put it in sport mode, it seems less willing to stall out...

I swear I have checked every wire under the sun, and can't find a bad ground (i've spent quite a bit of time staring at this thing in the garage).

Just to make sure there wasn't something mechanically wrong, this weekend I took off the heads and inspected lifters, pushrods, and valves to check for mechanical issues. Everything looked perfectly fine... I attached a video that somewhat demonstrates how the voltage is jumping around with my blipping the throttle in park, however when coming to a stop it is much more erratic. let me know what you think...

 

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2016 SXT Plus Blacktop
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Should be 14.1 to 14.3 generally. Assuming the belt is tight, almost seems like an alternator issue? I'm sure more "hands on" members will offer opinions

A Guy
 
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My Hellcat's battery voltage runs down to 13.8V but most of the time is hovers around 13.9V to 14.0V.

While what I saw in the video has the voltage level a bit lower than what I'm used to seeing with my Hellcat, there doesn't seem to be anything wrong.

Some years ago, with my first car with a real battery voltage gauge in it, when I had this car on a trip and at some point noted the battery voltage a bit lower than "normal" I got worried. Called the dealer service department and talked to a tech. He told me the battery voltage is what the alternator is putting out to satisfy the car's electrical needs. If the car's electrical needs are low the battery voltage reading will reflect this. I had been driving hundreds of miles. It was daylight and the lights were off but the A/C was on. But the A/C had been on ever since I left home and it was not working hard at all to keep the cabin at 72F. The A/C requires electricity to run the cabin vent fan and to control the mechanism that varies the A/C compressor's displacement which controls how much cooling the system generates.

Some many years after this I was driving the car and while the voltage level started out ok as I drove it fell. When it went under 13V I figured the alternator was bad and headed to the dealer. Made it. Left the car and tech diagnosed a bad alternator. A new one -- well a factory rebuilt one -- had the voltage back up in the 14.0V region.

With my Hellcat, occasionally the battery voltage level will be right on the border between say 13.9 and 14.0 volts. Thus the reading will "flicker" between these two values. I have seen this same "flicker" behavior when observing the coolant temperature and oil temperature.

The flicker is limited to adjacent values. I have never seen the variation to be larger than the smallest reading unit. IOWs, I have not seen the battery voltage flip between 13.9V to 14.1V.

Idle speed can affect alternator output. In the video I thought I saw the idle RPM dip a bit in the video. If so this can cause the reading to be lower than it might be with a higher RPM.

The dash tach is really a crude device. It might be a good idea to connect a more accurate tach and check that the car's idle speed is ok.

An erratic idle speed can also affect alternator output. The engine controller controls how much battery voltage is fed to the alternator's rotor. This controls how much electrical power the alternator will generate. As the RPMs go up and down due to an erratic idle the engine controller may not be able to "keep" up by varying the amount of voltage is supplied to the rotor and the alternator output varies more than it would otherwise.

Check the idle speed is ok and that is it stable. If either of these is not the case it could account for what you are seeing.

'course, since you have been at the engine you need to double check all the electrical connections are good. Check the condition of the battery leads both at the battery and where they connect to other places. Check the accessory drive belt tension is good.
 

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Since you had removed the heads, the ground straps are attached on the back - also the large gauge wire on the alternator is a nut that secures that down.

It appears that something is not securely bolted down to cause those issues. Also check the field wire connector on the alternator as well to make sure that doesn't have bent pins or not securely plugged in.

and of course the battery connections as well.
 
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Discussion Starter #5
Thank you all so much for your detailed responses. I am going to double check the things that the three of you mentioned once again, and I will update you soon.

I too agree that the alternator voltage might be fluctuating because of the weird idle speed and the engine wanting to die. It might even end up being a fuel issue (spark plugs or something silly).
 

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The Pork Wagon (‘14 Cop Charger)
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What if the erratic voltage output is a result of the low RPMs, not the cause of them?

If you have a tuner, datalog the engine while it’s doing this and see what’s out of the ordinary.

No DTCs stored or pending?
 

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Discussion Starter #7
What if the erratic voltage output is a result of the low RPMs, not the cause of them?

If you have a tuner, datalog the engine while it’s doing this and see what’s out of the ordinary.

No DTCs stored or pending?
You know, Im starting to think this as well. Since the idle is surging it's causing the alternator to produce unstable voltages...

Unfortunately, no codes are being thrown. I've had it plugged into 3 different code readers and nothing odd is showing up.

I'm starting to think now it's more a tune/fuel issue... or maybe even an electrical ground (even though I can't find a loose ground anywhere).

Tried datalogging for the tuner and now misfires or anything weird came up. Seriously scratching my head now...
 

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Don't get too hung up on the voltages. What you see in your video is normal. Rockster is totally right, about the alternator only producing what's needed. On a good day with a healthy battery it can sit at 13.2 V just cruising down the highway if that's all that's needed.

Focus on the idle and stalling issue. I am not trying to discredit anyone's tuning ability, but I would consider the possibility that the tune needs some adjustments.
 

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The Pork Wagon (‘14 Cop Charger)
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Yeah, I’ve seen an engine die due to lack of voltage from bad connections and such, but if that were the culprit here (and especially if there were a loose/bad ground), I would expect to see lots of seemingly unrelated DTCs and illuminated warning lights on the dash to go along with the engine dying.

My money is on this being a problem with air/fuel and not spark.
 
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2018 Dodge Challenger T/A Plus in Yellow Jacket w/5.7L and A8 automatic
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How old is the battery? It might not hurt to remove the battery and have it properly load tested....
 

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The Pork Wagon (‘14 Cop Charger)
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How old is the battery? It might not hurt to remove the battery and have it properly load tested....
battery?

What’s a battery?

You mean batt’ry?

Seems like someone who lives in the South would know how to say words correctly...

Here’s a refresher just in case:

Wrong Right
washwarsh
Pillowpiller
Windowwinder

ringing any bells yet??
 
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What does it idle at when its idled low? Id look at the tune. If the idle is to low its never going to charge correctly.
When you start the car and it runs fine does the voltage still drop off or only when its struggling to idle?
 

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Without a log showing spark, fuel trims, air charge, throttle voltage, commanded RPM, actual RPM...etc when it happens it is difficult to diagnose your issue. However what you describe is similar to what other folks with larger than stock cam installs have experienced when the tune is not dialed in. Basically you need to work with Jay to get it right seeing as you found no mechanical related issues. BTW when I set my idle to around 600 rpm my voltage bounces between mid 13 to low 14s. At around 750 rpm it is +14.

Although I do recall a couple of years ago I having an issue with my voltage where I would drive to work and it would stay in the high 13s, I get to work...shut off the engine and restart...then the voltage would be around 14.2. Never found out what it was but haven't had a issue with the battery or alternator yet. And when I looked at the stock desired voltages vs temp and MPH I saw that I was not too far off from what was programmed.
999902


In fact, just today my voltage was high 13s low 14s (AC was off) except where my RPMs dropped to 460...let the clutch out with barely any throttle. BTW I have a 2015 RT and with original battery and the car is not driven in the winter time but battery is left on a trickle charger.

999903
 

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Discussion Starter #14
Hi everyone. I agree with you that it's likely a tune issue, and the stalling/surging is causing the rotation of the alternator pulley to throw weird voltages.

He sent me a revised tune which worked a little better, but he claims to be running out of options and wants to set my idle to 900 RPM... The cam is very similar to a comp cam 270 and I haven't heard of anyone having this bad of issues, but I also know the 5.7 is a PITA to tune with a bigger cam sometimes.

I did a log with the Diablo tuner, if anyone wants to check it out I will gladly email it to you. I have multiple outside parties saying it's running too rich at idle.

Some think it's a vacuum leak, but I've replaced intake gaskets with all new ones and I made sure the brake booster hose was connected. Not sure what else I can do at this point...
 

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Wouldn't a vacuum leak result in a lean condition as more air is entering the cylinders than the PCM has not accounting for it? Are you running a wide band or relying on just the stock O2 sensors for tuning? Also are you running a stock torque converter?
 

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Hi everyone. I agree with you that it's likely a tune issue, and the stalling/surging is causing the rotation of the alternator pulley to throw weird voltages.

He sent me a revised tune which worked a little better, but he claims to be running out of options and wants to set my idle to 900 RPM... The cam is very similar to a comp cam 270 and I haven't heard of anyone having this bad of issues, but I also know the 5.7 is a PITA to tune with a bigger cam sometimes.

I did a log with the Diablo tuner, if anyone wants to check it out I will gladly email it to you. I have multiple outside parties saying it's running too rich at idle.

Some think it's a vacuum leak, but I've replaced intake gaskets with all new ones and I made sure the brake booster hose was connected. Not sure what else I can do at this point...
My idle is set to about 850 after my cam swap, it runs fine, you can feel the cam at a red light though, as the car shakes, I love it. Going next spring for a converter upgrade and a a tune tweak (I am sure they will dial the idle back after the converter is installed).
 

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Discussion Starter #17
My idle is set to about 850 after my cam swap, it runs fine, you can feel the cam at a red light though, as the car shakes, I love it. Going next spring for a converter upgrade and a a tune tweak (I am sure they will dial the idle back after the converter is installed).
What cam have you gone with? Mine is the HRT Stage 2 from comp cams. Apparently very similar to the comp 270. Tuner says he's familiar with it and has been able to work with ~750 RPM idle
 

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What cam have you gone with? Mine is the HRT Stage 2 from comp cams. Apparently very similar to the comp 270. Tuner says he's familiar with it and has been able to work with ~750 RPM idle
I have a copy of the cam specs at home, it is the OST Dyno Rumbler has over .6" lift and around 270 to 274 duration IIRC
It works as it dynoed 434 WHP on their Mustang Dyno.
 

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Discussion Starter #19
I have a copy of the cam specs at home, it is the OST Dyno Rumbler has ove .6" lift and around 270 to 274 duration IIRC
Yea sounds like that one is a bit more aggressive as mine is still sub 600. Don't remember the duration off top of my head.

I just figure that if I got the timing wrong when assembling the motor I wouldn't have been able to put 200 freeway miles on the thing.

Rotated the motor by hand, nothing wrong, no weird noises, nothing.

At this point it HAS to be either a sensor or tuning issue. I just can't pinpoint it and I'm losing it lol
 

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Yea sounds like that one is a bit more aggressive as mine is still sub 600. Don't remember the duration off top of my head.

I just figure that if I got the timing wrong when assembling the motor I wouldn't have been able to put 200 freeway miles on the thing.

Rotated the motor by hand, nothing wrong, no weird noises, nothing.

At this point it HAS to be either a sensor or tuning issue. I just can't pinpoint it and I'm losing it lol
Actually I forgot I have a pic of it on my phone. Is that an okay cam?
999944
 
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