Car falls flat on it's face at 4,200 rpm

badstang123 · May 20, 2006

I just switched back to stock pulleys on my car today (Don't give me crap for it, it was a must because of electrical draw. Now when driving, if I'm at WOT and it hits 4,200 rpm the car feels like it hits a wall. Before that everything seems normal. Anybody have any ideas why. I reset the battery and it made no difference. The belt did fit really tightly, but could that cause this kind of a problem? Also there were no other changes to anything else, only the pulleys.

wytstang · May 20, 2006

Thats weird I've never heard of that happening, why not just use the stock alt pulley and put the u/d h20/crank back on and see if that helps. If it doesn't your problems lie else were....

HISSIN50 · May 20, 2006

A sign of a bad coil or TFI is falling on one's face at about 4K - I wonder if you have a happy coincidence or something got bumped while doing the R/R.

Like Danny, I see no correlation with the issue and pulleys. If anything, at higher revs, you're keeping components further from their critical speed.................

Good luck.

mackey · May 20, 2006

Did you move the timing at all? Check to see your spout connector is still plugged in. I bet somehow you timing may have gotten bumped back a ton.

SWYZ721 · May 20, 2006

When you say flat on its face, do you actually feel a dive forwars?

Because mine seems to run out of gas at the higher RPMS but I was hoping that was due to my stockness.

badstang123 · May 21, 2006

wytstang said:
Thats weird I've never heard of that happening, why not just use the stock alt pulley and put the u/d h20/crank back on and see if that helps. If it doesn't your problems lie else were....

I could try that to see if it makes a difference. Just to find the problem though. I need the stock crank on there to because that affects the speed of all other accessories including the alt.

SWYZ721 said:
When you say flat on its face, do you actually feel a dive forwars?

Because mine seems to run out of gas at the higher RPMS but I was hoping that was due to my stockness.

I know what your talking about. There is a certain point where power will drop off depending on combo. For the stock it is probably somewhere just before 5,500. This is completely different from what is happening with my car. Mine drops off far earlies and way harder.

badstang123 · May 21, 2006

mackey said:
Did you move the timing at all? Check to see your spout connector is still plugged in. I bet somehow you timing may have gotten bumped back a ton.

If the spout wasn't in, believe me I would know. I will double check the timing tomorrow but I don't think that is it either. None of that was touched at all. I think I'm going to switch the belt anyway. Because I honestly had to max out the tensioner to get the thing on.

HISSIN50 said:
A sign of a bad coil or TFI is falling on one's face at about 4K - I wonder if you have a happy coincidence or something got bumped while doing the R/R.

Like Danny, I see no correlation with the issue and pulleys. If anything, at higher revs, you're keeping components further from their critical speed.................

Good luck.

I'm going to check over things tomorrow and make sure everything looks in line. I also have an extra coil so I can try that too. I don't think my MSD would have gone bad so quickly though.

badstang123 · May 21, 2006

I took a look at everything this morning, timing and coil are fine. I switched to a slightly bigger belt that didn't make a difference either.

I did notice something odd though. The alternator is charging much worse on idle then it did before. Also once I hit 4,000 rpm the voltage begins to dip from around 14.0+ to 12.8 volts by the time I hit 4,500. This makes me think it could be something with the alternator once it's spinning at high rpms. It seems like more than coincidence power and voltage drop at the same time. What do you guys think?

wytstang · May 21, 2006

Is the alt making any noise? I would assume it's a bearing inside binding perhaps

HISSIN50 · May 21, 2006

Sounds like it might be time to bench test the alt.

badstang123 · May 21, 2006

Aleady pulled it Going first thing tomorrow. I'll let you guys know how it goes.

badstang123 · May 23, 2006

Okay. So I took the alternator back to the shop that built it for me. They took it apart and checked everything and all looked good. They did replace the voltage regulator though. Then they ran it on the bench tester at 14.7 volts for 20 minutes without a problem. It was putting out right around 200 amps.

I brought it home stuck it in the car and it did the exact same things it did before. Voltage is low on idle (12.0 volts), about 14.4 through most of rpm band, and then drops down from 14.0 volts to around 12.8 as rpms rise after 4000 rpm.

Then after taking it around the block the alternator stopped charging at all. It isn't putting out anything no matter what the rpm, leaving my volts at 12.0 while driving. I checked the alternator fuse and it is fine. I checked all my connections and everything looks good. I checked for continuity between positive and negative off the alt and there was none. Nothing really seems to be wrong but something obviously is. Any ideas where something could be messed up in the wiring to the alt? Thanks guys.
- Justin

HISSIN50 · May 24, 2006

I know you checked the alt fuse, but did you check the fusible link on the charge cable? It's kinda to the side of the PS pump (in the stretch of alt charge cable as it goes from the alt to the distribution block).

How do your regulator wires look? Peel the wire loom back and look for vulcanized insulation, etc.

At that point, I would confirm the belt doesnt slip and that each pin on the voltage regulator looks good. Then you'll have hit the big players AFAICT.

Good luck.

badstang123 · May 24, 2006

HISSIN50 said:
I know you checked the alt fuse, but did you check the fusible link on the charge cable? It's kinda to the side of the PS pump (in the stretch of alt charge cable as it goes from the alt to the distribution block).

How do your regulator wires look? Peel the wire loom back and look for vulcanized insulation, etc.

At that point, I would confirm the belt doesnt slip and that each pin on the voltage regulator looks good. Then you'll have hit the big players AFAICT.

Good luck.

Okay. I saw the fusible links in the wiring schematic but wasn't sure exactly where they were. I made a run of 1/0 awg wire from the alternator to the distribution block though, so that would bypass the fusible link. In addition to this, I've tried two belts (Both my old one and new one). That is definately not the problem. Each pin on the regulator looks perfect as does the plug , but the wires on the plug for the regulator actually don't look to good. I'm going to probe them tomorrow to make sure they have voltage and take a closer look at them for any exposed wires or something of the sort. I think I'm looking at things along the same lines as you. What is AFAICT though? Thanks.
- Justin

HISSIN50 · May 24, 2006

badstang123 said:
Okay. I saw the fusible links in the wiring schematic but wasn't sure exactly where they were. I made a run of 1/0 awg wire from the alternator to the distribution block though, so that would bypass the fusible link. In addition to this, I've tried two belts (Both my old one and new one). That is definately not the problem. Each pin on the regulator looks perfect as does the plug , but the wires on the plug for the regulator actually don't look to good. I'm going to probe them tomorrow to make sure they have voltage and take a closer look at them for any exposed wires or something of the sort. I think I'm looking at things along the same lines as you. What is AFAICT though? Thanks.
- Justin

AFAICT = As Far As I Can Tell.

Your plan sounds good to me - you're going to rule everything out pretty soon. I wouldnt waste too much time on the reg wires - it's nice to rule them out, but I dont think that it's likely the source of the issue.
And you're right on - you bypassed the stock fusible links (you're right again - there are two. I couldnt remember, as I also ran a new charge cable awhile back).

I just cant figure out the RPM thing - it's acting almost like a reverse-wound unit. I gotta think on that a lil' bit.

Good luck Justin.

Pennywise2 · May 24, 2006

Possibly a clogged fuel filter robbing power? It sounds like something electrical.

gcomfx.com · May 24, 2006

How do you know it's the alt dropping the power and not the engine dropping off? Seems to me, you stop the engine from running, the alt has to stop charging.

Does it happen in every gear? Perhaps torque rotation of the engine is binding a connection somewhere? Very strange....

badstang123 · May 24, 2006

gcomfx.com said:
How do you know it's the alt dropping the power and not the engine dropping off? Seems to me, you stop the engine from running, the alt has to stop charging.

Does it happen in every gear? Perhaps torque rotation of the engine is binding a connection somewhere? Very strange....

I have a digital voltmeter in my car and I can see the voltage dropping off after the rpms pass 4,000 rpm. This is the same place that I begin to have a problem. Plus it is something new that the engine has done before. It's not power dropping off, it is more of a studder or miss. It does happen in every gear. STRANGE is for damn sure. It's driving me crazy. But now I don't get charge at any time.

badstang123 · May 24, 2006

Thanks for all your helps guys. One more quick question. I've been probing some things this morning and found continuity between the green/red wire on the plug for the alt regulator and ground. I shouldn't have this right? Thanks.
- Justin

gcomfx.com · May 24, 2006

I wouldn't think so, sounds like a clue to me. I would double check the power wire to a normal ground, might help confirm it.

Guess it's time to trace the power wire back.... might pull the fuse to see if it's before or after the fuse in the line. I would think if you were grounding out the power, there would be a burnt spot somewhere.

Did you unplug the alt. when putting the pulley on? Perhaps you smashed something?

If the above were true, I would suspect a blown fuse is the reason it stopped all together.

Car falls flat on it's face at 4,200 rpm

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