87 Iroc. Manual

Trying to figure this issue out. So in Neutral no matter the RPM, the engine runs fine. But sometimes when in gear the engine sputters and wants to stall. One thing I noticed is when it happens the amp gauge drops down dead.

Any pointers?

 

Electrical doesn't like to be below 9volts and goes wonky. If your alternator or battery are bad, change them.

 

Not sure about "amp" gauge; these cars don't have one of those. Only a "volts" gauge. Is that the one you're talking about? If so, what does "drops down dead" mean?

Sputtering under load is more often a fuel problem than electrical; however the only way to be sure is to get the electric issues sorted out first.

 

Yes volt gauge. I mean it goes down to zero.

Yeah from what I have been reading it's fuel. Could MAF do this?

I am going to change the battery and see if it helps. The battery died and I had to put it to charge with a motorcycle charger that took almost 3 days. Thanks

 

The volt gauge doesn't go to "zero". Only goes down to about 9 or some such. Not exactly a good diagnostic tool beyond "it's doing something different than it did when the car worked right". Helpful in its own way, butt not "absolute".

The combination of dead batt plus alt not working (or more accurately, not working enough at the moment), will result in very low system voltage, which will result in low meter readings, misc other electrical malfunctions, very weeeeeek ignition which can lead to misfires, inadequate voltage to operate fuel injectors, etc.

Start by getting a KNOWN GOOD hot fully-charged battery in there. All else depends on that. Then proceed. Butt, first things first; the batt. Once that's set straight we can move on.

Next thing will be to test out the charging system. What voltage is the alternator putting out WHILE IT'S IN THE ACT OF SCREWING UP? Not, while it's happily working right; not, while whatever else; WHILE IT'S IN THE ACT OF SCREWING UP?

 

While sputtering and acting up, the voltage points to the bottom. Twice now for the first 20 mints of driving it drove fine, then it started to sputter under load. In both cases what I had to do to get back home was holding the clutch down and rev the engine and slowly let the clutch go to move forward. This continued for about 10 mints, then suddenly the sputtering goes away and it drove fine and at this point when I looked at the voltage it was back to middle.

But if it's battery or alternator, why this happens only under load?

 

That isn't The Question. What we need to know is,

Get out your digital multimeter and measure.

:shrug: What difference does it make? At this point, the first question that must be answered is, are your batt & charging system working right?

One thing at a time. Be logical, rational, and orderly. Start at the beginning, not jump into the middle somewhere and chase your tail for awhile.

 

I charged the battery full. It reads at 12.95V. I started the car and measured the Voltage at the alternator. It read at 12.7V. All lights and AC off.

Shouldnt it be higher?

 

The alternator should be putting out 13.8 to 14.6 volts...

 

Alternator is not working, for whyever.

Forget about "revs fine in Neutral but..." for the time being and fix the alternator. Odds are, the driveability problem will magically disappear. Butt hay, even if it doesn't, at least you'll be able to drive the car for more than a few minutes without it dying completely.

 

Not sure about the alternator issue but the ignition really doesn't like going below 10v. 9v and stuff stops working properly. Sounds like you have a bad alternator. Batteries usually have a 5 year life span. If it lasts more than that, it's on borrowed time.

I had a vehicle do something similar many years ago. Reved up fine in neutral but in gear and trying to accelerate, it would sputter and try to die then would just pick back up again. After a lot of troubleshooting, it was found that the ignition pickup wires in the HEI distributor were worn and cracked. As the rpms picked up under load, the vacuum advance would rotate the ignition and this rotation would separate the wiring causing the miss or lack of power. The vehicle was old and a simple new distributor fixed the problem. The pickup could have been changed but who knows what kind of condition the distributor bushings etc were in. Easier to have a new distributor and not have to worry about weak advance springs or worn weights.

I remember looking for spare HEI weights in the junkyard. Pulled the cap off one distributor only to find the weights were seized. I can only guess the last owner drove like that and always complained about poor performance.