1993 Buick Regal 3.1l V6 Multiport injection, hard start and rough idle, will not start on occasion

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regal

#1

1993 Buick Regal 3.1l V6 Multiport injection

Problem: The care currently has a hard start, and a fluctuating idle. I bought the car a year and a half ago it still has low miles about 94,000. The care used to start fine but had a fluctuating idle in the range of 750 to 2500 rpm. My brother who is a mechanic and doesn’t live near helped me do all the gaskets when he visited. Then the idle fluctuation dropped to 750 to 1000rpm, when the car rpms fluctuate there is a whirring sound I can hear from the cab, like a pump or pull system. On occasion there is a vibration as well but it is inconstant and irregular. Fuel pressure seems to fluctuate as well. If the car will not start I give it a little gas and it will run fine after a minute or two, but then the idle starts to fluctuate.

No fuse issues I can tell and relays seem to be fine.
Checked for lose wiring connections found, none.

I have replaced:
-Hoses and gaskets
-Starter motor
-Battery
-Fule Pressure regulator
-Fule Filter
-Spark plugs and wires
-TPS
-Idle Air control Valve
-Crank shaft sensor
-PCV

Right now I’m thinking it could be the fuel pump (a nightmare to change on this car), a fuel injector failing, and the ignition switch.
If anyone has any ideas or has had issue with this motor before please let me know.


#2

You’ve spent a lot of money and time chasing this problem, can you tell what testing brought you to replace the TPS, crank sensor, IAC valve and fuel pressure regulator? I hate to say it, but I think the $100 diagnostic at your local independent repair shop would have gotten you closer to fixing the problem.

I think it’s time to get the car hooked to a scan tool and find out what’s going on. A wealth of information is available through the data port and an experienced mechanic can probably identify the problem within 10 minutes without opening the hood.

Fuel pump isn’t the likely culprit but also easily tested. I suspect a shorted injector but need a scan tool to check for that. BTW, the fuel pumps on these cars are among the easier ones to replace.


#3

I don’t know if it has a map or maf, but they can cause idle problems. Injector coils can easily be ohm checked. Fuel pump is old aand needs to be pressure tested.


#4

Before pulling the fuel pump I would measure the voltage at the fuel pump using insulation piercing probes.


#5

" Injector coils can easily be ohm checked. "

Only after you pull the upper intake manifold. Which I would never do until I was certain the problem was under there in the first place. Better to use scan data to find where the problem is.


#6

On the things replaced, “hoses and gaskets” is pretty vague. It sounds like you must have had a vacuum leak early on. About 2 minutes with a vacuum gauge can tell you if you still have one.

Mostly I agree with asemaster - it looks like there is a lot of parts throwing which rarely saves any money (or aggravation). So it would be best to get it on a scantool.

On the other hand, I also know what it’s like to not have anyplace nearby and not have anyplace that you really trust (both in terms of having the equipment and knowing how to use it). Shops are known to also throw a lot of parts - but much more expensively.

So anyway, if you’re not going to take it in, do a thorough check for vacuum leaks before doing anything else.


#7

I took it in to the local shop and they found nothing with the car. The care still has the issue of the idle varying but starts fine now. I replaced the TPS and some of the other sensors to see if they were the issue but also a lot of the original parts were meeting there end with wear and tear. The hoses that were replaced were for the Coolant system and the larger one off the Throttle body.

I will have to look in to getting it vacuum check, i don’t know how but i’m leaning that way.
Ill see if there’s another shop with the equipment to check it. Thank you!


#8

Good comments above, esp about getting a pro to do an OBD-based diagnosis at least. That would be money well spent.

Re vacuum leaks. Three are sometimes sneaky ways air can get into the engine. For example if your car has power steering, and you turn the steering wheel, there’s often a gadget in the power steering pump that opens an air valve and allows extra air into the engine to compensate for the extra drag of the power steering pump. To avoid stalling out when you turn the steering wheel at idle. And if you turn on an accessory that draws a lot of current, like a electrical rear window defroster, or the radiator fan turns on, the computer may activate a vacuum solenoid to allow extra air into the engine, to compensate for the add’l alternator load. Again to avoid stalling. These devices have to be tested one by one as part of determining the cause of inconsistent idle speed. The owner can sometimes discover a problem with these just by activating whatever is supposed to increase the idle speed and listen if it does. Usually the mechanic will just temporarily clamp off the fresh air hose going to or from them. I may have mentioned this to you before in another thread, but if your car has an idle adjustment screw, sometimes called an idle-air-bleed screw, that being out of it’s allowable range can cause this symptom too.


#9

@KeeganB‌

If you want to find vacuum leaks, tell the shop to use its evap/smoke machine

It’s the quickest and most effective way to go about it

If they don’t know what that is, it may not be the right shop for you