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Question about the motor in my 1984 Fiero 2m4... by 82-T/A
Started on: 12-26-2000 03:09 PM
Replies: 4
Last post by: Standard on 12-29-2000 03:15 AM
82-T/A
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Report this Post12-26-2000 03:09 PM Click Here to See the Profile for 82-T/AClick Here to visit 82-T/A's HomePageSend a Private Message to 82-T/ADirect Link to This Post
Ok ok.. just ran a compression test on all 4 cyls.

THis is my old 1984 Fiero 2m4 SE with the 2.5 liter Iron Duke.

Here is how it goes.

cyls are placed like this.

1-3-4-2

1 = 145 PSI
3 = 129 PSI
4 = 145 PSI
2 = 145 PSI

Ok, so obviously theres something up with Cyl #3.

Anyway, when I get in the car and start driving... the car shudders a little.. but it's very random.. totally sporatic.. like.. it will be studderning, then suddenly accelerate smooth as hell.. and then shudder again... and it makes a strange noise when it does this.

any ideas?

I'm guessing fuel pump maybe?

New plug wires, new spark plugs, new cap and rotor, new oil, new oil filter, new fuel filter.


Motor has 130 some thousand miles on it.

Thanks.

------------------
Todd Jaspers
1997 Pontiac GrandAm SE
1987 Pontiac Fiero SE/V6
1984 Pontiac Fiero 2m4 SE
http://www.ezshots.com/album.cgi?82tafiero/Apartment

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Motorhead
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Report this Post12-26-2000 04:06 PM Click Here to See the Profile for MotorheadSend a Private Message to MotorheadDirect Link to This Post
84's are notoriously
"Electrically Impaired!" Although trouble shooting one long distance by your description only is at best a foolhardy move!
However, here goes.

Something is definitely "up" with #3. But I really don't think it's enough to cause your problem.

There's only two things that can cause "Hesitation".

Prenuptual fears asside, it's fuel or spark.

Unfortunately we find ourselves dealing with those mysterious electrons passing through a myriad of devices known as sensors.

Having synced a few English carbs in my day. and puttered with a TR6 mechanical fuel injection, it seems the principal is the same, but the method of delivery is different.

KISS!!! KEEP IT SIMPLE!! Check the fuel filter and work toward the more expensive stuff!!

These cars like electrons! I spent a week chasing down a simple thing like a bad distributor!! Seems they use magnets in these new ones, and they like to lose their "attraction"! Not unlike myself at this ripe old age! Whatever happened to setting the points with a matchbook cover?!!

Hang in and set your troubleshooting guide by the cost of the part. Can't miss! At least you won't spend more than neccessary .
I'm Done!
Mike

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DavidHenshaw
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Report this Post12-26-2000 08:34 PM Click Here to See the Profile for DavidHenshawSend a Private Message to DavidHenshawDirect Link to This Post
82 T/A, I am in agreement with Motorman. You are showing about 10% difference in #3 cylinder compression which is within "this engine is still fine" range. I'm sure you also know that compression readings are to be taken with engine hot, all plugs removed, and allowing compression to build as the piston raises and lowers several times.

Now the problem. Like Motorman, I would go fuel dilivery first. Fuel pressure, fuel filter, maybe the carb is dirty. Run a couple cans of SEAFOAM through it. You add a can of SEAFOAM to a tank of gas and it might be all that's needed. I've used it with good results and have heard others recommend it highly. I bought mine a NAPA.

Good luck!

Dave

86 GT

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82-T/A
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Report this Post12-27-2000 08:19 AM Click Here to See the Profile for 82-T/AClick Here to visit 82-T/A's HomePageSend a Private Message to 82-T/ADirect Link to This Post
Thanks guys, I'll try that.

The throttle body is actually extremely dirty. I don't know what the hell it came from. The entire throttle body seems to be coated in some layer of oxidization... it was never like that before, but for some reason it just developed over the last really long drive I took it on.

The fuel filter is actually brand new.

I do have a fuel pressure gage.. where would I hook that up to on the 4 cyl? I've used it on the shrader valve on my V6 Fiero, but not on the 4 cyl. Should I hook it up to the fuel line directly?

By the way, the compression tests were taken when the engine was at it's coldest and with only one spark plug removed at a time.

Thanks guys.

------------------
Todd Jaspers
1997 Pontiac GrandAm SE
1987 Pontiac Fiero SE/V6
1984 Pontiac Fiero 2m4 SE
http://www.ezshots.com/album.cgi?82tafiero/Apartment

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Standard
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Report this Post12-29-2000 03:15 AM Click Here to See the Profile for StandardClick Here to visit Standard's HomePageSend a Private Message to StandardDirect Link to This Post
The fuel pressure gauge has to be hooked up in-line betwen the fuel filter and the inlet fitting of the TBI. Might have to get an adaptor.

I've been told to do compression checks on a warm engine with all sparkplugs out, holding the throttle wide open.

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