Formula engine knocking on mid revs when warming up (Page 1/1)
ufa JAN 16, 09:53 AM
Hello all,


Since a couple of days the engine start knocking when it warms up, driving on mid revs, driving on low revs will not provoke a knock.
Is it the bearings, or could it be pre ignition?
I had a burst water pump earlier this year that made the engine boil, no idea, but might have something to do with the issue.
The car has only ran 42000 KM so used very little.
The car is a fiero formula.
Thanks in advance!

Ulf

[This message has been edited by ufa (edited 01-16-2023).]

sleek fiero JAN 16, 09:13 PM
It is possible that the overheat might have caused damage to your pistons. If it was a bearing issue you would probably have a noticeable drop in your oil pressure at hot idle. Overheat can cause piston skirt damage and knocking/rattling. Just a possibility. Very unlikely ignition detonation.
ufa JAN 17, 04:39 AM
The drop in oil pressure only happens when I am driving in curves in the road.
The overheating happened early June and the ticking, knacking sound just started. The sound is quite subtle, I can not hear it with the stereo on.

What can be done about the piston issue if it is that? Do they have to be changed?
Mike in Sydney JAN 17, 05:12 PM

quote
Originally posted by ufa:

The drop in oil pressure only happens when I am driving in curves in the road.
The overheating happened early June and the ticking, knacking sound just started. The sound is quite subtle, I can not hear it with the stereo on.

What can be done about the piston issue if it is that? Do they have to be changed?



Out or curiosity, have you checked your oil level? If the oil is too low, you could experience the drop in oil pressure and possible the faint "knacking" sound.

What year model is your car? What engine do you have? Is it a 4-cylinder or a V-6?

In 1984, the manual said to fill the 4-cylinder Iron Duke engine with 3-US quarts / 2.8 litres for an oil change which was too little. This resulted in thrown rods and engine fires. The correct oil level is 4-US quarts / 3.8 Litres. A recall changed out the dipstick to one that reflected 4-US quarts of oil so if you have a 4-cyl, You should be running 4-US quarts / 3.8 litres of oil after an oil & filter change.

The 2.8L V-6 engine needs 5-US quarts / 4.7 litres of oil after an oil & filter change.

If I were you, I'd change the oil and filter. If it's a 4-cyl, I'd put in 3.8 litres. If it's a V-6, I'd put in 4.7 litres. Check the dipstick after filling to these levels and top up after cranking and letting the filter refill. If the oil level is higher on the 4-cyl dipstick than the full line, then you probably have one of the older improperly marked dipsticks. You should remark the dip stick with a punch or file to reflect the correct, 3.8 litre oil level.

[This message has been edited by Mike in Sydney (edited 01-17-2023).]

theogre JAN 17, 08:48 PM
Noise can be many things. Maybe related to Overheating or not.

OH may release old crap stuck to metal and oil flow can push it to anywhere... Valve Lifters and more and plug small holes/parts.

But "knocking on mid revs" can be Ignition, EGR and other problems too.

------------------
Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave

theogre JAN 17, 09:01 PM

quote
Originally posted by Mike in Sydney:
Out or curiosity, have you checked your oil level? If the oil is too low, you could experience the drop in oil pressure and possible the faint "knacking" sound.

What year model is your car? What engine do you have? Is it a 4-cylinder or a V-6?

In 1984, the manual said to fill the 4-cylinder Iron Duke engine with 3-US quarts / 2.8 litres for an oil change which was too little. This resulted in thrown rods and engine fires. The correct oil level is 4-US quarts / 3.8 Litres. A recall changed out the dipstick to one that reflected 4-US quarts of oil so if you have a 4-cyl, You should be running 4-US quarts / 3.8 litres of oil after an oil & filter change.

The 2.8L V-6 engine needs 5-US quarts / 4.7 litres of oil after an oil & filter change.

If I were you, I'd change the oil and filter. If it's a 4-cyl, I'd put in 3.8 litres. If it's a V-6, I'd put in 4.7 litres. Check the dipstick after filling to these levels and top up after cranking and letting the filter refill. If the oil level is higher on the 4-cyl dipstick than the full line, then you probably have one of the older improperly marked dipsticks. You should remark the dip stick with a punch or file to reflect the correct, 3.8 litre oil level.

Year and Engine Q are needed.... but is Formula so is 88 often w/ V6.

Miss quoted GM Recalls is often bad or worse then not having a recall done. And Not Applicable to 88 4 cyl.
84 4cyl Engine Recall covers many issues w/ this engine...
To Properly increase oil capacity:
1. Charge Dip Stick and Tube to change final level.
2. Change tiny PF47 to long PF51 but GM discontinued that so use PF52. Both added oil capacity but 52 also used anti-drain.
Both are required to add oil capacity.

But Current "PF52" are made different and has less volume and change oil capacity < 4q/3.8l
So to keep capacity @ 4q, use other brands still has long filter like number w/ 3980 (letters before and after change by grade and brand.)

All Fiero 4cyl...
If has to reach over the valve cover to check oil then Recall was Not done.
New stick and tube moves the handle next to the T-stat tube on end of the Head.
While Only 84 officially added oil capacity but 85-87 can use the long filter and expect to add some more oil to reach the Full mark. I use the long filter just because easier to reach them.

88 4cyl is nothing like 84-86, maybe shares some parts w/ 87 but use different oil filters in the oil pan.

Don't use the long filter on V6 because often too close to exhaust pipes and cat.
ufa JAN 21, 10:12 AM
I had the car at the mechanic and he managed to fix the issue.
A completely clogged filter in the end, oil pan was full of crap as well, but no big issues according to him. Thankfully.
Now running like a dream again.

I got the car last may, and there has been a seties of issues since, the car has sat in a barn for 9 years before that.

Couldnt find replacement plastic pucks for the headlight motors, so in the end i ended up printing them, so that works fine now as well.

Still need to fix the cassette player, always gets stuck when i put in a cassette.
Also the trunk lock is destroyed, so need to find a new one.
And some small issues.

But all in all, I am happy with my 1987 fiero formula.

Thanks for the input and help! Much appreciated!

Ulf
Notorio JAN 21, 11:23 AM
Ulf,

Welcome to the forum and the fun of driving (and fixing) a Fiero! The Mall is a good place to make a 'Want to Buy' post for items you need to find because many of the forum members have a large stash of parts. It is very typical when a car has not been run for many years in storage for several things to deteriorate to the point where they seem to be OK at first but then start to fail during the first year of driving: oil seals, brake-related seals, ignition module, etc.

Enjoy your Fiero!

John