JimRockford

Hi,
I am hoping one of you third gen experts can help me fix a problem I am having.
I have a 1990 Firebird with the TBI 305 and auto trans.
I am the second owner of the car and it was owned by an older adult since it was new,it is 100 per cent stock and was always maintained.

The car runs great in the morning when first started,accelerates quickly,no pinging,the gradually as the engine gets near the 220 area it pings upon acceleration going into 3rd and 4th and it doesn't seem to accelerate as fast.
It still idles fine though.

The owners manual says I can use 87 octane fuel so that's what I am currently using,according to the owners manual only the TPI needs 91,is this correct?

I have sent away for a new fan switch that will turn the fan on much sooner as it doesn't come on until the gauge is a little past 220.

This pinging is really bothering me,any advice would be greatly appreciated.

Have any of you had this problem?

camaronewbie

Might check timing. Disconnect the EST wire, start car, check timing with EST wire disconnected. Should be zero, but can bump it up, I think 4* BTDC is the max you want on a stock TBI car. If you have a Harbore Freight close by, they sell a fine basic timing light for about $15.

JimRockford

"Camaronewbie",
Thanks for the tip,I'm not sure the timing has ever been messed with but I will see of I can borrow a timing light and check it.

If that doest solve it what else would you suggest?

My previous firebirds didn't have all the computer stuff.

Should I be ok running 87 octane in a 305 TBI car?

camaronewbie

Should be fine with 87 otane, I always ran it when I had TBI.

Might also check spark plug gap, change plugs/wires/cap/rotor if it's been awhile.

JimRockford

Which is the Est wire?

camaronewbie

Oh - another thing that's obvious that I missed - knock sensor - might need to replace it, or make sure wire is good to it. Knock sensor pass side block, down low, by #6 and/or #8 spark plug, below those plugs on block.

EST wire should come out of pass side wiring harness, close to the pass side strut tower, will be tan/black wire, comes out of loom, has connector on it, then goes right back into same loom.

JimRockford

So the knock sensor is basically down near where the fan switch is then,right?
How do I check it to see of its good? Is that a part that fails often?

torque_is_good

you could also spend 10 cents more per gallon on 89 or about $1.50 per week and not mess with timing or knock sensor


octane is the ability of the fuel to resist detonation (pinging)

imagine that, your engine is pinging. Going up a grade will make the ping go buh bye.

None of my vehicles use 87 be it the Honda, Mazda, Nissan, Mercruiser, Camaro, Camaro (yes 2 camaros), Mustang, lawnmower, leaf blower, weed whacker, chain saw.

octane can be +- 2 so 87 could in fact be 85

cheapest performance upgrade is run higher octane and advance timing

In the newer cars the computer advances the timning automatically