Hesitation under load when hot - please help

[RAR]

Hello,

I just bought my car about a month ago (I have only driven it 130 miles), the car is a stock 95 Firebird with a 3.4 5-speed and 79,000 miles (also I paied 3,750 for it - did not seam bad...).

The problem is this: under a load (like going up a hill in 4th gear, or accelerating) the car will ping and knock and sometimes backfire. This gets worse when the car is hot (up to tempature).

Here is what I have done so far:
1. New plugs (the old ones were almost new and they looked fine)
2. New wires (again, the old ones were newer)
3. New fuel filter (I have a good feeling it was the orignal).
4. Changed the oil and filter

The car is not throwing the check engine light (I can not check the codes because paper clip trick does not work for some reason: I have an OBD II plug, but the car is OBD I (according to the sticker in the engine compartment)) - any suggestions? ? ?

I know the car faied the e-check here (emissions) twice (according to carfax) but it passed before I bought it (by the last owner) - although the test paper did not have the full results, but the BMV here accepted it - so I am good for two years.

As far as the service record of the car - I have no idea the guy that had it before me only owned it for 6 months and did not get plates on it. Before that it was a bank repo so who knows how it was taken care of....

Any suggestings would be greatly appreshiated (sp??)..

Thanks in advance.
RAR II

[StegsRide]

coils maybe?

[John D.]

<blockquote>quote:</font><hr>Originally posted by StegsRide:
coils maybe?<hr></blockquote>

Coils or check the catalytic converter. I would bet coils though.

[RAR]

I see John D is back helping me out...

Thanks,
Do you know of a way to test them?, also about how much do they go for?

Thanks,
Richard

[RAR]

Hello,

Ok I looked on autozone website $30 a piece (you need 3) for the wells brand or $50 for the accell should I replace them all or just one at a time?

Also would testing them do anything, because it is only a probem with heat and load.

Also how can you test a cat? - how would that cause this problem?

Thanks again,
Richard

[BradC]

Mine pings when I use 87. Try 89 octane.

[John D.]

<blockquote>quote:</font><hr>Originally posted by RAR:
I see John D is back helping me out...

Thanks,
Do you know of a way to test them?, also about how much do they go for?

Thanks,
Richard<hr></blockquote>

You can check them for resistance just like plug wires. I think some coils suffer from heat soak, which may be why you are only seeing the problem after the car is warmed up. I would only replace the one that is causing you problems.

As far as the cat: The only way I know to check it is by driving the car for a bit and see if the cat is exceptionally hot, it would be hotter than the rest of the exhaust, almost to the point of glowing. This can cause problems by not letting the exhaust gasses out well enough and basically choking the engine.

I still am leaning towards the coils though.

[ August 18, 2003: Message edited by: John D. ]</p>

[RAR]

Thanks,
I will pick up a new coil tonigt and give it a try...

Thanks again to all.

RAR II

[RAR]

Well thanks to all....

It was the spark module, - it was the one closest to the engine, go figure...

NOW ON TO THE NEXT PROBELM - LOW OIL PRESSURE !

Thanks,
RAR

[toast]

Hey Rar, who did you know it was the igntion modual? I assume your are refering to the thing that the coil packs plug into. My bro's 2.8 misses under load and it seems to get worse when the car heats up. I have tired new plus, wires, fuel filter, and coil packs. Nothing seemed to work. BTW how much was the igntion modual?