91hatchgt

Alright, here's the deal. I was driving to my home in AZ last week, and on the way I had to pass a couple big rigs. Well, when I downshifted to 4th, and hit the gas, it started to ping. My timing is at 10* so I know it's not that. So what could it be?

I think is must be running out of fuel when under a hard load, could it be the regulator going bad? or maybe the fuel pump? The car does have 200k on it so I'm sure I should replace both of them, but what should I start with? Could it be something else?

TIA

mjr46

could of been a crap tank of gas but with 200k probably have some carbon build up in cumbustion chambers try an induction cleaning

r.barn

The pinging is definitely detonation so you need to gets this fixed.

could any number of things, from low fuel supply to hot spot on the piston

Start by checking your plugs, they will tell you alot about how lean you might be running.
You might need to take the heads off and take a look insed the cylinders too eventually.

91hatchgt

Nah, it happened on the way there, and on the way back... I used 89 Octane on the way there, and 91 on the way back to see if it would help any. It did help, but it still pinged a little. I just put new plugs in it, and the old plugs looked fine, normal color no real signs of running lean. I think because is only runs lean when it is in the higher RPM's. So could it be the pump not being able to supply the needed amount of fuel when the engine is spinning at about 4k rpm's?

91hatchgt

Just another thought, I havent changed out the 02's yet, could the 02's be old and/or bad causing a lean condition?

mjr46

well since you've tried two diffrent grages of fuel and no change.detonation can occur if mixture is to lean best way to check car is run a koer test look for codes and or watch o/2 sensors on a data stream or use a multi metor and back probe pin connections. also detonation could be occuring as a result of excessive carbon build up in cumbustion chambers which will raise compression and cause detonation too.

94Blk5.0

I would try running a Fuel System Cleaner trough your next tank of gas. The good stuff, not just injector cleaner. Then a new fuel filter would be a good idea if it had not been done. I changed mine when i got my car, it was clogged bad, felt a difference. Possiblity the mass air flow senor is dirty clean with a q-tip and alcohol, carefully. As for O2 senors, if they are bad, you should get a OBD code with a scanner.

Sweet Car!

91hatchgt

What kind of fuel system cleaner would you recommend??? I have never used the stuff so I have no idea... I will change out the fuel filter asap, and maybe get some new 02's...

mjr46

Well we use at my shop BG PRODUCTS and the fuel induction cleaner is a 2 part system from them and it is sprayed in at the throttle body with a canister that is pressurized and has a light mist output. for the tank it comes with a can of 44k and for the pressurized system a industrial strength can of fuel induction cleaner (this crap works great!!!!) but you can't buy it at auto zone so just go down to the local parts store they should sell something like seafoam or a comparable product for decarbonizing your motor

94Blk5.0

Off the self products like STP Fuel System Cleaner, Chevron makes some good stuff. I like to run the tank low, stop for gas add cleaner First, then pump aboubt 12 or so gallons on top. then run the tank low again, repeat propcess if nessary. As for the STP it treats like 21 gallons and i like to run it a little stronger than that. considering there is prob. a few gallons stillin tank then i put in 10-12 gallons in, thatshould be fine.

Or you could have it professionally done as metioned above. But the off the self stuff sould remove most build up. And with 200K on it I wouldlook into the MAF that wire could be dirty and therefore creating a lean condition as it did in my car.
Good luck.