Ex540guy

Did the search, couldn't find an answer. It's always given a couple of rattles on hard tip-in, but now there's a slight pinging at light throttle as the revs climb. In the old days, I'd recurve the distributor (assuming fuel mixture was OK), or, in not-so-old-days, check to make sure the EGR was working properly, but I'm not sure what to do here. Any ideas? I'm running 91 octane, the best we can get around here. Everything's stock except for Borlas, no front resonator, K&N drop-in, and 11/2" hole in front of airbox.

LB Lex

I'm currious to know too. I had a pinging for a couple seconds, but this only occured twic since I got the car in October 2004. It happened also during throttle tip-in. It happens no other time (hot, full throttle acceleration, etc.). I have a feeling it might be the TPS sensor going bad because the sensor is probably telling the computer the throttle is almost closed when it's not, so the computer adjusts the timing wrong, hence the pinging.

beaterKU

I had a bit of pinging. I had my TPS sensor changed out for an unrelated problem and the pinging is no longer.

-Nick

Hollywood

Hmm that's interesting. I wouldnever guess a TPS would be responsible for knocking, but it's good to know. Usally I'm used it to be too much timing or too much PSI/af's.

LB Lex

You're right, it does have to do with timing. A malfunctioning TPS would tell the ECU the incorrect throttle position (opening), so when the ECU adjusts timing, it is wrong and the engine knocks.

Ex540guy

Are the TPSs adjustable on these cars? If so, does anyone have the spec?

BeaterKU - what did it cost to have the part changed out?

LB Lex

The TPS is adjustable, but by the dealer because they hook up a computer to calibrate it properly.

Your best bet is to buy the part from Carson Toyota because they are significantly cheaper than a Lexus dealership. Then bring it to a Toyota dealership to see if they can install it for you, if not, bring it to a Lexus dealership.

chicagoblknazn

What is pinging?

LB Lex

Unwanted ignition of the air/fuel mixture in the combustion chamber. Can be caused by improper timing, wrong octane, too much compression, etc. What happens is while the piston is travelling up the cylinder, the air/fuel mixture prematurely ignites (explodes) before the piston reaches the very top of the cylinder. This reduces engine power because the mixture ignites and tries to force the piston down the cylinder while the piston is trying to go up the cylinder. The premature ignition causes a rattling sound, sort of like shaking a soda can full of metal marbles.

Ideally, the mixture ignites when the piston is at the top of the cylinder so the explosion forces the piston down the cylinder.

chicagoblknazn

And this is how space travel in warp speed is achieved.....you are brilliant!!

I understand now. Thanks. If I were to have that happen, I think it would startle me.....

clarky86

I would think the check engine light would appear if the TPS was not functioning. It did on my Camry (according to the code) and it turned out to be a dirty connection.

Ex540guy

I think clarky86 is right about the CEL.

On every other car with MPFI I've had, the TPS could be set with a DVM. Do you really need a computer to set it on the GS4?

If it's bad, does anyone know the cost for part and labor off the top of their head?

Guitarman

I too have had tip-in throttle pinging since I've owned my GS4. It's very brief, and you really have to have the windows down and radio off to hear it for the split second it occurs, but it's there.

My shop said to run so Sea Foam through it, but others say not to worry about it since it's so minor.

I know some manufacturers cite light detonation in their owners' manuals as being normal, and actually improving gas mileage, and not to be concerned. I know my mother's Mercury Sable had this right in the book, but that wasn't a high performance vehicle either, so I'm not so sure this is normal for the GS since it IS.

Heavy pinging can cause serious damage to an engine, but light intermittent shouldn't be too big a concern.

3 years now, and mine was probably this way from the get-go. The car doesn't seem to mind.

Still, if anyone can offer a true clue, I'll follow up on it.

LB Lex

This was true with the 1st gen GS because I've actually done it myself, but the 2nd gen GS is different.

DASHOCKER

iTrader: (2)

Do a professional engine flush. That should quell the problem.