Right & Left Knock Sensors, Surging at Idle
We have a 95 Acura Legend. We recently had a new head gasket put in and some other repairs related to overheating. It also had a bad VSS, which I replaced. It now seems to be running okay - no overheating or VSS issues, but the check engine light still comes on. The radiator was also flushed and the coolant replaced. The codes (23 & 53) indicate right and left knock sensors. The check engine light does not come on immediately, but only after the vehicle is warmed up (generally within a couple of miles). It then stays on. Sometimes we see a quick animation on the check engine light in which it looks like the top of the engine comes up (I assume this indicates the knock sensors). I've read through this and other forums extensively looking for a answers to this. I drained the gas (which was old) and replaced it with fresh 91 Octain Shell. I also added some Sea Foam to the fuel. It seems to run a little better with the fresh gas, but the check engine light still comes on.
Also, the car starts fine cold, but after it is warmed up, if I turn it off, and then start it again without stepping on the gas at all, the engine will surge over and over as if I'm pumping the gas. The RPMs are between 1,000 and 1,500.
I'm not an experiencd auto mechanic at all - though I can follow instructions and generally figure things out with some help. I would be grateful for any suggestions. I have some specific questions below:
(1) If the knock sensors are bad, wouldn't the check engine light come on immediately - or does it make sense that the car has to warm up first.
(2) I'm not experienced enough to know if the engine is actually knocking, or if the problem is with the sensors - is there an easy way to tell?
(3) If the fresh gas I put in fixed the problem (knocking), do I need to clear the codes to prevent the check engine light from coming back on.
(4) Could air in the cooling system cause the knock sensor problem? The surging of the engine when restarted warm?
(5) Does the fact that I'm getting codes from both knock sensors indicate a wiring problem - it seems like of unlikely that both would be damaged (but maybe not - the mechanic who replaced the head gasket doesn't work on many Acuras).
Any suggestions about what I should try or where I should go from here? I've put around $2k into this car in the past few months and still can't get the thing registered here in CA due to the check engine light.
Thanks in advance for any help
Last edited by DougB59; 02-22-12 at 02:41 AM.