zbrewha863

I don't know if this is the right place to post this, so sorry if it needs to go somewhere else.

Spoiler -- skip to end for general question w/o back story

A couple months ago my engine blew up. One month before that, I had a valve adjustment done at a Honda dealership (I will call them Dealer 1). The night it blew, I was with a Honda mechanic who has an S2000, and he told me to pull the main relay fuse under the hood. At the time, neither one of us thought the engine blew at all, we thought there was a faulty sensor or something, the whole thing puzzled both of us and this guy knows about Hondas.

For reference, at the time I was crusing along, merging onto the interstate at about 45mph (nobody else around) when the car just suddenly wouldn't rev past 2k rpms, then just lost all power from the engine.

I take the car in to Dealer 2 (close to where I live, as Dealer 1 is about 500 miles away -- close to parents, had valve adjustment done while home for holidays), who tells me that my car's timing slipped, causing a valve to drop and get beaten up by my piston (retainer craked too). My car was one month out of Honda Certified Warranty. I call Honda to try to have them goodwill it, and they tell me that they will have to run a diagnostic first. They say that their diagnostic will pick up any overrevs, so if I overreved the car ever they will certainly not goodwill anything on the engine. I tell them about resetting the ECU (I honestly didn't even know that's what would happen when my buddy told me to pull the fuse), they tell me it won't matter, I tell them to go ahead and run a diagnostic b/c I've never overreved the car.

Diagnostic comes back clean, engine has never been overreved.

I tow the car 500 miles to Dealer 1 for teardown (per Honda's instructions, as they have at this point "unofficially" guaranteed me they will goodwill me a new engine). Dealer 1 refuses to look at engine, says I obviously overreved it, they are going to run a diagnostic to determine that that is the case. I tell them to go ahead, diagnostic comes back clean. Then the tech says that 15-20% of the time, the ECU doesn't pick up overrevs b/c it won't pick them up if you miss a shift and overrev it while in neutral (?). I tell him that is and he needs to tell Honda what to do about it.

The question is, is he right about what he is saying? My engine didn't even throw a code when I tried to restart it with the blown engine, and the log on the ECU came back clear (did say that I had redlined a few times and had missed some shifts, but that's it, never overreved). My parents basically believe the tech about the whole thing, that I somehow overreved it in neutral when I missed a shift and the ECU therefore wouldn't pick it up (parents ending up getting talked into paying the bill by Honda after Honda assured me they would goodwill it -- shady bastards).

Short synapsis -- does the ECU really miss 15-20% of overrevs becauese people overrev the engine by missing a shift and overreving it while in neutral?

Thanks in advance!

SpitfireS

The engine can't overrev in neutral.
The ECU will prevent it by cutting fuel supply (or stop ignition or both.. I donno for sure)
An OEM S2k ECU failing to prevent overrevs in neutral would be a first IMO.
(NOT mechanical overrevs, the ECU can't do anything to prevent them)

Blew up?
What happened to it?
Do you know?

Slows2k

02 S2k's will not store an overrev code. Never seen a slipped timing chain either. Both of the techs either don't know what they are talking about or what they did say was lost in translation.

The PCM's in 04's and later cars will store a overrev code and record Max RPM.

There is no way the PCM in your car said it was never over reved.

If the engine was overeved sometime in it's life it's very possible a valve retainer was cracked, and later dropped the valve, many miles later.

We've seen cars go 30K+ after an over rev then break.

zbrewha863

Yeah, that's what I thought.

Blew up -- this is the explanation I got. The timing chain skipped a tooth, causing the valve to be coming down while the piston was going up. The piston then hit the valve, snapping it in half and breaking the retainer, at which point the valve fell into the cylinder and was banged around by the piston about eight times.

Result -- scored cylinder wall, destroyed piston, destroyed valve, destroyed retainer.

zbrewha863

[QUOTE=Slows2k,May 9 2009, 10:43 AM] 02 S2k's will not store an overrev code. Never seen a slipped timing chain either. Both of the techs either don't know what they are talking about or what they did say was lost in translation.

The PCM's in 04's and later cars will store a overrev code and record Max RPM.

There is no way the PCM in your car said it was never over reved.

Slows2k

The customer service people at AHM don't have a clue either. even if the valves are horribly adjusted, the timing chain tension is not effected. The chain drives a single 2 piece gear than drives the cams gear to gear. The chain does not directly attach to the cams.

Now a bad valve adjustment will burn a valve seat, but not drop a valve.

If the valve's head was stuck in the piston crown directly over the valve relief, it's safe to say the car was overreved.

zbrewha863

It doesn't really have to do directly with the valve being adjusted improperly. The way it was described to me, the crank pulley wasn't tightened down properly after the valve adjustment, which caused the pulley to come loose, causing the timing chain to skip a tooth.

I didn't get a chance to look at any of this (since Honda took over the inspection), so I don't even know if it's possible for the sequence of events to play out that way. Since I didn't get to examine the piston or the valve, I don't know exactly what the case was, but I would guess that the valve head did make contact with the piston crown directly over the valve relief.

It just seems weird to me that nobody at AHM or either of the dealerships would know that the ECU wouldn't log overrevs, and then AHM would chalk the whole thing up to a faulty retainer and agree to pay for the engine if the only possible explanation was that it was overreved.

RedY2KS2k

More cluelessness. On the S2000 you tighten the bolt to rotate the engine from tdc to tdc.

negcamber

Just one other argument against the concept that the ecu won't log if the car is in neutral...ask them how the ecu knows what gear the car is in (or is not in)? What sensor tells the ecu the gear the tranny is in or if it is in neutral?

Slows2k

The crank pulley bolt should never have been loosened to do a valve adjustment, it takes a Pulley holder and 200+ftlbs of force to loosen the bolt. No to mention the engine is rotated clockwise to adjust valves, which wouldn't loosen the bolt in any way.

If you know what you are looking at on the data list you can determine if the engine is under load (in gear) or not. AHM doesn't publish over rev DTC's or list what cars will set them. The overrev DTC is to log that the car was mechanically overreved, and that what caused the failure.

I can tell you by experience after the S2k and RSX-S came out and owners started confusing 4th and 2nd gear then lunching the motor Honda added the overev DTC to cover themselves. When the AP2 and the Mid model run refresh on the RSX came out the overrev DTC was added to the PCM's.

There are also data stream differences in 00-01 cars vs 02-03 04-05 cars. The PCM's are changed with revisions and some parts of the datalist like misfire counters get added.