[kinghami3]

I have a 91 Honda Accord DX I'm having some issues with engine knock. It only happens once the engine has warmed up, but once it has I barely have to hit the pedal before it starts knocking. I just had the timing belt replaced (snapped on I-90 but the heads are OK), but that hasn't changed anything (it was doing this before). Any ideas of what it could be?

 

[MMike]

Knock is caused by preignition of your fuel charge. If your combustion chamber is really gunked up, it can reduce the volume, thus increasing the pressure which will cause the charge to ignite prematurely. It could be that. But are you sure it's actually engine knock?

 

[llkoolkeg]

Mileage? If excessive, it could be dirty comubustion chambers, bad sparkplug(s), etc.

Otherwise, improper engine timing, bad gas, engine overheating(thermostat?), overloaded(towing trailer), valve deposits or a hundred other things.

 

[spookydave]

is it a knock or a rattle. If it's in time with the RPM you could be hating it. Does it do it at all RPM's and at idle with no load?

If so it sounds like you have bearing problems or something like it. They don't knock (as bad) when it's cold and the oil is thick. Warm it up and it starts knocking in time with the engine you have something wrong in the bottom end.

If it's knocking at half time of the RPM it's in the valve train.

 

[kinghami3]

Mileage is about 178,000, fairly normal. When cruising or idling there's no knock, only after it's warmed up and I'm accelerating. I'm pretty certain it's knock, but I could try some higher octane fuel and see if that does anything. Is there anything that I could try (i.e. new spark plugs, specific engine cleaners) before I take it to the shop? Thanks

 

[spookydave]

well that's a good sign. First check the inginiton timming with a timming light.
If that's good then you could be one tooth off on the timming belt you replaced.

 

[kinghami3]

Ha, anyone got a timing light I can borrow? The timing belt is under warranty, so I guess I could ask the shop.

 

[mcA896]

some thing rather simple may be causing your engine knock. the solutuion: use better gasoline. my dad has a van that had engine knock when he puts regular gas in it, but it completely disappears when he fills the tank w/ premium gas. try that before replacing anything.

 

[dhtahoe]

Knock is caused by preignition of your fuel charge. If your combustion chamber is really gunked up, it can reduce the volume, thus increasing the pressure which will cause the charge to ignite prematurely. It could be that. But are you sure it's actually engine knock?

Almost!!! Sound like they got the cam timing off when they did the belt. This would ALSO cause a preignition issue. Because YOU SAID ABOVE that it was JUST CHANGED that is more likely the issue.

 

[kinghami3]

some thing rather simple may be causing your engine knock. the solutuion: use better gasoline. my dad has a van that had engine knock when he puts regular gas in it, but it completely disappears when he fills the tank w/ premium gas. try that before replacing anything.

Yeah, we did the same thing with my dad's Mustang and it solved the problem, but I would rather find a long term solution.
The knock was existent before the belt was fixed, but I still want to check it becaue it feels different than it did.

 

[Trailpimp]

If all else fails try a can of seafoam into the intake manifold via the brake booster line. This should help clear up any carbon build-up.

 

[dhtahoe]

The knock was existent before the belt was fixed, but I still want to check it becaue it feels different than it did.

Thanks for putting that in your first post :nuts:

 

[kinghami3]

Thanks for putting that in your first post :nuts:

I did.

I just had the timing belt replaced (snapped on I-90 but the heads are OK), but that hasn't changed anything (it was doing this before)

Maybe a slight over-use of parenthesis, but it's still there. My only problem with the timing belt theory is that it only happens after the car warms up, which would lead me to believe that it's some kind of gunk build-up in the engine. If the timing belt was off, wouldn't it happen all the time?

 

[Ian F]

Like MMike posted, I'd try premium gas and see if that helps any. I had an '86 Toyota that would only run well on 93 octane... pinged like crazy on anything less... very annoying... and expensive... If this helps, you probably have carbon deposit issues. You can try the various fuel treatments, but in the end it may require pulling the head to clean the chambers. I would lean away from the timing belt being off as if so it would really run like crap in all conditions.

Personally, I'm quite surprised a '91 Accord doesn't have an interference engine... My '91 Acura did... a broken timing belt = new engine (or at least a new head).

 

[kinghami3]

It does have an interference enginge, I'm just aparently one of the lucky few that have had their engine survive something like that. Carbon deposite would make more sense. Are there any cleaners that I can try? I could try the Seafoam into the break maifold thing, but what else would work?