Pre-cat emissions test...a good guide to engine health?

By no means am I an expert on the matter, but I believe most on here would recommend a compression and leak down test if you want to check the condition of the valve guides.

 

It is a very good test of state of tune but does not rule out mechanical condition problems. It will not test well if there are serious valve guide, ring or cylinder wear problems but a compression test/leak down test can predict it far better and measure it before it becomes symptomatic.

 

Cost of compression/ leak down test today - reasonable.
Cost of cylinder head removal/value guide replacement in a few months/years .... ?
I will leave that choice up to you, I did not have one done .... But thinking back

 

I would think Long term fuel trim numbers would give some indication of what the engine management system is trying to correct or not correct.

 

if it runs well and no smoke.
go for it.

I didn't care about any PPI or compression test either. didn't even test drive my car when I bought it.

I just wanted it

 

It gives you no idea what it is trying to correct, only that it is doing so.

 

Could be wrong but I believe what he meant is not that fuel trims being out would reveal the source of the problem but it's better to see little correction rather than a lot on one or both banks.

 

You could be right but I gave up mind reading a long time ago.

 

I get a lot of practice, my girlfriend expects this of me for some reason.

 

Thank you INTD8, I think LTFT can be helpful in evaluating overall running of the motor. Especially with dual banks.

What I meant was that if one bank had a high positive fuel trim, it would indicate the the ECu is trying to compensate for a lean condition.....what is causing the lean condition is for you to search for.

 

That's their job.


I still cant figure out when I say ABC she hears xyz.

 

It becomes a matter of how many tests to run but that one is easy.

Still, like the exhaust sniffer does not make a compression test redundant.

 

Good to know mine isn't unique!

 

Very Astute.


Every car that came with bronze guides will need them replaced. We know that even the information provided by Ferrari when they quit using them is incorrect and many have already been replaced.


Caveat Emptor

 

Im not sure if anyone else has seen this or not, but found emissions to not mean a lot when it comes to guide issues. I recently saw a car that undoubtedly needed guides pass like a new car but drank oil like a fish breathes water. Weird but I'm no expert

 

When the cars were still under warranty Ferrari had us try every method of measuring and testing, SD1 tests, emission tests, you name it we did it to support a suspected case of bad valve guides for warranty repair and it was never found. I must have personally turned in 50 SD1 print outs and exhaust analyzer print outs from known good cars and suspected bad cars for data comparison. It was all a waste of printer ink cartridges.

Compression and leak down tests were found to be the only reliable gauge and was only evidence and not proof until the motor was taken apart and guides measured.


BTDT years and years ago. Nothing new has been learned about any of this since about 1997.

 

At least this lasted longer then checking emission health via "choke tubes" on mission equipped carbureted cars in the mid to late 70's. That's was a joke also.

Yep I'm that old LOL