CRAZ8

When stepping on the gas my 8 sometimes hesitates, other times it seems ok.
Is there any way to tell if I have a clogged cat or a bad fuel pump?
I will be checking the cat very soon... Is there any way to know if the fuel pump isn't working properly? (Other than replacing cat and coils to see?)
Any info. would be greatly appreciated

RIWWP

iTrader: (2)

A clogged cat creates a cap on total airflow through the exhust. If you are flowing less than that, you may not notice anything.

For example, when I had a clogged cat on my MSM, I generated within 2hp of the same peak power number on the dyno, regardless of whether I had boost set to 4psi or 12psi (in 1 psi increments each run). When overlayed, the power would climb to that point, and then hold right there the whole way to redline, unable to make any more as there was a cap on how much it could flow.

A hesitation initially, but fine after that is the opposite of a clogged cat.

A fuel pump failure can be a pressure loss, in which case it is a gradual loss of power as the engine runs leaner and leaner (To the point of engine destruction), though usually it is a complete fuel pump shut down (which means the engine shuts off). Also doesn't fit your symptoms.

A brief hesitation on throttle tip-in is usually an AFR problem, normally from a fuel trim problem, which is in turn usually from a MAF or front O2 sensor problem. Take a look at the short and long term fuel trims at idle with the engine hot, and I would think that one or both is pretty far off from the -2% to +2% range it should be. If so, clean the ESS, clean the MAF, reset the NVRAM, reset the fuel trims, and let the engine idle itself warm again, and then re-check the fuel trims. If they are within reason, take it for a drive and see if the problem is still there. If so, test and/or replace the ignition.

Ignition isn't usually a problem only on throttle tip in, unless the AFR problem is making conditions too harsh for the ignition to make a proper spark. Ignition problems usually manifest first at idle or high RPM high load, but not really anywhere else until one of those two exists first.

CRAZ8

There has never been any problem at high rpm high load. Just notice sometimes on start-up when I first try to leave the driveway and sometimes on highway in 6th gear-always at low rpms. It seems the harder I drive it the less I notice there's a problem.

RIWWP

iTrader: (2)

That further points to fuel trims. Fuel trims are ignored the harder you drive.

Ber1n

You may be able to pressure test your fuel pump.

As for clogged cat, there's a guy on YouTube, Eric The Car Guy, and he shows you how to test for a clogged cat by using a laser gun, pew pew.

CRAZ8

So would a "Fuel trim" problem be a problem that would deteriorate quickly? It seemed even worse this morning...Hesitations seem to be lasting longer, as I push the pedal further to the floor it slowly seems to free up... and then I'm back in power.

CRAZ8

I'm doing the work on Saturday...
...Check cat
...Clean ESS
...Clean MAF
Reset. As well as change Coils, Plugs, and wires...
And hopefully this will solve all the problems.

CRAZ8

Just got back from garage. We ran a complete diagnostics to see what might appear. All seemed normal except timing was off and MAF had 0 volt reading (I got a new MAF on order getting put on Monday if all works out.)
If the MAF sensor is dead does that explain all my issues (difficult start, hesitations, loss of power..)?
Will installing the new MAF automatically correct my timing??

RIWWP

iTrader: (2)

Most crazy fuel trim problems are either a front O2 problem, or a MAF problem. Zero volts on the MAF would certainly cause all sorts of problems.

When you install the new one, reset the fuel trims and nvram again, then let it idle for 10 minutes or so before driving. You should be good to go after that.

CRAZ8

Cool, thanks RIWWP