Desperately need help - mechanic can't solve this problem
 

A little background first...

Bought my '01 Tip in early June. Got Kevin's UMW flash about 30 days thereafter. Within a week, I threw misfire CELs. Turns out the extra juice was exposing old spark plug incapabilities. Replaced the spark plugs and ignition coil packs (since I was in there already). Worked like a charm after that - no CELs, no bucking.

Fast forward a few weeks...

Accelerating on an off ramp, engine dies on me. Dash lights up like a Christmas tree. Still have juice, just no engine response. Have it towed to my mechanic, where he diagnoses a failed fuel pump. Replaces the fuel pump and, voila!, I'm back to running.

Fast forward two weeks...

On cold starts, I'm experiencing a peculiar behavior. I crank the car, it turns over, but idles lower/rougher than usual and has zero throttle response. It only idles. I turn it off, crank again, and it works. May take one or two attempts, but it would work. Had no issues at all on a restart/warm start. Mechanic suggests the drive-by-wire is acting up and may need to be "reset". I do the reset sequence - doesn't seem to do anything. Over the next week, it seems to be getting progressively more difficult to start without that peculiar behavior. Then, it wouldn't turn at all (but I hear the fuel pump priming)...just dead. Battery is a tad old, but given the intermittent cranking (when its not just "dead"), figured that wasn't likely the problem.

Hook up the durametric and reads a P0102/115 hit film MAF sensor. Oddly, it disappears when I run a second check.

Take it back to mechanic, who goes old school and runs a number of diagnostics with hand tools in addition to the computer. Says its running rich (it is - it always smells so). Replaces the MAF sensor and does another throttle adjustment.

Runs fine for about three weeks (though always smells like it is running rich). Then the problems return (either won't turn at all, or cranks, ignites and idles low/rough with no throttle response).

Today, I actually stalled out on the freeway at low speeds (bumpter-to-bumper idle+). Pull the car over to shoulder after engine quit on me. Restarts OK, drive to work.

I am absolutely clueless what is happening. Wondering if somehow the flash has anything to do with this - but it did not exhibit these symptoms for some time post-flash. I'm at the point where I feel I need to take it to the dealer/other mechanic - but have invested so much and don't want to have to start over on the learning curve.

Desperately need advice. Any ideas?

Clean and/or replace the MAF and perform a boost leak/pressure test to start. Rescan the ECU.

Low batteries and bad ignition switch cause gremmlins too. Might be one other place to look.

It sounds like an air leak to me. Have you talked to Kevin? He is usually pretty spot-on with diagnosis on such problems.

Jon

Sorry to hear of your recurrent issues. Best of luck getting it sorted out.

I just chuckled a bit reading your description of "accelerating on an OFF ramp", as I do that quite a bit too :D

Good idea.

Mechanic replaced the MAF sensor. Did a pressure test too. No leaks detected.

Running rich? O2 sensor not doing it's job? Low battery causes MANY problems...

you sure he did a pressure test? When I asked him to pressure test my all he did was want to hook it up to a smoke machine at 5 PSI.

let us know how he did the pressure test and to what psi...

It may be after maf but pre turbo leak.. are the o2s working right? did you swap exhaust recently?

Listen for your secondary air pump when cold. If it isn't running check the plug to make sure it is plugged in. The pump not running could cause the idle to be low and erratic seeing the ECU compensates for it running on cold start. Also check the air injection change over valves. I think it is related to vacuum line either in the air injection side or a check valve.

Maybe low voltage batt. clearing adaptive memory combined w/ dirty throttle body or just serviced or install k&n oiled type filter contaminating maf's,to add to the boost/vac leak & o2 possibilities ?

I will ask him how he pressure tested it. Mechanic said its unlikely related to O2 sensors. And of course I didn't swap the exhaust recently - unless you recall sending me an invoice (every time I get ready to have you build me one, I have to dump another grand to fix this love/hate relationship I now have)! ;)

Definitely going to replace the battery (its got an '08 stamp on it - so probably time in any event). He cleaned the throttle body when he did an adjustment last visit - and he also replaced the filter (using stock, not K&N) when he swapped out the MAF last trip as well.

I keep thinking that, as all of the fuel stuff seems to check out (well, need to verify the venturi tubes aren't kinked/broken), it is very likely related to air getting into the system. I'll raise this point with him and see what he says.