Backfires, rough idle, & stalling oh boy!

[far972]

I've developed some major problems with my engine at idle and starting over the past few days and I'm hoping for some help in diagnosing...

Here are the symptoms/history...

Two months ago the car became difficult to start on every 4th or 5th attempt, felt like I had to give it gas to get it to turn over.

Shortly after this started I get a CEL that was MAF related, I don't remember the code. After I replaced the MAF the CEL went away, the engine ran smoother, accelerated better, etc, however I still had the hard starting problem. This lasted for about three weeks.

Last week when trying to start the car, I got a pop/backfire and smoke for about 10 seconds. No CEL.

Last Friday I changed the oil and filter, it wasn't low, and then added a bottle of techron to an empty tank trying to deal with the hard starting (cleaning the fuel injectors). The car ran fine all weekend up until last night. At this point I was running on fumes, the last of the tank with the techron additive and as I pulled into the gas station the car started to sputter and seemed like it was about to stall. I figure, "Eh, I was just running the tank dry"

I figured wrong, now the car does not want to idle at all, RPM's are super low, and giving it gas causes some shuddering and a few pops... When I come to a stop I need to over rev the engine to prevent it from stalling, which it has done a few times already. Still no CEL

I am thinking I wanted to change the AOS/sparks/fuel filter as I am sure I could use all three, but I am not sure what the culprit may be...

Any words of advice/insight appreciated.

[por911]

Well, not knowing the year, or mileage on your car, I'd start with the basics first:

-If you have access to the durametric software, it might give you alot of insight into what is actually happening(lean, rich, throwing codes, etc).

-If the filters(fuel(97-01), air, etc) and spark plugs have not been done in the last 30k, you might consider changing them out to have a good basis to work off from.

-Changing out the AOS is a great place top start, Having just changed ours with 50k on it, it was time.

-You might also consider cleaning out the throttle body.

The maf could be giving secondary issues but from what your describing , the majority of the problem sounds like the AOS. :cheers:

[Loren]

Without your fault codes we are shooting in the dark. You can still have faults that don't turn the CEL on.

Autozone and some other parts stores will read your codes for free.

Get them read and then post them here.

[far972]

Without your fault codes we are shooting in the dark. You can still have faults that don't turn the CEL on.

Autozone and some other parts stores will read your codes for free.

Get them read and then post them here.

I actually ran out after I posted to read the codes, there are none.

Car is a 2000 BoxsterS with 33K miles. I bought it early spring with 25K miles on it (yes I have been enjoying my summer =-)

The previous owner obviously did not drive it all that much, 25K in 5+ years, and I have no idea how long it may have sat in a garage before I bought it.

[Loren]

Pretty much every misfire gets recorded as a pending code. If your tool does not read pending code then you will have to wait until a code triggers the CEL.

[far972]

By way of an update, I took a look at the engine on Friday figuring I would check out the throttle body, look for any obstructions, check for oil in the AOS line, etc.

Before I had a chance to get too far into anything, I noticed that a hose clamp had been left untightened (by who I have no idea) on what I can only guess is some kind of vacuum line... after reseating the line/hose and tightening up the hose clamp, all was back to normal.

A $0 and screwdriver fix!

Edited July 30, 2006 by far972