Hesitation - 99 Boxster

[johnj65]

Wife mentioned yesterday that when she got on the boxster she noticed the car was hesitating and let off the gas.

I've completed the following within the last week or so:

Oil Change
Air Filter Change
Coolant Flush

I drove the car this morning and let it get up to temp and got on it and felt the same hesitation?

Any ideas?

Thanks John

[joep]

If you noticed the tact when you felt the hesitation, did the engine not seem to respond to the gas halting around 2k? I've noticed the same symptom a could of times, but it didn't seem to last. Leave the car overnight, or work day and it was seemingly fine later on. Its been very intermittent for me and not chronic enough to investigate, yet.

[smdubovsky]

Just guessing: How many miles? Plugs been changed recently / on schedule? I did my wifes '01 on schedule and they looked merely 'ok'. Coils are known to go bad occasionally too. Easy enough to check their condition for cracks and such when changing plugs. Maybe scan the ecu for stored codes.

[jerome951]

I'm assuming the hesitation wasn't there before you completed your maintenance. If that's the case, check the air filter housing & lines up to the intake manifold to ensure they're on correctly (clamps tight) or didn't crack and there isn't a new air leak (this supposedly is common w/ the 996s when changing air filters).

[johnj65]

Thanks.... The hesitation did not happen before I changed the air filter. I'm going back in tonight and check the hoses and ensure the clamps are tight. Did have a hell of a time getting the filter in the housing.

John

[markwemple]

Just an outside shot. If it has e-throttle (throttle-by-wire) see if there is a recall or a re-code for the system. You'd be surprised how many cars have reflashes needed for this problem.

[johnj65]

Thanks... I'll check for recalls on the car. No check engine light, but I hookup and the following two codes were reported:

- 1128 (O2S Bank 1 1-3cyl)
- 1130 (O2S Bank 2 4-6cyl)

Not sure if this would be causing the hesitation?

John

[cmartin]

Double check the airbox. MAF connected? Super dirty?

[johnj65]

The air filter was super dirty (when I replaced it on Sunday) and I'll check the MAF tonight. What should I be looking for when checking the airbox? Just make sure the filter is seated properly?

John

[racer]

Aren't those codes posted related to 02 sensors? They fail too..

[cmartin]

Airbox fitted, electrical connector snug, MAF clean.

Aren't those codes posted related to 02 sensors?

Yes. Whenever I see a code for both, check upstream.

[johnj65]

Yes... It seems that the 02 sensor needs replacing... Not sure that's causing my performance issues? Pelican Parts listed the 02 sensor for a 99 Boxster as needs 4 o2 sensors?

[jerome951]

Yes... It seems that the 02 sensor needs replacing... Not sure that's causing my performance issues? Pelican Parts listed the 02 sensor for a 99 Boxster as needs 4 o2 sensors?

Clear the codes first and see if they come back (they may not). If they do, then replace.
They could be causing the performance issue, but unlikely both died at the same time.

[turbo23dog]

Since the codes indicated problems with both banks, my money is on MAF. Have you tried cleaning the MAF?

[markwemple]

FWIW, whenever I change the air filter, I clean the MAF. I agree that it sounds like the O2 sensors may be an issue, but I'd check and clean everything before replacing. My guess is that there is something loose giving a faulty reading. Also, put some good FI cleaner in there and see if that helps. You may be marginal on the fuel system.

[johnj65]

Thanks!!!

I'm going to clean the MAF tonight when I get home and check around for loose connections.

[racer]

iirc, there are four o2 sensors.. 2 before the cats (1 on each bank) and 2 after the cats (1 on each bank). Can't recall if code posted is the before or after ones.

I must say when I did the aircleaner on my boxster I was amazed how easy it was. if you had trouble, perhaps something could have been done better?

[johnj65]

Thanks for the count on the 02 sensors. Followed the replacement instructions from Pelican Parts. Getting the new filter in was a little difficult. I plan on repeating the steps tonight and see if I caused this issue.

John

[HateDCRoads]

Is it hesitation our stumble? Both pre-cat O2 sensors on my Boxster went bad a month ago and caused a progressively worsening ignition stumble, but I got misfire codes too. Checking the intake sounds like a good plan - if the O2 sensors are really bad your problem will get worse and you'll get more codes.

I am also tracking down and intermittent power loss at high revs and I am going to fiddle around with the AOS - I'll post back to the thread after I dig around in the car this weekend.

[johnj65]

Thanks for all the suggestions and help with this hesitation problem. Checked the air filter and hoses this evening and it looks good. I did find one problem in the air cleaner housing. I found leaves, rocks and pistachio shells????

Once I got the housing unit cleaned out and re-installed the filter I took it out for a drive. Hesitation is now gone and it's running properly. I still plan on cleaning the
MAF tonight and clearing the codes and see if the 02 sensor codes come back.

If I see the O2 sensor codes (1128/1130) again, I'm going to get these sensors replaced.

HateDCRoads - This morning it was a hesitation. I'm not convinced my problem is completely resolved, but I'm sort of looking forward to replacing the 02 sensors
when they finally go. Look forward to your update on the AOS testing.

John

[jrj3rd]

John

Don't be too quick to replace the O2 sensors for a P1128/1130 code set. When both banks show the "enrichment adaption limit" codes it is more likely caused upstream of the sensors. Normal causes are vacuum leaks, AOS issues or fuel pressure/delivery issues. My bet is a vacuum leak from when you did the original filter change, since they showed up coincidentally with the hesitation.

Clear the codes and drive the car, probably won't see the codes return since you say it is now running fine.

John

[johnj65]

Thanks John... I cleared the codes last night after cleaning the MAF (which was dirty). Car is running fine and it seems that the performance has improved. I know it sounds crazy but I really enjoy working on these cars.

John

[HateDCRoads]

Yeah, working on these cars is a lot of fun. And John 3rd is right - if your O2 sensors are really going bad, the problem will get progressively worse and you'll throw a lot more codes. My name is John as well, BTW. I will check my intake this weekend when I check the AOS and and report back on Sat/Sun.

BTW, not surprised you found that stuff. Does your car still have the air restrictor on it (in the intake box behind the left side mid-grill)

[HateDCRoads]

Update on my 98 Boxster hesitation problem. Replaced the AOS and cleaned the throttle body last weekend. Car is running better, no smoking so far. Did get a CEL after I did the work - turns out Camshaft Position Sensor was unplugged - I am guessing I knocked it loose when I was wrestling with the AOS. Might also be possible that it was already loose, which could cause the computer to do weird things.

I am also going to pay more attention to my oil from now on - making sure it is not overfilled and using a more appropriate weight for the track. The proof will be in the pudding at Summit Point next weekend.

[Vicegrip]

D00d don't say pudding when discussing your motor type. They can make some real $$$ chocolate pudding real quick. :p

[Lupin..the..3rd]

I did find one problem in the air cleaner housing. I found leaves, rocks and pistachio shells????

That happened to me one time. But it wasn't pistachio shells, it was Swedish fish. I was eating them out of a bag, but ended up spilling them everywhere. Little red fish all over the top of the motor, down around the cylinder heads, they were everywhere! My advice to you, is save the snacks until after you're finished wrenching.