Engine light and driveability issues after engine install
 

Hey guys,

Many of you have followed my thread about the engine noise, and ultimately engine replacement I performed on my 01 S, and now I am having a strange issue.

When the car is cold it runs perfect. As soon as the engine is warm it will develop a little misfire at idle. It is very random and acts like it maybe is leaning out? I drove the car approximately ~65miles to reset emission monitors for inspection, and it drove great. Again the hiccup/misfire was only at idle. Upon pulling in to the dealer for my inspection the CEL came on when I idled it in the turning lane. I pulled the codes and they are:

P1126, 1128, 1130, 1133: Which I remember from my Dad's 98 box that they were O2 idle enrichment above limit blah blah and it was a bad AOS.

Well this car has a new(swapped it off the bad 3.2 that was just replaced) AOS, and when running if you remove the oil cap there is no drop in RPM, nor large vacuum. The rpms actually go up about 200.

I removed the MAF and it was very dirty, so I cleaned it with MAF cleaner. Also there was a little knick in one of the harness wires for the MAF so I repaired that.

After doing those things I restarted it and again the random skip when idling. However now I am noticing the issue when cruising ~55-60mph. It will randomly feel like the car is leaning out quick and hesitating, then jumping back to life.

Also it will stall if you let the RPMs drop too quick.

Possibly related/unrelated it also has whine/noise from the secondary air pump when you do a cold start (I know that's when secondary air is working to warm the cats, but its MUCH louder than the 98 box we have) This noise was not there before I removed the engine. The cooling fan behind the passenger side, side intake will cycle on and off quickly. I don't remember the 98 doing this.

Any ideas? I don't have the factory manuals for proper troubleshooting so I am turning on you guys for some advice on where to start/go from here!

Thanks!

PS sorry for the lengthy description

disconnect the maf and drive it. sounds like bad maf.

If you have a Durametric, you can monitor the engine compartment temps in real-time. Maybe the sensor's toast. If the car's down on power the fuel pump may be slowly seizing. You can check the pressure with a standard Schrader valve gauge installed on the right side fuel rail.

Radium I forgot to mention when I cleaned the MAF I ran it with it disconnected. It ran like garbage.

Do you have the MAF from the old engine? I would try swapping them since cleaning it changed the behavior. There are degrees of failure, not just good or bad, so rough idle after disconnecting it doesn't necessarily mean that it's not failing.

An easy swap and good place to start ;)
This would also explain O2 codes.

From another site regarding 1126, 1133;

P1128 = Oxygen Sensing Adaptation, Idle Range, Bank 1 - Above Limit
P1130 = Oxygen Sensing Adaptation, Idle Range, Bank 2 - Above Limit

Common factors are MAF, air filter, vacuum leak, fuel pressure, just to name a few.
Fuel/air mix...

Particle that was a thread I read already. Had some good info in it. As far as the MAF this MAF is from the original engine that worked fine (during the swap I didn't remove the air box/MAF tube and the sensor remained in the car.

Yeah...it's the MAF. I'd wager on it ;)
If cleaning it changed the behavior, it's the obvious place to start.

Car is coming back from the bodyshop on Thursday so I will replace the MAF sometime next week and see what that does!

Well took a little longer than expected at the body shop! HA! I decided to have the whole gone refinished.

Anyway. Car is back and I still have the issue. Sputtering/hesitation off idle. Seems to drive ok at cruising speed, but I do get a occasional misfire around 55mph. I am going to replace the MAF since all fingers are pointing to that as the obvious.

Also I have a new issue where when the car is shut off and key removed the fan behind the passenger side air inlet runs for ~90seconds before shutting off. Also when idling it turns on and off very quickly. If I remember on my dads 98 box it will run as a normal cooling fan for a minute or so and then shut off. This fan seems to come on and off at a much quicker interval.

Any ideas?

Vacuum leak or low fuel delivery problem.

You need fuel trim values from the ECU to start this diagnostic process.

I am trying to get my hands on a durametric so I can see some live data from this thing. Seems to be getting better, and happening less frequently as I drive it and run new fuel through it. Might be just bad fuel after sitting while the engine swap was happening?

On a side note- the passenger side cooling fan runs for ~90 seconds after the ignition is switched off and key removed. Is that normal?

At idle:
Short Term FT Bank 1: -14.5%
Long Term FT Bank 1: -7.5%
STFT Bank 2: -14.7%
LTFT Bank 2: -7.7%

Ignition advance 7.5 deg
RPM normal

Holding the RPM at ~2000 (this is were the sputter happens). If "hmmmm" is normal idle it sounds like- hmmmmmm bum bum hmmmmmmmm bum hmmmmmm bum bum hmmmmmm

Under load driving it has no issue.

@2000 rpm hold
STFT Bank 1: -4.6%
LTFT Bank 1: -7.7%
STFT Bank 2: -4.6%
LTFT Bank 2: -8.0%

Ign Advnace 28.5 deg

Any chance the IAT could cause this? I am curious because the CEL came on over the weekend again with p1128 and p1130 and in conjunction the engine compartment fans runs erratically. It will come on and run for as short or long as it wants randomly. There is no pattern to it, and it will randomly run after the ignition is turned off for up to 20 mins for random lengths of time.

I'm having a similar stumble while driving and occasionally at idle with my 01 S.

It all started after my AOS failure a couple weeks ago. I replaced the AOS and also the MAF and it seemed to improve the idle stumble but I still get the stumble / hesitation while cruising around 50 mph or at about 5000 rpm when accelerating heavily.

I am also getting wrong readings from the electronic dipstick that reads low in varying degrees when the oil level is really one bar under full.

No codes being thrown which seems odd.

My new bosch MAF should be here today or tomorrow and I am anxious to see if that corrects the problem. I also ordered a new fuel filter (I didn't even know these cars had serviceable filters), and an IAT sensor.

The IAT is a gamble I am taking because it was inexpensive, and I've had some strange readings for IAT that may contribute to the fuel delivery issue as well as the engine compartment fan cycling erratically. Does the Boxster DME use IAT readings for fuel trim, or does it simply rely on the MAF and O2 sensors?

What are the specs for the MAF at idle and ~2000rpm no load in g/sec?

I have a feeling my readings are VERY low

If I had my Durametric handy (it's at my dad's house) I'd check mine for you. Alas... :(

I replaced the MAF with a new Bosch with the updated part (ending in .01) and the car is driving CONSIDERABLE better.

The fuel trims have come back to closer to 0% (+/- 2% for ST) Long term are holding around -1% on both banks.

Drove the car almost 300 miles and I still cannot get EVAP or secondary air to run their monitor. I have tried from 1/4 tank- 1 full tank and nothing. Hot starts, cold starts, idling for 5 mins in gear. Nothing. Secondary air pump does seem to run for a long time under cold start ~90 seconds.

Also there is an intermittent unevenness at idle occasionally (just doesnt seem to be super smooth no major jumps in RPM, no stalling). Always has great power and accel under load. Checked and the TPS, MAF, fuel trims all look ok in live data.

So now here I am. Stumped again as to what may be causing the idle. Does the DME just need to relearn to the new MAF?

And why the heck won't these last monitors run! Daddy needs an inspection haha

FYI after 300 miles of driving there are NO pending or stored codes.

Another note for those that may run into this issue the IAT sensor near the passenger side fuel rail was the culprit for the erratic operation of the engine compartment fan. After replacing that sensor ($16.50 for a forum sponsor) the fan now operates exactly as it should!

Not the right engine but I think its the same MAF.



http://986forum.com/forums/uploads01/maf1400084941.jpg



Do you still have the stumble?

The stumble is completely gone after replacing the MAF. My biggest issue now is the difficulty getting the remaining emission monitors to set, as well as the occasionally uneven idle. And its a very subtle bump in the idle, most wouldn't notice it, but I know its not as smooth as the idle in our 98 box

SUCCESS!!! After a (very long) drive last night on the highway after a cold start and brief warm up the EVAP monitor ran, and now I'm the proud owner of a (not so beautiful) neon yellow inspection sticker!