CEL - Rough Idle when Hot and Misfires

[OCNYPORSCHE]

I had 2 codes about 2 weeks ago: P0303, and P1315. I know that P0303 is misfire in cylinder 3, and P1315 is misfire in cylinder 3, emission relevant.

Loren recommended that I look at the coil packs, especially # 3. I changed all 6 coil packs and plugs. Interestingly, they all looked really good, and maybe spark plug 3 looked a little less good than the others, but nothing really extreme. I also cleaned the MAF.

Yesterday I drove about 40 miles, with some loss of power and hesitation at around 2500 to 3000RPM when the engine was warmed up. Then the CEL came on. It did not blink, it just came on. Then I need to drive home the 40 miles, and of course I got stuck in some bad traffic with the outside air temp around 95F. The hestitation got worse as the engine temp went up to 103-107C, and the steady CEL started to blink, and car wanted to stall, but never did. So the CEL went from solid, to a blink, back to solid again, and the car really ran terrible. since I was in traffic, the car idled back down to a shaky 600RPM.

When I finally got home, I used durametric and got:

P1319 - Misfire, Emission Relevant

P1314 - Misfire, Cylinder 2, Emission Relevant

P0300 - Misfire/Random

P0302 - Misfire, Cylinder 2

P0102 - Mass Air Flow Sensor - Below Lower Limit

P0112 - Intake Air Temperature Sensor - Below Lower Limit

But before I used Durametric to get this codes, I did disconnect the MAF, so the P0102 and P0112 might be from the disconnection. I only disconnected the MAF for a second or 2. I know that was a stupid thing to do, but I wanted to see if the MAF was going to make a difference. There was a noticable change when I disconnected the MAF, the engine went to about 800, then came back down.

I am thinking that the problem is MAF. I was very careful to put the new coil packs on. Before all of this the problem was cylinder 3, now it is cylinder 2, but the P0300 is really saying random misfire.

[RFM]

Buy a new MAF, cleaning is only in some cases useful bud always temporary, most of the time the fault will come back.

[wross996TT]

What he^ said. You can not resurrect a bad maf with cleaning.

[OCNYPORSCHE]

Thanks guys. I am even thinking that I may have messed the MAF up more by trying to clean it. What is surprising is how bad the car was working when it got hotter. So I am thinking that specifically the air temp sensor of the MAF is bad.

But can the MAF cause misfires to only come to 1 cylinder? I know that P0300 is a random misfire, but I also had P0302.

[wross996TT]

P0300: 507 Misfire detection (sum total)

Diagnosis conditions

• A cycle of 1,000 crankshaft revolutions is evaluated (for misfire

damaging to the TWC, 200 crankshaft revolutions). The misfire

rates are compared with a threshold value. If the misfire rate is

greater than the threshold value, a fault is recorded in the memory.

• The Check Engine Malfunction Indicator Lamp (MIL) is switched

on and stays on when the misfire rate lies above the threshold

value at which the emission limit values are exceeded during two

consecutive driving cycles (in the case of EOBD 3 driving

cycles).

• If the misfire rate may lead to permanent damage to the TWC,

the Check Engine MIL flashes. If the misfire rate is no longer

reached during the first journey, the MIL goes out. If the rate is

reached during the next journey, the MIL flashes. If this misfire

rate is subsequently no longer reached, the MIL changes to a

continuous light.

Possible fault cause

♦ Fault in ignition system

♦ Fault in injection system

♦ Flat-base tappets (valve lift fault)

♦ Mixture too rich

♦ Mixture too lean

♦ Mechanical causes:

Valve lifter chattering

This is caused by dirt in the valve lifter.

When the Check Engine MIL lights up, a chattering valve lifter may

also occur for a certain time. The DME control module registers

(sporadic) misfiring at one or more cylinders. The mixture adaptation

values are normal.

I could not find P1319 or P1314???

[Loren]

P1314 Misfire, Cylinder 2, Emission Relevant

P1319 Misfire, Emission Relevant

- Fouled, faulty or incorrect

- Contact resistance

- Loose contacts

Are you sure the coil pack electrical is properly connected on cylinder 2?

[OCNYPORSCHE]

P1314 Misfire, Cylinder 2, Emission Relevant

P1319 Misfire, Emission Relevant

- Fouled, faulty or incorrect

- Contact resistance

- Loose contacts

Are you sure the coil pack electrical is properly connected on cylinder 2?

Hi Loren,

I am pretty sure that I connected that one well. It is a very tough plug to get to. I changed the coil and plug. But since it seems to get worse with heat, and there is the P0300 error, wouldn't that suggest the MAF instead?

[1999Porsche911]

You have all the tools your need to determine if the MAF is the problem. Have your looked at the airflow rate and the intake temperature reading and the engine load? Why replace something when you you haven't determined it is bad? It is also common that the contacts on the connector get oxidized and a good cleaning may correct the problem.

Edited July 17, 2008 by 1999Porsche911

[OCNYPORSCHE]

You have all the tools your need to determine if the MAF is the problem. Have your looked at the airflow rate and the intake temperature reading and the engine load? Why replace something when you you haven't determined it is bad? It is also common that the contacts on the connector get oxidized and a good cleaning may correct the problem.

Thanks. You are right, with Durametric I can get all of the values. But from searching other threads, it seems that cleaning is only temporary, and I think that mine is shot, since I changed the coil packs and plugs, and the problem gets worse when the car is hot. If it was coils or plugs, the problem would not likely happen when cold too.

I ordered a new MAF on Wed, so it should arrive today. I will post back to let everyone know if it solved the problem. If it doesn't I will need all of your help :)

[dcporsche99]

Had a similar problem about a month or two ago and the folks on the forum helped me out. After I had replaced all the plugs and coil packs I had a different misfire / CEL light. As a few of the folks noted earlier----- just double & triple check the coil on the spark plug for cylinder #2. If you tug on it lightly you may find that the coil actually didn't click onto the spark plug.

Anyway, good luck with that. Let us know what happens.

Cheers,

Dana

[OCNYPORSCHE]

Well I put in a new MAF, and guess what? The new MAF did NOT fix the problem.

Then I figured it must be cylinder 2, so I removed the coil again and carefully inserted the coil and made sure that I put it on squarely. Long story short, the car works perfectly now!!!

Thanks everyone for helping, especially Loren! Loren, this forum is amazing and you taking the time to help really makes a huge difference (and you are always right!)

Thanks again!