otakurx

For the past couple weeks since I put a new motor in the car I've been experiencing a longer start and a rough idle. On start up I often have to barely tap the gas pedal and the engine fires right up. At first I thought it was a vacuum leak so I went through and checked and tested every vacuum line in the car including using a vacuum pump to test out actuators and everything. I then measured vacuum at idle with showed ~20inHG or higher at 800-850rpms. I then replaced the front O2 since the previous was old and had been exposed to coolant due to a cooling seal failure in the rear rotor. That smoothed things out a bit but still was acting funny so I cleaned then shortly after replaced the MAF sensor and the primary injectors which were pretty dirty. Still no cure for the long start and intermediate rough idle but the car runs smooth otherwise. All the equipment that is on the car now, other then the new sensors obviously was on with the old engine and it ran fine till the coolant seal went.

Here is the current setup:
-BHR Ignition (10k miles on it) plugs only have ~2200miles and look clean tho maybe a bit hot
-AEM Intake
-Custom Header and header back exhaust (no cat or rear O2)
-2200miles on a fresh Atkins build
-BHR fuel pump

I've checked the Jet Air line, I've gone over the entire manifold and every vacuum line that's left and I've replaced all the seals on the injectors and the fuel lines. I was able to pull a code for a double circuit voltage failure on the throttle body once but was never able to repeat it. I also got a circuit voltage failure on the MAF just before I replaced it. For the first while after the MAF was replaced I was noticing a drop in power above 4000rpms, last night I went out and pushed it and soon as it got past 6200rpms it opened up like something freed up that blocking a passageway, shortly after I got a P0103 again, MAF circuit voltage high but she continues to run strong now tho the long start and rough idle persist. I'm leaning toward it being the throttle body but I'm really running out of ideas.

Last night while I was out I was monitoring data from the PCM and my idle lambda sits around .998 to 1.005, timing around -5.5 to -4, MAF readings from .74 to .88lbs/min, and the throttle position readings were all different, one would be at 3.1 then suddenly drop to 2.2-2.4 then shoot up before sitting at 3.1 for a while, the other would be saying 4.7 and never move till I hit the gas and I don't remember the exact readings off the sensors Throttle Position Sensors A and B but one was at 15 and the other was closer to 28. If the logs are of interest I'll pull them and post the data up.

Any help would be greatly appreciated before I just start replacing any more parts on the car.

Thanks,
Mike

otakurx

Okay, so I think I'm leaning toward a reflash/refresh of the PCM right now. From human senses (sound, smell) and fuel consumption so far recorded as well as noticing the coolant temps going up when over 4000rpms and under load and throttle I'm beginning to firmly believe the car is running lean. I've had several other mechanics and professionals in the area here agree with me and tell me the PCM may be bad because I showed them the live data feed and they said there is no way that can be right.

Just a little extra info from this a visit to a friends shop this morning.

otakurx

SO I tried re-flashing the PCM, made a bit of a difference. Then I decided to flash it again but with a couple changes, like a raised idle. This seemed to have done the trick, power was feeling good and all but the rough idle came back. I'm not in stop and go traffic or even where I have to worry about stop signs much so I may have just never noticed it. But with that in mind, I went back to double checking the throttle body. So I was looking at the position sensor numbers with the car off when I noticed the throttle body starting to make a lot of noise, like it was plainly audible in the car with the hood closed. Then yesterday while I was letting it idle and just listening (hood closed again), I was able to hear a buzzing and clicking sound under the hood (of the faint metallic kind) revved the engine to see if it would change with the RPM, which it didn't but it sure did change as I pressed on the gas. So unless I've got some crazy gremlins I seem to have pin-pointed the issue. I'm not sure what was up with the PCM but re-flashing cleaned it up nice and it has been behaving fine not, even the readouts changed but no need to get into all that.

SO I feel like this problem is solved, will know for sure by mid-week when the new throttle body comes in.