Hey gang,

First things first, Codes: misfire on all cyls, and evap errors, I will be more specific when they come back, I cleared them by mistake.

I am trying to diagnose a weird idle issue. Initially I found that the truck (2003 D2 4.6 auto) would rev up to 2000rpm and hang there for like 10 seconds or so before dropping down to normal range. I replaced plugs removed IACV, cleaned and tested it, cleaned throttle body. I also found that the SAI pump was destroyed and the tube leading from it was full of gross water, probably from the pumphousing being open and water getting in there.

After cleaning, replacing and testing components, the cold start will rev up to about 2000 and then drop down to 1200 a second later, two seconds after that it drops to 7-800ish. I think that's still too high and I don't like it.

Furthermore I have a rough idle when the engine is warm, it seems to be worst when I have it parked for a bit and kept it idling.

This is a project truck and is new to me, as such I am unfamiliar with how long its been like this. I have looked for vacuum leaks but I cant seem to find any. What should I be looking for at this point?

Here is some data from my Hawkeye:
Engine Rough Cyl 8: .74
Engine Rough Cyl 6: .60
Engine Rough Cyl 3: .31
Engine Rough Cyl 1: .49

others are 8

O2 sensor US A
0.004
O2 sensor US b
0.049
O2 sensor DS A
0.1.28
O2 sensor DS B
0.018

TPS seems to be working well, 0.00 on idle and about 78 WOT.

 

I'm not familiar with the Hawkeye numbers you're seeing but someone here will chime in with some wisdom. How do the plug wires look? Maybe a fuel pressure issue? Have you done a compression test, although misfire on all cylinders makes me think air or fuel more than mechanical. Evap codes should not affect the idle (I think). I have a persistent 0441 but my idle is rock solid.

Just for comparison, mine cold starts at around 1800. If I do nothing, it settles to 600 after about 10 seconds, faster if I shift out of P.

 

@Tristan... you didn't mention if you checked your MAF sensor.
Unplug it and see if your Disco has the same problems. If it does doe the same, the MAF is possibly bad or it's wire connector is not seated securely.

I might be wrong but those numbers look pretty good.
Compared what I get on my Nanocom, I should be more worried than you.
I don't have any issues but my numbers look like:
Cyl 1 :1.48 / Cyl 2: 1.97
Cyl 3: 1.26 / Cyl 4: 2.19
Cyl 5: 2.58 / Cyl 6: 3.08
Cyl 7: 1.78 / Cyl 8: 2.38

 

Misfire on all or multiple cylinders sounds like coilpacks.

 

normal idle speed should be right around 750. sounds like yours is perfectly fine on that front.

 

Here are the error codes that just came up:

P1415 SAI functionality bank 2

P1412 SAI functionality bank 1.

P0302 Misfire cyl 2 (emission)

P0304 Misfire Cyl 2 (emission)

Vacuum leak?


P0300 Misfire multiple cyls

 

I checked and cleaned the MAF sensor, I noticed that the values changed when the throttle does, so I assumed that its working.

tonight ill unplug it and see if the problem continues.

 

1412/1415 are SAI faults either the main hose, pump, or vacuum lines. My 04 D2 will go to 1,800RPM upon startup then about 10sec later it goes to 1,200RPM, then when the SAI Pump turns off it’s around 1k until it’s warmed up. Then 750-800RPM with the AC off.

 

Thanks man,

Could any of those be related to rough/choppy running when stopped? or is it likely a totally different issue?

Thanks in advance

 

Coil pack or plug wires possibly. Look under the hood when its dark at the cyl 2 wire for possible arcing.