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E39 (1997 - 2003)
The BMW 5-Series (E39 chassis) was introduced in the United States as a 1997 model year car and lasted until the 2004 when the E60 chassis was released. The United States saw several variations including the 525i, 528i, 530i and 540i. -- View the E39 Wiki

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  #1  
Old 11-22-2019, 09:22 PM
DaddyBender DaddyBender is offline
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Mein Auto: 1997 528i
P0116

1997 528i. Recently repaired head gasket. Here's the thread for that if y'all wanna read up:

https://www.bimmerfest.com/forums/sh...274166?page=10

Three days ago, wife goes to start the car and it didn't start first try. Or second. On the 4th, it spit and sputtered. 5th try, it started, but ran real rough. She gave it some gas and it cleared up, then ran fine. To me, the way she described it, sounded like a flooded carb. No other indications of issues. I didn't have my code reader to check the CEL. This was the first starting of the car that day. Ambient temps 40 hi/25 low.

Today, same thing. When I get home, I grabbed the keys, and she fired right up. No stutter, stumble, nothing. Perfectly normal. I pull the codes. P0116, among others, but this one has me a little, confused...and concerned.

So with my phone and TorquePro, the ECT was at 60C. Messed around adding gauges for a bit...maybe 10 minutes...and went back to the page to check the temp. 66C. Oh! Unlocked the cluster for mode 7...and it said 60C. Wha? That's...funny.

I know the temp sending unit sends one signal to the ECM, and one to the gauge. What has me confused is how the OBD was off from the dash. I had assumed the unlocked dash was the same signal as the ECM. Perhaps I am wrong?

Moving on. Another 10-15 minutes go by. Dash says 70C, but the gauge on TP was blinking...141C!!! What the wholly hell?!??! Looked at the dash...74C. Temp gauge still coming up to normal zone. Just in case, I cranked the heater to 90 and cranked the fan. Was warm, but not melting my face.

I was already planning on dropping in a new coolant temp sensor, as well as a new radiator fan sensor, and some Pentosin Smurf Juice.

Issue is, wife needs the car, but parts are two days out at the earliest. Is this an absolutely don't drive it until fixed kind of issue?

Can anyone verify the Mode 7 temp is in fact from the same feed that feeds the gauge?

-Bender
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  #2  
Old 11-22-2019, 09:28 PM
DaddyBender DaddyBender is offline
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If any of y'all are wondering what the other codes were:

P0420-Catalyst Efficiency Below Threahold-Bank 1
P0440-Evap Emission Control System
P1421-Powertrain-Looks like it's related to the air pump
P1423-Powertrain-Looks like it's related to the air pump

I'm already looking into these individually.

-Bender
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  #3  
Old 11-23-2019, 06:30 AM
rdl rdl is offline
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Mein Auto: 530i 2003
Quote:
Originally Posted by DaddyBender View Post
...
Can anyone verify the Mode 7 temp is in fact from the same feed that feeds the gauge?

-Bender
No, but ...

I've read posts that said with ignition key in position 2 (run), the cluster test 7.0 reports temperature from the DME, while with key in position 1 (accessory), it reports gauge temperature. Or is it vice versa? In any case, no confirmation from any BMW documentation.

I can confirm that I've tried switching from 1 to 2 to 1 etc. and the reading does usually change by a degree, e.g. 96 - 95 - 96 -95 etc. But not always - sometimes both key positions result in the same value. Which is what one would expect if the key position did change which value is displayed.

Over my 10 years of ownership, I've experienced the same difficult start symptoms you report 2 or 3 times. Each instance years apart; I've never had consecutive or even close in time instances. And as you found, no DTC's whatever set. Nor any other clues as to the cause.

I'm more inclined to think that the issue might be a hicup with the intake air temp (IAT) sensor rather than engine coolant. At least in my MS43 DME, the crank/start cycle ignores the MAF and relies on the IAT to calculate injection time, i.e. mixture control. This is done because during cranking there are pressure pulses in the inlet manifold that push air forward and backward across the MAF. Since the MAF is unable to determine flow direction, (only velocity which corresponds to air volume) that would result in a false high reading of the volume of air entering the engine. If the DME used the MAF value it would result in a very rich mixture.

Or perhaps the fault is the DME "forgetting" to ignore the MAF and to rely on IAT only, which would result in a very rich mixture. Or perhaps a sticky fuel pressure regulator. Or perhaps a fuel pump or fuel pump relay problem. Or, or, or.
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RDL
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  #4  
Old 11-23-2019, 07:25 AM
DaddyBender DaddyBender is offline
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***x1f602;
The "or, or, or" part got me!!!!! Thanks for that.
Trying to talk 'mechanic' to my wife, I might as well be speaking jibberish.
I equate mechanicing to her like being a doctor. You explain the symptoms, I have to figure it out from there.

Back to the task at hand.

To be a bit more accurate, the CEL has been on for a bit. It has always been the P0420 code. Pretty sure it's just an O2 sensor, but considering that my mileage went from 20MPG to 27+ (pre and post head gasket/refresh), I'm reasonably sure I don't have a plugged CAT causing that code.

The P0116 code....I've never seen that one before. The P0440? Last time I saw that was when the hose from the air pump to the valve was rotted, and the vacuum line to the valve was cracked. P1421 & 3 look to be associated with the air pump as well. I did clear the codes, and the P0116 was a pending fault in TP while I was sitting there, so I for sure have something not right with the temp sensor, be it wiring or the sensor itself. I just found it odd that the dash wasn't reflecting what the OBD was reporting for temp. Kindof sucks if the Mode 7 is just a digital version of the analog. Still good for the wife to watch that instead of the analog, but not a true representation of the ENGINE temp.

My HEAD tells me none of these should have caused the hard start. I'm thinking the cold is giving the old bones some trouble this year, and I'm betting dollars-to-doughnuts it's fuel pump related. Relay, pump, or regulator.

It's 7am, and it's 30 degrees outside. I'm gonna go see what she does for me for first start.
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  #5  
Old 11-23-2019, 08:04 AM
DaddyBender DaddyBender is offline
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Before starting:
Visually inspected ECT wiring-looks normal.
Visually inspected air pump hoses-looks normal.

Fired up TP-temp still at 141C and blinking.
Made another vehicle profile and loaded that-same thing, so it's not a TP issue. Mode 7 reports 0/1C (it's freezing out)-looks normal.
With key ON (engine NOT running), disconnected ECT connector. Mode 7 now says -40C, as does TP. Reconnected the ECT connector-Dash changed back to 0/1C, TO now shows 3C.
Scanned for codes-none set or pending.

Key in position 1: Dash at 1C. Position 2: same.

Car started perfectly fine. No hiccups whatsoever.

Mode 7: 42C
TP: 44C
Air pump didn't come on right at engine start like I think it used to. Took a minute. Ran for its usual time, then shut off.
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  #6  
Old 11-23-2019, 08:06 AM
DaddyBender DaddyBender is offline
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Mein Auto: 1997 528i
7: 46
tp: 48
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  #7  
Old 11-23-2019, 08:08 AM
DaddyBender DaddyBender is offline
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Mein Auto: 1997 528i
7: 50
tp: 52
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  #8  
Old 11-23-2019, 08:13 AM
DaddyBender DaddyBender is offline
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Mein Auto: 1997 528i
7: 58
tp: 60
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  #9  
Old 11-23-2019, 08:22 AM
DaddyBender DaddyBender is offline
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Mein Auto: 1997 528i
7: 64
TP: 67
Analog: almost to left side white tick.
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  #10  
Old 11-23-2019, 08:27 AM
DaddyBender DaddyBender is offline
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Mein Auto: 1997 528i
7: 68
TP:70
A: on left white tick
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  #11  
Old 11-23-2019, 08:42 AM
DaddyBender DaddyBender is offline
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Mein Auto: 1997 528i
7: 73
TP: 75
A: one needle to left of straight up. This is where the analog always sits. Always.
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  #12  
Old 11-23-2019, 08:53 AM
DaddyBender DaddyBender is offline
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I calling it here. No issues found. No set or pending faults. No spike in temp in any of three gauges. Set-up wife's phone with TP and a single HUGE temp gauge. See where it goes from here.

Still ordering the two sensors and the coolant.
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  #13  
Old 11-26-2019, 02:14 PM
DaddyBender DaddyBender is offline
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Car hasn't been started since I started it last. While I was at it, I hauled out the laptop and got 'into' the car. Some more codes there that weren't on the OBD. Took screenshots and deleted them.

Wife goes to start it today. Same hiccup/no start. No CEL. I had her cycle the key a few times thinking maybe the fuel pump. Car started. She drove it 30 miles, no issues. Into bank and came out...fired right up.

What in the ever-loving-hell????

-Bender
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