Alltrac with st215 motor running rich.

U

UtahSleeper

Active member
I have an 88 Alltrac with a st215 motor. Runs, starts and drives, but is running pig rich. I can share the emission numbers if wanted.

Torque Pro recording of readings

So, I made a short video of what my ecu is showing while idling. No audio, but figure the gauges tell the story. I did idle and 2500 rpm hold.

I have replaced o2 sensor and plugs. Not sure where to look next. The fact it shows a high load makes me wonder if that is tied to the issue.

Thanks for any feed back.
 
Z

zaluss

Member
UtahSleeper":3dnurrgf said:
I have an 88 Alltrac with a st215 motor. Runs, starts and drives, but is running pig rich. I can share the emission numbers if wanted.

Torque Pro recording of readings

So, I made a short video of what my ecu is showing while idling. No audio, but figure the gauges tell the story. I did idle and 2500 rpm hold.

I have replaced o2 sensor and plugs. Not sure where to look next. The fact it shows a high load makes me wonder if that is tied to the issue.

Thanks for any feed back.
Click to expand...

Based on a quick google search, I would check the turbo pressure sensor and ECU.

http://www.6gc.net/forums/index.php?showtopic=93897
 
U

UtahSleeper

Active member
zaluss":2cjnu56l said:
UtahSleeper":2cjnu56l said:
I have an 88 Alltrac with a st215 motor. Runs, starts and drives, but is running pig rich. I can share the emission numbers if wanted.

Torque Pro recording of readings

So, I made a short video of what my ecu is showing while idling. No audio, but figure the gauges tell the story. I did idle and 2500 rpm hold.

I have replaced o2 sensor and plugs. Not sure where to look next. The fact it shows a high load makes me wonder if that is tied to the issue.

Thanks for any feed back.
Click to expand...

Based on a quick google search, I would check the turbo pressure sensor and ECU.

http://www.6gc.net/forums/index.php?showtopic=93897
Click to expand...

I had seen that link. My problem is that the ecu sells for 200. Dont want to spend that much if it isnt a guarantee fix. I did have a dent in my ecu that was causing grounding, but fixed that. The board didn't seem to have any issues in the ecu
 
U

UtahSleeper

Active member
Pardon me as I keep looking at things.

I decided to connect with torque with the key on, but not started to see what my readings were and here is what I saw.

20151012MAP.png


Am I correct in my assumptions that vacuum and intake psi should be zero when the engine is not running?
 
___Scott___

___Scott___

Active member
The intake manifold should read atmospheric pressure, but "vacuum" should be zero.

I'm not sure why you even have a "vacuum" gauge. The ECU doesn't have any need to know about it. All that matters is the absolute pressure.
 
U

UtahSleeper

Active member
Think torque just does the calculations from the ecu and displays it. Either way, it tells a little. Wanted something to compare to mechanical.

I figured intake pressure should be zero since the car wasn't running.
 
U

UtahSleeper

Active member
So, update and recap. Still looking for suggestions.

I have replaced the coolant temp sensor(at water neck), MAP and TPS. No changes in readings interpreted by the ECU and it still reads and smells rich.

I unplugged the fan for troubleshooting. Got the engine temp up to 200 to 220 F and took it around the block. ECU still shows rich(.9v from o2).

Got my fuel rail/injectors flushed, just in case they were getting stuck open. No change in performance and richness.

Fuel pressure at rail shows around 35 psi at idle.

Torque shows 35%-ish load at idle.

Motor will occasionally pop in the exhaust an declaration.

As per the previous video, feels great driving and accelerates well.

ECU had a dent when I got my motor. Caused power issues for the ECU during initial install. After removing dent all "seems" fine. I have checked the board, but there seems to be no burn marks or popped caps.
----------------------------------------------------------------------------

So, I am at the point of just replacing the remaining electronics/sensors that deal with fueling. I know the ECU could be an issue, how ever unlikely, and hope to save that for last as its a steep cost for a hope.

I keep thinking electronics cause it seems to mostly be an issue at idle, but I am shooting in the dark honestly.

Does anyone use torque that has a st215 motor? Curious what your o2 and load show at idle, just to see if I am barking up the wrong tree.

Any other suggestions?

Again, thanks for the help so far.
 
underscore

underscore

Well-known member
Your O2 sensor shows rich but your ECU isn't doesn't anything to correct that? Sounds odd to me.
 
U

UtahSleeper

Active member
underscore":2w7cxmf2 said:
Your O2 sensor shows rich but your ECU isn't doesn't anything to correct that? Sounds odd to me.
Click to expand...

Yea, thats what is wierd. The ECU shows a negative -20% fuel trim, so it seems like the ECU knows and may be trying to remove fuel...........but I dont know enough to understand. When driving it adds fuel when under load.
 
underscore

underscore

Well-known member
Is your fuel system modified in any way, or is it stock? If the ECU knows it's overfueling but can't correct it then I'd imagine it could only be the fuel system, injector wiring, or the ECU.

edit: stupid idea, does the 215 have a cold start injector or no?
 
U

UtahSleeper

Active member
underscore":2imxnhar said:
Is your fuel system modified in any way, or is it stock? If the ECU knows it's overfueling but can't correct it then I'd imagine it could only be the fuel system, injector wiring, or the ECU.

edit: stupid idea, does the 215 have a cold start injector or no?
Click to expand...

I dont think it does have a cold start. No extra fuel lines.

Fuel system is mostly stock. Walbro pump and an inline fuel filter. Nothing special.

That could be right, just not sure what other fuel related systems I can mess with.
 
___Scott___

___Scott___

Active member
You haven't mentioned the intake air temperature sensor, but in a speed-density engine management system it is an important input that the ECU uses to determine load.

If the ECU is getting good IAT info, then excess fuel suggests either a leaky injector, incorrectly too large injectors, or fuel pressure that's way too high (which you've already checked.)
 
U

UtahSleeper

Active member
___Scott___":1fkyy7gn said:
You haven't mentioned the intake air temperature sensor, but in a speed-density engine management system it is an important input that the ECU uses to determine load.

If the ECU is getting good IAT info, then excess fuel suggests either a leaky injector, incorrectly too large injectors, or fuel pressure that's way too high (which you've already checked.)
Click to expand...

Thing is, there are 2 intake temp sensors, from what I understand. One pre turbo and one on the intake manifold. I know I have 1 valid intake reading, but not sure which one. I may need to look at torque again and see if there is another sensor I haven't noticed.

Injectors appear to be stock. I plan on pulling the injectors again and verifying if there is leakage.
 
underscore

underscore

Well-known member
UtahSleeper":1sigw9ca said:
Thing is, there are 2 intake temp sensors, from what I understand. One pre turbo and one on the intake manifold. I know I have 1 valid intake reading, but not sure which one.
Click to expand...

Easy, unplug one and see if torque changes or not.
 
U

UtahSleeper

Active member
CSAlltrac":14bkmc3u said:
I imagine you have already contacted Prime or Doug
Click to expand...

Yes, prime has been very helpful, but I have not been able to call so not brainstorming.

I plan on trying the unplug idea tonight and see if I can use that to pinpoint a bad sensor.
 
C

CSAlltrac

New member
Have you played in boost yet? Im asking because in the build thread you showed some damage to the bottom side of the IC. If its leaking it could cause some issues for you.
 
___Scott___

___Scott___

Active member
UtahSleeper":2d3nwh2d said:
Thing is, there are 2 intake temp sensors, from what I understand. One pre turbo and one on the intake manifold.
Click to expand...
The reason for there being two IAT sensors is that the one in the manifold will "heat soak" during "pit stops," like a brief stop for gas and snacks. A heat soaked IAT sensor will provide erroneous info to the ECU and make the engine hard to start and it will run poorly until the IAT closes in on correct info. The pre-turbo IAT sensor provides more reliable info for that time interval, so the ECU will use it until the other sensor settles down.

I'll also note that speed-density systems are very tolerant of vacuum and boost leaks, since there is no "metered air." Systems that rely on an AFM or MAF are sensitive to air leaks because the ECU expects correct info from those sensors. In a speed density system, the ECU needs to know the intake manifold absolute pressure, the air temperature in the manifold, the engine displacement and a good estimate of the volumetric efficiency of the engine. With that info it can calculate the amount of air entering the engine and the amount of fuel to inject (I'm omitting a bunch of details of course.)
 
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