View Full Version : Alltrac with st215 motor running rich.

10-11-2015, 02:02 AM
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 (https://www.youtube.com/watch?v=_lP7lxU-PYU)

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.

10-12-2015, 12:23 AM
You probably have, but have you checked the voltages out of the MAP sensor?

I know that the 215 is ODB2 but I had some issues with mine when I did the 3rd gen electronics conversion. I was getting some weird readings at first and it was dumping a ton of fuel.

One other thing. Probably not this but I've had it happen with mine with the 3rd gen electronics, make sure that the vacuum hose that attaches to the throttle body and feeds the MAP sensor is tight and sealed. Mine slipped off a couple of times and instead of the normal vacuum leak symptoms, it dumped super rich and ran really weird.

10-12-2015, 03:34 AM
I will check the map sensor, but on this motor the sensor runs to a vacuum splitter on the intake manifold right below it, so not much hose to check.

10-13-2015, 12:45 AM
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.


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

10-14-2015, 09:27 PM
Im not sure I trust that stuff.

It should see some readings from sensors that are powered up with ignition set to on, but like, timing, should see none, and it shouldnt see any boost or vacuum at all.

Id do a calibration of the TPS personally. It shouldnt read 10 percent like that. That will mess with your fueling and timing in closed loop.

Id also probe the MAP sensor and see where it is with ignition set to on. Theres a 0psi value that you should be off. If its calibration/reading wrong, that would certainly bone you as well.

10-14-2015, 09:38 PM
Im not sure I trust that stuff.

It should see some readings from sensors that are powered up with ignition set to on, but like, timing, should see none, and it shouldnt see any boost or vacuum at all.

Id do a calibration of the TPS personally. It shouldnt read 10 percent like that. That will mess with your fueling and timing in closed loop.

Id also probe the MAP sensor and see where it is with ignition set to on. Theres a 0psi value that you should be off. If its calibration/reading wrong, that would certainly bone you as well.

I was wondering if the ecu was showing advance cause it appears to be getting readings from the MAP. May or may not be the case, but thats what I was thinking. And since the car showed positive intake pressure at idle, which it shouldn't be, I was thinking the MAP is out of whack. I think the boost gauge used in torque is just taking values from the ECU and calculating from there.

How do you calibrate the TPS? I thought the 10% was weird as well and tried to adjust it, but there is really no room for adjustment.

And on the MAP probing, I just haven't been able to find anything that says what its resistance/voltage/etc should be so haven't really been able to check it with my multimeter.

10-23-2015, 12:46 AM
There are instructions in the BGB's. I know we don't have a 215 book here but the ones we do have would give you at least a general idea of how to check it. This guy in Australia has a translated 215 service manual in PDF form. I downloaded it but it doesn't appear to be searchable BUT it looks like it would have what you're looking for in it.


As for the MAP sensor, from what I read while doing my 3rd gen electronics conversion, the 3rd & 4th gen MAP sensors, while looking different, have the same basic, if not identical, output. Give that, what I found was that the 3rd gen MAP sensor output at 0 psi should be around 2.3V or so and at idle probably less than 1V. Here's a graph that I found during my research showing the 3rd gen voltages.


Hopefully this might help.

10-23-2015, 02:23 AM
I have a bunch of CEL code stuff for the 215 on my desktop. I have access to some awesome enterprise PDF software. Tomorrow morning I'll run it through my system and get a searchable OCR'd PDF of it.

10-23-2015, 03:06 AM
Cool stuff and thanks to both.

Small update. I have replaced the MAP and TPS just on a hunch with no change, so still searching. I will have to look through that manual and see if there is more then 1 coolant sensor. Someone suggested replacing it and it makes sense in most cases, but since I am seeing an accurate temp through torque, I striggle to think thats the issue.

10-24-2015, 06:02 PM
That would be great Tim.

The coolant sensor could make sense. If it were showing a continuous cold condition that would leave things in warm up mode. Might be worth a try.

10-31-2015, 10:19 PM
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.

11-03-2015, 02:03 AM
Another small update with the troubleshooting I did tonight. This was with torque connected and engine running.

Disconnect MAP - Car died

Disconnected intake temp sensor on manifold - No change in output from ecu or idle.

Disconnected intake temp sensor pre turbo - intake temp changed to -40/nothing in torque. No other changes.

Disconnected sensor that has 2 vacuum lines going to it, on transmission side of motor - No change in output from ecu or idle.

Disconnected IAC - Idle went up, no other changes observed with load or o2.

Any other sensors worth checking? I know its not a very precise testing method, but figure of one of these sensors is feeding bad data then unplugging it should change what the ECU see's.

11-04-2015, 05:35 AM
So, here is a question.

Do the st215's have an ECU that learns at idle/idle circuit? Or a circuit that just deals with idle? I know megasquirt has specific circuits that deal with idle and I know newer cars relearns, but not sure on these ECU's.

I also know that ECU's dont tend to be an issue, but just discuss.

I ask cause cause at idle is when I seem to be having the issues. Revving seems fine on the ECU and driving also seems to give the idea that things are fine. Its only idle.......from the data I can see.

11-15-2015, 03:10 PM
Here's that document. It's now searchable so should be easy to find what you're looking for (if of course it's present).


11-16-2015, 09:40 PM
You know anyone else with a 4th gen ECU you could try? It honestly sounds like you got a bad capacitor like the Gen2s and Gen3s sometimes get.

11-18-2015, 06:45 AM
I need to update this. I ended up buying a used ECU, known to work, and the behavior is still the same. Prime Performance would have loaned me one to test if they had any in stock. After I spoke with Doug, think that was his name, we both agreed it was the next logical step.

So, today I drove her to work and recorded the ecu readings through torque. Thought the o2 was more stable in boost, but this time it was going full lean or full rich when driving. May have to drive again on a more straight and traffic less road.


What I need to do is find someone running this motor and who has torque, just to compare readings and see if it can pin something specific.

11-20-2015, 06:03 PM
So, I have done some more investigating and have a question. Anyone think the timing belt being off could cause my running rich issue? I have searched a bit online and it seems like a possibility, but just want a second opinion.

Another reason I am looking this direction is I did a compression check on 1 cylinder last night(plan to do the rest today) and It seems I am at 150, which is a bit low as far as I know. If the remaining 3 have similar reading and spark plug condition then I am going to assume my timing belt isn't set right.

So, feedback?

11-20-2015, 07:48 PM
That's easy enough to check on the 4th gen. Just pop the upper timing cover and peek at the crankcase (or pull out #1 spark plug and use a long extension to find TDC). I didn't have any of these issues with my 4th gen...so I'm not much help.

11-21-2015, 06:15 AM
I will have to do that. It was 150 across the board +/-. Seems a little low to me. Plus I noticed the idle bounces around 50 up and down(between 900 and 950). Not sure if this can be related or just normal.

11-22-2015, 11:52 PM
Well, here is another update with no solution.

Ran a compression check. All cylinders appear to be at 150 +/-. Seems low to me, but workable.
Removed the upper timing cover and moved the crank to 0. Both cam gear marks lined up with the back of the timing cover. This motor also had a timing belt done to it before, based on the additional purple markings on the cam gears.

This is what the plugs look like after about 50 something miles. Sorry for some blurry pics, but they all looked about the same.

And here is my previous emissions readings. My last check had about the same results.

Also had my friend rerun an emissions test and the motor is still insanely rich. I averaged 10 mpg out of the last tank.

And here is a recap of everything else done with no changes in behavior.

-Replaced coolant sensor
-Replaced TPS
-Replaced MAP
-Replaced ECU
-Replaced O2 sensor
-Added fuel pressure gauge. At idle, reads 35 psi.
-Ran a fuel rail flush/injector cleaner

And as a quick summary of car:
-ST165 with Caldina engine
-DP from prime mr2
-eBay exhaust
-Walbro FP
-Straight intake
-Some random grounds added to the block

Are there any other sensors I should look at or any other troubleshooting I should be trying? Anyone have any electrical infor where I could verify data coming in and out of the ECU and sensors? Just frustrated cause she drives great and pulls hard(for my experience) but is running too rich.

02-04-2016, 12:41 AM
So, I kind of quit updating this here. I have slightly more up to date info here


Would like any suggestions on ways to test the harness while installed or any other ideas on why my car runs pig rich.

Recently had the injectors cleaned, but no change. They were no measured with specs, just had cleaners ran through and verified flow rate between the 4. All 4 were really close to each other.

Thanks for any input.

02-05-2016, 11:45 PM
So I dont know if youve answered this or not but have you tried a different ECU?

02-06-2016, 11:29 PM
So I dont know if youve answered this or not but have you tried a different ECU?

Yup. Behavior was the same. I am going to start troubleshooting the harness cause I have replaced so much else.

02-12-2016, 03:03 AM
Bump. Still accepting suggestions. Also, any good write ups on testing a harness?

02-28-2016, 12:58 AM
Figured I would update.

I believe I found my running rich issue. The sensor for the FPR(located under the manifold). Today I ran a vacuum line from the intake to the FPR(bypass sensor, but leave it connected to the harness) and it appeared to started idling cleaner after it warmed up a little bit. The fuel trim gauge in torque initially showed no data, but after idling a little it seemed the ECU started adjusting the fuel trim. So, not I am going to get a new sensor and see if it behaves correctly.