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I wanna go fast!
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Discussion Starter #1 (Edited)
Good evening everyone,

I'm having an intermittent code 25 on my 94. According to my aem wbo2 and the led on my fuel controller I'm not running lean but the code still pops up. It's not predictable as far as how long it takes to come on but I would say it always happens at below highway speed. Also I believe it happens faster if it's hot and sunny out but i cant say for certain on that. I've searched extensively but haven't read any good resolutions for this.

First, about the car.
All stock internals
6766 single
3 inch turbo back exhaust and 4 inch muffler
Greddy 3 row
Bcc
Field boxer 3 sfc
Vpc
Walbro 450 in the tank and -6 line to a dual feed fic rail with fic 850 injectors and aeromotive fpr.

Car runs, idles and pulls great. Just the annoying code.

Troubleshooting so far,
1. Increase gain in the vpc. Minimal difference but it does take longer to come on.
2. Replace o2 sensor. This didn't make a difference with the code but I can tell a difference in general. Car runs closer to stoich and responds faster with regard to fueling (according to my aem wbo2 anyway).
3. Checked all charge piping for leaks.

As for manifold leaks, etc. I don't think I have any. I have all new vacuum lines and manifold/throttle body gaskets.

All 6 spark plugs look identical and perfect. All coils look good and are fairly new. Injectors were recently flow tested and were good.

I read a single thread that someone said they replaced the igniter and it solved their issue. Before I go spend $200 on an igniter I would like to know if there is anything else I should be looking at. If anyone has a good way to troubleshoot this to help narrow it down and confirm what's bad I would appreciate it.

One more thing I noticed and read in another thread (but again no resolution posted) was that one of the temp sensors could cause this. My temp gauge works perfectly but I know it's common for the gauge pickup to be a different sensor than the one that goes to the ECU. Below is a picture of my water neck. The sensor with the green plug has 2 wires but I can rotate the plug around 360 degrees. Is this normal or is this sensor broken?
 

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I wanna go fast!
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Discussion Starter #2
Bump and also wondering if you guys have any idea about the water sensor? As stated above, the plug rotates. I don't think that's right but I'm not getting a code 22 either. As always, any insight is appreciated.
 

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Code 25 means you are probably maxing out your long term fuel trim. Sounds like you have been messing with the fueling below 4k rpms too much.
 

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I wanna go fast!
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Discussion Starter #4 (Edited)
Code 25 means you are probably maxing out your long term fuel trim. Sounds like you have been messing with the fueling below 4k rpms too much.
I know maxing out the fuel trims throws the code but the AFR numbers I'm reading don't add up.

I'm rich on the AFR according to my AEM gauge. Never goes over mid 13s! That's why I'm confused (unless my sensor is lying to me). My normal procedure for troubleshooting (so far) has been to add extra fuel in the 1-3k range on the SFC and then reset the ECU. Now when I am cruising I am at VERY rich AFRs (11s and maybe 12s). I don't know if the code will kick back on or not. I'll advise if it does.

I also tested my AEM sensor with the air and gas rag trick. Responded very quickly. I also notice that the AEM appears to match the LED on the SFC display. SFC will switch rich to lean when the o2 sensors on the car show lean. My aem switches at the exact same time (over 14.8). I tested this at idle.

I'm going to test my engine temp sensor when I get home today and see if I get any love there.
 

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I wanna go fast!
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Discussion Starter #5 (Edited)
Couple updates.

I developed an intermittent miss. It's clearly running on 5 and then it will clean up and be fine. This was actually good and helped me confirm my suspicions.

1. Despite the plug rotating on the temp sensor it functions correctly. I have a spare just in case but it's fine.

2. My ngk 6282 coppers had about 6000 miles on them and were fouled. I noticed a carbon trail on one of the insulators so I'm pretty sure that's where my miss came from.

I have pulled a bunch of fuel and replaced the plugs. My full temp idle is now about 14.2:1. Cruising at highway speed I'm mid 13s and wot is high 10 to low 11. I've driven a few hundred miles without a code and it runs great. I don't know if it will come back but plugs definitely solved the miss.

I'll pull the plugs again next weekend and see how they look. Definitely happy so far. I also went out on a limb and retarded the exhaust cam a few degrees. I feel like the power is much better where you use it (mid throttle acceleration onto highway, etc.).

I'll post another update soon but for now it looks like new plugs solved it for me.
 

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hks is the best get the full kit
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My ngk 6282 coppers had about 6000 miles on them and were fouled. I noticed a carbon trail on one of the insulators so I'm pretty sure that's where my miss came from.
copper plugs = great heat conduction = better engine response = shorter life. You have to change them with oil change (3000 mile).
 

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I wanna go fast!
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Discussion Starter #7
New update although not code 25 related. I drove to my parents yesterday and today. Car mostly did great. I made it through the place where I used to get the code without any problems. That's the good news.

On my drive out today I was on the highway doing 65 and the car started to shudder. I exited and parked as I knew I had lost a cylinder. Car was idling rough so I pulled coil plugs one by one and determined it was cylinder 6. Afr was super lean so I decided to check injector. I unplugged the injector, started the car, plugged injector back in and viola! The car ran perfect! Ran great the rest of the way to my parents and the whole way home. All in over 60 miles.

The injectors are FIC 850 low impedance. Less than 10,000 miles on them.

Does anyone have any guesses? I never moved the injector, just the plug. Thinking bad connection but I would like some input if anyone has it. What do you think? Bad injector or bad electrical connection?
 

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I wanna go fast!
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Discussion Starter #8
Another update! I decided to poke around a bit tonight. The car has fic injectors with the adapter pigtails so you don't have to hack your wiring harness. I inspected the plugs and there was a bad crimp on one pin on the #6 injector. I fixed it so hopefully that was the issue. Good thing I wasn't beating on it.
 

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I wanna go fast!
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Discussion Starter #9
Couple new updates on this.

A short while after my last post I noticed another smaller miss. Upon further inspection it turned out pretty much all the crimps on all the injector adapters were bad. I fixed this and noticed an immediate improvement.

A few das after that I pulled the plugs to inspect everything and discovered #1 was starting to foul. The other 5 looked perfect. I swapped the plugs thinking it was just left over from the injector adapters but I was wrong. I checked again tonight and #1 is still fouling.

Tonight I swapped the coil pack with a different one. If the problem remains on that cylinder I will swap 1 and 2 injectors and see if it follows that. If that still doesn't solve my issue I hit a fork in the road and have a question for the forum.

As a next step if #1 is still fouling after coil and injector swap what would you check? I am currently thinking of removing the dli first, if that fails, swapping the igniter and if that fails I guess I have to trace all the wires? I have already inspected my ignition harness and the wires are in good shape. Do you think a bad connection in the coil plug is likely? Those were replaced and are not the originals. I'm assuming due to the cracking issue.

I'll update again in a week or 2 after I get some gentle miles on her.
 

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I wanna go fast!
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Discussion Starter #10 (Edited)
I'm back from my trip and wrenching again. I ran compression and checked valve clearance yesterday. Then I decided to pull apart the coil harness again. Apparently i had neglected to check #1 the last time it was apart. Sure enough, I find this.



So I cut the green wire back about 6 inches to get past the corrosion and re crimp.

Then when I was putting the valve covers back on I cracked the ear off the exhaust side at the front stud. WTH!!! I was using a 1/4 drive torque wrench at 74 in lb, tightening in sequence and stages and it still broke. Bad times. So now it's off with my buddy who has a good tig welder. With any luck it will be fixed tonight. Hopefully that resolves the issue once and for all.

Each time I fix one of these issues I get a noticeable increase in power which is kind of fun. I can spin the Toyo R888s easily if I get on it in 1st now. I'm going to try to order up a set of matching work wheels in a 10.5 this weekend to see if that will hold me down better.
 

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I wanna go fast!
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Discussion Starter #11
Quick update. I drove the car to Lafayette IN and back today. Roughly 400 miles. Car did great but #1 still fouled although only about half as bad. I figure I'm on the right track so after I got home I de-pinned the connector and swapped the leads with fresh ones from a prius harness I had laying around. I also cut back 8 inches on both leads harness side and soldered my newly rebuilt pigtail in. I'll report back after a couple hundred miles of drive time.

If this doesn't work I have a new igniter to try and after that I'll probably have to cut the trigger wire further back. The trigger wire still wasn't 100% shiny clean even cut 8 inches back. To go any more I'll have to remove the upper manifold and open up the harness so that's a big job. This time I soldered the connection so that should get around minor corrosion better than the simple crimp did last time.

I'll update later with results.
 

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hey Kyle!! long time no see(Red '94 you met downtown off Orleans). I am having the same issues actually!!! is your check engine light/traction lights on(how did you diagnose code 25)? I checked around a couple things as well.I tried plugs, checking injectors, checking for oil on plugs, and coil packs all to no avail as being problematic. I "fiddled" around with the connector for the igniter and i see that the copper for the sensor that goes into the igniter(the big one not the small one) is a little misaligned. My car ran regular for a little bit then i am back at square one. I too have another igniter to try but one other thing it could be, in case you haven't mentioned it, have you checked your maf?

-Xavier
 

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I wanna go fast!
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Discussion Starter #13
hey Kyle!! long time no see(Red '94 you met downtown off Orleans). I am having the same issues actually!!! is your check engine light/traction lights on(how did you diagnose code 25)? I checked around a couple things as well.I tried plugs, checking injectors, checking for oil on plugs, and coil packs all to no avail as being problematic. I "fiddled" around with the connector for the igniter and i see that the copper for the sensor that goes into the igniter(the big one not the small one) is a little misaligned. My car ran regular for a little bit then i am back at square one. I too have another igniter to try but one other thing it could be, in case you haven't mentioned it, have you checked your maf?

-Xavier
Hey Xavier! I remember you. Good to hear from you!

Do you know you are getting a code 25 or you don't know the code? What are your symptoms?

I have a scan tool to read the codes so it's easy for me. If you need to do it manually it's not difficult on the Supra. You need to jump 2 pins on the diagnostic port and read the CEL flashes. Here is a link...

http://mkiv.com/techarticles/engine_codes/obd1_codes.html

My car doesn't have a MAF because I have a VPC so that's not it. Plus I have narrowed it down to only cylinder 1 now and I am making progress.

If I recall correctly you are on an infinity ECU, correct? That may change the troubleshooting procedure for you. I'm not familiar with it so I can't say for sure. Either way, let me know your symptoms and I'll be happy to help where I can!
 

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I wanna go fast!
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Discussion Starter #14
Quick update again for anyone interested. I rewired the #1 coil connector completely after I noticed #1 was still fouling a bit, drove it around some and still the same thing. That pretty much rules out the wiring so I figure injector issue now.

I pulled the injectors and shipped them off to FIC for cleaning and flow testing. I'm currently waiting on the results. I'm hoping to hear 1 injector was leaky.

I also wanted to replace valve stem seals and since I would be down for 1-2 weeks waiting on injectors I figured I would lump it all in. I was occasionally getting blue puffs from the exhaust when I would take off from a stop. Funny thing I wouldn't really get them on startup so maybe intake seals, maybe turbo seal, maybe turbo oil return, I don't know for certain yet. It doesn't smoke any other time and it uses about 1qt of oil per 1000 miles. I got the seals in over the holiday weekend so now I'm just waiting on the injectors. I also switched back to stock cam gears because I really wasn't happy with the Titans. It's not enough of a power adder to justify the risk of breaking them, maintenance and relatively quick wear.

Hopefully that solves my smoke issue and the plug fouling issue. I'll update again in about a week when I get my injectors back.
 

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hks is the best get the full kit
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why do not you get a used supra 550 or 3sgte injectors??

They are really cheap and keep the fic for more power.
 

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I wanna go fast!
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Discussion Starter #17
Another quick update with a question.

Injectors tested out fine. Only 4% variance. After cleaning it went down to 2%.

I got the car all back together and it runs pretty well. I haven't seen any smoke so it looks like the stem seals resolved that. I also installed a new aeromotive fpr (same as the one that was in there) and swapped the igniter. I think the plugs will read consistently after some driving. Now for the question...

I set the base fuel pressure at 38psi and did a pull. I have boost set to 14 psi. Afr was in the 11.6 to 11.8 range. I think no big deal, I'll add fuel. I added fuel with the sfc but the ecu wouldn't increase injector duty over around 15% on the sfc. I bumped base pressure to 43 and now afr is 11. Great. The question is, will the stock ecu stop adding injector duty at some point before the field unit is maxed out? That's what it seems like to me. The sfc wasn't doing anything past 15% enrichment. Adding fuel pressure obviously corrected this and I only went to 43 base so I'm happy with that. Just wondering. I can add and remove fuel in the lower rpm ranges no problem but I'm only around the 5% range either way on those.

If anyone has insight let me know. Not a huge deal because it's sorted but I would like to know for future reference.
 

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hks is the best get the full kit
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FIC recommend 43.5 base fuel pressure.

about why the ecu wouldn't increase injector duty over around 15%....... jdm ecu will be blind above 4.3v map volatge , so it will never accept further fuel addtion by piggyback. I do not know about the USDM ecu, but I think you reach the blind point.
 

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I wanna go fast!
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Discussion Starter #19
FIC recommend 43.5 base fuel pressure.

about why the ecu wouldn't increase injector duty over around 15%....... jdm ecu will be blind above 4.3v map volatge , so it will never accept further fuel addtion by piggyback. I do not about the USDM ecu, but I think you reach the blind point.
I have VPC/FIeld SFC combo. Is that still the case? Regardless it seems like enrichment pretty much stops after roughly 15%. I took it out again tonight with the 43 base pressure and it was great. Running strong at just over 11:1.
 

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I wanna go fast!
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Discussion Starter #20
Well it's been a few more days and I'm super happy with it. Upon discussion with my tech buddy we decided that one or more of the transistors in the old igniter must have been collapsing and not fully saturating the coil(s). No more code 25 so you can mark this down as the second time in history that a faulty igniter caused something like this. I found one other thread from ancient times where someone said this was their issue. Stem seals took care of the smoking too and at then end of the day the injector cleaning just gave me peace of mind.

Thanks to everyone for their input as always.
 
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