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Discussion Starter · #1 · (Edited)
well i finally got my car put back togethor. As of yesterday the only issue was it stalling in between shifts. But starting today it wont boost good. it gets to about 4k( when boost comes on hard) and sputters and hesitates really bad. It did this on the twins before i went single. It also backfires while it is sputtering. Some times it will only do it for a second then take off decent. But sometimes it wont even get past 4k. I have checked for IC piping leaks and everything looks good.

And i cant get any codes either. I cant get the CEL to do anything. Also, my engine has always ticked(sounds like injectors) but it is pretty bad now. It has brand new plugs. ngk 6097 stock gap.

This blows.
 

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T88 YOU
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backfiring can only mean a few things, the major ones being late ignition timing and running rich or lean to the point of misfire... how "brand new" are the plugs, have they been changed since the problem started occuring? what kind of fuel/spark control are you running, try to get ahold of a toyota scanner so you can take a video of you spark and fuel trim to see what they are doing. what kind of fuel system do you have, if any at all?
 

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Discussion Starter · #3 ·
Stock fuel and maf. t78 turbo. Plugs are as new as the turbo( 10 miles on them maybe). The car did this before i went single.
 

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Alpine Hardtopper
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Coils are also a potential place to look. Does it rev through 4000 easily if you're only at part throttle (not trying to make lots of boost)? If the coils are on their way out, higher boost and higher RPM can cause fits.

As a help, you may consider reducing your plug gap quite a bit. Seems like AEM recommends going to something ~0.023" when using their box (converts to wasted spark). Maybe try gapping them more like this and see if it's better. If it is, I'd suspect the coils.
 

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Discussion Starter · #5 ·
It will rev up to redline fine if i dont boost. I gapped plugs to .25 on twins trying to fix the problem and it didnt fix it.
 

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Alpine Hardtopper
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Well, that's good that it can rev to redline w/o boost. It rules out a lot of potential places to look. It would be interesting to plug in a scanner that can read the ECU real-time. Would be good to know if the injector signal is changing at all, or if the ignition timing is being pulled for some reason. Also, you could look at the boost sensor output as well. What are you using for a fuel cut defense? I thought when fuel cut hit, the CEL came on and left a code.

Is this OBD I or II? When you say you aren't getting a CEL, does that only mean you're not getting one when you scan for codes, or do you not get one at all (even when key is first turned on)?
 

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Discussion Starter · #7 ·
Not even getting one when the key is on!!! Is this bad??? I did get one once but it kept going on and off when i was checking for codes. But i cant get the light to come on no matter what. OBD1
 

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T88 YOU
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pull the plugs and see if they are black, if they are you are running rich, if they are white its probablly running lean, if they look normal, then you can do an old trick. put new plugs in the car and run it hard (as you can) for a few mins then turn the car off and coast to a stop. pull the plugs and look at the light line on the electrode, it should be right on the 90 degree bend of the electrode, if it is closer to the tip your timing is retarded, if its further from the tip its too advanced. those are just a couple things to check.
 

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Alpine Hardtopper
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Ahhh. I would probably start working on the CEL first, as having it functional will make troubleshooting the other problem a lot easier.

Have you checked the bulb behind the light at all? Could be going out/gone, or a lose connector. Also, I think I saw it on the MKIV.com site about the paths going to some of the warning lights having trouble on some cars. The fix was to route small wire from the harness straight to the connector. Here's the direct link:
http://www.mkiv.com/techarticles/trac_off_mil_odo/index.html

Another thing to check is in the diagnostics port. You can jump two pins to check the codes, but you can also just two other pins to start a self diagnostic. Also, I thought that one of the pins was an output just like the light, so if your bulb was out, you could hook a light up to this and read the codes. I don't have my FSM's nearby or I'd check the pin for you. Let me know if you don't have the manuals and I can go look at mine. See this link for diagnostics codes and such:
http://www.mkiv.com/techarticles/engine_codes/obd1_codes.html
 

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Discussion Starter · #11 ·
Well the connector behind my cel was loose. Fixed that but still no codes. It just blinks telling me its ok. I think im gonna have toyota hook up to it tomorrow.
 

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Alpine Hardtopper
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I suppose it could be from bad injectors. Hard thing is that it's difficult to tell even with a wide band because a mis-fire will show up as a false lean reading.

Try this: Warm it up and do a full throttle pull. While it's popping/sputtering, turn off the key and coast to a stop. Then, pull a few of your plugs and see what the tips look like. If they're dark/wet, then it's either WAY too rich, or the ignition system isn't very happy. If they're white/chalky, then it's because it's WAY too lean.

I was just reading on a different post about the crank sensor reluctor ring going out can give a problem similar to what you're describing. Starts to run super rich under boost. It's about mid way down this topic:
http://www.supraforums.com/forum/showthread.php?t=366488
 

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Kwan Jul Sul Freak
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The Supra's ECU is very good at throwing ECU codes if there is any problem with the crank sensor or cam sensors. If you are referring to the crank sensor trigger wheel (star) that is bound to the lower timing gear, you can actually see if it is off without removing the cover, crank pulley, and all the crap in front of it. You can look down the right (drivers) side of the lower half of the timing belt cover with a bright flashlight and see if the trigger wheel if pressed flush against the lower timing gear or not.

If you are not throwing codes sounds like you have a different problem. I would check:

- Coils with a digital ohm meter
- Voltage calibration of your BCC
- Plugs (cheap fix. ya never know. 6097's on a single, gap'em at .28")
- Stock pressure sensor on the manifold.
- Engine, chassis, and ECU grounds.
- Fuel filter (clogged, going lean?).
- Fuel pump (bad, going lean under boost?).

Check that your check engine light works too. Sounds stupid I know, but they do burn out. You can force an easy code by pulling the plug to the temp sensor in the water neck, start the car for 2 or 3 min, then turn it off. Then check for the associated code.

Keep us posted on your progress bro!


cord4530 said:
I was just reading on a different post about the crank sensor reluctor ring going out can give a problem similar to what you're describing. Starts to run super rich under boost. It's about mid way down this topic:
http://www.supraforums.com/forum/showthread.php?t=366488
 
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