Options; 1. SURGE or 2. MISS FIRE / STUMBLE

[johnny]

BACKGROUND;

I have had an 88 Mk3 supra in my garage for 4yrs. I blew out the original engine which was a 7MGE. I replaced it with a 2JZGE from a Lexus SC300. I finally got the thing to start, but.... It surges.

PROBLEM;

So, it surges at idle. I drove it to the end of the block and back (.5 of a block). Every time i pressed the gas the engine would studder and the check engine light would flash. I take that indication to mean there is a misfire, because, it probabley is right? I carefuly made it back home and check for vacuum leaks. I thought that maybe it was the idle set screw, so I adjusted it. When adjusting the throttle plate set screw, I could make the engine surge or stumble and misfire depending upon if the throttle plate was more or less open. If I perfectly set the set screw, I can make it idle normally. The point at which it idles is in between "stumble" and "surge". The sweet spot is very very small.

WHAT I HAVE DONE;

1. Checked for vacuum leaks with throttle body cleaner.
2. double checked all the intake manifold seals.
3. Cleaned the Idle Air Control Valve.
4. Checked the Coolant to see if I blew a gasket.
5. Checked the Oil for Coolant.
6. Checked the Spark Plugs to see if there was oil on the plugs or anything unusual.

Does anyone have any bright ideas why this isn't working?:1zhelp:

 

[veedubin]

Did you check the TPS adjustment? Check your codes?
Put the throttle adjustment BA k to factory and set the TPS.

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[IBoughtASupra]

Checked codes?

You can take out one wire at a time and see which coil is misfiring.

Does your MAF have a filter one it? If the fan clutch is blowing air in it, it will surge.

 

[johnny]

Did not check TPS adjustment. I will have to look up how to do that.

There are no locked in codes.

There is a filter on the MAF sensor and I have an electric fan on it so the fan isn't blowing into an open MAF.

I'm willing to put a bounty on this problem. If someone can tell me what is going on, I'll send you a fruit basket or something.

 

[johnny]

the TPS was slightly out of adjustment. The limit switch was not closed during idle position of the butterfly. Give me a couple of hours and we shall see if that was it. I would kind of be surprised if it was, but my knowledge is limited.

More to follow.....

 

[veedubin]

the TPS was slightly out of adjustment. The limit switch was not closed during idle position of the butterfly. Give me a couple of hours and we shall see if that was it. I would kind of be surprised if it was, but my knowledge is limited.

More to follow.....

Yea TPS adjustment is critical on these cars. Look through my last couple of started threads. Almost every drivability issue I had was due to mis-adjusted TPS.

Also I have 2spare TPS sensors a distributor and harness from a 95 Lexus SC300 if you need them.
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[johnny]

I set the throttle plate.

I adjusted the TPS so that the switch is closed at idle.

Now when I try to start it, the engine starts smoothly but then chokes out and dies.

RPMs taper off quickly then it stalls.

Whaaaaaaaaaaaat???????:1zhelp:

at least I am on the right track right?

Now what?

 

[veedubin]

I set the throttle plate.

I adjusted the TPS so that the switch is closed at idle.

Now when I try to start it, the engine starts smoothly but then chokes out and dies.

RPMs taper off quickly then it stalls.

Whaaaaaaaaaaaat???????:1zhelp:

at least I am on the right track right?

Now what?

Now with the TPS adjusted properly, reset the timing per TSRM procedure and specs. That should take care of that issue.

 

[johnny]

you are correct sir, now it revs up twice and then settles out to 1200 rpm.

I drove it around the block a bunch of times and whenever I come off throttle the RPMs drop to 650-700 for a moment and then go back up to 1200.

I already owe Veedubin for telling me the issue. Can anyone tell me why RPMs jump back up to 1200rpm after momentarily being at 650?

I can't get this thing registered until I get the RPMs right, otherwise it will fail inspection.

 

[veedubin]

Have you cleaned the idle valve? Also reset the ECU by pulling efi fuse for a few minutes.

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[johnny]

I disconnected the positive battery cable. Will that reset also?

I cleaned the IAC previously.

 

[veedubin]

I disconnected the positive battery cable. Will that reset also?

I cleaned the IAC previously.

Sorry I wasn't able to text you, if you're available I should be able to tomorrow.
Yes disconnecting the batt works to.
I did forget to ask tho, are you on 2j or 7m electronics? One of my biggest issues (on 7m gte electronics) was I accidentally wired the TPS backwards. It was seeing 5V @ idle. Needless to say it didn't like that too much. Use a DMM to see the voltage going to the ECU. Make sure @ closed throttle its around .5V and at WOT is around 4 - 5V.

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[gsxr141]

since you mentioned the tps voltage, here's one for you. i had an issue with an intermittent high/surging idle. i set my tps at idle to .5 volts, and the problem seems to be gone. the strange part is, it only reads 3.xx volts wide open. i am nowhere near 5 volts. should i swap out the tps?