ACIS and a vaccumm leak?

[Chris R]

ISC idle speed control. CSI cold start injector, another possiblity that you should check.

Okay. I'll search for those, thanks.

How about the fuel pump or filter? Or the fuel pressure regulator?

I've also got a three inch exhaust, custom headers super dragger muffler (From the previous owner, haven't replaced it yet)

The throttle is weird, it's I have to floor it to really get it going. It'll accelerate at 50% or 70%, but above 2.5k only slightly, and sometimes not at all. Below 2.5k it misses pretty hard sometimes on acceleration. Once it gets up to 3.5k it kicks in pretty hard.

 

[Chris R]

Every now and then when you crank it, it'll idle very roughly and just keep going lower until it dies. If you try to accelerate it, it'll drive but with a huge miss for about 5 miles and then it'll slowly return to normal.

It usually cranks alright, so I really don't see that problem being the CSI or ISC.

And if its not plug wires, then I'm guessing its fuel related? Filter? Pump? Relay? Or Injectors? Hell, those are all pretty expensive.

To really get a response from the car I have to push it all the way to the floor. I'm kind of lost here guys, I've tried to test everything but it feels like I'm starting to just throw parts at the car and hope something works.

 

[Chris R]

Another update here. I threw some MSD plug wires on there. It helped a bit, but there's still a lot of missing. Finally convinced my dad to drive it, and this is what he noticed:

Under 3200 (or so) rpms, the car misses pretty bad, still kind of a sputter. At the really low rpms (2000 and below) it misses really bad.

Every now and then, when you start the car at an idle, it will idle very rough, lobing and hunting. From the smell the car was giving off, he proposed that it must be running pretty rich. We plan to replace the O2 sensor tonight, but we think that there might be more involved here.

I noticed that my injectors are yellow tipped, and thus I'm guessing they are the low impedance ones. But that I may be missing the injector resistance pack. There's some blank screw holes right above the drivers side strut tower, with nothing there. Would a missing resistance pack cause any of these symptoms, or simply burn up the injectors over a period of time?

I'm looking at trying to bypass the relay for the fuel pump to see if its a bad relay. Come to think of it, if fuel pressure may be the culprit, could be fuel pump be stuck on "high" and be dumping too much fuel into the motor at the lower rpms? I don't know if the switch from running like shit to completely smooth would be instantaneous though.

Above 3200 rpms, the engine smooths out, pulls like hell, and barely misses.

In 1st, 2nd, and 3rd gears it pulls alright throughout the rpm ranges. In 4th and 5th, you really have to floor it to get a proper response from the car. Once the ACIS kicks in, or whatever is helping it out, it responds pretty well.

The hunting idle seems to be the worst after the car has warmed up. When the car starts cold, it misfires, but the motor does not have a lobe/hunt to it. We have replaced the AFM.

So either it's not getting adequate fuel, or something is causing the thing to run stupidly rich, at least sometimes. again, any ideas guys?

-edit- Did a little bit more searching, could be fuel pressure? Guess we'll try and check that.

 

[Chris R]

Cleaned out the ISC yesterday. Guess we'll see what that does.

No ideas on what the cause of my problem could be? I'm trying to get a good idea here instead of just trying a relay, pump, switch and injectors at it.

Local mechanic said the problem could be valve guides.

 

[Chris R]

This is probably my last update as I haven't gotten a response in about six days.

I cleaned out the ISC. It seems to have helped a little bit. Before the loabing/hunting starts, the car idles a bit higher, but the misfire isn't as pronounced at first.

Spraying carb cleaner on the vacuum lines (recommended by a local mechanic) didn't do anything for the loabing once it started. But that isn't exactly a scientific test, so we'll try and hook up a vacuum test early next week and see where that gets us.

When testing out the cleaned ISC, I noticed that at first, even when the car warms up, you can run and restart it all you want. It'll idle about 1000 every now and then, and the misfire is prounounced, but for the most part it'll act alright.

But when you let the car set after it has warmed up for about 15-30 minutes, then the very rough idle, the loabing, the hunting will start. After that started, I shut the car off, left it for about 45 minutes again, and it cooled down a bit. But it the engine still did that rhythmic shudder/loab/hunting deal.

So after replacing, the AFM, the TPS, cleaning out the ISC, replacing the wires, checking the plugs, and checking for vacuum leaks I am completely lost as to what it could be. Bypassing the fuel pump did nothing by the way.

I really don't know how else to describe the problem guys, so I really don't know what else to say to garner further suggestions here. It feels like I'm wasting my time by continuing to update this thread on my progress, so I'm just gonna stop here.
I've search and I've searched, but I haven't found much to pertain to this specific problem.

If anyone feels the notion to respond, I have this thread subscribed so I'll get an e-mail when you respond. Same with PMs. Thanks for those that helped.

 

[CRE]

Hey sorry you're still having trouble. I haven't been on much lately and haven't really had the energy for the more involved threads (I figured I'd leave it to those with more energy and motivation).

Have you tested the distributor and igniter? Have you checked the voltage at Vf both when it's doing this and when it's fine? Have you checked all of the grounds in the engine bay?

 

[Chris R]

Hey sorry you're still having trouble. I haven't been on much lately and haven't really had the energy for the more involved threads (I figured I'd leave it to those with more energy and motivation).

Have you tested the distributor and igniter? Have you checked the voltage at Vf both when it's doing this and when it's fine? Have you checked all of the grounds in the engine bay?

Thanks for the response.

The distributor is odd. We ordered a cap and rotor for a 7mge supra, but the kid had kept the cressida distributor from before in there. So we have the proper rotor, but a USDM 7MGE cap on there. Both caps looked pretty similar, and the car ran better with the newer cap.

The voltage at Vf? I'm a little bit confused on that. I've been doing most of my testing for resistance, but that is just hooking up two connectors to the mutli-meter. By ignitor I'm guessing you mean the ignitor coil. Are you talking about the VF on the distributor cap?

I do know that when we checked the timing, and had one of the wires partially out of the distributor, it was putting out a hell of a spark. So we're thinking the coil is pretty healthy since it had no trouble with producing spark on the #1 wire.

Negative on the grounds, and I guess I didn't think about the ECU ground.

As a side note, could this be a symptom of a blown headgasket? Someone suggested a leakdown test, so I figured I'd ask.

 

[CRE]

It could definitely be indicative of a BHG... it's not a given, but it is quite possible.

The igniter is mounted below the ignition coil... look it up in the TSRM.

Vf is a feedback line where the ECU presents data regarding what it's doing, if codes are stored and so on... Look at the link below for more info:
http://www.supramania.com/forums/showthread.php?t=39856 Don't assume you know what's going on just from the result of that test. I can't remember if the Vf line is actually run to the diagnostic box in our car or if you have to read it at the ECU. If it is run to the diagnostic box you'll find it's location in the box here:
http://www.fadingworld.com/Supra/El...x Demystified/Diagnostic Box Demystified.html

How is the distributor "odd"? Be specific and post pics if you can.

By the way, carb cleaner works quite well for locating vacuum leaks. I prefer using propane myself, but either will do the trick... Personally, I've had better luck with propane.

 

[CRE]

Oh, and I know you've checked the ignition advance timing, but have you physically checked the timing? You know, made sure that when the crank is at 0º (TDC) that the cam gears are and that the distributor's drive gear is also lined up right.

Good spark from one plug wire at idle doesn't rule out much of anything either. You could still have a distributor problem or an issue with the igniter.

 

[AJ'S 88NA]

Check and clean your cold start injector?http://cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?Section=FI&P=77

 

[CRE]

The cold start injector is only powered WHILE you're cranking the engine... if it fails you may have difficulty starting, but that's really about it. If it's leaking you may run rich, which the ECU would trim for as much as possible, but the cylinders may see varying amounts of fuel from one another.

when you let the car set after it has warmed up for about 15-30 minutes, then the very rough idle, the loabing, the hunting will start. After that started, I shut the car off, left it for about 45 minutes again, and it cooled down a bit. But it the engine still did that rhythmic shudder/loab/hunting deal.

This has my interest. Test the ECU coolant temp sensor when the engine's cold and when the coolant system is up to temp. See if the resistance is pretty steady or if it fluctuates.

http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?Section=FI&P=113

You could also try taking a resister with a value of, oh, 470Ω or 680Ω and plug that into the ECU's water temp sensor's harness connector. This will let you see how the ECU's behaving when you know you're getting a solid temp reading that's in the normal "warm" range. I think even 1KΩ would be fine for this.

 

[Chris R]

It could definitely be indicative of a BHG... it's not a given, but it is quite possible.

I hope not.

The igniter is mounted below the ignition coil... look it up in the TSRM.

Alright.

Vf is a feedback line where the ECU presents data regarding what it's doing, if codes are stored and so on... Look at the link below for more info:
http://www.supramania.com/forums/showthread.php?t=39856 Don't assume you know what's going on just from the result of that test. I can't remember if the Vf line is actually run to the diagnostic box in our car or if you have to read it at the ECU. If it is run to the diagnostic box you'll find it's location in the box here:
http://www.fadingworld.com/Supra/El...x Demystified/Diagnostic Box Demystified.html

Ah, okay, I understand now. In that link that shows the diag box, it has a VF1 connector. It says to link it to E1 for TCCS Fuel Trim feedback. That sounds the right lead.

How is the distributor "odd"? Be specific and post pics if you can.

It's just got a USDM cap (looks the same as my old one) with a Cressida rotor. I'm thinking that despite the rotor difference between the Cressida and the USDM 7MGE, the caps are the same.

By the way, carb cleaner works quite well for locating vacuum leaks. I prefer using propane myself, but either will do the trick... Personally, I've had better luck with propane.

Would spaying it on the head gasket give any indication what so ever of a leak opening up there under those certain conditions?

Check and clean your cold start injector?

I'll definitely check that tomorrow. The only reason I had discounted that is because it seemed like the car didn't have much trouble starting. But it's worth it to know either way.

This has my interest. Test the ECU coolant temp sensor when the engine's cold and when the coolant system is up to temp. See if the resistance is pretty steady or if it fluctuates.

Okay. Could this be causing the engine to be overly rich once it warms up and then sets?

You could also try taking a resister with a value of, oh, 470Ω or 680Ω and plug that into the ECU's water temp sensor's harness connector. This will let you see how the ECU's behaving when you know you're getting a solid temp reading that's in the normal "warm" range. I think even 1KΩ would be fine for this.

So I could hook up a resister to the harness, kind of like I would hook up a mutli-meter? And then see how the engine (ECU, really) reacts?

 

[CRE]

Ah, okay, I understand now. In that link that shows the diag box, it has a VF1 connector. It says to link it to E1 for TCCS Fuel Trim feedback. That sounds the right lead.

Whoa.... you put a multimeter to it. The positive lead connects to Vf1 and the negative connects to E1. Do NOT jumper the two, you could damage the ECU... you may have meant that, but the word "link" makes me think of a jumper. That'd be bad.

Just buy a new rotor, they're very inexpensive. sheesh.

No, propane or carb cleaner will probably not help diagnose a BHG... none that i can think of anyway.

A faulty temp sensor can cause enrichment and timing issues. So, you unplug it and then insert one wire from each side of the right size resistor into each of the two holes in the connector on the harness. This will make the ECU think the coolant is at a certain temp and not changing... it'll at least help knock out one possibility. Put in the resistor BEFORE starting the car and make sure the harness can't swing into the fan.... watch them fingers.

 

[Chris R]

Whoa.... you put a multimeter to it. The positive lead connects to Vf1 and the negative connects to E1. Do NOT jumper the two, you could damage the ECU... you may have meant that, but the word "link" makes me think of a jumper. That'd be bad.

Yep, that's what I meant, just using a mutlimeter to read the voltage when it's normal and when it's loabing. No jumpers, haha.

Just buy a new rotor, they're very inexpensive. sheesh.

We did. It's just got a USDM 7MGE dist cap on it, as opposed to a JDM Cressida 7MGE dist cap. I'm just saying that despite the rotor difference, I don't think there's any differences between the Supra cap and the Cressida cap. The rotor is new.

No, propane or carb cleaner will probably not help diagnose a BHG... none that i can think of anyway.

Alright, thanks.

A faulty temp sensor can cause enrichment and timing issues. So, you unplug it and then insert one wire from each side of the right size resistor into each of the two holes in the connector on the harness. This will make the ECU think the coolant is at a certain temp and not changing... it'll at least help knock out one possibility. Put in the resistor BEFORE starting the car and make sure the harness can't swing into the fan.... watch them fingers.

Gotcha. That's worth a shot then. I have to head up to Wichita on monday, so I can grab some resistors.

It's raining out, so I haven't gone out to test the CSI,Coolant temp sensor, or the VF, with the multi-meter yet. But I'll come back here and give the voltages to you guys when I do later on today.

 

[jetjock]

No resistors needed. Simply unplug it...

 

[Chris R]

Alright, here's what I got on the Water Temp Sensor. I used two alligator clips so I could keep the multi-meter plugged into the sensor without having to hold it. But one wire was a slightly larger than the other. Does this matter when measuring resistance, or are my results skewed?

It reads 1.2k ohms just sitting there.

On an idle, it goes down to .08k.

Idle gets a bit rougher as it heads down to .06k

After a couple minutes the resistance has moved down to .04k

On the first mark on the temp gauge (the bold one) the resistance was about .02k

At the third mark, barely above .02k

5th Mark, just below .02k

6th mark, a little bit above .01k

Between the six and seventh marks it reads exactly .01k. This is where the gauge usually reads once it has warmed up.

A little bit later, still between the sixth and seventh marks, it went down to .01k

Hope that's not too much information overload.

I noticed that the car would not start when I unplugged the water temp sensor. I had to plug it in, start it, unplug it and then get my readings.

This time, it started hunting without having to warm up and sit. Once we plugged the sensor back in after the car had fully warmed up, the engine smoothed out a bit.


Btw, I think the cold start injector is fubar'd. The resistance didn't measure right, it was barely registering. We have an extra from the old motor. I'm going to test the resistance on that and throw it on the car, see if that does anything.

 

[jetjock]

What you saw is normal. The engine will be hard starting (at least when cold) without the coolant sensor because unplugging it makes the ECU think the coolant is hot. If it thinks it's hot it won't supply the extra fuel needed for cold start and warm up enrichment.

Btw a quick check shows that's an interesting town you live in. Dorothy and Toto would be proud

 

[Chris R]

What you saw is normal. The engine will be hard starting (at least when cold) without the coolant sensor because unplugging it makes the ECU think the coolant is hot. If it thinks it's hot it won't supply the extra fuel needed for cold start and warm up enrichment.

So the resistance readings are normal? I tried my best to compare it to the chart in the TSRM, but it's hard given that the temp gauge gives absolutely no indication as to what the actual temperature is. How the rougher idle when the sensor is unplugged?

Btw a quick check shows that's an interesting town you live in. Dorothy and Toto would be proud

Heh, probably so. My parents, both Army retirees, settled in this town after my mom left the Army with 27 years of service in 2007. I stay here over the summers.


I'm thinking that I'm dealing with a two-part problem here. I drove it to church, and had planned to take it out on the highway to see if the ECU threw any other codes than the code 43 (starter) it has been throwing.

I never got the chance to do that, as we had an incoming hail-storm, so the Supra went safely under the barn. But it acted ridiculously sluggish. In 1st gear it would rev, but it would mis. In second it would rev, but at about 2.5k the engine would start missing like crazy. It did this every time in second gear for about a mile. After that I took it out on the highway and it behaved itself a little bit better. When I started the engine up to get to church in the first place, the car ran flawlessly. Barely missing, if at all. I'm waiting to get that fuel pressure test done on Monday or Tuesday. I think that'll be telling. That and the compression (and hopefully a leakdown, if the guy has it) test.

I can still smell a sweet smell outside the car, but my dad or I really can't tell if its coolant or gas from running rich. Its hard to tell if we've burned any coolant, we've spilled so much taking the throttle body on and off, heh.

 

[A-model_]

While reading on a mr2 forum I found a thread that described the problem you were having.

" is my ecu dieing? car bogging out
I turn the car on after sitting lets say over night and it runs fine, will go into the upper rpm range no problem. Then after maybe 10 minutes or so of driving, it bogs and doesn't want to move past 4k rpm and then just bogs completely to where I'm sputtering when I push the gas at all but it will idle just fine.

Then If I turn the car off and let it sit for a while, it will run fine for a few minutes then start bogging again. Man it is frustrating!!

any ideas? could my ecu be crapping out and it sort of resets itself after being off for a bit?"

Turned out to be the coil.

"ok, just for future reference, I changed out my ignition coil and have driven it about 100 miles or so and it hasn't hesitated at all so that should be a good fix!

My old coil was an accel universal coil, looked a bit old so out with the old and in with the new.

Thank a bunch papo J and everyone for your help."

Some thing to think about in case you have checked everything.

 

[Chris R]

While reading on a mr2 forum I found a thread that described the problem you were having.

" is my ecu dieing? car bogging out
I turn the car on after sitting lets say over night and it runs fine, will go into the upper rpm range no problem. Then after maybe 10 minutes or so of driving, it bogs and doesn't want to move past 4k rpm and then just bogs completely to where I'm sputtering when I push the gas at all but it will idle just fine.

Then If I turn the car off and let it sit for a while, it will run fine for a few minutes then start bogging again. Man it is frustrating!!

any ideas? could my ecu be crapping out and it sort of resets itself after being off for a bit?"

Turned out to be the coil.

"ok, just for future reference, I changed out my ignition coil and have driven it about 100 miles or so and it hasn't hesitated at all so that should be a good fix!

My old coil was an accel universal coil, looked a bit old so out with the old and in with the new.

Thank a bunch papo J and everyone for your help."

Some thing to think about in case you have checked everything.

I was searching for testing the ignitor in the TSRM earlier and also read up on how to test the coil. So that's definitely on my to do list. Thanks man.