Throttle stuck after 3rd gear pulls

[99gst_racer]

Here's the rundown. I've been throwing the P0505 CEL (idle control malfunction), so last week, I changed the sensor, and I cleaned my throttle body while I was at it. After that, the car started/ran fine. So we did a 3rd gear pull on the logger, and after that, my throttle was stuck open and it was riding at 2500 rpm's. We manually turned it down via the little screw that acts as a stopper. And everything has been fine since, until yesterday. I did another WOT 3rd gear pull and this time, it stuck at 4000 rpm's. (It’s extremely embarrassing to try to park your car at the beach @ 4K and then wait for it to turbo time)

What could be causing the throttle to stick like that? What should I check?
There isn’t any foreign objects interfering with the throttle cable or the cruise control parts.

(It’s 80* outside right now, and I'm stuck driving the winter beater. I need to fix this asap!)

 

[VBGSX]

Here's the rundown. I've been throwing the P0505 CEL (idle control malfunction), so last week, I changed the sensor, and I cleaned my throttle body while I was at it. After that, the car started/ran fine. So we did a 3rd gear pull on the logger, and after that, my throttle was stuck open and it was riding at 2500 rpm's. We manually turned it down via the little screw that acts as a stopper. And everything has been fine since, until yesterday. I did another WOT 3rd gear pull and this time, it stuck at 4000 rpm's. (It’s extremely embarrassing to try to park your car at the beach @ 4K and then wait for it to turbo time)

What could be causing the throttle to stick like that? What should I check?
There isn’t any foreign objects interfering with the throttle cable or the cruise control parts.

(It’s 80* outside right now, and I'm stuck driving the winter beater. I need to fix this asap!)

Well from what I'm reading, the stuck throttle didn't start happening until after you cleaned the TB and changed the ISC. Correct me if I'm wrong.

So that's where we start.
Is the throttle plate stuck open? If you're not sure, try to open the TB by hand and see if it opens and closes smoothly.
If the TB plate is stuck open, go directly to the throttle cable. See if it's tight or has plenty of slack while the plate is stuck open.
If the plate is stuck open, the throttle cable is tight(pulling on it) and your foot is off the gas, then follow the cable back and find the problem.
If the plate is stuck open and the throttle cable has slack(lots of play). It's in the TB
Make sure the cable is connected and routed properly on the TB.
Are you still using the 2g TB or have you swapped in a 1g TB?
How did you clean the TB?

If the TB(throttle plate)is shutting all the way and sealing properly, I would go back and take another look at the ISC.
If the ISC is not opperating properly(stuck open), it will allow the extra air in, increasing your RPM's
Usually if the ISC is bad, the car won't stay at 4000 RPM. It will usually surge if it gets that high.

Let me know if I missed anything in your post.
I think this might be a good start.

I hope it helps

 

[99gst_racer]

Well from what I'm reading, the stuck throttle didn't start happening until after you cleaned the TB and changed the ISC. Correct me if I'm wrong.

Yes, that is correct.

If the plate is stuck open and the throttle cable has slack(lots of play). It's in the TB
Make sure the cable is connected and routed properly on the TB.
Are you still using the 2g TB or have you swapped in a 1g TB?
How did you clean the TB?

The cable is definitely routed and connected properly. I'm going to pull the TB elbow off tonight to check, but I'm 99% sure that the throttle plate is slightly open. There is some slack in the cable. I am still using my stock 2G throttle body. I cleaned it with a rag and carb cleaner.

If the TB is shutting all the way I would go back and take another look at the ISC.
If the ISC is not opporating properly(stuck open), it will allow the extra air in, increasing your RPM's
Usually if the ISC is bad, the car won't stay at 4000 RPM. It will usually surge if it gets that high.

I unplugged the ISC while it was reving high, and I saw no change. It has been surging now and then for the past week too. But the CEL hasnt came on since I swapped out sensors.

What do you recommend I do?

 

[VBGSX]

Yes, that is correct.


The cable is definitely routed and connected properly. I'm going to pull the TB elbow off tonight to check, but I'm 99% sure that the throttle plate is slightly open. There is some slack in the cable. I am still using my stock 2G throttle body. I cleaned it with a rag and carb cleaner.

If it's stuck open, then you've located the problem. Now you just have to figure out why it's open. You said the cable has slack so it's not keeping it open. So lets look at the the throttle position stop screw. As you probably know it adjusts where the throttle plate stops(set from the factory). It's possible that someone adjusted it(and probably the BISS screw also) a while back because of an idle issue. With the carbon there, it sealed pretty well. Now that you've cleaned all that carbon out, the TB plate closes as far as it can(screw stops it) but it no longer has all that carbon to seal it up.......just a theory

Check the TB plate issue first. The best way is to pull the entire TB off so you can see both sides. You can then easily examine the TB plate to make sure it's closing properly. You may have to adjust the screw. I wouldn't suggest people even mess with it but you've already had to adjust it. By the way, changing the screws posion will obviously rotate the TB shaft which in return could change the reading of the TPS also.

The weird thing is that your problem doesn't happen all the time.

I unplugged the ISC while it was reving high, and I saw no change. It has been surging now and then for the past week too. But the CEL hasnt came on since I swapped out sensors.?

Do you know how to test the ISC? Just in case you don't
http://dmtalon.v8eaters.com/ISC.html
I've seen a bad ISC and it never threw a code....no clue why though.

Well at least you've narrowed it down to the TB itself.
I would say it's 1 or 4 things and I would probably also start in this order.
1. TB plate not closing
2. ISC
3. FIAV
4. BISS screw

Surging issues are usually #2 and/or 3. Other things can affect it but those two rank at the top.

Out of curiosity, did your vacuum reading change(drop) after the cleaning?

Sorry I don't have more for you at this second

 

[99gst_racer]

If it's stuck open, then you've located the problem. Now you just have to figure out why it's open. You said the cable has slack so it's not keeping it open. So lets look at the the throttle position stop screw. As you probably know it adjusts where the throttle plate stops(set from the factory). It's possible that someone adjusted it(and probably the BISS screw also) a while back because of an idle issue. With the carbon there, it sealed pretty well. Now that you've cleaned all that carbon out, the TB plate closes as far as it can(screw stops it) but it no longer has all that carbon to seal it up.......just a theory

This only happens when I got WOT across 3rd gear, so I dont feel it's directly related to the adjustment screw. I just cant figure out why the throttle plate is all of the suddden not closing. And how/why would a 3rd gear pull affect it?

Check the TB plate issue first. The best way is to pull the entire TB off so you can see both sides. You can then easily examine the TB plate to make sure it's closing properly. You may have to adjust the screw. I wouldn't suggest people even mess with it but you've already had to adjust it. By the way, changing the screws posion will obviously rotate the TB shaft which in return could change the reading of the TPS also.

Well, 2 days ago, my idle was setting perfectly at 1000 rpm's where I had it set, and my throttle position was at 0..... I just ran home an hour ago on my lunch break, and started it up with the logger hooked up. Now she's idling at 2800 and my throttle position is at 7%. I wonder why the change just from sitting overnight??

The weird thing is that your problem doesn't happen all the time.

Yeah, that and it changes from perfectly fine to 4000 to 2800..... Thats why I cant figure it out.

Do you know how to test the ISC? Just in case you don't
http://dmtalon.v8eaters.com/ISC.html
I've seen a bad ISC and it never threw a code....no clue why though.

Yeah, I just havent got around to borrowing my buddy's multimeter to test either one of my ISC sensors yet.

Well at least you've narrowed it down to the TB itself.
I would say it's 1 or 4 things and I would probably also start in this order.
1. TB plate not closing
2. ISC
3. FIAV
4. BISS screw

What could cause the throttle plate to spratically not close all the way? How do I check my FIAV and BISS? (edit: I'll search on those two)

Out of curiosity, did your vacuum reading change(drop) after the cleaning?

You know, I never noticed. Thats one thing I didnt pay attention to. But one funny thing I havent noticed, my boost gauge now takes about 20 sec after the engine is started for it to start reading vacuum. It used to be instant, but not anymore. Any ideas why?

Sorry I don't have more for you at this second

Hey, I really appreciate the help. If I get this fixed, I'll owe you.

 

[VBGSX]

This only happens when I got WOT across 3rd gear, so I don’t feel it's directly related to the adjustment screw. I just can’t figure out why the throttle plate is all of the sudden not closing. And how/why would a 3rd gear pull affect it?

If it were intermittent, I would have to agree. I couldn't even think of a reason why 3rd gear would affect it. Maybe it's just a coincidence. Plus you've said that when you've started it up and it acted strange(higher RPM at idle)

Well, 2 days ago, my idle was setting perfectly at 1000 rpm's where I had it set, and my throttle position was at 0..... I just ran home an hour ago on my lunch break, and started it up with the logger hooked up. Now she's idling at 2800 and my throttle position is at 7%. I wonder why the change, just from sitting overnight??

OK this is what you need to try. Start it up. See if the idle goes higher than what you've set it at. If it does, leave the car running and immediately pop the hood. Grab the TB actuator arm(what the throttle cable connects to) and see if you can manually close the TB plate more. If you can close it and the RPM's drop, then you know it's getting stuck on something. I really hope it's something that easy

Yeah, I just haven’t got around to borrowing my buddy's multimeter to test either one of my ISC sensors yet.

Definitely do that when you get a chance. But, you posting that your throttle position changing to 7% is a clue that it's probably not the ISC. It could still be bad(just adding to your problems) but it has nothing to do with changing the throttle pos.

What could cause the throttle plate to spratically not close all the way? How do I check my FIAV and BISS? (edit: I'll search on those two)

Carbon, TB plate not being centered, The spring, the screw, throttle cable(mis aligned on the TB, misadjusted, etc), I'm sure there's a few more.

I've never come across a way to check the FIAV. The only reason I found mine was bad was because I had checked and rechecked everything and the last thing untouched was the FIAV. Oh my problem was a high idle surge. Like yours, it wasn't consistent. You know though. I never looked at my throttle pos though. Again, the FIAV shouldn't affect that. Anyway, I swapped my 2g FIAV onto the 1g TB and everything worked perfectly.

You know, I never noticed. That’s one thing I didn’t pay attention to. But one funny thing I havent noticed, my boost gauge now takes about 20 sec after the engine is started for it to start reading vacuum. It used to be instant, but not anymore. Any ideas why?

Does this only happen when it has the high idle? What's your vacuum showing?

Hey, I really appreciate the help. If I get this fixed, I'll owe you.

Any time. I just hope we can get it taken care of. Hopefully we can come up with it or at least get you in the right direction.

 

[VBGSX]

You don't know anyone that happens to have done a 1g TB swap and still has their 2g TB?
If so you could eliminate the TB. Just take the other TB swap your sensors on and give it a try. If you still get the same problem then you know it's not the TB itself.

If all else fails, I have one around here. Maybe we could work something out with shipping you could try it. Mine just doesn't have the sensors(TPS or FIAV). I used them on 1g TB swap. I would hate to have you spend any money though. Maybe someone local will let you try one. This will be a thought though after everything else has been exhausted.

I'm pretty confident that you'll find the problem though.
Good luck

by the way I editted a few things on the last post in case you missed it.

 

[99gst_racer]

I got it fixed!!

My SAS and BISS screw were way out of adjustment. My TPS was also. And I guess I didnt clean the TB as good as I thought I did the first time. So I re-cleaned it and did a much better job this time around.

After I got it pulled off, I inspected it very closely and nothing appeared to be out of place. I then proceeded to test the ISC sensor per VFAQ ------> http://dmtalon.v8eaters.com/ISC.html . I tested the old sensor that I had removed, and the new one that is currently installed. They both read 30 ohms across the board.

I then proceeded to reset my SAS screw per VFAQ ------> http://www.vfaq.com/mods/BISS-2G.html . Mine was way out of adjustment. It was bad.

After that, I tested my TPS. It was also out of adjustment. I was reading 1.5 ohms with the throttle plate closed. I readjusted it to .9 ohms per VFAQ -------> http://www.plymouthlaser.com/tps.htm .

I reinstalled the throttle body and fired the engine up. Perfectly smooth idle at 1000 rpm (thats where I've always had it set). I went for a 15 min drive, and after it warmed up, I noticed it was surging a little bit. The idle surge used to be fast and powerful, but this was more of a 8 second hickup. It would surge for about 8-10 sec. and then idle would smooth out. I knew I was surging because I never did reset my BISS screw (I dont have access to a Scan Tool). I made one small turn on the BISS screw and the surge stopped and the idle levled out. I now have a perfect idle (for the time being).

VBGSX - Thanks again for all your help. Between your advice and the VFAQ site, I got this fixed pretty quick.

 

[VBGSX]

Very nice.
Hopefully this thread will help others with similiar problems.
I knew you would figure it out.

 

[1fast97gsx]

I got it fixed!!


After that, I tested my TPS. It was also out of adjustment. I was reading 1.5 ohms with the throttle plate closed. I readjusted it to .9 ohms per VFAQ -------> http://www.plymouthlaser.com/tps.htm

Paul, the problem is that vfaq is not the proper tps adjustment procedure on a 2g. 2gs have a 4 wire tps and must be adjusted via the factory service manual. It might be fine for now, but if not done properly you will have problems in the future.

What you need to do is put a .017" feeler guage between the actual throttle linkage or whatever you want to call it and the stop screw. This basically opens the plate just a tad. The purpose of this is the get the tps thinking you are NOT in the idle position, but rather you are apply just a tiny bit of throttle. Once you do that you loosen the tps bolts and rotate it all the way counter clockwise. You then take an ohm meter and measure resistance across pins 3 and 4 on the tps with the harness unplugged. You have to keep the ohm meter connected and then you turn the tps VERY slowly until you start seeing an infinite amount of resistance. Your ohm meter will at this point read 1. I usually double check it by turning it back counter clockwise just a tad and see if you once again get a measureable amount of resistance, then turn it clockwise again until you read infinite. Once this happens tighen the 2 tps mounting screws to keep it from rotating. Then check it again and it should read infinite. If you did it properly when you pull the feeler guage out and measure resistance once again you will get a measureable number, put it back in it's infinite again. The purpose of this is to set the tps so it knows when you aren't on the throttle at all it's in idle mode, then when you apply throttle resitance will go to an infinite number. ( pin 4 is the ground pin, pin 3 is the idle switch pin ) This is very important and will help a lot with surging or random higher rev sticks as well as choppy parking lot driving. This will only work if your throttle stop screw is properly adjusted as well. If not, then that MUST be done first. Although it sounds confusing the first time you read it, once you do it once you'll see its very simple and can be done in less than 5 minutes.

Also, a bad isc will NOT throw a cel. I'm guessing your light is from a poorly adjusted tps or random boost leaks. Throttle body shaft seals and the biss O ring made a HUGE difference for me and cost less than $1 to replace. I would reset that tps again and search around a little on here or on nabr if you are a member on there. Steve had a few good posts on how to properly set a 2g tps on tuners, and it also has the correct method listed on roadraceengineering.com under the 1g tb swap. ( even on a stock 2g tb this method still applies. Good luck.

Edit: Check out:

http://www.dsmtuners.com/forums/showthread.php?t=191288&highlight=2g+tps+adjustment

and

http://www.roadraceengineering.com/2gtbswap.htm

Sorry to bring back an old thread, but I'm sure it may help others.

 

[99gst_racer]

Thanks Cedric. I have not had any idle issues since my last post in this thread, however, when spring time comes around, I will re-adjust my TPS anyway. By the way, nice post.