+++++++++++ Other tt.net members have written:+++++++++++

I have been trying to track down this problem for months, through this forum and help of members I was able to (finally) track this issue down. I was also having intermittent issues with fuel smell, this got MUCH worse over the past week. Upon investigation found the fuel pressure regulator and fuel damper were both leaking - a bbq grill waiting to happen!! These have both been replaced and the engine hesitation is gone!!!!!! Special thanks to Steve (Guapo) on this one! Thanks y'all.

=================================================================

with a new OEM standard 170F (actually cheaper than Stant thermo at a Jobber). I checked the temp at the coolant temp sensor with an infared temp gun and found it at 152F after warmed up. Pulled thermo and found it was opening at 150+F and it was a std 170F unit. So those out there fighting idle issues don't forget the thermostat. Check the new one in a pot of water on the stove before installing.

ZUL8TR in Orlando,FL
=================================================================

Thanks!
checked out the injectors again and there it was... one of them that had
tested 12.8 ohms no longer even had a reading...

thanks again!
Marco
=================================================================
posted by: Z1TRUTH on June 07, 2005 at 6:37 PM

rough! While warming up (and purring like a lion I might add) I heard the rpm drop and it start to run rough. Well I drove it around the block and it was running real rough. I thought it was maybe the tps so I cleaned all the connectors and the CAS connectors as they had this weird white caked residue on the terminals. Nothing ......still rough running. !!!! ARGGGGGG!
So today I decide to do the TPS diagnostic and check the ECU codes. The TPS had good ohm readings 1k at closed and 9k wide open but I couldn't get a voltage reading for some reason??????
So I proceeded to do the ECU code and got a 55.....all is well. Hmmmmmm the TPS must be good, right?
Then I did the ECU O2 sensor test all is well!?!?!?!
So next I do the power test disconnecting the coil power connectors one by one and I get a power drop and rise one by one. Dang what is it.
Wait a minute ....what is that I hear........the engine is running smoothly again!!!!!!!!!!!
Took it for a spin and WHAAAA LAAAAAA no more rough running engine. Don't you just love spending a entire afternoon diagnosing aproblem and then it just disappears. Make you wonder if it will REAPPEAR!
Anyone else have this kinda fun?
=============================================================
osted by: CRAZZEPETE. on August 30, 2005 at 10:26 AM

In Reply To: Problem with the Idle posted by CRAZZEPETE. on August 30, 2005 at 09:55 AM

I found in FAQ that there are 2 solenoids, I thought just one, one for AC and other for idle...sounds like I'm going to have to bring in my reserve IAA and swap them out, maybe I have a problem with one of them, the idle controler for cold starts, I could start by testing the resistance of it, and if it's outta whack...regular is near 23 ohms, I know I have a problem
===============================================================
Posted by: Velox on September 10, 2005 at 3:42 PM

It ended up being corrosion on the positive end! I cant believe it. I got so fed up with the negative side that I thought to myself, I'm just going to clean and inspect this whole assembly. So I took it all apart and wire brushed the crap out of it. When I put it back together, she ran fine!

I didn't mean to cry wolf, but I really do appreciate the help! That spacer idea worked for the negative and put my mind at ease about the tension I had on the cable.

Thanks again,
-Derek

===============================================================
Posted by: zx spinner on September 13, 2005 at 5:40 AM

Tryed everything to get my Z to idle properly and every procedure still left it idling 1500-2000 rps. Some days it would idle closer to 1100, but it was problematic for the last 12 months. I even replaced the whole AAC or Idle Air Controller from another Z and still had the problem. So finally after much sould serching i unplugged the selenoid from the AAC and no more problem. A perfect 800 rpm Idle.

So with the AAC selenoid unplugged the car has no problems.

1. Cold starts are normal (1500 rpm spike right down to 800)
2. Hot starts are normal
3. A/C or any other acessories run fine and no engine stalling.

So all in all I'm suprised that car runs so well without the unit, if you're in a pinch i would suggest doing this untill you get a replacement, the car performs just fine without it.
================================================================
Posted by: ZNoob on September 16, 2005 at 9:01 AM

In Reply To: Intermittant Hesitation at WOT posted by TpLsZ on September 16, 2005 at 08:06 AM

I recently had a issue similar to that with my 91 NA... it would idle fine but as soon as i tried to go with any reasonable speed it would choke and sometimes just die...i traced it down to the Crank Angle Sensor...i dont know whether it was just a corrosion or it was going out because we swapped them and cleaned the connector at the same time. but something you might want to try
===============================================================
Posted by: DanDLT on September 18, 2005 at 11:05 PM

ok so had a stumbling idle after an injector error code after running low on fuel, the dealer checked the injectors.
said they work.. but i still had a low rough idle..it would shake alot.. so after much reading and learning i decided i need to learn how to work on this car, so thanks to twinturbo.net for all the information, also thanks to other members ofcourse.
so i suspected the idle problem is somewhere in the injectors or fuel line.. like the regulator, the dampner, o2 sensors, EGR.
so i learned how to do a balance test..i was able unplug each coil and they all reacted the same..so then i wanted to check the ohms, so off to pep boys bought a 19 dollar multimeter digital.. i was able to unplug each injector and they all tested at 12 ohms..so then i was thinkin the fuel pump..i was planning to go to pep boys today and buy a pressure gage to check the fuel pressure.. because i could not find and leaks or bad connections.. i even cleaned the throttle bodies..changed the fuel filter and checked spark plugs.. which looked fine..
i opened up the intake and checked the MAS but the two screens and connector looked fine. maybe the TPS..
ok ill get to the point,, so finally last night at like 2am still up reading trying to find what it could be...i was reading a thread bout this other member was having an idle problem and had been trying to fix it for 3 months, anyway he said it ended up being a fuse for the AAC, a blown 10A fuse ..another guy had the other fuse by the battery blown..so 2am last night i went to garage half asleep went to garage and popped open the fuse box.. got the needlenoses and started pluckin out each one, i did not find any blown , they were all fine, .. then i noticed the fuse box in front of the battery, one of them is the fuel pump, they all look fine.. but pop off the fuel pump fuse and waited a few minutes, put it back in and went to bed, so this morning was gonna go to pep boys to buy a pressure gage and do a fuel pressure test.. so start her up and she sounds much better, so i let her warm up and find that the shaky idle is gone!..purring nicely .. much smoother,, so jump on freeway and run her a bit,, used up the remaining gas that had injector cleaner that i put in... and shes running good and has a nice smooth idle.. so i bet it was the fuel pump fuse by the battery , it prob just needed to be reset or somthin.. anyway im so happy now..took her to get a wash.
===============================================================
Okay, 3k miles after the 60 k (@76k), I was noticing that the idle on my 92TT was really rough. Not up/down oscillation, but more like sitting in a mustang. It was rumbling, not smooth like it used to be. I could see the mirrors shaking when I was at a stop light. Also, the pulley on the front of the power steering pump was wobbling (uh oh) at low RPM, like the bolt on it was loose on it or something. After trying everything else, I decided that maybe it was the spark plugs. I put in colder plugs and my Z is still stock (I know, I need to get a job). So I took out the coil from the #1 cylinder and went to take it out with a torque wrench to see how much torque was still on it. It took 1/2 FT/LB!! to get it off. The spec is 14-22. I know that the torque that it takes to get a bolt off isn't exactly the same as it take to put it on, but D@MN!!. So I retorqued everything. Now the engine runs really smoothly and the pulley doesn't wobble. The plugs must have come loose, because I toqued them myself during the 60k. Is this normal?? I know that it is not good, but I remember hearing something like this from other guys. Is it the aluminum heads? Thanks a lot and enjoy the ride!!
=================================================================
Posted by: DAYTONAZ on September 25, 2005 at 4:10 PM

In Reply To: I'm at a loss for my idle issues. posted by zx spinner on September 25, 2005 at 12:17 PM

It sits in line with the IACV unit towards the center of the engine. It controls your cold start-up idle and have been known to stick open. Two things to try. First is the tap test. Take an extension or something solid and tap the body of the regulator to see if it is stuck. If it is you should see an immediate response to your idle. Second, check the connection. If you have a meter you should see 12 volts at the plug whenever the key is on. It's hidden behind the balance tube and a pain to get to but check that before you start changing settings on other stuff.
======================================================================
Posted by: testingzwaters on October 13, 2005 at 1:32 PM

I was going to take the Z on a 3 hour one-way trip monday with it missing, but was talked out of it by ya'll. Today I change the plugs, reset the ecu, and cleaned transistor connectors. It ran better but it was still missing a cyl. So next I started pulling coil pack connectors until I found the one that didn't change the engine attitude. Checked coil pack and found it to be ok, so I put it back on, started the car and unplugged the injector connector. Sure as shit that was it. I cleaned it up, restarted the car and plugged it in and the lady purred like a kitten. Today is a good day!
=============================================================
After two days non stop searching for the problem I finally found it. To make a long story short, I did plenum removal, aiv, prvr, and water coolant hose bypass, changed, pcv's and hoses, exhaust gaskets, valve cover gaskets, all new vaccum hoses and etc.. after all done car ran like crap, hesitating missfiring, and very rough idle. After checking all injectors, connectors and hoses the problem was nowhere near there, it was on the throttle body! Where the tps screws on the driver side throttle body the threads were completely worn allowing the tps to constantly change votls. So I replaced the throttle body and now car runs awesome! Few I was starting to go crazy and I could not even sleep. Well now its all good. One more thing all my injectors are reading 11.6 ohms is that good? And thankyou tt.net I could not have done all this without your help.
==============================================================
Many Thanks to all who answered my plea for help on my 90 NA. (10-05-05) Several of you "hit it on the nail head". It was the CAS crank angle sensor. It now runs as it should very smooth. Thanks to ALL and the TT Forum, Tom, B'ham, AL
==============================================================
CollegeBoy
Anyways, I finally decided to try a random test of my own about 3 weeks ago. I let the car idle with both o2s disconnected. Not really sure why i did it, but I just figured..what the hell..why not. Then, i noticed something crazy...when they were both disconnected, the car ran fine. This puzzled me to say the least. The air fuel mixture was off im sure, but overall it ran fine without them. Then i would let the car run with them hooked up, and it would run bad again. I did this test several times and came to the conclusion that it was them that was causing my problem. Even looking at them on the conzult, everything seemed pretty normal, but occasionally it would do weird things, but I didn't think that was really them, since mine were practically new. I talked to several well known forum members here and most of them told me that it couldn't be them also, since i just replaced them about 1000 miles ago. I ended up testing a few others things after that, but then decided to just go by my gut and shell out the $120 at a local dealership to see if it was them.

The moment of truth had arrived today as I drove home with them in the truck. Rolled up and under the Z as usual, then installed them. Turned the key, let it warm up, and listened. It had a good idle! Then i started giving it gas and holding it at like 2k rpms then 3k rpms. Both of them sounded beutiful! Started reving the car, and just plain going all over the place with the power band holding it at various places and letting it idle. It all worked good! I can not believe that I finally fixed it. The car is running great, and I couldn't be happier. Hard to believe that the o2s went bad so fast, but I'm sure weirder things have happened in the world ;) And before you say this was an easy diagnostic, since it was just them, you have to remember that they were basically pretty new, and they looked pretty good, but only a "little weird" on the conzult.

=============================================================
I am pleased to report that the root cause of this problem was the presence of the shorter NA plugs in my TT engine. The bad readings (1.0 - 1.7 ohm) I obtained on my coils were a result of a weak battery in the meter. All checked out at .7 after the battery was replaced. New o-rings were installed under the balance tube as well as a couple of other vacuum hoses I discovered had holes in them. Both problems were inflicted on the car by the previuos owner. I figure he paid his good money for the worng iridium plugs and he was going to use them regardless. The holes in the hoses likely came from using pliers to remove them. The car runs a litle stronger now and the idle is much smoother at 750. Next I will begin the installation of the Blitz EBC and GD SS downpipes. Next the ECU chip and cat-back and I will be done with my 1st stage* mods.