Hydrocarbons = unburned fuel

quote Originally posted by RhinoDj: ....what the hell is HC???

I think Jazz is referring to HydroCarbons emissions.

Yep, HC=HydroCarbons (fuel), NOx = Nitrogen Oxides. NOx comes in different "flavors" such as NO1, NO2, NO3, etc., so NOx is used as a generic reference. CO=Carbon Monoxide, CO2 is Carbon Dioxide. O2 is Oxygen.

JazzMan

Well, this thread is getting some milage, huh? I wound up putting the 87 (now that it runs well) in the garage or the winter/spring until I can rebuild the suspension, it's in really bad shape. Considering the car has 190,000 miles on it, no suprise.

Now I need help with the 85. No DIS on this one. Here's what I have done, the symptoms - so anyone with experience and advice feel free to post! The car has the 4 cylinder just in case that's not clear.
I have replaced the O2 sensor, the TPS, PVC valve, plugs, wires, and fuel/air filters all in the last 700 miles. The car sat for a while and I don't know if maybe there was enough trash to plug up the new filter... it's possible, though I drained the fuel tank before changing the filter. I replaced the head gasket and the intake/exhaust gaskets. Found later that I hadn't tightened down the EGR bolts enough on one side, since fixed that. Replaced virtually all the vacuum tubing. I pulled the vacuum line off at the brake booster in the front, it about gave me a hickey when I put my hand over it. Guess that's okay. I had to clean the contacts on the temp sensor on the thermostat to get that to register... I think. Cleaned the IAC as it was all crudded up and re-installed it.
The engine still idles a little high... it was over 2000 RPM at first, now it's down to 1600 or so. And the manifold glows at night enough to concern me. The origional throttle cable melted on me prior to getting the idle reduced. I have tried the carb cleaner around the throttle body base technique to try to locate vacuum leaks, and after losing my nerve switched to a spray bottle of water... no changes... Usually this means a vacuum leak or lean condition... But the car doesn't stall and runs smooth albeit at high RPMS. I may have an issue with the vent line on the gas tank even though I have replaced the filter at the bottom of the evap can. I'm unsure of the history on this car, and I don't know the potential effect of a poor vent system on TBI. The fuel lines have all been replaced too. I can rev as high as I want, and I can keep up with highway traffic.
unplugged the IAC, no change. Unplugged the temp sensor, there is a change in idle briefly then it resumes. Same with the MAP sensor - on my car that's the one on the air cleaner housing (right?).
My next move is to replace the fuel filter, since that resolved some issues with the 87 even though I don't lack power. If anyone can help with the glowing exhaust manifold/high idle issue, I'm all ears.

Thanks!

I'm not particularly familiar with the DIS L4 motors. The O2 sensor can be damaged by an excessively lean mixture, as well as by contamination by metals such as lead. A short in the O2 sensor circuit can cause the sensor to fail as well since the sensor is essentially a Zirconium/Oxygen battery and a short will blow the Z/O2 junction.

JazzMan

I'm getting no codes, and if the O2 failed, it would go into a 'limp' mode right? Just run rich? So somehow it would have to read wrong to try to lean out my mix. The thing that perplexes me is that I haven't seemed to have lost any top end power in spite of the manifold glowing (not super intense, but visibly) at night (can't see it in the day). I simply haven't found any vacuum leaks.

Check your timing.

quote Originally posted by Fiero STS: Check your timing.

This was a good idea since I had no idea about the history on the car. So, I checked the timing; jumped the A and B terminals on the ALDL (this is supposed to put the car to a 1000 RPM, but my electronic tach I hooked up said it was more like 1250 RPM)... Clamped the number one ignition wire and number four and averaged the two and was pretty much on the money (8°). The marks jumped all over the place, so I replaced the throttle body gasket... there was a good amount of carbon under that thing, it was the only gasket I didn't replace when I did the head gasket and quite a mess under there. The timing settled down a little, but the manifold still glows and idles high for eight or nine minutes, then the idle comes down and the glowing subsides. By the time the thing has been running for 12-15 minutes, the glow is barely perceptible and the idle is just below 1500 RPM. No loss of power, no codes. If I rev it, the glow returns. I thought I had replaced the distributor and rotor previously, but I found the new ones on the shelf in the garage, so on they went. I noticed a GP Sorenson module in the distributor, great.
Anyone else have any ideas?
Should I blow $30 on a new IAC? The origional is still on the car.
Could it be the O2 sensor?
Remember no codes, and I can't seem to find any vacuum leaks. Plenty of power, and the idle is smooth.
It looks like I'll be driving this car daily from Hampton to Norfolk or as far as Virginia Beach - 30-40 miles each way. I don't want to be a news story on the late news with a car-b-que; Fiero flambe. I already had to replace the throttle cable after it melted from the exhaust manifold, thank goodness the Fiero Store replacement has a heat shield!

[This message has been edited by USFiero (edited 11-05-2005).]

<bumping it a little closer to the top>
I've done some looking through the Forum regarding the IAC, and right now this is what I'm working with...

quote Originally posted by JazzMan: Needs a gasket. The IAC works by allowing air to bleed past its pintle. The threads will allow air past without the gasket. Stick your finger into the throttle throat, there's a hole in the bottom just in front of the throttle plate. That's the inlet to the IAC bypass air passage. If you put your finger over that hole to block it and the engine still idles high then the IAC isn't the problem. JazzMan

That'll be my first thought. I don't recall the IAC buzzing when I jumped the A and B terminals, wonder if the thing isn't working? I can unplug it when the motor is running and it doesn't effect it at all, unlike unplugging the temp sensor or MAP sensor.

quote Originally posted by avengador1: You might want to double check your EGR tube. It could have developed a crack when you took the intake off. They tend to get brittle with age and can develop cracks if disturbed. These cracks make the engine idle go up.

Avengador is refering to a V6, but I can press on the diaphram of the EGR valve and the motor will stumble, I suppose it's working like it should. I used a hose to listen for air leaks, but couldn't detect any.
Found this referring to a V6 again (I took those references out):

quote Originally posted by Skybax: If everything is working properly, no exhaust leaks, no EGR leaks, and the engine is properly tuned, you can go through the IAC system. Idle is controled by the IAC valve (idle air control) via the computer and is not adjustable. You can go over the system if your not happy with where it is idleing. The ECM wants to be in control of the idle and is not happy when it can't control it. If the normal learn limits of the ECM are exceeded, they will be reset to nominal, causing an erratic idle. The IAC and associated passages need to be clean to work right. Remove the IAC carefully. You can clean it (the nipple) using carb cleaner and a small brass brush or rag. At this time also clean the throttle palte. Once clean, install the IAC back in the throttle body and reconnect the IAC wires. For the ECM to properly control idle, the throttle stop screw must be set for "minimum air". This is a process that sets the idle with the IAC fully extended. To fully extend the IAC, jumper ALDL pins A and B together (just like when you check codes) and turn the key on, but do not start the car. With the key on, not running, and in diags mode, the ECM will keep trying to fully extend the IAC. After 30 seconds or so, pull the IAC connector off the IAC *before* doing anything else. This will capture the IAC fully extended. Now pull out the jumper in the ALDL, and start the car. Typically the "minimum air" idle speed is in the 500 RPM range. I find the car can bearly run at 550. So as long as you can get it to idle on its own between 600 & 700 your good. Set the idle using the throttle stop screw. (The engine should be fully warm to do this.) Now shut the engine off and reconnect the IAC wires. The ECM does not know where the IAC present position is, so pull the ECM fuse (or disconnect the battery) for 20-30 seconds. (This will cause a complete ECM reset of all learned parameters, including the learned IAC ones. Then reinstall the ECM fuse. Turn the key on, wait 10 seconds or so, and turn the key back off. This will now reset the IAC to a known key-off "park" position. Now start the car. The engine should idle properly under control of the ECM. There are some learned values, such as an IAC offset for A/C, etc that need to be learned, but this will happen under normal driving conditions. I suggest driving the car right away under all conditions. Stop & go, steady cruising over 45 mph, full throttle, and so on. Pull over a few times and turn the car off, then restart it. The IAC can only learn X amount of counts with each run position.

Even with my 4 cylinder in diagnostic mode, it did not go to 1000 RPM like I understand it is supposed to. At this point I'm trying to figure, is it the IAC, EGR or now the O2? I can tell when the temperature rises, the idle comes down. The car must be lean if the exhaust manifold glows, but that diminishes when the idles goes lower unless I rev it some more. I really don't want to burn this one up.

I have not had to do this on my Fiero yet, but whenever I have wanted to test my IAC on my other cars I do the following.

It's shade tree stuff but it work.

I remover the IAC, put my finger in place of the pintle and have some one start the engine. I then use my fingerto simulate the pintle of the IAC. I use my other hand to hold the IAC and keep a couple fingers on the pintle so I don't shoot it into no mans land.

Doing this, you can adjust the idle up and down which will cause the IAC to move in response.(If it is good, clean , etc. )

I have done this on several different make of car and has alway worked. Of course you don't want to do it on a really hot engine unless you like fried finger.

Since I have not had to deal with a bad idle,,,,yet mine is still perfect,, but has anyone ever tried hooking up a battery charger to their car while the idle hunting to see if that would make it settle out. Just have wondered if a hunting idle condition could be cause by voltage fluctuation causing the ECM to keep adjusting. If the idle drops and the voltage decreases could be possible that the ECM sees some input change due to the voltage and adjust causing the idle to go up. The Voltage would then increase which would cause an input change and correction again by the ECM. I know the sensors are on a lower regulated voltage, but don't know if all inputs are.
Just have alway wanted to try this to see if it makes any difference.

Has anyone?

[This message has been edited by Dodgerunner (edited 11-06-2005).]

Have you checked to see if someone has taken out your factory stop idle screw cap and fooled with the screw?? Someone did this on mine,I spent a small fortune and alot of time replacing sensors and about everything on the engine, it had the exact same symptoms yours does , cold start idles 1500 to 500 to 1500 to 500--well you know. I finally after many attempts messing with that idle screw and iac proceedure, ---put on a T.B. off my 87GT that still had the cap on the idle stop screw--it does not do the 1500 to 500 anymore, the down side is I still have Glowing Manifolds , including the Y-pipe. The car runs perfect, idle on cold start is 1500rpms, 3-4 minutes later its rock steady around 950rpms. Iv`e about had it with the glowing manifolds, all that is left to do, is re-try another pressure regulator and injectors again. Speaking of which--where does one buy a new pressure regulator and fuel rail for a 2.8 ?? Or how do you get those torx/starz screws off the top of it??? I hope someone is able to figure this idle issue and glowing manifolds out, as I now have 3 Fieros that have glowing manifolds, they all run perfect--but light up bright RED/ORANGE while stopped in my shop and holding pedal at 2000 or a little higher rpms..

quote Originally posted by 3800superfast: Have you checked to see if someone has taken out your factory stop idle screw cap and fooled with the screw?? Someone did this on mine,I spent a small fortune and alot of time replacing sensors and about everything on the engine, it had the exact same symptoms yours does , cold start idles 1500 to 500 to 1500 to 500--well you know. I still have Glowing Manifolds , including the Y-pipe. The car runs perfect, idle on cold start is 1500rpms, 3-4 minutes later its rock steady around 950rpms. Iv`e about had it with the glowing manifolds, all that is left to do, is re-try another pressure regulator and injectors again..

I don't know where that would be on my four cylinder Duke, but the glowing manifolds are apparently normal - to a degree. There are many threads referring to this in the Archives, I guess the real challenge is to decide what is 'normal' and which is 'terminal'. As far as finding parts, check the Fiero Store, although many Fiero engine parts were common to other GM front drive motors.

I burped the cooling system today, there was some air in there. Now my temp gauge registers again. Still high idle, the manifolds glow a little more than I am happy with, still takes 8-12 minutes for the idle to come down and even then still high... I haven't checked the IAC yet.

[This message has been edited by USFiero (edited 11-08-2005).]

Replace the coil if you haven't already. I did a buncha stuff to mine, and it turned out it was a bad 12 dollar coil. It ohmed out good, and fired the car well, but it still made mine surge like crazy.

-E

quote Originally posted by Shibbypoopalot: Replace the coil if you haven't already. I did a buncha stuff to mine, and it turned out it was a bad 12 dollar coil. It ohmed out good, and fired the car well, but it still made mine surge like crazy. -E

This may be in my list of things to do. Did you have issues with the manifolds glowing?

Well, I wanted to bring some closure to this thread. Got to messing around today, found a 50megohm resistor in the junk box, so I unplugged the temp gauge and stuck it in (it's too high to be a legit value for the temp sensor) and started the car. The idle hunted a bit for a minute or so, then settled to a steady 1000 RPM. I rummaged around the garage and found another temp sensor and plugged it in and the idle went up to 2300 or so and the manifolds turned red. Ah hah! I held the temp sensor against the exhaust manifolds to heat it up and the idle started to drop after I plugged it back in. I think I've solved the problem. The weird thing is the temp gauge would register after I burped the cooling system again, although never very high. I credited that to the Trans Am vents and the V6 radiator up front. I tried to loosen the old (but still shiney) temp sensor and managed to cause the gasket on the thermostat housing to start leaking. I have a spare gasket and will replace that (and the sensor) tomorrow morning before work.

Hi, Glad to hear you got it fixed --and more over you took the time to post it--don`t see alot of that happening here sadly enough. I did have a question for you, I have 3 x-- 2.8 Fieros, all the manifolds glow---but this is while setting still --and holding rpms to 2500--3000rpms ---which would put you at 60mph if you where on the road driving--ok--my manifolds will not glow at idle anymore--but they will if I do the before mentioned--so I guess my question is --at 60mph while driving or 2500-3000rpms --how do we know if the manifolds are still glowing or not ??? I realize there is some air movement in the engine bay --so I duplicated it with some heavy duty shop fans--right over the manifolds--they still glowed ?? Including the Y-Pipes.. Does this lead us to believe that all manifolds glow when the engine is under load ?? Say --anything above 2500rpms ?? This is what has had me perplexed for quite some time, after searching the archives--and I mean all of them--every post.... And the internet and so on, no one can say they fixed their glowing manifolds---maybe at idle--but if anyone raises their rpms above 2500 for a minute or so on any Fiero while setting still--my guess would be, they would see RED Glowing manifolds. Does the fact that they glow at idle become a issue --more than the fact that they glow most of the time one would drive their Fiero anyway ?? I`m truely interested in getting to the bottom of the Glowing Manifold issues we all seem to have... If you don`t have a glowing manifolds, open your deck lid at night and bring your rpms up to 2500-3000 , then take a look. Again glad to hear you got your idle problem fixed and posted.....

quote Originally posted by JazzMan: I'm not particularly familiar with the DIS L4 motors. The O2 sensor can be damaged by an excessively lean mixture. A short in the O2 sensor circuit can cause the sensor to fail as well since the sensor is essentially a Zirconium/Oxygen battery and a short will blow the Z/O2 junction.

To keep everyone in the loop, the first Fiero I had issues with was an 87 DIS Duke. That was resolved a page ago. This one is the 85 HEI Duke. I felt keeping this thread active would help others with the 4 cyl. If it becomes a thread for V6 owbers that would be cool I think.

quote Originally posted by 3800superfast: Hi, Glad to hear you got it fixed --and more over you took the time to post it--don`t see alot of that happening here sadly enough. I have 3 x-- 2.8 Fieros, all the manifolds glow---but this is while setting still --and holding rpms to 2500--3000rpms--ok--my manifolds will not glow at idle anymore--but they will if I do the before mentioned--so I guess my question is --at 60mph while driving or 2500-3000rpms --how do we know if the manifolds are still glowing or not ??? This is what has had me perplexed for quite some time, after searching the archives--and I mean all of them--every post.... And the internet and so on, no one can say they fixed their glowing manifolds---maybe at idle--but if anyone raises their rpms above 2500 for a minute or so on any Fiero while setting still--my guess would be, they would see RED Glowing manifolds. Does the fact that they glow at idle become a issue --more than the fact that they glow most of the time one would drive their Fiero anyway ?? I`m truely interested in getting to the bottom of the Glowing Manifold issues we all seem to have... If you don`t have a glowing manifolds, open your deck lid at night and bring your rpms up to 2500-3000 , then take a look.

I checked mine in the dark, and the manifolds do not glow at idle at all now. I didn't check with the idle up, since it seems to be behaving like it's supposed to. My next test will be to see if my gas milage goes up, I'll probably bump this again at the end of the week when I figure it out.

I know Ed Parks was quoted as saying that Fiero manifolds do glow some when revved but I'm not sure what is the limit of that since mine was hot enough to melt my throttle cable (not good when on the highway...) The Fiero Store replacement widely has heat sheilding the origonal didn't come with, but I knew there was a problem that had to be resolved. With the Fiero poised to be either a 'valued collector car' or an 'automotive debacle' I just feel that something as critical as this needs to be addressed!

I still haven't checked the IAC, I may not until I get a code or next year when it warms back up. Odd thing about the temp sensor I removed is that the probe end was larger than the spare I put in even tho the connector was the same. I wound up replacing the neck as well since the thermostat housing flange was stamped on mine and the spare I found had a thick solid flange on it. Sealed up real well with just a FelPro gasket and no RTV.

Superfast, I'm no expert in this still, I'd love to have the ALDL interface and the software to see what the ECM is seeing and doing, but from what I have gathered all I can offer is this: vacuum leaks seem to be the most common problem in old cars - it wasn't the only problem I had, but I'm sure it wasn't helping. A dirty fuel filter, deteriorated fuel lines, or evaporator canister filter can reduce fuel flow and cause a loss of top end power but might not result in glowing manifolds at idle when there is no load on the motor. While you're staring at it in the dark, look at your ignition wires and see if there's any arcing. V6 manifolds are notorious for developing cracks, letting in air and fooling the O2 sensor. The Fiero has more than one water temp sensor, and I'm still not sure which one does what now. But that one obviously had an effect on the fuel mixture. Air in the cooling system doesn't help either. While the IAC is not controlled by the ECM in the 4 cylinder coupes, it is in the V6 models. Buddycraigg has a thread with detailed pics on that somewhere. There are a lot of helpful suggestions above, my issue was a high idle with glowing manifolds at idle, but a rough idle is a different issue, my 87 didn't have a glowing manifold but the exhaust was glowing and it had no power (ignition coil not working/unburnt fuel burning in catalytic converter). Checking ECM codes helped me to fine tune a few things (TPS for instance). The 85 was elusive because there were no codes being displayed. I wound up cleaning a lot of carbon out and doing a pretty thorough tuneup on these two cars, so I'm happy about that.

[QUOTE]Originally posted by USFiero:

Superfast, I'm no expert in this still, I'd love to have the ALDL interface and the software to see what the ECM is seeing and doing.

Hi, I do have the winaldl interface and aldlview--but have no idea what the #`s mean along with what MAULF1 MUALF2 , ect , ect mean ??? I can get the winaldl to bring up the #`s --after that I`m lost..

any time my car isnt warmes up to opperatin temp and i give it gas it tries to stummble and quite who ever can help gets a pos ratin from me

fierosrule, are you getting a 'check engine' light? You may have to check codes. What motor/year/trans do you have? My initial thought would be the throttle position sensor (TPS) but I have discovered that these problems can be caused by a combination of issues inherent in 20 year old cars, especially if you haven't been the one who has owned or maintained the car for long. More info, please!

EDIT: I filled my gas tank today, the first after doing the above repair{s}. I am getting about 21 MPG at this point, that is a 2 1/2 MPG improvement. Guess I could do better if I'd just slow down.

[This message has been edited by USFiero (edited 12-04-2005).]

quote Originally posted by USFiero: fierosrule, are you getting a 'check engine' light? You may have to check codes. What motor/year/trans do you have? My initial thought would be the throttle position sensor (TPS) but I have discovered that these problems can be caused by a combination of issues inherent in 20 year old cars, especially if you haven't been the one who has owned or maintained the car for long. More info, please!

I agree with the TPS theory, just for good measure it wouldn`t hurt to check/clean out the T.B. and IAC passage.............USFiero:---Did you ever recheck your manifolds ???

bumpin it 'cause good theads deserve it... and the manifolds have been fine I guess, been driving the car (85) with no problems. The glow is barely perceptable afte a hard drive on the interstate, getting to a stop and leaping out to check.

USFiero, glad you brought it back around, have learned winaldl and alot more since this post. When the car is sitting still, hold throttle cable to around 1800-2500rpms and take a look at the manifolds, give it a minute or so. let me know what happens...

Glad to see this thread is still doing some good!

-Sean W.

85' Fiero GT

quote Originally posted by HummelHund: Glad to see this thread is still doing some good! -Sean W. 85' Fiero GT

Thought I'd BUMP it once again... I see other threads about Dukes with issues...