So here's the deal: I have a 1986 Fiero GT (155,000 miles, stock 2.8, 4-speed manual) with a persistant idle issue that has me a bit stumped.
When I bought this car a couple months ago, it had a high/erratic idle. No check engine light, but the computer did show the infamous code 32. While idling, it revved up and down between about 1800-2800 RPMs. I've spent some time fixing a few things on the car since then; the idle is now a little smoother and has come down to about 1400-1600 RPMs, not nearly as erratic but still not 100% right.
When the engine is cold, the RPMs stay at about 2300+RPMs, then they slowly come down after the engine gets to operating temperature. It seems to run decent otherwise, with the exception of a very light, sporadic sputter (or miss) while cruising.
The engine always starts immediately with no hesitation.
Catalytic converter is fairly new from previous owner.
I'm missing something... somewhere.
So far, here's what I've done and replaced:
EGR valve EGR solenoid EGR tube (Rodney's stainless unit) Stainless steel vacuum lines (from Rodney) Zip-tied/clamped all vacuum connections TPS sensor MAP sensor MAT sensor CTS sensor O2 sensor IAC valve PCV valve Cleaned throttle body New fuel filter New gas cap New vapor canister filter
Also: Distributor is new Plugs are new Wires are new K&N air filter freshly cleaned/oiled
I also cleaned several grounds and added a 4 gauge engine-to-battery ground cable, which did help the idle stabilize a bit. I've tested the intake and vacuum system for leaks by spraying carb cleaner around possible problem areas, but no luck (idle doesn't change). The idle air control tube going from the lower intake to the throttle body is leak free, and idle doesn't change with the brake booster nipple blocked off... same with the two lines running to the trunk wall; no change after the supply lines were capped.
I'm a bit stumped at this point and looking for any suggestions as to what I might look at next. About the only thing I can think of that's left is the possibility of having a bad connector on one (or more) of the sensors... before I bust out the Ohm meter and start diagnosing everything, does anybody out there have any other suggestions or ideas as to what I'm missing here?
Thanks in advance!
[This message has been edited by ITALGT (edited 01-18-2015).]
Yes, it does have cruise control, however it currently does not work.
For diagnosing, I capped the supply lines off at the engine that go to the trunk wall to see if the idle would change... but there was no difference. Also disconnected the vacuum supply line to the can and capped the supply nipple... no luck. I believe that the cruise control and vapor canisters are leak free.
Not sure why the cruise isn't working though... haven't checked into that yet.
[This message has been edited by ITALGT (edited 01-07-2015).]
your post reads almost identical to mine, I'm sure there are many people on here thinking we are idiots for 'throwing money at the problem' but since parts are so cheap, I figure it's not such a bad thing, especially considering how old my parts were. The main difference is I had somewhat different symptoms, rough running at low speeds, but my idle was kind of high as well. What finally fixed it was new injectors, $125 shipped from Rock Auto, and about 4 hours time.
I don't typically throw parts at a problem, but with 155,000 miles on the clock, I wanted to replace the sensors and vacuum lines anyway. And as you said, the parts were all fairly cheap so I went ahead and replaced them first. I'm glad I did, because it's running a lot better now, and all the sensors I replaced looked like the factory Delco originals.
Fuel injectors... yeah, that does sound like a possibility, especially with the miles and symptoms I'm having. That may be next.
I did run a can of Seafoam through the gas tank, but didn't seem to help.
[This message has been edited by ITALGT (edited 01-09-2015).]
I had been experiencing high idle of about the same rpm on my 87 but I also had a hesitation when accelerating immediately after changing gears. I replaced the TPS and both problems went away. Fortunately I had about a half dozen on hand so it didn't cost anything.
Then, because I had a coolant leak, I pulled the thermostat to reduce some of the pressure so I could get the car back home and the idle went back up. That later went away when I fixed the leak and replaced the thermostat. Apparently the ECM wasn't going into closed loop.
I installed the new IAC after cleaning the throttle body, making sure the pintle was protruding under 1-1/8" inch from the mounting surface per the instructions (it was about an inch or so when I put it in). I also thoroughly cleaned the pintle seat on the throttle body before installing it. Then I drove it for a few miles over 40mph to set it.
A couple nights ago, I pulled the IAC out to check the pintle length, and it was right at 1-1/4", which is what I've heard from others is correct. My understanding is that the IAC valve reseats itself every time you turn the ignition on, so I'm not sure what else needs to be done to "reset" it.
Or am I missing something?
[This message has been edited by ITALGT (edited 01-09-2015).]
I spent some time on my lunch break today listening a little closer to what the engine is doing.
RPMs are still high when the engine is cold, around 2500 RPMs then drops while warming up to temperature. I know it's normal for it to come up some when cold, but this seems too high.
Once warmed up and idling, it fluctuates randomly between 1350-1550 RPM's.. It's much more stable than before I fixed the vacuum leaks and replaced the sensors.
When holding the throttle above idle, the exhaust randomly "pops" like it has an occasional miss; it's not nearly as noticeable at idle, just a small random shake as the engine runs. It almost acts like an ignition issue, or as previously mentioned, maybe some bad fuel injectors.
The previous owner replaced the distributor with a new one, and also installed new plug wires. I changed the spark plugs to NGK V-Powers just a couple weeks ago. However... the wires look like generic cheapies and I didn't install the distributor, so there may be an ignition issue here I've been overlooking. Also, the coil is the factory original.
I've been wanting to replace the cap, rotor, coil and wires with MSDs and Taylors; now might be a good time to do it.
I'm SO looking forward to when the engine is idling like it should... this has been bugging the sh!t out of me since the day I bought it the car.
[This message has been edited by ITALGT (edited 01-14-2015).]
I don't know if just driving "reset" it either. I followed this from another thread. 10-12-2006 02:59 AM
Heres the proceedure --how ever --as above mentioned I don`t think it will fix the problem, it will work the 1st time you use it, but after the engine cools, it will be back, hope not.
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. Proper idle for the V6 is roughly 900 RPM.
The set screw in the throttle body is for minimum air flow through the throttle plate which is often misunderstood as the idle screw. Any tweaking of the throttle stop screw will give the ECM fits. 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. If everything else on the engine is in good condition and operating properly it should be around 900 RPM after coming to a complete stop with slight variations and improve over time.
i found idle quality was affected quite a bit by engine timing (my balancer marks are off so setting it to 10 degrees resulted in erratic hot idle and an oscillation in idle at cold start). Another thing I found was swapping the ecm made quite a difference as well. Not sure if the old chips in these ecms are getting out of tolerance specs or what, but three different ecms had differing idle qualities for me.
No luck with the IAC reset... idle is still sporadic at 1350-1500 RPMs.
quote
Originally posted by Toontown Fiero:
i found idle quality was affected quite a bit by engine timing (my balancer marks are off so setting it to 10 degrees resulted in erratic hot idle and an oscillation in idle at cold start). Another thing I found was swapping the ecm made quite a difference as well. Not sure if the old chips in these ecms are getting out of tolerance specs or what, but three different ecms had differing idle qualities for me.
I have another ECM laying around from an '86 2.8 5-speed car, maybe I'll try swapping it in and see what happens.
Any other suggestions?
[This message has been edited by ITALGT (edited 01-11-2015).]
Definition: The engine runs unevenly at idle. If bad enough, the car may shake. Also, the idle may vary in RPM (called “hunting”). Either condition may be severe enough to cause stalling. Engine idles at incorrect speed.
Check: - Park/Neutral switch circuit. See CHART C-1A - For injector leaking, Check Fuel Pressure CHART A-7. - If a sticking throttle shaft or binding linkage causes a high TPS Voltage (open throttle indication) the ECM will not control idle. Monitor TPS voltage. “Scan” and/or Voltmeter should read less than 1.2 volts with throttle closed. - EGR “ON” while idling will cause roughness, stalling and hard starting. CHART C-7. - Battery cables and ground straps should be clean and secure. Erratic voltage will cause IAC to change its position resulting in poor idle quality. - IAC valve will not move if system voltage is below 9 or greater than 17.8 volts. - Power Steering – CHART C-1E. ECM should compensate for Power Steering loads. Loss of this signal would be most noticeable when parking and steering loads are high. - MAP Sensor – Ignition on engine stopped. Compare MAP voltage with known good vehicle. Voltage should be the same +/- 400 mv (.4 volts). OR Start and idle engine. Disconnect MAP sensor electric connector. If idle improves substitute a known good sensor and recheck. - A/C compressor or relay. If inoperative, refer to CHART C-10. - A/C Refrigerant Pressure too high. Chick for overcharge or faulty pressure switch. - Cooling fan inoperative – See CHART C-12. - PCV valve for proper operation by placing finger over inlet hole in valve end several times. Valve should snap back. If not, replace valve. - Run a cylinder compression check. See Section “6”. - Inspect oxygen sensor for silicon contamination from fuel, or use of improper RTV sealant. The sensor will have a white powdery coating, and will result in a high but false signal voltage (rich exhaust indication). The ECM will then reduce the amount of fuel delivered to the engine, causing a severe drivability problem.
I'm done messing with it for today, but I'm going to have a closer look at this list. A few of these things I've already covered, but I already know that my AC compressor is bad for one thing. Who knows what else this idle thing might be caused by.
[This message has been edited by ITALGT (edited 01-18-2015).]
So... the check engine light came on briefly today, on at idle then off as soon as I gave it some revs.
Looks like I have a code 22 (throttle position sensor voltage low). I've never had this code before. It's possibly a damaged connector or poor connection, but more likely the IAC reset procedure caused the TPS voltage to go out of it's readable range at idle. Because the idle didn't change after the IAC reset, I'll first turn the idle stop screw back to it's original position and reset ECM as a precaution.
Could a bad connector to the TPS really be the cause of all this headache?
I'm about to find out I guess.
Stay tuned.
[This message has been edited by ITALGT (edited 01-14-2015).]
So... the check engine light came on briefly today... first time it's really made an appearance.
Looks like I have a code 22 (throttle position sensor voltage low)... possibly a damaged connector or poor connection, unless the IAC procedure somehow caused the TPS voltage to go out of range. Because the idle didn't change after the IAC reset, I will first turn the idle stop screw back to it's original position and reset ECM as a precaution.
Could a bad connector to the TPS be the cause of all this headache?
I'm about to find out I guess.
Stay tuned.
An ALDL cable may help. I need to understand the info more. I just found another website that has some test for the map sensor. Mine shows .39 ( I think it was) at idle but from this other site I believe it should be over 1 volt. http://www.reddevilriver.com/aldl.html
[This message has been edited by LornesGT (edited 01-12-2015).]
Yes, everything appears to be good with the IAC...
Tonight I turned the idle screw back to its original position and reset the computer. After warming up and some driving, idle is right back where it was... this time with no TPS code 22. That doesn't necessarily mean that the IAC reset procedure listed above doesn't work... what it more than likely means is that because other issues are currently causing the high idle condition, the IAC reset cannot be performed correctly.
I will be driving it to and from work tomorrow to see if the light comes on again, but so far no check engine light.
I also installed a new coolant temperature sensor tonight, as it was really the only major sensor I hadn't replaced yet. Idle did not change, but at least I can take a bad CTS off the list.
The closer I inspect some of my sensor connectors, the more I think I need to replace them... in particular, the EGR solenoid connector. Tonight I noticed that it has one prong that is bulged in the connector (connected to the bottom white-ish wire) that is preventing it to fully seat into the solenoid receptacle. When you plug it in to the solenoid, the bottom white wire literally gets pushed back and out of the connector spade. I tried my best to make it seat good, but no luck... it obviously needs to be replaced.
Any idea what this wire controls or does? This could be a problem I have overlooked (if it's not making a proper connection).
[This message has been edited by ITALGT (edited 01-14-2015).]
Since your cruise doesn't work here is another link. Mine doesn't work either so I google this but I don't have a high idle, infact I don't have a cold idle, it always low. Between the two of use I think we will nail this down.
Put some more miles on the Fiero today... so far, no codes whatsoever... the code 22 I had appears to have been caused by the IAC reset using the screw. No code 32 anymore for the EGR system as well. Interesting.
I have a hunch why my cruise control isn't working... pretty sure it is switch related and not vacuum. One pedal switch is hanging loose from where it mounts, so it isn't closing with the pedal (can't remember if it's clutch or brake). Not sure it can be fixed or if it just needs to be replaced, as I haven't had a close look at it yet.
As for the idle issue, it's still the same.
Next up, I think that I'm going to replace the EGR/IAC/TPS sensor connectors, as they look very beat up and tired. As mentioned earlier, the EGR solenoid connector is first on that list, as it has an obvious issue.
I am also going to bite the bullet and put in some new injectors, since they are relatively cheap and easy to install... after that, new MSD and Taylor ignition components.
Stay tuned.
[This message has been edited by ITALGT (edited 01-14-2015).]
I fixed mine, it was the IAC. It would move to the closed postion but would not open back up. Testing before I put the original one in it always moved, I guess I must have broke it. I threw in one that a mechanic friend had laying around and I had a cold idle back. I was afraid that it was going to close back down to lower the idle but it did with in about 2 minutes, no driving at this point. I had to blip the throttle then it can back down. I am going to try it again after it sets for a while and I know the engine is good and cold. I hooked up the aldl cable and the IAC positions was shown as it should from my google searches. 78 and as the idle reduced I could see the IAC position close more.
Glad to hear that! I am really looking forward to having a couple cold beers after my idle is normal; this is one of those irritating problems that seem to last forever!
Tonight I shopped around a bit online for a new EGR solenoid connector, but so far I am having no luck finding one.
Rock Auto or Summit Racing might also have it, or do a search on AuVeCo.Com website. The above link is one of their catalog pages. You will have to make sure that the little keyways on the terminals are correct for the EGR solenoid connection. These connectors usually come multiples in a box, but they are still cheaper than buying just one from a dealer.
Turns out, this EGR solenoid 4-way connector is not very common, and can be a real pain-in-the-butt to find.
Clipsandfasteners.com has a WeatherPack 4-way connector shell, but it's exactly that; no wires, no pins... just the shell. I did some more searching on-line, but had no luck with any of the normal go-to parts places, including RockAuto, Advance Auto Parts and Summit Racing.
I have ordered rebuilt and flow-matched fuel injectors from Precision Auto Injectors located right next door in Orlando, FL. The current advertised price for the set is $89.99 plus shipping and Florida sales tax. I found the discount code "jeep" online and got $9 off my order. Total shipped: $94.28... not bad at all. Note: for a little more money (about $125) you can buy brand new injectors (non-AC Delco). I may have spent the extra money if RockAuto had enough of one of the cheaper X-Brands in stock... but they didn't at the time. These rebuilt units will do the job just fine... there is a ton of great online reviews for this company, and the injectors come with a one year warranty too:
Hey Thanks for posting what you are finding out I have an 86 GT that is running very ruff n back fires at times., please let us know when you find out what the main problem is.
I hope they are your problem but I am thinking not. To much fuel should be just rich and you would smell the fuel at the exshaust. You have high idle so the air has to be there too. Doesn't hurt to change them except for the wallet. I had mine cleaned and the guy said they had a good pattern. Since you already eliminated vac leak, I still think the IAC is stuck or commanded open for some reason.
[This message has been edited by LornesGT (edited 01-15-2015).]
I hope they are your problem but I am thinking not. To much fuel should be just rich and you would smell the fuel at the exshaust. You have high idle so the air has to be there too. Doesn't hurt to change them except for the wallet. I had mine cleaned and the guy said they had a good pattern. Since you already eliminated vac leak, I still think the IAC is stuck or commanded open for some reason.
I hear ya'... replacing the injectors may end up not fixing the idle issue, but with 155,000 miles on the originals, I think it's worth doing at this point. On a side note, the exhaust fumes right now are very potent/stinky/smelly.
I will of course report back to this thread with results. I still need to replace a the sensor connectors at some point too.
I want to install the injectors first so I can see how the engine responds... and I'll take it from there.
Stay tuned.
[This message has been edited by ITALGT (edited 01-18-2015).]
You say that the last owner put in a new distributor but you don't say if you checked the timing. I would check it, make sure to do it properly by jumping the pins in the ALDL connector.
There is a tube running from the bottom side of the intake to where the cold start injector is located (it just delivers air). I don't know what it's technical term is; however, it can cause problems if not sealed correctly. One of my fieros had this problem and that was the culprit.
You say that the last owner put in a new distributor but you don't say if you checked the timing. I would check it, make sure to do it properly by jumping the pins in the ALDL connector.
Yes, that's on the to-do list as well... just need to get my hands on a timing light and check it out.
quote
Originally posted by fieromatty:
There is a tube running from the bottom side of the intake to where the cold start injector is located (it just delivers air). I don't know what it's technical term is; however, it can cause problems if not sealed correctly. One of my fieros had this problem and that was the culprit.
Thanks for the heads-up... I will take a look at that while I have the upper intake off.
Did you determine what the actual leak was caused by (bad o-ring, small crack, loose fitting, etc)?
[This message has been edited by ITALGT (edited 01-16-2015).]
Engine runs MUCH smoother; idle is still high though at about 1500 RPMs. I will try the IAC reset procedure again to see if there's any change.
Now I have a code 45... which is basically the O2 sensor telling the computer that the engine is running rich. This is the first time I've seen it with this car.
Next up I think I will do a cold start injector delete and replace the TPS/IAC/EGR/MAP sensor connectors. I goofed and ordered the wrong connectors (partly the vendors fault), so I will at least replace the TPS pigtail connector that I do have tomorrow and try to get the others coming.
More details coming soon.
[This message has been edited by ITALGT (edited 01-17-2015).]
... replacing the injectors may end up not fixing the idle issue, but with 155,000 miles on the originals, I think it's worth doing at this point. On a side note, the exhaust fumes right now are very potent/stinky/smelly.
quote
Originally posted by ITALGT:
Ok... rebuilt injectors are in. Engine runs MUCH smoother... Now I have a code 45... which is basically the O2 sensor telling the computer that the engine is running rich. This is the first time I've seen it with this car.
How's the exhaust smell with the rebuilt injectors installed? Any improvement?
How's the exhaust smell with the rebuilt injectors installed? Any improvement?
Yes... BIGTIME improvement with the exhaust smell, much less potent. That's actually one of the very fist things I noticed after starting it up. I pulled and inspected the new NGK plugs before putting the injectors in, and 4 of the 6 plugs were definitely getting black and sooty. The other two looked good. I bet if I pulled them out now, they would all look perfect.
I had a chance to reset the IAC and had no change in idle; still a steady 1500 RPMs.
I finally had a chance to put a few miles on it today, and I quickly realized there is now a HUGE difference in terms of power and drive-ability. The engine wants to rev easier now and pulls harder in all gears. The idle even stays rock-steady at 1500 RPMs... that is UNTIL the check engine light appears (code 45 again for O2 sensor reading rich) and the engine idle suddenly drops about 200 RPMs or so and becomes erratic. After keeping the engine revved above idle for a bit, the check engine light disappears and idle returns to being steady at 1500 RPMs. If it sits and idles for a minute or so, the light comes right back on and idle returns to being erratic.
The new O2 sensor I installed is NOT a Bosch unit, BTW.
Anyone have an idea what might be causing this to happen?
[This message has been edited by ITALGT (edited 01-18-2015).]
