The cold start switch is near the coolant fill tube....just to the right...if looking from the passinger side..SOUNDS like this is you problem......there is also a cold INJECTOR....MIGHT check this out also

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1988 Gary Tucker (GT)

http://img78.photobucket.com/albums/v248/GARYTUCKER/Coolest_shot_ever.jpg

http://img.photobucket.com/albums/v248/GARYTUCKER/REDNECKHORSESHOES.jpg

[This message has been edited by GARY TUCKER (edited 08-01-2004).]

Has this ever been resolved? After disconnecting the battery, mine stated fine too...does that mean it is the MAP or the O2 sensor? Or is it the cold start switch? It runs absolutely fin any other time.

Hey Bigfieroman hows it going upstate?
Ok, here is what I did.

quote Originally posted by chameleogaz: Any trouble codes? After checking the codes, disconnect the battery and reconnect it about 5-10 min later to clear all ECM info, let the car cool completely (like overnight), and try starting it up again. If it starts normal, your ECM most likely is learning improper values to adjust the air/fuel ratio, and it's most likely either the o2 sensor or the MAP sensor giving false readings messing things up. At least this is my understanding of GM EFI. -Jeff

Disconnected and it ran allot better at start so I replaced the MAP and O2 sensor. The MAP was probably still original but the O2 sensor was a year old. Now it started better but after a restart, half hour or so, it would do the hunting idle warm.

quote Originally posted by Master Tuner Akimoto: This sounds like a classic case of the coolant temp sensor and what generally happens is the sensor sends a signal to the ECM telling it how much gas to send to the engine on start up and warm-up,if this is defective the ECM will get mixed or false information and can cause erratic start up and idling ....try to get a scanner and obtain a code readout and that should pinpoint your problem.

I replaced my engine coolant sensor and reconnected the negative ( - ) cable and it started up running very well, going to 1450 RPMs without hunting at all and stepping down as the engine warmed up. Took it for a drive to set the IAC and started it back up after a half hour and it was doing the hunting idle warm.

I found this following quote in this achieved thread

quote 00lE The ECM will not initiate the EGR status test until the engine has fully warmed up (closed loop) and the TPS has moved a certain percent (increase RPM) resulting in about 2500-3000 rpm increase at least once. Once the test has initiated, if the ECM does not see the change in values from certain sensors (change in MAP, etc.), the test fails and the ECM will continue to loop the test at a specific interval until the conditions are met (e.g. forever). Note that during the test execution, the ECM opens the EGR valve a certain percent and adjusts fuel and timing accordingly (this value is a constant set in the code commonly referred to as: Egr Diagnositics Retard). This will result in an RPM flucuation if the correct amount of EGR gasses do not enter the combustion chamber during the test. A failure of this status test will generally not set a trouble code unless considerable highway driving has occured with multiple test failures.

I ordered a EGR valve today and gasket and I plan on installing it this week and will post my results. My other thought is that I am questioning my fuel vapor canister. I will switch the canister from my 86 for testing. Been working on and off for some time now on this difficulty and will hopefully understand it soon.

Hey connecticutFIERO, how did the diagnostic testing go this weekend?
Inquiring minds want to know.

quote Originally posted by jetman: Hey connecticutFIERO, how did the diagnostic testing go this weekend? Inquiring minds want to know.

Me and Jnco never connected, but I am working on my car all day tomorrow so I wil try to get ahold of him. I am having another issue right now with my clutch that I have to resolve first, but I will try to fix both tomorrow. John if you read this, I hope you are home tomorrow cause I'll be calling. I'll update tomorrow.

My car has a pretty much rock-solid idle when warm. It does the surging thing after cold start, as well as hesitation and some light backfiring on initial throttle application. It has absolutely no poor-running characteristics after about a minute or two. I will try the O2 sensor and MAP sensor…then the cold start switch. My EGR system is working fine. (Gasp! No code 32?!!)

Hey, I tried callin ya, spoke to the lady, you weren't home. Ahh well, I'm here almost all day today. Let me know...

Jnco hasn't come by yet, but i fooled around and seem to have improved the problem. I replaced the rpm sender and I swapped IAT senors. The car was running great, but I think it could just be because it warmed up. So I don't know for sure if that helped. I'll start it again i a few hours to see if it changes.

quote Originally posted by connecticutFIERO: Jnco hasn't come by yet, but i fooled around and seem to have improved the problem. I replaced the rpm sender and I swapped IAT senors. The car was running great, but I think it could just be because it warmed up. So I don't know for sure if that helped. I'll start it again i a few hours to see if it changes.

What other possible names for the IAT sensor? I believe I'm going to try replacing mine, as well as the rpm sender... they are original, so what the hell.

Matt

quote Originally posted by fiero go fast: What other possible names for the IAT sensor? I believe I'm going to try replacing mine, as well as the rpm sender... they are original, so what the hell. Matt

I think its officialy called the Air Charge Sensor. But everyone calls it the IAT.

Bad news, I never hooked up with Jnco and when I started the engine again when it was cold it still surged, but a lot less this time. I bet it will be worse in the morning when its truly cold. My clutch isuue is still unresolved as well. I still am not sure if my master or slave cylinder is bad, but I'll find out soon enough when it finally stops working all together.

On the the brighter side I installed a new battery in my motorcycle and then i fixed the ignition switch.

[This message has been edited by connecticutFIERO (edited 08-02-2004).]

quote Originally posted by fiero go fast: What other possible names for the IAT sensor? Matt

MAT...manifold air temperature.

bump

What Master said. The ECM sensor, the one under the thermostat housing. one way you can test it is to pull off the connector and start the engine. If it idles fast then the sensor is bad.
Don

Are you free this weekend?? I didn't sell my fiero. I drove 250miles to PA and blew a headgasket on the way. what a PITA! Thanks to stick who is very kind and courteous for understanding my bad luck. So time for an engine swap in that baby (I drove it 250 miles home smoking like crazy, smoke barreling out). Marc and erin picked up 2 more fieros today, a red coupe 4cyl, and a Gold Aero 4cyl se (making 7 Fieros in the family). We will be doing V6 swap in those and probably mine this weekend. We will be very busy as I also have to swap all the black 85GT panels onto my red 84 coupe but you're more than welcome to stop by. Call me.

[This message has been edited by Jncomutt (edited 08-06-2004).]

I have the same surging problem.. Anyone with a GT or SE does your volt meter light stay on until you rev the motor up on an initial cold start???

could this have anything to do with it.??

My ammeter always indicates 'low' (and the idiot light is on) until I give the engine a few revs. One quick stab brings it in line.

I've always understood this to mean one diode in the array (I think there are three) is 'weak' ... but otherwise this indicates nothing important. Theoretically you could replace the one diode, though the usual is to replace the alternator.

I don't think this could be related to your problem, but as I have a similar problem with part throttle acceleration under 1800 rpm I'd be happy to hear from anyone that reasons otherwise.

GB

quote Originally posted by RGBaker: My ammeter always indicates 'low' (and the idiot light is on) until I give the engine a few revs. One quick stab brings it in line. I've always understood this to mean one diode in the array (I think there are three) is 'weak' ... but otherwise this indicates nothing important. Theoretically you could replace the one diode, though the usual is to replace the alternator. I don't think this could be related to your problem, but as I have a similar problem with part throttle acceleration under 1800 rpm I'd be happy to hear from anyone that reasons otherwise. GB

If the belt isn't tight enough, you could also have these symptoms.

i thought the belt would squeal if it wasnt tight enough?

The low volt thing started for me when I put in my underdrive pully. When I switched back, it went all the way right on first start. I just used to give the car a quick touch of the gas, and it was fine.

I have lot of experience with the 2.8 engine and i have had the same problem with several engines. Usually this problem is fixed with a new MAP sensor, however if you do not use a new GM map sensor the problem may stay. A cheap map sensor from a local parts store is sometimes no good. One other thing to check is your computer. i installed a brand new computer once t try and fix this problem, but it was a cheap canadian tire computer. After the new computer did not wor i tryed a junk yard computer and the problem was solved. GM products are fussy when it comes to electrical.

UPDATE:

I still have this problem, I just read the last post and I will try to swap MAP sensors. I checked all my exhasut bolts to look for a leak and looked around for a vac leak and found nothing. I already tried the Air Intake sensor with no results. I checked all my plugs and wires to see if they were tight. I pulled one plug and it seemed to be OK, possible a little lean as there was some white residue. But that couldv'e been from way before when I had the vac leak. I will try to hook up with Jnco again this week to scan the ECM.

BTW I replaced the ECM once already, and every single sensor and switch. Nothing is original. Wait except for the EGR solenoid itself? Hmmm? I think its either coolant temp switch or the 02 sensor, but I am broke and want to replace only the bad part. I DL'ed winALDL but couldn't find a spare serial cable to butcher. Not to mention the diagram on how to do it was kind of confusing.

Oh and I still haven't rebled my clutch system... no time.

have you replaced the 'cold start' coolant sensor? it's the only coolant sensor with a fuel injector type plug on it. not talking about the cold start fuel valve itself but the sensor that controls it, which is also near the coolant filler tube. I beleive the ecm doesnt read this sensor so a scan wont tell you if its faulty or not. it's controls the cold start valve directly. i had the same problem you had until i replaced it with a spare .

quote Originally posted by LordBoOsT: have you replaced the 'cold start' coolant sensor? it's the only coolant sensor with a fuel injector type plug on it. not talking about the cold start fuel valve itself but the sensor that controls it, which is also near the coolant filler tube. I beleive the ecm doesnt read this sensor so a scan wont tell you if its faulty or not. it's controls the cold start valve directly. i had the same problem you had until i replaced it with a spare .

Yeah I replaced that last year. I don't want to go out and start buying sensors again like last year without knowing exactly which one I need. I wil have to once I runn out of options however.

Today I swapped the EGR solenoid to see if that changed anything. Nope.
I also replaced the IAC a few weeks ago with another good unit I had.

On a side note my indiglo gauges suddenly stopped shining as bright and my volt gauge is in the red, yet the light doesn't come on. Yippie! More BS!!

connecticut, where are you getting all your sensors? I want to start replacing mine since a lot of them are original except don't want to pay tons and tons of money on them. Like the water temp sensor and air temp sensor. My map sensor is only like 2 years old.

quote Originally posted by fiero go fast: connecticut, where are you getting all your sensors? I want to start replacing mine since a lot of them are original except don't want to pay tons and tons of money on them. Like the water temp sensor and air temp sensor. My map sensor is only like 2 years old.

Well I am on my second engine, and I parted out a car with a 2.8 so I have some lying around to check against the new ones I bought last year.

Need a new or rebuilt alt. That solved the wandering idle for me. A bad alt may do bad stuff to your new parts.

quote Originally posted by connecticutFIERO: Jnco hasn't come by yet, but i fooled around and seem to have improved the problem. I replaced the rpm sender and I swapped IAT senors. The car was running great, but I think it could just be because it warmed up. So I don't know for sure if that helped. I'll start it again i a few hours to see if it changes.

where is the rpm sender located? I am talking about a duke in case you have a 2.8

quote Originally posted by Wesley: where is the rpm sender located? I am talking about a duke in case you have a 2.8

Yeah mine is a 2.8. i thinks its called a tach filter.

Some parts stores will test the alt on the car for you. I too have a funky idle, and surging when cold. I thought it was the alternator. I had it tested on car, and they said the diodes were fine. I thought I knew better, so I went and installed a remanneed alternator last week. I still have the problem, and a good used alternator as a spare. But, I am out $80. If it tests good, it probably is.
I am really curious to hear what fixes yours. I literally have the exact problem, and have replaced a TON of electrical items myself. I need to stop shelling out money to replace good parts.

Regarding the Cold Start Injector (CSI) circuit, it is unlikely that this is the problem. The CSI does not inject any extra fuel except when the temperature is under 95°F and the starter is actually cranking, and it runs on a temperature-controlled timer so that the colder it is the longer it runs, up to a maximum of 8 seconds at -20°F. The run time varies proportional to temperature down to -20°, lower than that it stays at the maximum of 8 seconds. Remember, no matter what, it's only injecting when the starter is actually cranking the engine and in no case runs longer than 8 seconds.

JazzMan

[This message has been edited by JazzMan (edited 09-04-2004).]

I had my car at Dale Starcher's, and he replaced the map sensor to fix the problem. He thought it was fixed, but it just seems less noticable now. It is just as bad when really cold, but when it is warm outside, it is better.

I finally got around to running winALDL on the car, this is what I cam up with. I don't see any problems with the sensors, but this is the first time I have ever tried to decypher winALDL. http://members.cox.net/rags-n-tags/Dans_pics/20040915_171516_LOG.txt

Is that negative voltage?

Its the readings from winALDL, I guess it is spposed to be voltage. GTdude mentioned that it is a bug in winALDL, so I think its probably not whatever the problem is.

I had a 93 Ford escort do exactly what you described with the surging and all. With mine, it was a crack in the vacuum line that went into the top of the valve cover. It had softened and split to the point it would collapse as the pressure increased, and then when the engine choked, it would open back up and allow it to surge.

Long story short, I cut it, inserted a piece of copper tubing and she ran better than ever before.

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Jay Brintnell
Owner / Design Lead
WordMark.ca Communications

[This message has been edited by Eclipse (edited 09-16-2004).]

Cold start switch has nothing to do with this problem - it only operates during inital cranking until then engine starts.

I suspect EGR - to test, when engine cold, start it up and press up on the EGR diaphram. There should be a noticable difference in the way the engine idles when the EGR is opened (it should stall). Of course if your valve is stuck open (or partial open), you could just try blocking off the EGR tube going to the intake and then start the car and see if it runs better when cold. I don't think the EGR solenoid should be a problem unless it is leaking a bit causing the EGR to open slightly as well (but the hose can be disconnected from the valve to verify this). The EGR only opens once the engine reaches a certain operating temp.

Maybe you also have a problem with the pick-up coil or ignition coil also - maybe they have a weak connection inside and once it warms up and expands the connection become better? Just a thought.

sorry, I didn't read all the posts, so if any has been covered before just ignore it

hope that helps some,
Tim

Check for a negative spike at your tps, I had found a negative spike with my muti. meter of neg. 100 volts. It would spike so quickly I could hardly see it. IT will damage all your [my new!] sensors if you have a cs alt.

quote Originally posted by alienfiero: Check for a negative spike at your tps, I had found a negative spike with my muti. meter of neg. 100 volts. It would spike so quickly I could hardly see it. IT will damage all your [my new!] sensors if you have a cs alt.

I'm not sure I am following you. Are you saying a negative spike in the TPS would be caused by my alternator, and that would damage other sensors? I have an 87 engine with an 87 alternator, I'm not sure is its CS or not.

I was looking at the tps voltage, More then likely be the same at other sensors. I could see a spike but I could not tell how much untell I binked my eyes fast anought see it. Most 88 and pre 88 have the si alt.

Check your canister purge valve and filter and replace the rubber vacuum lines. May not solve the problem but may idle a little smother.

I just replaced all the old old 10year + rubber vacuum lines and now have a little smother idle.