I am sill having problems with the little beast. It is hard starting, usually have to pump the accelerator to get it to start, runs extremely rich, and won't idle less than 1200-1300 rpm. I can't hear any vaccuum leaks, have changed out the the EGR, TPS, MAT, MAP (AC Delco unit), O2, plugs, wires, battery, ECM, Checked water level, replaced TBI gaskets, welded up the exhaust manifold cracks. The temperature gage and the fan seem to be working normally. This last time that I checked the codes I got a 35 and a 45. I know the idle speed is wrong and the exhaust is too rich. Any other thoughts out there in Fiero-Land? One thing I almost forgot, the cap thingy is gone over the idle screw. I have been playing with the idle screw, I need the procedure for setting it properly. Thanks for everyone's help, Scott

It shouldn't mater if the plug to the idle screw is missing.I guessing that the temperature swich prongs are rusted (engine compartment) remove the connector and inspect for corosion.You didnt mess with the timeing or remove the distributor did you?

[This message has been edited by James Bond 007 (edited 08-01-2006).]

Its an 88..... aint got no distributor thingy. The temperature gage works and the fan seems to come on around 180F or so. I have adjusted the idle by ear. Thaqnks, Scott

This is an 88 so theres no distributor to pull or futz with. Its a DIS motor. I would start with the simple stuff, check grounds and stuff like that. Probably not it, but 9 out of 10 times the simple stuff is what burns a hole thru the wallet. An audible check of vacume lines is not sufficient to trouble shoot bad vacume conditions. Especially as senstive as the MAP sensor can be. A small spray of WD-40 on the lines will usually result in a idle change of some sort. Plug in vacume gage and see what you have for vacume at the map sensor line while running. Vacume should be around 18 to 22 inches at idle I think.

I don't know what the procedure for setting the idle screw is, but stop messing with it. I think when the fuel rich condition and hard starting is nailed down a final setting of the screw will be in order. Have you pulled the IAC and inspected it? It can "work" fine and yet not operate properly. The IACs have a known tendenacy to get fouled with garbage from the PCV system. Make sure its clean and neat. If all looks well and there are no codes its probably not the culprit.

Thats all I got right now.
Good luck
88Ironduke

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Pilots with out maintainers are just pedestrians with a cool jacket and sunglasses.
I.Y.A.M.Y.A.S.

There's THREE temp sensors on that engine. One for the gauge, one for the fan and one for the ECM. So even if the fan comes on and the gauge reads right, the ECM can still be confused.

You Really don't want to try setting the idle on a fuel injected, computerized engine via that screw. If you search the forum, you'll find a thread on the proper way to reset it.

Take a look at the fuel injector while someone turns the key on. It could be leaking gas when the fuel pressure comes up. It shouldnt let a drop past until you try to start the engine.

Same excat thing was wrong with my 88 duke motor before I pulled it, and I suspected a faulty fuel regulator, as it dumps so much gas into the motor it seems to pool in the intake runner.

I never fixed it, technicly, I pulled the motor and put in somthing with a bit more power.

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Check out my 3800 swap thread and lend your advice!

https://www.fiero.nl/forum/Forum2/HTML/072877.html

Since you have allready fooled with the stop idle screw , heres the proceedure and what I thought about it with a 2.8. I had alot of problems with the stop idle screw adjustment-- I fooled with it for a year, I finally bought a used t.b. with the cap installed and it fixed the problem, I went threw every sensor that car had, fuel pump, injectors, intakes, gaskets, you name it, I replaced it--then the used t.b. did the trick--in either case if you haven`t allready you can try this, it will work the day you do it--then maybe for a few more days, then back to --well you know--hope this helps.

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 have only been able to find 2 temp sensors, where is the 3rd? I do believe the ones that I have are working. 3800, thanks for that, I will give that a try in the next day or 2. Something just hit me while in the thinking room, could the slow start be caused by the fuel pump not coming on when the key is turned to on? Or does the pump not run until the key is put to start? Is the fuel pressure regulator inside the pump assembly or is it external to the tank? Thanks everyone, we'll get it. Thanks Scott

The pump should run for a moment when you turn the key to on, unless the fuel pump relay has failed. It's on the firewall, next to the one for A/C.

The pressure regulator is part of the throttle body.

The pressure regulator is in the TBI. It's the red rubber diaphram shown in the picture below. A spring holds tension on the center metal piece to control pressure.

Off topic, but where does one get the gaskets shown in that picture? I partly dismantled my throttle body to clean it without realizing no one seems to sell the gaskets I ruined...

I got that same kit from Advance Auto. Let me get the box and I will get the part #. Scott

Thank you Spark1, that is what I have been looking for. Hopefully I will fix any fuel delivery problems this evening. Thanks again, Scott

quote Originally posted by racer37: I have only been able to find 2 temp sensors, where is the 3rd?

Which 2 did you find ?

On the Duke, the ECT sensor is screwed into the side of the thermostat housing. If this sensor (or it's connector) is bad it'd cause all the problems you're describing.

May as well change the O2 sensor while you're at it; it's probably contaminated.

Probably a really dumb question, but:

Have you replaced the air filter element? A restrictive element would cause most of the problems you describe.

I played with the TBI this afternoon, replaced the fuel pressure regulator and pulled the injector to replace the o-rings and the screen. It didn't look like there was anything wrong with the regulator, just a little corrosion. When I started the car, that didn't change the rich condition. I did notice that fuel pump starts with oil pressure, it does come on with the key. Something else to fix. After it was running, I unplugged the IAC and that did not change anything. Does that mean that the IAC is not electrically, or is the ECM reading some many parameters out of whack that it is confused? What do ya'll think?

The temp sensors that have located are on the head (straight up to the right of the thermostat housing) and in the thermostat housing. It seems like I read somewhere on here that the 88 only had 2.

Thanks for everyones help. Thanks, Scott

Went and got a new temp sensor and a new thermostat. Still no change, it still blows black smoke like a mosquito fogger. Tried to set the idle using the procedure outlined by 3800. After I got it to idle down to what was about 700 rpm and put everything back to normal, the car will not idle at all. Has the IAC gone bad and everything else was covering it up? Thanks, Scott

If the fuel pump always come on with the key, does that mean the pump is going bad? Thanks, Scott

Anyone have any thoughts?

Each time you turn on the ignition, the fuel pump will run for a few seconds. The injector will also squirt a little gas onto the throttle plate. You should never "pump" the accelerator when starting a fuel injected car cause the computer senses the throttle position and will dump way too much gas causing the engine to flood. Then you have to go to the "clear flood" mode (wide open throttle) to get the engine to start.

Are you sure your injector isn't leaking? Also check to see if there is a restriction in the return line to the gas tank. The vapor recovery cannister may also be flooded. Check everything.

I can`t remember in all this --if the 02 sensor was replaced or not ? And if the coolant to ecm sensor was replaced? Mat sensor?

You might consider pulling the ignition coil module and makinfg sure the Crank Position Sensor mounted underneath is functional. They cost like four bucks, just get one. You could have a bad coil, they can be had for twelve bucks or so.

------------------
John DuRette
Custom 85 SE/87 Coupe
"Kinda makes you nostalgic for a Members Only jacket"

Yep all of the above mentioned sensors have been replaced. Where do you get a crank sensor for $4.00? It was over $20.00 here at Autozone. Anyway, was playing with the IAC this afternoon. I had it removed and started the car, controlling the idle with my thumb. I would slow the idle and the pintle would retract, I would idle it up and the pintle would move out. Then the pintle went flying through the air like it was shot from a gun. I looked and looked, finally found it. It had come unscrewed. I screwed it back it in, got out a tape and adjusted the pintle to less than 1 1/8 inch. When I restarted the car it seems to be running a lot better, not nearly as rich. Since the pintle came unscrewed is the IAC AFU? I will try to set the idle again using 3800's directions later this evening. Thanks for everyone's suggestions. Scott

There are only two water temperature sensors on the 88 cause the ECM controls the fan motor. There is another temperature sensor (air) in the intake manifold, called either IAT or MAT.

Just 2, I was thinking right. Thanks for the picture. Now if I could just get the IAC thingy working, I think it will run decent. Thanks, Scott

Scott, If fooling with the iac has made an improvement --may also want to check the connector & wires that lead to it--sounds like your getting real close, if you use that iac/idle preceedure, make sure to drive the car right away when your done with the adjustments, also mark which postion the screw is in with some type of colored maker system you can write down on paper --as when the engine cools down , overnight, you may have to adjust the screw again until its correct. If this happens, make sure the engine is up to operating temp each time you make an adjustment, so your not chasing it around & around.

quote Originally posted by racer37:Where do you get a crank sensor for $4.00? It was over $20.00 here at Autozone.

RockAuto.com ... if you do a PFF search you should find a current discount code (5%). Shipping is extra, but they've been an excellent source for parts for me. Sometimes a combination of problems can lead to an incorrectly percieved diagnosis. Here's a question: at night, after the car idles a bit, does the exhaust manifold glow? Or any other part of the exhaust system? I found this thread very helpful with my 85 and 87 four cylinder equipped coupes.

edit to add thread for rockauto discount

[This message has been edited by USFiero (edited 08-02-2006).]

Hey racer37, a tip I'd like to point out. The part of the ALDL you short out to get trouble codes can help tune the ECM while you drive (highway driving recommended for this). When you short out the link while the engine is running, you'll see the Check Engine Light blinking at different rates. The slower it blinks the richer the car is running, and the faster it blinks the leaner it's running. If it blinks about once per second, you're stoich (a good thing), and the ECM has tuned itself.

Before doing this, I recommend pulling your ECM fuse for about a minute to reset it. Once the fuse is back in, start the car, short out the link, and drive on the highway for about an hour. Afterwards, turn off the vehicle. Re-check your trouble codes. Typically, all should be well.

Another tip to point out with the hot summer months... a current ailment, which is causing me to go all custom on the ECM and motor, is that my ECM is overheating... ALOT! Take the center console off and feel the case. If it's too hot to touch, something is wrong with the ECM.

Hope this all helps bud!

[This message has been edited by fieroturbo (edited 08-02-2006).]

Thanks for the tips/ advice. I was a mini-vacation for the last few days and have to spend this week catching up on the rest of life's little things to do. But the vacation was great, too expensive, but my sanity just might be worth it. Anyway, I am going to try to spend at least one evening this week on it. What does everyone clean the wiring connectors with? I picked up some stuff from CRC at the Zone, is there anything better? What about grease? Good ol' white lithium? Thanks again everyone, Scott

A checklist as to what has been done:
new TPS
new MAP (AC Delco)
new MAT
new O2 (Bosch)
2 new temp sensors
New plugs & wires
rebuilt TBI
replaced several vacuum hoses
swapped ECM and back again
swapped EGR
new fuel pressure regulator
new fuel filter
new IAC
welded up a cracked exhaust manifold
determined that fuel pump does not come on w/key, pump starts with oil pressure
determined coolant was low, added about 3/4 gal

car now has a lumpy idle, really bad smelling exhaust (not sulfer, CAT appears to flowing), ECM keeps spitting out codes that the exhaust is rich. I want to tell the computer that I know that, tell me what is wrong. The fan comes on around 200F, doesn't that mean the ECM is reading coolant temperature properly?

I just swapped ECMs again, seemed to run much better, but won't idle. I tried to set the idle using the procedure above. After I get it to just barely run with the IAC unplugged, it wont idle at all after resetting the ECM. If I do get it to idle by adjusting the screw, it runs extremely rich and blows a tremendous amount of black smoke. Maybe I just need a throttle body that hasn't been messed with.

Before I give up on the TBI, does anyone a manual with the GM procedure?

Thanks for any and all advice. This thing is about to drive to smoke again. Thanks, Scott

BUMP.. I now own this car and am trying to pick up were he left off. Thought I would bump this to keep it out of the archives and possibly get advice in the next few days when I try to fix this idle problem. It still idles high and has some smoke. I didn't check the fuel pump at startup but because it started and I thought nothing of it.

Cory

Maybe I'm missing it, but.....nowhere do I see that you have replaced the ignition module. This can cause all kinds of problems depending on what part is acting up. It is feeding info to thte ECM and many other components so it can affect them all. Tthe coils are $23.00 each - you need 2, of course (Autozone). I don't think they are a problem for you so don't buy them. The ignition module is $100.00 (also Autozone) so try to borrow one to check it out on your car.

Advance Auto checked my ignition module for free. Had to find the only store in town with the correct adapter, but it checked fine. Odds are that a bad IM will mean a dead car. Rich and Idle problems usually are not IM.

Try this with a helper. Get a flashlight and remove the air cleaner so you can see the top of the throttle body. Have the helper crank the car. Look in the throttle body as it cranks. The fuel injector will start pulsing fuel as the car is cranking. It should continue to pulse fuel as the car starts until it looks like a steady stream (its not, just appears steady as it pulses quite fast). If the car starts on the initial crank, but dies because the fuel injector quits pulsing, the fuel pump relay is not working. A new relay can be purchased at the auto parts store. Another sign is the car won't start until the oil pressure comes up.

After everything that has been replaced by the previous owner, I have not seen where he checked the fuel pressure. The duke should have about 12 psi. The hard part is getting the correct fittings on the fuel feed line as it does not have a shrader valve.

[This message has been edited by Hudini (edited 03-12-2007).]

quote Originally posted by Hudini: Advance Auto checked my ignition module for free. Had to find the only store in town with the correct adapter, but it checked fine. Odds are that a bad IM will mean a dead car. Rich and Idle problems usually are not IM.

I had mine "checked" at Autozone. It "checked fine", too. I replaced the coils. No better. I replaced the crank sensor. No better. I wondered about my wiring hook up. I checked and double checked. Finally, I replaced the IM with a loaner - car started and ran fine. The initial problem was hard starting on hot start AND a hunting hot idle. The IM can send out signal to many parts of the electronic control components.

Because the problems can be multifarious, I suggested he replace the IM with a loaner - not buy one unless he needs it. Everything else has been suggested and nothing seems to "fix" the problem. The IM is relatively easy to replace - so my suggestion is just that, a suggestion.