FIRECHICKEN

iTrader: (3)

Hello everyone.

I'm sure your thinking, why doesn't he just do a search. Answer: I did but nothing helped my particular situation.

Here is the problem. My car runs just fine 93.72% of the time. The other 6.28% of the time I find myself restarting the car at stoplights. You see the car likes to stall on me right after it lets me know it's going to. The idle will stutter or surge between 1,200 rpms and about 400. I watch the guage and it freaks out like an epileptic at a pink floyd concert. If i put it in neutral it will only prolong the stalling until the light turns green and will still idle wierd. The car idles fine while parked if the stuttering hasn't started yet, but once it starts it's all down hill. The car doesn't surge only the idle.
I thought it was my HI-6 ignition box so I disconnected it. NOPE.
I thought it was my TPS out of adjustment. NOPE
I thought it was my timing off.NOPE
I thought the computer neded resetting.NOPE
Beats me.



What do ya think??

burnout88

Good luck! My 88 also has a similar problem. Car has pretty much become unreliable and zero fun to drive. I have been chasing it for a year now. I do not know of anyone on the board who has been able to fix these problems on the MAF cars. Once the problem's start on a MAF car they are pretty much un-repairable.

The only solution I know of is to remove the ecm and harness and start from scratch with all new ECM, harness and sensors either GM speed density or an aftermarket injection setup.

Morley

TPS may be TU even though it reads ok at idle setting.

bobsroc

Yes, the TPS will cause that issue. Flat spots at idle ranges which cause the output voltage back to the ecm to be flakey. The fix was take the TPS off, soak with carb cleaner, work wiper arm (LOTS), reinstall. BTW, the TPS setting is.54vdc at idle and 4plus vdc at WOT. When setting the vdc to .54 at idle, watch the vdc as you open throttle, do it slowly and watch vdc, it should rise steady and not bounce around alot or zero out. Hope this helps.
I would also check and set the IAC, might need to clean it good as well.

FIRECHICKEN

iTrader: (3)

I am going to check the IAC next. The TPS was changed yesterday and I set it to almost exactly .54 +/- .015. I did watch the sweep from .54 to 4.98. It sweeps good. But my volt meter converts over 1 decimal point at 4 volts. other than that all good. Maybe idle screw setting is to low so when the idle drops back to the screws setting it's to low and flounders.
Thanx for the help guys. It's appreciated.

LinuxGuy

iTrader: (1)

First, I would clean the IAC. Just need a bottle of Fuel Injection Intake Cleaner (not carb cleaner - I can't remember exactly what it was that it could harm in an EFI system...). TomP posted a step-by-step for the V6's in this thread: https://www.thirdgen.org/techbb2/sho...hreadid=175177
The V8's are similar enough I am sure it will work just fine.

Next, you might try adjusting the minimum air screw (aka idle screw, aka adjusting base idle speed). I don't know for sure if it'll help, but it worked great on both of my 2.8L Camaros to get the idle back to normal. Especially on my 89 that was stalling just like your car. The throttle plate was not even close to being open a "normal" amount at idle. I see you were thinking of adjusting the idle screw. Don't just start the car normally and adjust it. The ECM will still be making changes with the IAC. I have included an idle adjustment procedure below from the Chilton's manual with some notes of my own.

Hope the idle adjustment procedure below helps. Let me know how it goes and if you have any problems with the procedure.
One thing I will point out is that when I performed this procedure, I was following the directions in the Chilton's manual which do not include removing the A & B jumper in step 5 and re-inserting it after starting the engine. The Chilton's manual instructs you to start the engine with the jumper in place. I had no problems with this, but I changed the procedure after some warnings from Vader in this thread: https://www.thirdgen.org/techbb2/sho...hreadid=211733
(And here is the discussion in which TomP made me aware of Vader's post: https://www.thirdgen.org/techbb2/sho...hreadid=257457 ). I modified the procedure so that you remove the jumper, start the engine, then re-insert it. The reason for leaving the jumper in place when starting the engine running is to place the ECM in Field Service Diag. mode. Placing the jumper in A & B after the engine has been started will accomplish this without risk of damaging the ECM.

-------------------
My own comments have been added in italics.

Before you do any of these adjustments, make sure your timing is where you want it. I have found that changing timing will subtely affect the idle.

Tuned Port Injection (TPI)
1.) Using an awl or equivalent, pierce the idle stop plug and remove it. This is the plug covering the idle speed adjustment screw (aka idle stop screw, aka minimum air adjustment screw) on the back side of the throttle body.
2.) Leave the Idle Air Control motor connected and ground the ALDL diagnostic terminal (connect a wire between the A & B terminals on the ALDL connector). Turn the ignition to the ON position, but do not start the engine.
3.) Wait 30 seconds, and with the ignition switch still in the ON position, disconnect the Idle Air Control connector. (Since the A & B terminals are connected on the ALDL, the ECM will place the Idle Air Control Valve in the park position. Disconnecting the IAC connector will keep the IAC at this setting.)
4.) Turn the ignition switch OFF. Disconnect the distributor set-timing connector. (i.e. - The wire on the firewall you disconnect before adjusting timing.)
5.) Remove the ground wire from the ALDL connector. Starting the engine with this jumper wire in place may damage the ECM. See more info from "Vader" here: https://www.thirdgen.org/techbb2/sho...hreadid=211733
6.) Start the engine, then connect the A & B terminals on the ALDL again. This will place the ECM in Field Service Diagnostics mode which will flash the SES light according to open/closed loop status. Allow the engine to reach operating temperature and go into closed-loop operation. Watch the Service Engine Soon light on the dash. When the light is flashing 2-3 times per second (i.e. - rapidly), the engine is in open-loop mode. When the light is flashing about once every second (i.e. - slowly), the engine is in closed-loop mode. Once the engine is in closed-loop mode, continue to step 7.
7.) Adjust the idle stop screw to 400RPM on the 5.0L engine or 450RPM on the 5.7L engine. Adjust the RPM with the transmission in neutral.
8.) Turn the ignition OFF and reconnect the Idle Air Control connector and and the distributor set-timing connector. Remove the A & B jumper wire from the ALDL connector.
9.) Adjust the throttle position sensor to 0.54v at closed throttle since adjusting the idle screw has changed the position for closed throttle. Start the engine and check for proper idle operation. You will have to disconnect the battery to clear the code set from disconnecting the distributor set timing connector.

FIRECHICKEN

iTrader: (3)

Ok I think I may have found the problem. While I was going to change the control module, part of the relucter wheel in the distributor fell out. One of the teeth had broken off due to rusting through. So I'll be replacing the distributor and hopefully this will fix the problem. Funny thing is it still runs fine with one tooth missing.

1320 Right Ln.

weird
good chance that's your prob tho

LinuxGuy

iTrader: (1)

Heh, rusted right through...

Let us know how it goes and if that takes care of the problem!

FIRECHICKEN

iTrader: (3)

Well I have now installed my new billet distributor along with a MSD bronze gear. Wouldn't you know it, all good. It was the distributor after all. So for all you people with the above mentioned symptoms check out that distributor real good.

LinuxGuy

iTrader: (1)

Great! Good to hear that you got it fixed!

MerF

Kick-*** post above though...I believe I'll be doing this today when I get home!

LinuxGuy

iTrader: (1)

Thanks!

MerF

Just for the sake of cconversation, I checked out the TB last night. Holy **** I need to clean it out thoroughly before I go adjusting anything...it's no wonder my car won't idle right!

LinuxGuy

iTrader: (1)

LOL! Sounds pretty bad!

86 Cali IROC

Ok guys. Here's MY problem. I had all the above changed out. Had the same thing happen on my distributor. Changed that. My problem is. When I start it. It runs great. Go through the gears and then when I get to the stop light I put it in neutral and then, only once and a while it starts to die then dies. I can hear the Idle air control valve start to work, but it's just too late. any other suggestions guys.