Viking

hey guys, any ideas why I might have a lope at idle, and while in drive with foot on the brake? The RPM's dip like the car is going to stall, recovers, then dips again. Never stalls though.
I did a tune up on it to try and fix. Did cap/rotor, O2 Sensor, fuel filter, PCV, plugs. Still doing it.... maybe a clogged injector?

five7kid

iTrader: (14)

Maybe. Or a cylinder with low compression - do a compression check.

Viking

Thanks, I will. I raised the idle setting a little bit too, to see if it solved the lope, but now the car is hard to start. Can raising the idle cause that??

Air_Adam

Is the SES light coming on?

Have you checked all the plug wires to make sure they are all tight? Are all the plugs tight? Is a plug wire maybe burned on the exhaust manifold?

I had a problem with a dead cylinder that ran similar to what you described with my '97 LT1 a few weeks back - checked all the wires with a timing light and found #8 was not firing. Plug wire was tight on both ends, and the spark plug was tight. Took out the wire and found it rubbed through on the PS pulley (all the passnger bank wires are routed between the block and PS pump) and was grounded out. Replaced the wire and its all OK now.
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How did you raise the idle on a TPI car?

Viking

I hear you about the dead cylinder thing, but the car runs fine when at speed. On the highway, for example, you would never know there was a issue. Its just when stopped with foot on brake mostly in drive.

Air_Adam

Check your IAC (idle air control) solenoid. It may be having some issues, or is maybe just dirty.

Viprklr

iTrader: (5)

The minimum air/idle adjustment screw on the drivers side of the throttle body.

Viking

Thanks Air Adam, I will have that check out, good idea

golden

Well maybe its your torque converter ....

Air_Adam

I highly doubt it. When a lock-up mechanism in a converter fails, it will act just like the clutch in a manual trans car. When you come to a stop (or put it in drive) it will just stall, just like if you try to stop in a manual trans car when in gear without pushing down the clutch pedal.

Viking

yes, the T/C is fairly new. Had the tranny rebuilt not too long ago, and I know I paid for a beefier T/C in anticapation of when the original 305 finally gives up the ghost, I'd put a stronger mill in there.

I'm going to try replacing the Idle air Control, and return the idle back to normal.

Still cannot figure out why adjusting the idle might cause the car to be hard to start. Hopefully the new IAC and returning the idle back to where it belongs will solve all.

Air_Adam

It may be harder to start because some of the 'base' settings the ECM looks for are all out of whack with that stop screw changed positions. I'm not sure if thats an issue the way the TPI cars' controls are set up (my 3rdgen has a carb, the LT1 car is an OBD2 car), but lots of imports with EFI can have issues like that.

Set the idle stop back to stock, and I would suggest removing the entire throttle body unit and cleaning it out thoroughly with Throttle Body Cleaner spray (not carb cleaner, its got too much oil in it) to get all the carbon off the throttle bores & blades, and out of the IAC passage. Clean the IAC solenoid at the same time with the cleaner spray.

My LT1 had a few odd gremlins like a sticky fast idle - would randomly get 'stuck' idling at 1200-1500 rpm after letting off the throttle - that were cured just by removing, disassembling, and cleaning the throttle body. Clean the MAF at the same time also with throttle body cleaner (you cannot use carb cleaner on the MAF due to the oil in it - that could make your problem worse).

Even if that doesn't solve the problem, it at least eliminates two possible issues, and its cheap and fairly quick job to do - cleaning the throttle body and MAF - and it can only help it run better.

Supervisor42

Eliminate the power brake booster as a source of a vacuum leak by plugging it off and see if it makes any difference. (don't forget you won't have power brakes when you test drive it)

Viking

Well - after 2 weeks I am still grappeling with this issue. Here is what I have done to to solve the surging at idle, with foot on brake. Also now the car is starting to surge while driving with foot lightly on gas. Seems almost like its gas is being cut back with each "surge". Car does not do this when cold, its worth saying, only when its warmed up.

I have so far:
-Replaced the idle air control
-Replaced O2 sensor
-Replaced fuel filter
-Replaced Cap and rotor
-Replaced spark plugs
-Cleaned throttle body
-Eliminated the brake booster as possible cause.

I received a reccomendation to replace the Throttle Position sensor. Please let me know if is this worthwhile, or any other suggestions. Thanks!

jtrescot

What did you find when you did the very first suggestion - the compression check?

Viking

As far as I know, my guy did not do a compression check. I will ask why.

Viking

Yes, all cylinders were checked, all equal.

Air_Adam

What where the numbers?

Viking

for anyone interested, finally fixed my issue. All injectors tested low to bad. Replaced all 8 injectors.

ckyfreak2010

have an automatic 92 v6 3.1 l camaro...i just pulled it out of my drive way it started fine...as i got out of the driveway it got really shaky like it would stall....then a few seconds later it did stall..i tried to start it but it would turn over...i tried a few more times it still didnt work...i came back a few minutes later and it still didnt work.. i have 3/4 left in my gas tank ...any ideas what could wrong