Still Idling rough even after.....

both the TPS and the idle bypass value have been replaced OEM. Ran good for about 2 to 3 weeks as far the idling, now it is starting to do the same thing again!! Any Ideas at this point what else and can do or check? Perhaps my MAF sensor, What does this actual do?

Please help me out here!

Thanks In Advance!

Jeff Bratton

Have you tried spritzing the MAF filaments with Windex or anything? If you haven't, take the sensor out of the housing and give the 2 filaments a little bath and then reassemble. If this doesn't clear things up then you might try adjusting your IAC.

'bird

UPDATE!

I checked the codes from the EEC-IV and what I get are Codes 41 and 91. Both the O2 Sensors are saying that the system is running to 'lean'. What would be causing this? I just bought brand new a TPS and a IAC value. It acts like it is getting worse, now, it is stalling on me at stop lights, RPM's are dropping below 500.

Tbird88 - I did what you suggested in cleaning the 2 little filaments on the MAF sensor and still no good idling. You mentioned something about adjusting the IAC Value..... How?

Help me please?

Jeff Bratton

Turn the adjusting screw in until it seats, then back it out about 1-1/2 turns. I think that'll getcha in the ballpark, someone else might have a more exact technique & hopefully they'll chime in on this thread.

'bird

I don't think you can adjust the IAC; that's the computer's job

You could have a vcauum leak...

That is why the O2 sensors are going lean. There is more air in the system than the MAF is taking account for. Try and look for some vacuum leaks. The I/C tubes are notorious.....

Deep6-

That brings up a good point! There sounds like there is some sort of vacuum leak coming from the back of the passenger side value cover area or somewhere beyond the plenum. what do you think that could be. I have an Automatic, so I do not have an EGR Value, right? I definetly can hear a Vacuum leak back in that area though, and it is driving me banana's, since I can not locate it.

Sometimes it'll run (idle okay) and sometimes it runs very rough.

So a Vacuum leak can cause the car to run lean EH?

Thanks for the info fellows!

Jeff Bratton

The PCV valve is located behind the plenum on the passenger side valve cover. You could have a bad PCV, a leaking rubber grommet, or have a cracked vacuum line.

I checked out the pcv Value and it looked good, still had that rattle sound, plus it was clean looking as well. I did notice that the little hose was cracked though, so I replaced it. RUNS(Idles) must better now.

Anyways it still sounds like there is a vacuum leak back there somewhere, Still here a hessing sound! I'll keep looking!

Thanks for all your help my friends, It's great to have people like you guys!! 'A BIG'

Thanks Much, and have a good rest of the week!

Jeff Bratton

If the idle is somewhat stabilized....

Try spraying something around various vacuum connections and what not back there.

Some guys will use Propane which will INCREASE the idle, but I'm a little nervous using propane around a hot engine.

Other guys will use some carb cleaner or even soapy water which will bog and stall the engine should it get sucked into a vacuum leak.

The soapy water has the bonus of making bubbles in the area.

Usually the I/C tubes leak at the collar nut and the joints that connect to the I/C itself, but if you are hearing hissing from behind the engine, it sounds like you have a gross vacuum leak. I'm sure that you're not pulling a steady 18-20" of Hg vacuum on your boost guage either in neutral?

Like mentioned earlier, it could be one vacuum line that has a crack in it, or it could be a gasket, like the plenum to intake manifold connection that has a leak. Test around and see if you come up with anything.

Re: If the idle is somewhat stabilized....

I'm sure that you're not pulling a steady 18-20" of Hg vacuum on your boost guage either in neutral?

Click to expand...

-Deep6: Right, I'm not. I'm pulling looks to be 15" Hg. so I'll get out this weekend and do more Vacuum checks and check the I/C tubes as well. I'll let you know if I find anything.

Thanks...

Jeff Bratton

Also might have the EGR tube off. If you get underneathe the passenger side ofthe car and look up the backside of the engine you should see a tube running from the engine to the exhaust manifold. Make sure that tube is connected as mine was off for about 2 years and I could never fugure out what was making that damn flutter noise on the passenger side.

Rob... What's Up? By the way, I got your package today(Friday).
Thank you so much!

Ok... Automatic's, Do they have EGR values? I can't really til cause of the cramped quarters.

Thanks for your response Rob!!

Jeff

Some cars do and some don't....

I *think* that all of the 89 SC's had EGR.

However, in 90 only the sticks had it and then in like 91-92 only the auto's had it and then in 93 no one had it only in 94-95 did it return to both models. I *think*. It's something like that.

Check and see if you have a fitting on the intake plenum just behind where the Throttle body connects to it. If you see a tube there, you might have to look from the passenger side of the engine and really get some good light back there, you'll see a 1/4" diameter metal pipe, then you know you have EGR.

At any rate, you're loosing anywhere from 3"-5" of Hg Vacuum at Idle in Neutral, so you're drawing in unmetered air that the computer doesn't know about and it's running your Fuel mix toward the lean end of things, that leads to driveablility probs and stalling.

If you can, see if you can remove the wiper's cowl and weather stripping, you'd get a better vantage point and might actually be able to fit a tool in there.