OK so after buying my T/A and getting it home after more than a 2 hour drive she decides she doesnt want to idle anymore. Ive tried correcting issues that could be the problem but now i dont know where to go, or how to check to find out what is causing the problem.

The car sometimes has a hard time starting, ill turn the key and sometimes it wil start then immediatly die. Other times it will start, but the idle will be low, like 200rpms then it will swing up to like 1500 and drop again slowly down to around 1000 for about 15-20 seconds then it does the same thing again, down to like 200, maybe dying or shooting back up. I checked my TPS, and Checked out my IAC. My IAC looks bad, i originally thought it was the IAC pigtail connector, when the car would idle there was a ticking noise coming from the IAC, i pulled out the connector to find the plastic cracked and the metal prongs exposed. The connector looked junked. I replaced the connector, plugged it in, same problem. SO then i decided to clean the IAC, after taking my damn throttle body off to get to the IAC(why the hell GM made it so hard to get to on a TPI is beyond me) Im stumped. Im replacing the sensor with a brand new one because some plastic around mine is cracked when i inspected it to clean it but i feel as if this is not the problem. My car is throwing no codes and if my IAC was bad wouldnt it throw a code? I also reset my IAC and TPS using the FAQ and that didnt work.

So im looking for direction on what to do when i get home, after i replace the IAC i dont know what else to look at. The car is completly stock, my next guess would be the O2 sensor, and some kind of fuel problem but im new to TPI so im not sure really where to start trouble shooting after that...


Chris

 

Did you check for vacuum leaks Chris? Another thing is to go over all the grounds and make sure they've all got good contact. Dunno if this helps but you never know....

 

I didnt check for any vaccum leaks, would that cause such a big problem? Most of my vaccum lines in and near the TB are hooked up, ive looked at them for days, ill trace them back and check them thouroughly tonight. Ill also check the grounds also, ill go at them with a wire brush and clean and tighten them up.

Thanks for the help, any more is greatly appreciated
Chris

 

Unplug the maf sensor and see if it runs better, one or both of your maf relays could have gone bad

 

Replaced the MAF with a sourced used one. I have 2 MAF's when i unplug the maf the car idles at 1500rpm. I doubt both MAF's are bad, they are both intact inside and look good. Is there any way to test a MAF? ANd what are the relays? I have not checked any MAF relays.

 

The maf relays are on the firewall near the brake booster. There are three, one for the fuel pump, one for the maf power circuit and one for the maf burn off circuit. Not sure which is which.

 

FOrgot to add, that when i bought the car it had a MAF code, but idled fine. After getting the car home the idle **** the bed, before i replaced the MAF, replacing the MAF got rid of the code, but not the idle problem. How would you test the relays?

 

I never bothered to test them, the one time I had a problem I replaced them. they're cheap 10-12 dollars each.

What was the code?

 

The Code was code 33. Im no longer throwing that code though, it went away when i changed MAF's. Is there anything to check on the fuel side of things? Tonight im going to go and buy a new IAC, and hook everythng up, ill look into the MAF relays but i dont see how those could be bad, if something went on that wouldnt the car throw a code?

 

So i got out there today and went over everything. I fixed my major surge at idle and was able to drive the car, the issue was a combination of a small crack in a vacuum line and the IAC. However i still have a small surge in idle, probably about 100-200RPMs. Car idles at 800 and fluctuates a little bit. In park the car idles at 1000 and goes between 900-1100RPM. I have a small ticking noise coming from under the plenum.... Any ideas on what that could be? Im pretty sure thats whats causing the surge.

 

i would check your injectors....thats probably the ticking your hearing

 

How exactly would you test injectors, im assuming its with a multimeter. The ticking is coming from the passenger side of the engine, i orignially thought it was injectors, but it seems more pronounced and louder. I was thinking it might be the EGR valve but that doesnt tick at all does it?

 

The injectors ticking is normal I wouldn't worry about it.
Stickey lifters or worn out rockers may make a ticking sound.
I'd also be concerned about the idle speed, 1000 rpm in park is too high, should be around 650.