I have a 1987 Camaro, 5.0 TPI/Automatic and am having some idle issues.

1. Without driving the car, the engine idles between 1,200 and 1,500 RPM hot or cold, it doesn’t matter.
2. I have adjusted the throttle position sensor to the appropriate ohms
3. I’ve backed the idle adjustment screw off all the way; it doesn’t touch the throttle plate.
4. The exhaust has a weird burnt odor.

Once I drive the car, the engine idle will:
1. Randomly drop to a normal operating RPM of approximately 700 RPM. (Which doesn’t make any sense to me because the idle adjustment screw now has no bearing on the idle, and I’m guessing the engine should probably die.)
2. When the car is in gear, it idles below 500RPM, and sometimes it acts like it wants to die.
3. While driving, as I start to apply breaks, I can see the idle drop almost to 0 RPM then it jumps back up to around 500 RPM. If it doesn’t recover from the near 0 RPM, the engine will die. (I did notice that when it does this, the brake pedal is not as stiff and will depress almost to its maximum)

I accessed the ALDL (Assembly Line Diagnostic Link) connector and jumped terminals A and B and received trouble Code 15.

15 Engine coolant temp sensor error (low temp indicated)

After changing out the sensor, I again jumped terminals A and B and now received trouble Codes 33 and 34.

33 MAP sensor circuit error (signal high indicating low vacuum)
34 MAP sensor circuit error (signal low indicating high vacuum)

I disconnected the Mass Airflow Sensor while the engine was running, and nothing changed.

How can you have high and low vacuum in unison, and how can I check to see if the Mass Airflow Sensor is defective?

This has me boggled and I want to get this fixed. Any help is appreciated.

James

 

Jamesv, one quick question. You have a 87 TPI. You mention about the MAP sensor. 87 TPI should have a Mass Air Flow Sensor, not a MAP sensor. Did you change your car to speed density?

 

No Sir, its all stock. That's just the error code I'm getting from the ECM. Not sure what it means; the car has a mass airflow sensor.

 

I was thinking maybe take a snap shot of the engine bay for us? Try doing the IAC relearn procedure. I had a friend with a camaro and he had idle issues and they were resolved with this procedure. I cleaned out the IAC port and the valve on the tip had some carbon and i lightly wet sanded the tip and it cleaned out good. follow everything here its pretty easy and i agree with the original poste to the article that most idle issues are traced to IAC problems or misadjustments. here is the link. Post back if this works for you so any future searchers can get an anwer.

https://www.thirdgen.org/forums/tech...ml#post1304610

 

Thanks guys... I'll try this and get back with you on the outcome!

 

 

Well i went a head and replaced the Idle air control sensor, inserted a clip in the ALDL, 'A' and 'B' sockets and followed the directions with the exception of the EST bypass. I have no clue what EST is or where it is! I then started the car and it wouldn't run, it would die immediately. I then began to gas it to keep it running and suddenly it ran on its own, but just like it was before, high idle and the check engine light continued to stay illuminated. I checked the code again and got a 34. All together I've replaced the Temperature Cooling sensor and now the Idle air control sensor, and still no normal idle. Any other advice?

Thank you,
James

 

You are looking at the wrong list of codes. That is for the later models with MAP/Speed Density. You have a MAF and that is high and low volume flow.

This would be a big indicator to me. While it can run without it... you should notice a difference

You can't, getting those codes together should tell you something. Yes, I think you have a problem with the MAF... but there is a lot of digging to do to solve it.

Could be relays (Cheap)
Could be a Fuse (Cheap)
Could be wiring
Could be the MAF itself. (Not Cheap)

I don't have it handy, but there is a FSM flow chart on troubleshooting the MAF circuit. I know tuned Performance has posted it multiple times on these threads. Try searching around for Code 34 or Code 36. Should come up in one of those threads.

Always start by fixing the codes.

 

Thanks Kyle

 

Following along to this one. I have an 89' 350 TPI and it's doing basically the same thing. I had a code 33 and 36, and after changing the MAF, TPS, IAC, and both MAF relays, I'm now code free but the idle is still a bit weird. Stumped

 

That same car that had the issue with idling problems also had at the same time a vacuum leak by the egr solenoid runner. This after the owner changed all the plenum gaskets and base manifold gaskets, I think he did not torque it at all from i suspect. The idle issue went away but the vacuum leak makes the engine run rough. I used throttle body spray to find the leak. Try doing the IAC relearn procedure step by step and disconnecting the est wire by the back of the firewall when doing the relearn. Also adjust the tps to, if i remember correctly .55v.

 

Do you disconnect that wire for the whole re-learn process, or only at a certain step? Also my idle is kind of junk, but any acceleration is perfect and responsive

 

I am proud to report that the idle issue has been resolved! A third-gen buddy of mine found that a hard plastic vacuum line that runs along the right side of the plenum, and then under the throttle body was disconnected from a "T" fitting. Connected it and BOOM, no more codes!

I still have other posts out there with other issues, thank you all for the help

James

 

Which vacuum line is that? Can you post a picture?

 

Left side of throttle body

From photo of left side of throttle body to vapor canister

Hard plastic line runs from intake manifold to under runners, to under throttle body and to vapor canister.

 

Vin there are vacuum lines that run underneath the throttle body that intersect there in a “T”. The “T” is held in place (suspended) under the throttle body by the vacuum lines. It was difficult for me to see that the line was disconnected.