Hello all,

I have recently acquired an '88 Firebird and noticed that it takes awhile for it to come down from fast idle (about 3 minutes) and bogs a little when put in gear when cold. I have changed the IAT sensor, IAC valve, EGR valve and solenoid and MAP sensor (battery was also disconnected when installing these so that ECM could reset itself). The situation still exists, but when the car is at operating temperature it is fine - no issues. The check engine light is not on. This is my first TBI vehicle and am wondering if this is normal or if there is an issue?

Thanks

 

Welcome aboard BigRed9000!

I'm a little hesitant to mention it, because I dislike throwing parts at something without some diagnosis to narrow the field of candidates, but...

Of all the sensors, the ECM looks to the coolant temp. sensor for engine temp. info, and thus the need for a faster cold idle. If a failing sensor is to blame, then I'd be looking in that direction.

 

The reason that I replaced all the parts that I did is because the car basically sat for 28 years, accumulating a little over 31,000 miles in that time span. I also knew that all of the parts I was replacing did have an effect on the way the vehicle idled. From my experience with electronics and instrumentation I know that electrical components, when not used frequently will have a significantly shorter lifespan. That being said, I did look through the receipts and saw that the coolant temp sensor was indeed replaced once in 2006. I will take your advice and probably replace it again.

Thanks for the input

 

...that proper diagnosis eliminates a lot of blind groping and wishful parts replacement.

Put a scan-tool on that vehicle and find out what is REALLY wrong.

 

bought a code reader... no codes

 

Code-readers are 10% of a scan tool.

 

which model do you use

 

Snap-On MTG2500 with software so old that it won't perform VIN-specific scanning of vehicles newer than 2006.

VERY similar to the more-common MT2500. The MTG includes some rudimentary graphing functions.

Thousands of dollars when new, several hundred dollars now. Snap-On has discontinued support for these years ago, they cannnot be updated to work with 2010 and newer vehicles.

There are many other solutions; that just happens to be the one I chose.

 

its hard to find scanners that support all makes and models of OBD1 vehicles, luckily I do not own anything newer than 2001 I'll browse the net to see if I can find the MT or MTG2500.

Thanks

 

As far as the MT/MTG2500, it's the software and the physical vehicle adapters you need to be concerned with.

Software from 2003 and back seems fairly common; but ask before buying. There are two cartridges; the required vehicle "primary" cartridge which must cover the vehicle you intend to use the scanner on. The optional "Fast-Track Troubleshooter" is a database of most-likely causes and repairs.

You'll need an OBD-II adapter along with various "keys" that allow the scanner to communicate with OBD-II vehicles. OBD-I vehicles use different adapters (and there's a bunch of them) along with a cigarette-lighter power supply cord.

Again, that's the system I went with--there are other options.