So I was just cruising down the road and abstaining from WOT runs, driving like a civilized human being and suddenly the SES light came on again. WTF is its problem now??? When I shifted it in neutral, it turned off. Feeling uneasy, I pull over to the side of the road and popped the hood. Everything looked and smelled normal. Coolant and oil temps were in the 180s, alternator was making 14 volts, oil pressure was in the normal operating range, and I am getting unusually good gas mileage. Can you say 24 mpg around town and 33 mpg on the highway @ 70 mph????? At least that is what my average is, plus I had a full tank of gas and the range was 535 miles. Hmmmm... I think I am driving a little too slow and not giving it enough pedal like I usually do.

The second time the SES light came on, I was just accelerating normally and I felt a slight hesitation or bucking for about 3 seconds when I pressed the pedal. It was like as if the engine was choking. I thought to myself, I'm gonna be stuck again, I can feel it!!! So as soon as it shifted from 3rd to OD, it turned off and ran like a champ again.

Well last Saturday, all I did after I installed my new MAF sensor and both of the relays for it, was turn the idle screw clockwise so the Vette would idle at 800 rpms in P or N, and 600 rpms when in D or R. Before that, the idle speed would be so low that it would stall out, and/or choke, if that's really what it is doing. Could adjusting the idle speed have messed something up? I'm now guessing I'd have to replace or adjust the TPS and/or the IAC valve and clean the TB a bit. I hear IAC valve can sometimes get stuck or clogged up causing the engine to stall. I hear the TPS would sometimes give a bad reading that would cause the engine to get either too little or too much fuel and just stall out. That's probably the problem right there, but I really would have to get a Gen 1 SBC/Vette mechanic or shop to help me with the ruckus I'm going through now.

Its too bad that there are not many people around town willing to work on Vettes and will overcharge + over quote if you own one. Now I am in search of a shop specializing in the art of fixing Vettes and making them run right.

 

does you 89 have on board diagnostics(OBD1) and a supporting ALDL connector under your steering wheel and off to the right? If yes, you can jumper pinA to PinB with a paper clip to retrieve any stored error codes(even if ses flashes and then goes out, your ECM will store the error code in memory for later retrieval). Adjusting your TB butterfly screw is just a bandaid to the real problem. At idle, your TB butterflies should be in nearly closed position, and the IAC should open enough to maintain programmed idle speed. If your symtpoms only occur after engine reaches normal operating temperature, you could have a faulty O2 sensor(s) or plugged cat(s). An inoperative IAC and/or heavily carbonized IAC pintle could also cause poor and erratic idle.

 

My cats were gutted by the previous owner. I think I only have 1 O2 sensor since 89 is an OBD-1 car. I will now have someone check the TPS, IAC and the O2 sensor.

What do I have to do to find out the codes? How do I interpret/translate the SES light flashes?

 

C4 Corvette Diagnostic Code Recovery Techniques

ECM (Engine Control Module) technique for recovering codes on the 1984 through 1993 model Corvette is explained first then the 1994 through 1996 16 pin ALDL connector OBD-II (On Board Diagnostics - Version 2) system explained below that.

Code Recovery: 1984 through 1993:

To recover ECM codes from the 1984 through 1993 Corvette, place a short as shown below between pins "A" and "B" on the ALDL (Assembly Line Diagnostic Link) connector. This connector is located under the dash just to the right of the steering column and has space for 12 pins although not all of the cavities will be populated.

Turn the ignition switch to "On" but do not start the engine.

Depending on the model year, either the "Check Engine Light" or the "Service Engine Soon" will begin to flash.

As the code display sequence begins, you will see a flash followed by a pause and then two flashes. This is the indication for the number "12". The number 12 is a delimiter intended to show where the ECM code display starts and stops.

Code 12 will flash three times and then any stored codes will flash. When all codes have been displayed or if there are no stored codes, the number 12 will again flash three times.

For example, a problem with the EGR system (code 32) will be shown as 12, 12, 12, 32, 32, 32, 12, 12, 12.

This would be displayed on the Check Engine/Service Engine Soon light like this:

12: flash (pause), flash, flash, (long pause)
12: flash (pause), flash, flash, (long pause)
12: flash (pause), flash, flash, (long pause)
32: flash, flash, flash (pause) flash, flash (long pause)
32: flash, flash, flash (pause), flash, flash (long pause)
32: flash, flash, flash (pause), flash, flash (long pause)
12: flash (pause), flash, flash, (long pause)
12: flash (pause), flash, flash, (long pause)
12: flash (pause), flash, flash (long pause)

The ECM code display will repeat until you turn off the ignition switch and remove the short.

 

Got these codes just now.

ses..ses.ses
ses..ses.ses
ses..ses.ses
p
ses.ses.ses
ses.ses.ses
p
ses.ses.ses
ses.ses.ses
p
ses.ses.ses
ses.ses.ses

"ses" = the light actually coming on.
"." = the very short pauses
".." = the slightly longer pauses.
"p" = the longest pauses.

 

So there I have code 33. Hmmmmm..... I'm wondering why I still have this even if I just replaced the MAF and all the relay involved with it. What other stuff do I have to replace???

 

Beyond the paperclip method... since your running OBDI, if you have a laptop and feel like making a cable, check out WinALDL. You can build a cable to go between your diagnostic connector and your laptop and it will record all the codes as well as IAC, TPS and more realtime data...

Sometimes it's handy to drive teh car, record all this stuff in realtime and figure out exactly whats going on.

 

Code 33 is maf sensors. I had this code for months in my 88. Replaced the two relays and Maf sensor to no avail. Turned out to be my ECM. Replace it and no more codes. Funny thing was when my code 33 appeared it felt like someone dropped a boat anchor behind me.