Okay, now I'm stumped. My 1991 Firebird was running fine up til today. When we started it, it would die going into gear. Now, it idles rough and can't stay running. In fact, I can't get it to rev without feeling like it's starving for gas. I checked the injectors with my ohm meter, and I'm getting right at 1.4 and 1.5 ohms. I also can hear the fuel pump whining, so I know it's getting fuel. When it is running, I can see gas pulsing from the injectors. I checked for cracked or unplugged vacuum lines, but didn't find anything. Basically it's just dying. My WINALDL doesn't work, so I went the old fashioned route and connected pins A -> B. I just got the following codes:

Code 15 - Low temperature indicated at engine coolant temp. sensor.

I just changed my stat to 160*. So I'm sure that could be throwing a code.

Code 24 - Circuit fault in vehicle speed sensor.

My speedometer worked sometimes and sometimes it wouldn't. But it stopped working a few days ago. I checked the wires and everything is hooked up.

Code 32 - Fault in barometric pressure sensor circuit OR Fault in exhaust gas recirculation valve diagnostic switch OR Fault in electronic vacuum regulator valve

Could the VSS cause a problem with it running? I looked on the board posts and someone stated that the VSS controls EGR. Well, before I go spending $40-$60 for a new speed sensor, I want to be sure that it is what's causing my rough idle and won't rev up.

 

I'd try and solve the code 15 problem first, because that's probably what's causing the most trouble.

First thing to do is make sure the coolant temperature sensor (CTS) is working properly. It's located in the front coolant passage on the intake manifold, on the left side of the thermostat housing. Make sure the 2-wire electrical connector is plugged in and tight. Then, using a multimeter, unplug the electrical connector, turn the key on, and check for 5 volts between the yellow and black wire.

You can also check if the CTS is reading the right temperature. Use your multimeter and attach the leads to the 2 pins where the electrical connector connects, and measure the resistance and see if it matches the actual coolant temp. You could also remove the CTS and put it in a pot on the stove and measure cold and hot temperatures compared to the real temp. For example, if it says its 60* when the waters boiling, you know the CTS is bad.

 

So, in other words, my putting a 160* stat will not cause the CTS to flag, right? I did a preliminary check last night and made sure the wires were connected. But what I'll do, is pull the wires, and check the voltage with the ignition in the on position. If I'm getting the 5v, then I'll turn to the CTS itself. They're cheap. But I'll post back later tonight with the results. Thanks a bunch.

 

No, it shouldn't. The only negative effect of a 160* thermostat are that the car can sometimes take longer to warm up and reach closed loop. Technically though, the computer still thinks you have a 195* thermostat, of course.

 

Like these guys said your CTS is probably shot, or just has a crappy connection, I had this happen a couple of weeks ago. If your CTS pukes or your connector comes loose or becomes corroded it'll tell the ECM your at -40 deg. This will cause all kinds of problems, mainly just flooding the motor and running crappy. Fix this first.

The 165* won't throw a code, but it could keep you from going into closed loop. I don't have my laptop handy, can one of you DIY prom guys check the stock bin and see at what temp that CL is enabled.

 

First of all, lemme state that the Mastach.com or Mastach ALDL cable did NOT work with my Winaldl program for the 160 baud. I had it working with the 8192 connection on my last TPI car, but it didn't want to work on this car. I had to goto the Winaldl site and build my own cable. I also found out that my laptop wasn't giving a full 12 volts on the DTR that powers this cable. It was giving 8 volts, so I made sure to run a 12V connection to the car.

Swing!!!! I'm getting ALDL data (first time for this car).

After the car warmed up, the idle that swinging from 500 to 1800 RPM smoothed out. It also went into closed loop. I didn't get any codes at all, but I haven't tested the VSS by taking the car down the road, so that might flag an error code later. BLM was high (150 if my memory serves me right, I believe it's running lean), but I'm not too sure of the other items. I think the O2 looks right, but I thought TPS was suppose to be around 52 or something. Anyway, I logged data in Winaldl, so if anybody wants to look over it and let me know what may be wrong...PLEASE FEEL FREE!

Anyway, here's a pic:

 

Now, I don't have much experience with WinALDL, but I definitely think your right about it running lean, considering the BLM and INT values. Do you remember if the O2 sensor voltage switched constantly once it got in closed loop, like going from .2 to .8 constantly, or did it stay low? Only other weird thing I see is no data from the IAC, can't explain that one.

Pretty much everything else looks OK to me. RPMs are high for just sitting there idling, was it still surging? The TPS voltage is a little low, but it's nothing to worry about. From what I understand, when you first start the car, the computer takes the given TPS value as a reference point for being closed throttle. As long as it's close to .5 volts closed, and at or above 4.5 volts at WOT, your fine.

 

Any mods on this vehicle?

 

None that I'm aware of. It was previously wrecked and I don't think any engine work has been done. I am going to change the fuel filter this weekend. I've already cleaned the IAC. But I'll do a tuneup this weekend and see if that helps. If the fuel pump is a problem, I'm replacing it anyway because I'm upgrading the motor in a few months.

 

Last night, I replaced the fuel filter. I believe it had problems, but it didn't fix the surge at idle. The only thing I can think of, is the fuel pump. I've already got a 255lph fuel pump I was going to put on next tuesday because I'll be replacing the engine in the near future.

I read some posts, but has anybody put a 255 lph fuel pump on a tbi with success? I read where the tbi regulator will regulate the fuel pump properly, but I wanted to be sure.

Thanks.

 

anyone?

 

If that win ALDL shot is at idle, with your IAC steps at 0, and an idle at 1100 RPM, I would check for vacume leaks. You may also disconect the IAC, and manual set the idle to about 450-500 RPM, then plug the IAC back in, and see what happens. (( ***NOTE*** -- Do not set the static idle on the car, without first verifing there isn't a vacume leak at all, if there is a leak, and you try to mask it with a manual idle adjustment, you are doing yourself no good.))

 

But has anyone stuck a 255lph fuel pump in their tbi? I'm already swapping the rear end out for a 3.27 BW, aluminum driveshaft and have a 255lph to put in it. Just want to be sure I won't be tearing anything up with that 255lph on my tbi.

 

You should be fine, from what I understand. I have seen plenty of people swap in 255 lph fuel pumps in their TBIs, and it only seems that a couple of people have had problems over the years with the 255 overpowering the regulator and return line.

 

Cool. Thanks.

 

I had a smiliar problem last night. I started my car and the idle was all over the place. It would go up, and than slow down. Than when I put it in park after driving, it would go to 1200rpms or higher. With a big sucking noise. So, I check the vacum lines yesterday and they were fine. Than I went here to read up on the problems . I checked my EGR early this morning, and I checked my vacum lines again. Guess what??? A vacum line that came out of the TBI on the front pass. side was unhooked 10 inches away from a connector that led to EGR control dude (sorry for terminology). Anyway, I hooked it back up, she fired up no problem, No codes, and she ideled like a new f'n car. So, check your vacum lines thouroughly and make sure you don't miss any. If you cant follow it dont give up on it. Find a way to follow it all the way.

If you did follow all of them, and you are still having problems, I'd push the EGR diaphragm in and see if its sticking. My was a bit stuck, so I pushed it and now it works fine. I'll clean it later today, but for now it'll do the trick.

Vacum can cause you some serious headaches, and its defenetly a lot more trouble than anything else since its hard to pin point it.

Good luck and get under that hood and fix her up.

 

Okay, I've fixed the problem. I swapped out the old 2.73 rear-end for my borg-warner 3.27. While doing the swap, I changed my fuel pump to the 255 lph fuel pump.

Wala!

It's running like a top.

The old fuel pump was the problem!