1990 Cutlass 3.1 problems...

[broke_rodder]

Hey everyone, first post here. I been lurking here for the past couple weeks but haven't found anyone else with my particular problem.

 

I got "stuck" with my brother's 1990 Cutlass Supreme, 3.1L. It has an idle problem. I replaced the fuel pump and fuel filter because it was loud and it was getting 32 psi.

 

Now the problem is when cranking it will not start at all. Only when you press the gas down will it start. Once you let off the gas it immediately dies out again. I put a screw driver between the idle screw and throttle, it was about a 1/8" open. I reached in and cranked it and it fired right up. As soon as I pulled the screw driver out it died. The only way to keep it running is to keep the throttle open. It revs fine all the way up.

 

I checked the fuel pressure regulator, no gas and it holds vacuum.

The TPS ohms at 1.2 closed and about 4.8 open. TPS voltage is .7v closed and 5.2 open.

The IAC ohms at 50 on the first two pins and 50 ohms on the third and fourth pins. With the key on engine off I get voltage to only one wire on the IAC.

I cleaned out the EGR passage and the IAC.

 

When I unplug the TPS it will idle fine. Which lead me believe a bad TPS at first but after checking the ohms and voltage I'm a little confused.

 

 

Anyone have any ideas?

 

I'm stumped. Thanks in advance:o

[RobertISaar]

reset the ECM by pulling the underhood ECM fuse(it is on the oassenger-side strut tower) for 30 seconds or so, put it back in and then see if anything changed.

 

the voltages you're seeing are a bit off of expected... .7 is likely within spec for closed throttle(though .5-.6 is more common), but 5.2 fully open shouldn't be possible. most i see top around 4.6 volts. too high of a voltage will actually set a TPS DTC(anything above 4.8 volts at any time the key is on).

[broke_rodder]

Thanks for answering.

 

There is no ECM fuse. Just an empty slot that says 3.4/3.8. My motor is a 3.1.

 

I disconnected the battery for about 10 mins. During that time I put in a new TPS. Still the same.

I checked voltage again and I got .7v closed and 4.8v wide open. (I don't know where I got 5.2 from, I may have been thinking reference volts)

 

I'm stumped. It's weird because it runs as long the throttle is open at least about 1/8". Once you let off it dies.

 

Anyone else run into this.

 

 

[l67ss]

Kinda sounds like a fuel issue

Thanks for answering.

 

There is no ECM fuse. Just an empty slot that says 3.4/3.8. My motor is a 3.1.

 

I disconnected the battery for about 10 mins. During that time I put in a new TPS. Still the same.

I checked voltage again and I got .7v closed and 4.8v wide open. (I don't know where I got 5.2 from, I may have been thinking reference volts)

 

I'm stumped. It's weird because it runs as long the throttle is open at least about 1/8". Once you let off it dies.

 

Anyone else run into this.

 

 

[Garrett Powered]

I agree it could be a fuel issue. voltages at a sensor tells nothing about the battery voltage and operating voltage. voltage at the fuel pump changes at different running conditions if there is a problem the fuel will not stay the same pressure which it needs to be consistent. 13.9+ running at all times. having the battery voltage surging around while driving will lead to problems.

[broke_rodder]

!!SOLVED!!

 

 

Thanks for the answers but I figured it out. The IAC was bad. I knew it wasn't a fuel issue because I always had at least 42psi after I put in the new fuel pump and filter.

 

Anyway, even though the IAC was getting voltage and it even ohmed out good it still bothered me. I was getting fuel and spark and the injectors were pulsing. After reading up about IAC I came across an article that said the printle should be extended out 28mm from the flange of the IAC. I took mine back out and it was way past 28mm. After looking at it closely I noticed the little rod that extends out of the IAC was loose. It is threaded so I just screwed it back in to 28 mm. Reinstalled the IAC and she fired right up. I went ahead and bought a new IAC and now the car runs great. No problems.

 

 

 

Thanks for the input.