So my alternator started going out on a 750 mile trip in my 90. I made it to my destination and swapped out the alt. On the test drive to verify the alternator was charging the engine started idling at 500-600 rpm. After disconnecting the battery for 5 minutes the car idled smooth again. (Its always idled kind of high 850-900)

I drive it home and park it. Well I tried to start it later on and it just didnt want to stay running. It would run if I tapped on the gas and forced it to idle.
I drive it around the block having to rev it to keep it running. It smells really rich and was slightly backfiring.. but it accelerated well. Like it is supposed to.

So my first assumption is TPS.
I checked it and I was getting .7v - 4.54v. No dead spots or anything. I am thinking maybe the density sensor? Fuel pressure checked out a week ago. What do you guys think?

 

Now it is idling between 350-700. It really does not want to run. But its holding on.

It accelerates just fine.

any input it great

 

And now its idling strong and smooth. ..(last 2 hours). hmm. Well im gonna hope that what the auto Service guy said about military mode at low voltage was accurate.

 

Well. Its not a military mode.

Its running very rich and its idling horribly and low. 450 average now.
Im assuming its idling low because the motor is getting too much fuel. Thats also the reason I think its running rich and runs fine when I'm accelerating.

I think it could be the FPR, IAC (not sure if this being bad could send a false signal making it dump fuel), TPS (the voltage was in range but could it still be bad?), or the speed density sensor.

really reallly would like some input so I can know if im on the right track and how to test the speed density, IAC and FPR

 

Did you watch it to see if it holds fuel pressure. OEM injectors are always suspect on the 90. Have you ohmed them writing down each result?

 

The injectors were recently replaced (2 months or so) and they all sit at 15.1ohms. I will do a pressure test tomorrow. How long should I wait for the pressure to go down?

 

Within an hour it shouldn't lose more than 10 psi. Did this issue occur prior to replacing injectors? Can you identify these injectors? What number and brand?

 

No. It just recently happened within the last couple days. Injectors are bosch3 yellow 22lb, im not sure exact number.

Its running really rich. Like it will backfire if I shift at 2800rpm.

Im just really confused with this issue. If I start the car with the a/c on it will run for 2 seconds at 500rpm then sputter out. So I am thinking IAC. Maybe the spring is old and is sticking. Idk.

if I start it without the a/c on then it will struggle for a bit but it will rev quickly if I press the gas. The ill switch the a/c on (diagnostic purposes only I dont need it on) it will sputter out.

Now if I drive it around the block a few times it will start idling a little higher but now smooth and like I said earlier it will bounce around(why I thought TPS)
but if I turn the a/c on now it will drop 50 or so rpm. In about a second it will jump back up to its original rpm (about 550-650)

Its really weird and now a constant issue. When I first posted this thread it did it for twenty minutes then was normal for a few hours. Then for a few hours was weird. Then it was normal for a few minutes and now its been like this for a day? So I think its permanent now. (Till I fix it)


Also if this helps it has no permanent check engine light but if I drive it for more than twenty minutes it will come on. I dont have a obd1 code reader... might help.

 

You could be a victim of the Bosch type III yellow 280-155-700 which is way lean at about 20 lbs vs 22 which is required. Once the ecm reaches closed loop the BLM makes up for it's undersize. Your memcal can be reprogrammed for 20 lbs which would help, or these unscrupulous salesmen can be made honest. I deal with this dishonestly almost daily that these salesman will not admit.

At first you think they run better, because the other were crap, but then you're stuck with an inferior product.

 

Pressure is good

I unplugged my IAC while the car was running and nothing happened. So I ordered a new one. Fingers crossed

 

It was the IAC. Problem solved