1990 Engine Idle Issue
#1
1990 Engine Idle Issue
From time to time the engine idles too low and on a rare occasion too high. Also, when idles too low, the battery gauge is extremely low and builds back up once the car eventually starts. To remedy the problem I have done the following:
- Cleaned the throttle body
- Replaced the alternator
- Reset the computer
Despite this, the problem still remains. Can anyone offer any advise on what the root problem is?
Thanks,
Ryan
- Cleaned the throttle body
- Replaced the alternator
- Reset the computer
Despite this, the problem still remains. Can anyone offer any advise on what the root problem is?
Thanks,
Ryan
#2
Team Owner
Why was the alternator replaced? Did you have it tested at a rebuild shop or Autozone? There is a huge difference. 2 places tested my alternators and starters and pronounced them OK. A rebuild shop took them apart and they were not.
Reset the computer. How and why?
#3
Define "cleaned the throttle body". Did you take the IAC and the IAC housing off and clean the passages? Did you reinstall with new gaskets?
Why was the alternator replaced? Did you have it tested at a rebuild shop or Autozone? There is a huge difference. 2 places tested my alternators and starters and pronounced them OK. A rebuild shop took them apart and they were not.
Reset the computer. How and why?
Why was the alternator replaced? Did you have it tested at a rebuild shop or Autozone? There is a huge difference. 2 places tested my alternators and starters and pronounced them OK. A rebuild shop took them apart and they were not.
Reset the computer. How and why?
I replaced the alternator because I thought it could be related to the idle issue. When I would start up the car, on occasion, the car would sputter and then die. When it did this I noticed the battery gauge was reading extremely low. I had the battery tested (which is only three months old) and it read it was 70%. At that point I recharged the batter up to 100% and then three days later tested its power and it read 80%. From this, I concluded that the alternator wasn't recharging the battery. So I replaced the alternator yesterday and I thought all was good, she felt good at first. But then, the issue came back.
As far as the computer reset, I turned my car into the shop and had it looked at for three weeks. All they could come up with was that scrub of the throttle body and reset of the computer. Luckily they didn't charge me because they didn't feel that they truly fixed the problem. Sadly they did not. From these details, what do you recommend?
Thanks,
Ryan
#4
Team Owner
Good questions. For the throttle body, I gave it a good scrubbing on the inside the butterfly covers, but it wasn't that dirty. That's all I did and I wasn't sure what else could be done in regards to the throttle body.
I replaced the alternator because I thought it could be related to the idle issue. When I would start up the car, on occasion, the car would sputter and then die. When it did this I noticed the battery gauge was reading extremely low. I had the battery tested (which is only three months old) and it read it was 70%. At that point I recharged the batter up to 100% and then three days later tested its power and it read 80%. From this, I concluded that the alternator wasn't recharging the battery. So I replaced the alternator yesterday and I thought all was good, she felt good at first. But then, the issue came back.
As far as the computer reset, I turned my car into the shop and had it looked at for three weeks. All they could come up with was that scrub of the throttle body and reset of the computer. Luckily they didn't charge me because they didn't feel that they truly fixed the problem. Sadly they did not. From these details, what do you recommend?
Thanks,
Ryan
I replaced the alternator because I thought it could be related to the idle issue. When I would start up the car, on occasion, the car would sputter and then die. When it did this I noticed the battery gauge was reading extremely low. I had the battery tested (which is only three months old) and it read it was 70%. At that point I recharged the batter up to 100% and then three days later tested its power and it read 80%. From this, I concluded that the alternator wasn't recharging the battery. So I replaced the alternator yesterday and I thought all was good, she felt good at first. But then, the issue came back.
As far as the computer reset, I turned my car into the shop and had it looked at for three weeks. All they could come up with was that scrub of the throttle body and reset of the computer. Luckily they didn't charge me because they didn't feel that they truly fixed the problem. Sadly they did not. From these details, what do you recommend?
Thanks,
Ryan
It could be that when it is dying, the alternator is not able to charge up the system hence the low reading? IDK. I would still have the rebuild shop test it before condemning it and throwing parts at a problem. When I change a battery, I test the alternator and vice versa.
You can't reset the computer and hope it fixes the world. It has a LIMITED learning curve in that it adjusts settings TO A POINT. You have reached a part of the ownership where you have to decide if you want to keep it and keep throwing parts at it or buy a scanner and some simple tools. For now, go to autozone after the cleaning and check what the IAC counts are when everything else but the motor is off and engine in closed loop. Before that, check timing
The following users liked this post:
eltoro1990 (06-16-2016)
#5
Team Owner
Once you have it all cleaned with new gaskets, I can tell you how to use the scanner to check for air leaks and set the minimum air rate. Make sure the timing is right first or we can be chasing our tails all day long. Ask me how I know
Last edited by aklim; 06-16-2016 at 08:32 PM.
#6
Thanks again,
Ryan
#7
Team Owner
If it is warmed up in closed loop with nothing else running but the motor and you hook up the scanner and see what the IAC counts are, it might give you a hint at what is wrong. Your target is 20-30 counts on the IAC. If it is too high, it means the ECM wants more air so it commands it to open up more than your target count. If it is lower, the ECM thinks it has too much air and wants to shut down the "controlled air leak". Higher count, turn the screw in. Lower count, turn the screw out. Rev and re read. If it at 0 and you have turned out the screw as much as you can, you need to chase an air leak in the hoses which is why I told you to change the gaskets.
#9
Team Owner