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stumble then stall - strange codes 1986

Old 01-10-2019, 07:05 PM
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rharker
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Default stumble then stall - strange codes 1986

I've been driving my car all week since I fixed (batee) my digital dash and have been noticing a slight stumble sometimes idling and decelerating. Today while at a drive through it happened again when I was at the window and stalled with the SES light on. I started it immediately and it ran for another minute and stalled. So I left it off until I finished my business and when I started it, it stalled again … and when I restarted it and it jumped to life with a loud pop out the exhaust but it stayed running until I got home.

Checked codes … normal 6-12s

So I started it and left it idling in the driveway for about 10 minutes and it stumbled and stalled again. Immediately checked codes and this time the SES light stayed on! No 12s. I turned the key off and removed the jumper and restarted OK. Let it idle another 20 minutes before it stumbled and stalled again and this time the codes were normal, 6-12s.

What am I looking at here? Do I have a bad or intermittent ECM?
Thanks

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Old 01-10-2019, 07:59 PM
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Hello again,

It "is" possible to have a "lazy" O2 sensor, some cars with higher mileage tend to be good candidates. I was taught to install a new one every 50 K miles.

I have also heard and read that heated and un-heated O2 sensors sometimes cool down too fast to go out of "Closed Loop" and idle in "Open Loop" which could be bad for the emissions of the car not to mention idle badly.
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Old 01-10-2019, 11:22 PM
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My Blk/Blk 1990 6sp coupe has a similar problem. Started giving a code 44 --> Code 44 is set when O2 sensor voltage remains low below .3 volts for 50 seconds or more and the system is operating in "closed loop". The car ran rough then would run OK. Put in the Chevron Techron, started running OK for about 3 months. (forums say the injectors are dirty)

Took it for a drive on Wednesday and it started stumbling and had no power, changed ECM and Chip (I have a few) same problem. Did it 2 more times same problem.

Got it home and checked fuel pressure 42 PSI vacuum a little low at 14 HG (indicates timing off?). I checked spark and it's OK doing a compression check left side is 159 160 158 160, will do other side (the hard side this weekend) Measured the fuel injectors and they all measured around 12.9 to 13.2 Ohms a little low S/B 16 Ohms.

I replaced the injectors about 15 years ago (brought the car new on Memorial day Weekend 1990). It had a similar problem only when it was hot after driving in close loop for a while, always ran great when cold.

I just cleaned the throttle body and replaced the idle control (third one) last year. Will check for vacuum leaks, and throttle position resister this weekend.

Suspect the injectors are bad again, but the resistance is not that low so any help would be appreciated.

Ray
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Old 01-10-2019, 11:41 PM
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Originally Posted by raya123_2000 View Post
I replaced the injectors about 15 years ago (brought the car new on Memorial day Weekend 1990). It had a similar problem only when it was hot after driving in close loop for a while, always ran great when cold.

I just cleaned the throttle body and replaced the idle control (third one) last year. Will check for vacuum leaks, and throttle position resister this weekend.

Suspect the injectors are bad again, but the resistance is not that low so any help would be appreciated.
Replaced with what? Bosch, Multec, etc?

Doesn't that seem a little extreme? What exactly prompted you to change the IAC? How was it discovered to be bad?

You sure it isn't ignition? Have you tested that module? Could it be the coil? If you think the injectors are bad and they are Multecs, give FIC a call and see what they can do for a reman set. I'd get reman if they are Multecs.
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Old 01-11-2019, 12:24 AM
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The injectors I installed were Ford 24LB injectors brought them on Ebay.

The Idle control valve would clog up with old gas and stop controlling the idle and the car would die at the light, it was pretty easy fix. I did try cleaning them but the new ones always worked.

I checked the ignition with a spark gap is like a spark plug, you just look at the spark color as the engine runs. But I may change the ignition as I have only change the cap and rotor once.

I'm looking at injector on ebay for $60.00 for 8. I didn't pay a lot for the injector in ti now and they lasted 15 years. Not sure I want to spend $400.00 for tested injectors.

Ray
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Old 01-11-2019, 12:39 AM
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Originally Posted by raya123_2000 View Post
The injectors I installed were Ford 24LB injectors brought them on Ebay.

The Idle control valve would clog up with old gas and stop controlling the idle and the car would die at the light, it was pretty easy fix. I did try cleaning them but the new ones always worked.

I checked the ignition with a spark gap is like a spark plug, you just look at the spark color as the engine runs. But I may change the ignition as I have only change the cap and rotor once.

I'm looking at injector on ebay for $60.00 for 8. I didn't pay a lot for the injector in ti now and they lasted 15 years. Not sure I want to spend $400.00 for tested injectors.

Ray
IF they are NOT the Multecs, then you are good. You can run any gas instead of being tied to a few that have 100% gas.

That DOES NOT sound right. How does it get that much gas? I haven't got that problem yet and. I'm missing a lot of things emissions related.

Could the module be problematic when warm? Probably won't hurt to change the cap and roror.

Cheap is always lacking. FIC has a reman set for about $200
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Old 01-11-2019, 12:52 AM
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Yea I live in Las Vegas, it gets hot here, I have to clean my radiator and condenser every 5 years. The radiator clogs with dirt could be the real reason.

My sister was in town, it was 115 and she wanted to go for a drive, the car never over heated but some of the plastic trim melted. I have had multiple ecm die in the heat.

Could be why the IAC's go bad.

The first time I lost the injector I was coming home from Laughlin Nevada, it was about 120 and all the casino's are on the Colorado river.
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Old 01-11-2019, 09:30 AM
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This morning it ran much worse. Started popped and stalled ... wouldn't restart for a while, finally did when I floored it. Engine died with SES set but only 6 - 12s codes. If it were my O2 sensor wouldn't it set a code? I'll put my fuel pressure gauge on it this afternoon and check fuel.

I don't understand why one time when it died the SES light stayed burning during the code check procedure.
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Old 01-11-2019, 09:54 AM
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Originally Posted by raya123_2000 View Post
Yea I live in Las Vegas, it gets hot here, I have to clean my radiator and condenser every 5 years. The radiator clogs with dirt could be the real reason.

My sister was in town, it was 115 and she wanted to go for a drive, the car never over heated but some of the plastic trim melted. I have had multiple ecm die in the heat.

Could be why the IAC's go bad.

The first time I lost the injector I was coming home from Laughlin Nevada, it was about 120 and all the casino's are on the Colorado river.
Does the motor go out or what? I'm curious about this IACs dying situation. If it happens everywhere it is hot, sure. If not, there may be an issue in your system.
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Old 01-11-2019, 11:11 AM
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I had similar problems when my MAF relay was dying. Try cleaning your MAF and replacing the relays? Helped my 89
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Old 01-11-2019, 11:30 AM
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Originally Posted by FelixP View Post
I had similar problems when my MAF relay was dying. Try cleaning your MAF and replacing the relays? Helped my 89
Thanks FelixP but I recently had this problem which was repaired by replacing the relays. It's the strange behavior of the SES that has me stumped.

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Old 01-11-2019, 06:58 PM
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Well I dropped in the spare ECM I had and it started no problem and has been running in my driveway for 1/2 Hr no stumbles, no stalling. This thing might have been part of the problem with the code 33 and 36 I had a while back which took 2 sets of relays to fix. The only thing it is doing now is idling ~650 and when the fan kicks on the idle drops for just a second. Wish me luck on the test drive

Well the test drive failed! Popping and stalling. Parked it on the side of a side street. Went to dinner and came back, it started and drove home OK.

What next????????????

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Old 01-12-2019, 03:11 PM
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90 Vet – I finished testing compression on the right side all were around 160. The spark gap test shows an Orange light – Oxygen. This is good. The injector resistance is 14 Ohms which is good 4 Ohms would be bad. Fuel pressure is 42 PSI which is good.

Next I checked the resistance of my spark plugs using a DMM. They all failed showing an open.

I will throw in a new set today and see.

URL for Spark test :

Ray
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Old 01-12-2019, 03:26 PM
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I brought the car new in May 1990 the dealer had a $10,000.00 off sale and the car was fully loaded only missing the engine upgrade which was $35,000.00.

I never had this problem when I lived in San Jose Ca. I lived there 11 Years with the car. I have lived in Las Vegas, since 2001 and have replaced the IAC 3 times. I do take it to the coast in the summer Pismo Beach area so you go from a hot condition to cool air.

The problem starts out intermittent: you come to a stop light and the car dies, but starts up and idles great, then it progresses to where it doesn’t idle anymore. I have cleaned it with carb cleaner and it works for a while.

I always clean out the Throttle body and it’s always has fuel residue, always thought this was normal.

Ray
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Old 01-12-2019, 04:04 PM
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Today it started up fine and has been running in the driveway 42PSI fuel pressure since 2PM.

Ran for 2 solid hours no stumbles not stalls --- not convinced

Last edited by rharker; 01-12-2019 at 06:09 PM.
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Old 01-12-2019, 09:41 PM
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90 Vet replaced spark plugs idles great but dies when you give it gas, I am going to replace the injectors.

Ray
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Old 01-13-2019, 08:48 PM
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Default this is what a 33 Yr old IAC looks like

My IAC was very carbonized:




Didn't bother cleaning it just replaced it. Test drove OK but it had previously been running at least in the driveway no troubles so I'm still not convinced.
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Old 01-13-2019, 09:29 PM
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Smart To replace it, that's not the problem right. When the IAC is bad it doesn't idle. Have you checked you cat on the the exhaust.

Ray
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Old 01-13-2019, 11:49 PM
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Originally Posted by rharker View Post
My IAC was very carbonized:




Didn't bother cleaning it just replaced it. Test drove OK but it had previously been running at least in the driveway no troubles so I'm still not convinced.
Did you clean the IAC passages by removing the TB and the IAC housing
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Old 01-14-2019, 12:07 PM
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Originally Posted by aklim View Post
Did you clean the IAC passages by removing the TB and the IAC housing
I cleaned out the passages with throttle body cleaner spray as best as I could but I didn't remove the TB.
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