1st Generation Specific (1979-1985) 1979-1985 Discussion including performance modifications and technical support sections

operating temps changing afr to extremely rich 13b

Old 06-16-19, 10:03 AM
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operating temps changing afr to extremely rich 13b

Hello everyone, I am having an issue with my car. My air fuel ratio is a 13.2-13.6 at idle and low speed driving until 190-200 degrees operating temp. When my engine temp hits around 190-200 degrees my wideband is showing a 10.2 ratio and my engine starts running like crap. The only thing I can think of is fuel boiling in the line or bowl. I have my exhaust wrapped and coated to reduce heat as well as a heat shield between the exhaust and carb with reflective tape on it. My first thought is fuel boil would lean the motor out not flood it, I am asking to get an idea basically where to look.
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Old 06-16-19, 02:27 PM
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and... I don't even know what type of carb you are running because I can't remember when you mentioned it last.

But yes, temps can play a role on AFR. My thought is to jet it leaner on the main primary and richen up the idle circuit. Is that possible on your carb? Whatever type of carb it happens to be...
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Old 06-16-19, 05:25 PM
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It is a Weber Ida 48, my idle jet is a 70 now and my air corrector jet is a 160. My main circuit jet is a 200 I know I would do better with a 140 or 150 ac jet but do not have any right now on hand.
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Old 06-16-19, 05:37 PM
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symptoms don't make sense to me, although i don't doubt that it is doing the problem you say it is. are you running a fuel pressure regulator? and what pump do you have?

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Old 06-16-19, 06:35 PM
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Are you certain your ignition system is solid? Poor/intermittent/no spark can definitely change AFRs. Have you put eyes on plugs? This could be early symptoms of igniter failure,early in failure process they are heat sensitive,don't work as well as failure progresses they shut down altogether. Letting car cool off and starting later,symptoms appear to be gone-til it warms up. Sounds similar to your complaint. Eventually the igniter will fail completely.
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Old 06-16-19, 07:06 PM
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I am running a Mallory 4150 fuel pump and fuel pressure regulator set at 3.5 psi of fuel pressure. I have never did a full tune up on the car maybe it is time to do a tune up and go from there.
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Old 06-16-19, 09:01 PM
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Good place to start.
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Old 06-21-19, 08:26 PM
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Is the carb getting enough cool air? As the intake charge warms up, it will tend to go rich.
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Old 06-23-19, 02:14 PM
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I think I figured it out. I took apart the carb and soaked the needle and seat and jets in carb cleaner for a few hours and blew out the carb, It still ran the same. Double checked the float level and everything was spot on. Then I disconnected the trailing coil pack and tried to turn it over and nothing. Then I hooked the trailing coil pack back up and disconnected the leading coil pack and it fired up and ran exactly how it was running before. So basically the motor is definitely just running on the trailing side coil pack. Just waiting on parts to come in.
Thanks guys, you saved my a#$ again!
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Old 06-23-19, 05:08 PM
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What did you determine not to be working on leading ignition side,what parts are you replacing.

There has to be @ 5 threads currently running with no start/driveability/performance problems that are ignition related. Members reading my responses must think that my fix for everything has to do with the ignition system,lol. As i'm posting to tell them to check ignition basics before looking elsewhere. Reading thru their threads looking for common denominator for all complaints listed,like this poster... my thoughts went immediately to an electronic heat soak igniter failure in early stages.
Waiting to see op respond about what he found and what he replaced to fix it.

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Old 06-23-19, 07:32 PM
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The leading ignitor isn't firing at all anymore making the problem obvious to me now based off just how the engine sounds alone that I have a ignition problem. I have been chasing fuel related issues because the carb I put on was fresh out of the box thinking it was that. I noticed on a hot summer day my engine temps get up pretty high when the car isn't on the highway. I think heat soak like you said is what killed my coilpack. I will be adding a heat extractor vent over the radiator and doing a full tune up. My engine temps get up to around 210 degrees when it is really hot outside in slower speed driving. Any other day I see around 185-190 degrees engine temp, but then again flordia heat is pretty brutal mid summer.
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Old 06-23-19, 08:26 PM
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Underhood heat didn't kill that igniter,that's a pattern failure all J109s show when they go bad."Electronic heat soak igniter failure", is what happens when the switching transistors in igniter become heat sensitive to heat generated by the igniter. Have seen this more times on 1st gens than i have fingers and toes,several here will chime in on their experiences. Curious as to presence or lack of thermal paste on back of igniter. So you know,you MUST apply thermal paste to backside of igniter,it acts as a thermocouple and allows igniter to shed its heat into distributor housing. Without thermal paste,lifespan of replacement igniter can be measured in weeks,days,hours.

1st product line i experienced this on was a 1983 Volvo Turbo,subsequently saw quite a few of them. Learned on a hunch that on tow ins that would run for 1/2 hr or so,i could revive the ignition module by spraying it down with brakleen to cool it and car would run for a few minutes til it quit again. Saved a lot of diag time. Couple times i was able to drive a car back to dealership with a can of brakleen,some cars wouldn't fail idling in the shop,had to drive them to duplicate problem. I had a spare distributor with me in case the module in the car was pronounced dead

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Old 06-25-19, 03:49 PM
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i hav new ones if u need
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