Hello all. This is my first post on this forum. I thank you in advance for the time and consideration you give to my issue. So, I just picked up a 1987 Ford Mustang LX 5.0, hatchback, 5 speed, all original, 100% stock, 27k miles. The thing looks like it was buried in an air tight time capsule for the last 30 years. Unbelievable condition. Here is my question - the car runs great, starts fine, but does have a tendency to "hunt" a little bit for idle. The issue is intermittent. Sometimes the car will idle at around 1700 RPM and other times it idles around 800 RPM. The other thing it does which is extremely annoying is . . . sometimes when you are shifting up, when you push in the clutch and take your foot off the gas, the RPM's will increase. I love the fox body mustang it was on my bucket list to own one, but I'm not sure if this is normal behavior for these cars or what. So far, I've replaced the IAC, adjusted the TPS to 0.93 (it shows 4.7 @ WOT), and OBD1 shows no issues, it's a clear scan. If you were in my shoes (I'm not a gearhead - I can wrench on my two stroke dirt bike but cars are out of my league), what would you do? Thank you very much for your time and consideration to my post. I can post photos if anyone is interested.
Engine 1987 LX 5.0 5 Speed - idle and . . .
- Thread starter nathan_erie
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- hanging rpm idle idle issues
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On the main tech page there is a technical/how to thread, in there you will find the surging idle checklist, go through the list step by step and it will resolve most all idle/stall issues. It shows you what to look for when checking for codes too. Thanks to jrichker it has solved many a mustang owners problems, even makes me look like a hero when talking to others about their stangs, and post some pics of the stang you have too, we are kinda picture whores around here, no pics, didn't happen!
And welcome to stangnet!
And welcome to stangnet!
Check the sweep on the TPS with an analog volt meter. You can also do it with a digital, but it's easier to see a dead spot with an analog meter.
Then check for vacuum leaks. These things are SUPER sensitive to vacuum leaks, so even a little bitty one can cause the surge. Many people never find them and just get tired of chasing their tail.
Then check for vacuum leaks. These things are SUPER sensitive to vacuum leaks, so even a little bitty one can cause the surge. Many people never find them and just get tired of chasing their tail.
Given the low mileage, I assume this car sits more than drives. How is it stored? Battery disconnected? Or on a trickle charger?
Often times cars that have the battery disconnected don't regain idle control for some time...over s period of starts. Of course if car gets stored and battery disconnected, it starts all over again.
Have you actually performed the idle reset procedure?
Often times cars that have the battery disconnected don't regain idle control for some time...over s period of starts. Of course if car gets stored and battery disconnected, it starts all over again.
Have you actually performed the idle reset procedure?
Drive the car at highway speeds for 15-20 minutes to give the computer a chance to relearn the adaptive settings again. If that doesn't fix it, do the next 2 steps in order that they are listed.
No code 11 (two flashes when the computer dumps the codes)? A perfectly functioning system will always get a code 11, it is the everything is OK code. The 11 code is computer passed its internal self test.
If you don't get an 11, you have computer or wiring problems.
Please check and repost.
You guys with idle/stall problems could save a lot of time chasing your tails if you would go through the Surging Idle Checklist. Over 50 different people contributed information to it. The first two posts have all the fixes, and steps through the how to find and fix your idle problems without spending a lot of time and money. It includes how to dump the computer codes quickly and simply as one of the first steps. I continue to update it as more people post fixes or ask questions. You can post questions to that sticky and have your name and idle problem recognized. The guys with original problems and fixes get their posts added to the main fix.
It's free, I don't get anything for the use of it except knowing I helped a fellow Mustang enthusiast with his car. At last check, it had more than 250,000 hits, which indicates it does help fix idle problems quickly and inexpensively.
No code 11 (two flashes when the computer dumps the codes)? A perfectly functioning system will always get a code 11, it is the everything is OK code. The 11 code is computer passed its internal self test.
If you don't get an 11, you have computer or wiring problems.
Please check and repost.
You guys with idle/stall problems could save a lot of time chasing your tails if you would go through the Surging Idle Checklist. Over 50 different people contributed information to it. The first two posts have all the fixes, and steps through the how to find and fix your idle problems without spending a lot of time and money. It includes how to dump the computer codes quickly and simply as one of the first steps. I continue to update it as more people post fixes or ask questions. You can post questions to that sticky and have your name and idle problem recognized. The guys with original problems and fixes get their posts added to the main fix.
It's free, I don't get anything for the use of it except knowing I helped a fellow Mustang enthusiast with his car. At last check, it had more than 250,000 hits, which indicates it does help fix idle problems quickly and inexpensively.
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