88 5.0 Rpm drop when going from gear to neutral! Help
A problem recently started to surface.
I was driving along and the rpm sit's steady at 1000 rpm and i am going to slow down from going 30mph and when i put it in neutral (5spd) and press the brake (not necessarily caused by the braking action), the rpm drops about 250 (down to 800 or so now), then jumps up about 250 more than normal (up to 1200 rpm now). It repeated that process about 3 times (up down up down up down) , then when i was coming to a complete stop it turned off dead. Then when I went to turn it on, it didnt respond to the crank immediately , i had to wait about 3 seconds then it would crank but go ERRR..... Errrr..... Errrrr... Errrr. for about 4 seconds and it would have a hard time turning over. But it wasnt like the cars you see holding the key to the ignition for 10 seconds , it seemed like it was out of juice or something.
Some side notes that I think you should know are, I have a new alternator, new belt, no a/c is on the belt, no smog pump on the belt, and i have an MSD ignition.
My car is not running hot (about 185 degrees on thermostat). I have an ADS superchip. But my car has been running fine for about 4 months now with it. I have 9mm FMS wires and the ignition module tested good.
You may be saying "starter starter starter". Well I replaced that yesterday. It seems to crank stronger when cold. But I havent driven it long enough (it turned off after driving earlier after 20 minutes of 105 degree texas weather) to see if it will, but it sitll does that rpm jumping crap.
in the morning it cranks perfect, no fuss at all. But if i drive around then stop and try to crank it, it cranks, but it has a little bit of a fuss.
I hope it's not compression related!
I have been told maybe fuel intank pump is going out? I have new fuel filter and clean air filter.
The first thing that came to mind when you said brakes-was vacuum leak. The brakes require vacuum to work properly. I would check for a leak. Check your fuel pressure and check your regulator. If these are starting to fail that could cause this problem. Have you also done a tune-up lately?
Yes , I changed the plugs (Autolite 24) and just added the 9mm wires not too long ago. Tomorrow I am going to add an extension so i can read the fuel pressure inside the vehicle and see if it goes down or fluctuates out of spec.
I am going to replace the fuel pressure regulator sunday probably because I will be busy till then with school and work. A mechanic friend of mine told me if the pressure goes down from in gear to idle that it would behave like that is a fuel pump going out.
I like working on my car , but this maintenance **** is annoying!
I just got done adding a/c to a mustang that was used for purely racing, that was a pain in the butt. I had to purchase all the brackets, lines, condenser, evap core and everything else you can imagine.
Feel free to ask any more questions, i paid very good attention to the situation.
it does it at idle, or just when you slow to an idle?
can you duplicate it when you want? i mean enough time to check spark? The pick-up coil could be on its way out... have you checked cap&rotor?
I tend to read too fast over things... did you mention new battery? compacted cells tend to start faster.. id get it load tested..
I have a brand new 130amp alternator and a brand new duralast gold 800 cold cranking amps and 1000 warm cranking amps battery. Both are less than 7 months old. The alternator is about 2 months old.
I havent been able to reproduce the car turning off because the past two days have been relatively cooler (about 90 degrees) but i still havent driven it for a long period of time.
the cap and rotor are new also and no signs of carbon build up.
After driving the car for about 10 minutes, I was coming upon a light so I put the clutch in and as soon as i did that the car just died- just shut off. I was able to crank it back on after about 2 seconds of cranking.
Then as I was driving home, it got worse. Every single time i pressed the clutch in regardless of speed, it would turn off. So everytime i wanted to stop i had to push the clutch in and have the gas pressed and slowly let it out.
AFter it shutting off about 4 times, I got home. Then I went to turn it on, it would ERR and ERR and Err for the the time that I held it but it would never turn over.
Im thinking now that it's not the fuel pump or fuel pressure regulator , but maybe the ignition module? When it was cold and i cranked it, it turned over beautifully, without a hiccup.
In about an hour I am going to have a friend come over to start the car while i put a screw driver in the 1st spark plug wire and see if there is spark. If there isnt, im assuming it's the ignition module. Do mustangs have a idle air control motor?
Whenever I tried the car after it's dead and wont crank, i turn the key up to the accessory on position, i can hear the fuel pump turn on.
Ugh... After a long night under the hood I got it, pretty much.
I tried another battery just for S's & Giggles. Didn't do anything. Tried another ignition module. Same effect as the other one.
So I took the ground wire and moved it to where the a/c compressor bracket bolts on. I also sanded the contact lightly to clean it up.
I noticed that when my car was on , I could induce a turn off if i turned the steering wheel all the way. I adjusted the throttle to on the side and it idles now at 1100 and doesnt turn off when the steering wheel is turned. IT runs great!
After cleaning up the wires and the throttle adjustment, it worked great. I will be reporting the status of it tomorrow. I will drive it hard too.
I was thinking a ground wire myself when I first read the post. Now I see that you have cleaned it and moved it. I think that may solve it for you.
Another thing to check is corrosion on the cable near the battery. I work in the battery business and I have seen many cables that look fine fromt he outside. But they are completely corroded on the inside. Corrosion can creap up the cables under the plastic.
I would also consider adding a ground strap between the block and the frame.
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-1998 Black Cobra, Kenne Bell 2.1L Supercharged
-2005 Mustang GT, Premium, 5spd, Redfire, Mac Catback
-2007 Roush Nitemare Stage 3 Supercharged #48 of 100
Bad news, It turned off on the way to work and on the way home. It was both after about 10 minutes of driving. I noticed it was whenever I pushed the clutch in to slow down. I wasnt braking while i did it. So it's weird, it couldnt be the vaccuum of the brakes .
Here are the things I have that are good or i've tried
1. Another ignition module
2. Retightening spark plugs / Push wires on all the way
3. I have a new battery / tried another battery
4. Alternator is less than 4 months old
5. Brand new rotor and distributor cap
6. New belt
7. New spark plugs
8. New starter (less than 3 days old)
9. Checked the fuel injector pressure regulator hose - it's good
I might be leaving something out.
So my main question is , is there a vaccuum from the clutch being pressed to not being pressed? Could this possible vaccuum be related to a hard start after it turns off?
One side note is. This all started happening after I took off the dash to put in a new evaporator core and heater core. Is there a vacuum that runs from the dash to the motor that I miight of missed? I know there is a black vaccuum hose that goes to the back of the intake
Another note is, At a light once it's warm, it jumps from 1000rpm to 1300 rpm and back down to 1000, what could cause that? TPS sensor? Im going to replace all the cables from starter to battery and ground to battery.
I replaced the TPS sensor and it seemed to of taken care of the turning off problem. But it still revs on its own from 1000 to 1300 and back to 1000 and repeats that, at idle.
I replaced the ground cable with a new one, maybe that's what stopped it from turning off.
88 LX 5.0 convertible. And whenever I am at a stop, and I turn the steering wheel all the way to one direction and hold it there, the RPM will drop from 1100 to about 600 rpm and back up to normal , then repeat itself again.
Also, when I am at a light, sometimes the rpm will jump from 1000 - 1100 rpm to around 1400 rpm , then back down to the 1050 range, then go back up.
Here are the things I have already done.
1. Changed fuel filter
2. Changed TPS sensor
3. Tried another battery / Had one tested
4. Tested alternator and is very good (less than 4 months old)
5. Bought new ground wires and Solenoid to starter wires (4 gauge both)
6. Changed the ignition module
7. Checked the vaccuum from the Fuel pressure regulator to intake (no leaks)
The problems are more noticeable once the car is warm (180 degrees).
Sometimes the car will turn off! Whenever I am driving , at a random speed, and I press the clutch in , it will drop the rpm to around idle (like normal) but it will continue to drop, and sometimes it drops so low that the car will turn off. It seems like it is catching itself and sometimes it doesn't!
Any ideas are welcome. Thanks for reading. I am knowledgable about the problem so dont think I havent examined the situation.
Did you check the fluid in the power steering pump? Does it make a strange whining noise while you're turning your steering wheel? WHen your steering fluid is low, you'll notice both of those things. Also, because the parasitc drag of the pump worsens while turning, it will make your rpms go down. Try taking off the serpentine belt and spinning the power steering pulley. If you can hear or feel the pulley drag, you might have a pump that's on its way out.
As for the idle searching, try checking all the vacuum hoses. I had the exact same problem and it was a hose that was leaking big time.
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89 GT Convertible 306, Port Polished GT40 Aluminum Heads,Self polished GT40 Upper and lower Intake, 30 lbs injectors, carter intank fuel pump, bosch piggyback inline fuel pump, Intercooled Procharger, Southside lower rear control arms, suspension technik lowering springs, tokico rear shocks, 4:11 gears, aluminum driveshaft, weld in subframe connectors
I recently took off the dash to put in a new evaporator core and heater core. I know there is a black vacuum that goes through the dash but that wasnt connected before because i had no a/c.
Please elaborate, i am desperate. Where was that hose?
My vacuum leak was either the boost guage that I have hooked up or the big ass vacuum line to the base of my lower intake. I'm not sure exactly what it's called. You said you took off your dash to change your heater core and a evaporator core? Is this when you started to run into this problem?
I think link will show you the vacuums lines for your car. Check them all out and see if all your lines are good to go.
88 5.0 Rpm drop when going from gear to neutral! Help 
