Stall when shifted to neutral

Mrit · 11-11-2012, 04:41 AM

Got a problem with the '86 302 FI

I got an odd one and search turned up nothing for me. Once the engine warms up or after driving a while and I shift to neutral the truck will usually stall. Sometimes it will drop really low 2-300rpm, then surge to 12-1400rpm and settle back to 800rpm. It is only when shifted to neutral, I could drive for a full tank and have no issues otherwise.

No codes or other issues that I know of. Fuel pressure is good, and runs awesome at all other times. No lack of power at any rpm, and will haul all the way to 5500.

Only thing I can think of is the IAC, but haven't tried messing with it yet.

Steve83 · 11-11-2012, 12:04 PM

Read this caption:

Mrit · 11-13-2012, 03:23 AM

Cool thanks

Bit more research done, and I believe the IAC is bad. It was relatively clean and moved free. Did a resistance check on it and was only 3 ohms, and in both directions. IIRC it was supposed to be a min of 7 ohms in only one direction due to a diode?

fdtdx18 · 11-13-2012, 05:35 PM

check your tps too. mine did that a while back and it was the tps.

Mrit · 01-13-2013, 07:01 PM

So I still have this problem, but it is even worse now. If the engine is warm or hot, it will stall in neutral every time. Even when cold, after it drops down from high idle it will run low and rough. Sometimes stalling.

In drive or reverse its still perfect, cold or hot. One shifted to neutral, it dies like I turned the key off.

I replaced the IAC and it made no difference. Voltage at IAC read 11.5, S/B about 10.5 from what I read, but would that cause it? Tested the TPS and it checks out good .9v at idle and 4.5 at full throttle. Im lost, I cant even check codes anymore since it wont stay running.

fdtdx18 · 01-13-2013, 07:45 PM

what trans do you have? ive read about people having issues with the PSOM (nuetral safety switch). mine personally had a weird idle and shifted really hard. turned out to be a bad connection

Mrit · 01-13-2013, 08:27 PM

Its the non-electronic AOD. I can try a jumper for the neutral switch tomorrow, way too cold right now

omp · 01-14-2013, 09:10 AM

Have u tried running it with iac disconnected?

KManBronco95 · 01-16-2013, 02:28 PM

I have a manual 95 w/ a 302 that is doing the same thing. Seems to be getting worse as it stalls after doing the erratic up and down 2 or 3 times.

Mrit · 01-19-2013, 07:25 PM

So, I was a bit slow working on it(frickin cold right now), but I think I got it figured out. I disconnected the IAC, and it was trying hard just to idle, maybe 4-500 rpm. In gear in was close to the same. Just happened to check the throttle stop screw and it was pretty loose. Im thinking that it may have slowly backed off over time and the IAC couldn't compensate for it anymore. Im putting a lock nut/loctite on it now. Its running great again!

95calibronco · 02-01-2013, 06:01 PM

had a similar problem with my brothers bronco, ill show him this thread to see if we can fix this problem also. thanks

11-11-2012, 04:41 AM	#1
Mrit Registered User Join Date: Aug 2003 Location: Snohomish, Wa Posts: 1,080 iTrader: (1) Bronco Info: 1986 Eddie Bauer	Stall when shifted to neutral Got a problem with the '86 302 FI I got an odd one and search turned up nothing for me. Once the engine warms up or after driving a while and I shift to neutral the truck will usually stall. Sometimes it will drop really low 2-300rpm, then surge to 12-1400rpm and settle back to 800rpm. It is only when shifted to neutral, I could drive for a full tank and have no issues otherwise. No codes or other issues that I know of. Fuel pressure is good, and runs awesome at all other times. No lack of power at any rpm, and will haul all the way to 5500. Only thing I can think of is the IAC, but haven't tried messing with it yet. __________________ '86 Eddie Bauer, '99 F350 Lariat, '75 Corvette Stingray. It's got safety tubes, but I ain't scared, Brakes are good, tires fair... "Hot rod Bronco" My truck http://www.supermotors.net/registry/3868

11-11-2012, 12:04 PM	#2
Steve83 Registered User Join Date: Jul 2003 Location: Memphis, TN Posts: 32,133 iTrader: (98) Bronco Info: '83 VIN & title on '93 frame/body w/'95 4.9L & EB paint	Read this caption: __________________ Walk softly & carry a BIG SIX ! ! ! . .

11-13-2012, 03:23 AM	#3
Mrit Registered User Join Date: Aug 2003 Location: Snohomish, Wa Posts: 1,080 iTrader: (1) Bronco Info: 1986 Eddie Bauer	Cool thanks Bit more research done, and I believe the IAC is bad. It was relatively clean and moved free. Did a resistance check on it and was only 3 ohms, and in both directions. IIRC it was supposed to be a min of 7 ohms in only one direction due to a diode? __________________ '86 Eddie Bauer, '99 F350 Lariat, '75 Corvette Stingray. It's got safety tubes, but I ain't scared, Brakes are good, tires fair... "Hot rod Bronco" My truck http://www.supermotors.net/registry/3868

01-13-2013, 07:01 PM	#5
Mrit Registered User Join Date: Aug 2003 Location: Snohomish, Wa Posts: 1,080 iTrader: (1) Bronco Info: 1986 Eddie Bauer	So I still have this problem, but it is even worse now. If the engine is warm or hot, it will stall in neutral every time. Even when cold, after it drops down from high idle it will run low and rough. Sometimes stalling. In drive or reverse its still perfect, cold or hot. One shifted to neutral, it dies like I turned the key off. I replaced the IAC and it made no difference. Voltage at IAC read 11.5, S/B about 10.5 from what I read, but would that cause it? Tested the TPS and it checks out good .9v at idle and 4.5 at full throttle. Im lost, I cant even check codes anymore since it wont stay running. __________________ '86 Eddie Bauer, '99 F350 Lariat, '75 Corvette Stingray. It's got safety tubes, but I ain't scared, Brakes are good, tires fair... "Hot rod Bronco" My truck http://www.supermotors.net/registry/3868

01-13-2013, 08:27 PM	#7
Mrit Registered User Join Date: Aug 2003 Location: Snohomish, Wa Posts: 1,080 iTrader: (1) Bronco Info: 1986 Eddie Bauer	Its the non-electronic AOD. I can try a jumper for the neutral switch tomorrow, way too cold right now __________________ '86 Eddie Bauer, '99 F350 Lariat, '75 Corvette Stingray. It's got safety tubes, but I ain't scared, Brakes are good, tires fair... "Hot rod Bronco" My truck http://www.supermotors.net/registry/3868

11-13-2012, 05:35 PM	#4
fdtdx18 Registered User Join Date: Feb 2012 Location: edgemoor delaware Posts: 189 iTrader: (0) Bronco Info: 1993 custom 302, flowmaster super 10, interco tsl's 33x12.5x15, rancho rs5000's, summit shortys	check your tps too. mine did that a while back and it was the tps.

01-13-2013, 07:45 PM	#6
fdtdx18 Registered User Join Date: Feb 2012 Location: edgemoor delaware Posts: 189 iTrader: (0) Bronco Info: 1993 custom 302, flowmaster super 10, interco tsl's 33x12.5x15, rancho rs5000's, summit shortys	what trans do you have? ive read about people having issues with the PSOM (nuetral safety switch). mine personally had a weird idle and shifted really hard. turned out to be a bad connection

01-14-2013, 09:10 AM	#8
omp Registered User Join Date: Oct 2010 Location: Denver Posts: 279 iTrader: (0) Bronco Info: 96 302, 5spd, 4" lift	Have u tried running it with iac disconnected?

01-16-2013, 02:28 PM	#9
KManBronco95 Registered User Join Date: Jan 2013 Location: Hanover, PA Posts: 2 iTrader: (0) Bronco Info: 1995 XLT - Modified 302 / Headers / Custom Intake & Exhaust --- 5 Speed Manual	I have a manual 95 w/ a 302 that is doing the same thing. Seems to be getting worse as it stalls after doing the erratic up and down 2 or 3 times.

01-19-2013, 07:25 PM	#10
Mrit Registered User Join Date: Aug 2003 Location: Snohomish, Wa Posts: 1,080 iTrader: (1) Bronco Info: 1986 Eddie Bauer	So, I was a bit slow working on it(frickin cold right now), but I think I got it figured out. I disconnected the IAC, and it was trying hard just to idle, maybe 4-500 rpm. In gear in was close to the same. Just happened to check the throttle stop screw and it was pretty loose. Im thinking that it may have slowly backed off over time and the IAC couldn't compensate for it anymore. Im putting a lock nut/loctite on it now. Its running great again! __________________ '86 Eddie Bauer, '99 F350 Lariat, '75 Corvette Stingray. It's got safety tubes, but I ain't scared, Brakes are good, tires fair... "Hot rod Bronco" My truck http://www.supermotors.net/registry/3868

02-01-2013, 06:01 PM	#11
95calibronco Registered User Join Date: Feb 2012 Posts: 17 iTrader: (0)	had a similar problem with my brothers bronco, ill show him this thread to see if we can fix this problem also. thanks

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