hunting idle

clint c · April 29th, 2007, 09:36 PM

hello, new to site. ive got a 90 gt with 5 speed. i just rrebult the motor with b cam, 1.7 rr, lightly port e7s, long tube flowtechs and off road h pipe. the problem im having is with idle. its hunting up and down and then dies. runs fine when im on the throttle, and pulls strong. any help would be greatly appreciated

2007calispecial · April 29th, 2007, 09:42 PM

check the plugs

clint c · April 29th, 2007, 09:57 PM

new plugs, around 600 mile. been in since i replaced motor. just pulled them and they have a red tint .

homebrewed · April 29th, 2007, 11:57 PM

IAC motor???

clint c · April 30th, 2007, 07:54 AM

i changed iac with ford unit, did not change anything. last night i was looking around the web and found a mass air adjuster by ist products. they say with the b cam and long tubes ive got the air fuel ratio out of range and the computer is running from one end to the other of the tables trying to correct the problem . they say with their unit u can adjust mass air meter. has anyone ever use this or have any opinions on it. check it out at mass-air.com

Red Hot 92 · May 1st, 2007, 08:37 PM

I was dealing with this, and just resolved it on Saturday with my 347. It is basically due to air starvation, the IAC can't compensate enough, the engine rpm fluctuates, as does the ouput (voltage) of the alternator. The idle hunts, and unless you throttle it some to preovide more air is can stall. Mine was intermittent but I think it had to do with how I would slow down or let the engine idle down. First you may want to try to increase the idle speed, maybe try 900 rmp or so. Reset thr TPS also to .98-.99 volts. If that dosent help you can try drilling a hole in the throttle blade, start with a 1/8". I did not want to do that. I used an idle air bypass plate that was used in a Ford TSB entitled engine hard cold starts, hesitation, stalls on startup. (TSB 91-25-7). The kit listed is Ford part #f2pz-9f939-a I went to the dealer they didn't have one and it was $50.00. I went to pick-n-pull seared all the fords and found 2 of them on older Tarus's. I installed it. It basically has 2 need an seet style orfices that are the air bleeds. I opened them both about 3 turns (adjusts with 2.5mm allen) and it works great! Note the larger u shaped operning of the bypass plate faced the connector end of the IAC. If the parts department is nice they will print the TSB for you. I will try and attach a picture.

fogged306 · May 1st, 2007, 09:59 PM

Check out this page too. someone posted this a few weeks back and I saved it because I had the same problem with my car before I took it apart.http://www.fordmuscle.com/archives/2...in/index.shtml

clint c · May 2nd, 2007, 08:42 AM

thanks for the info guys, fogged 306 that was some good info i didnt even think of. i tried that but still no luck. red hot 92 i will stop by the local dealer for the plate. until then i will just idle it up with tb screw. thanks again for the help guys.

nolife · May 2nd, 2007, 09:27 AM

I had a hunting problem in the past and it was caused by fuel leaking past the FPR through the vacuum line directly into the upper intake. Frustrating because I went through the entire list of common problems like the 10 pin connectors, the IAB, EGR, TPS, water temp sensor, MAF, vacuum leak, and others. Looking back, I guess this was a little more then just hunting at idle, it was hunting at anything below 1500 even with some throttle applied while driving. Oh well. Good luck!

clint c · May 3rd, 2007, 12:06 PM

nolife hw did you find fpr leakin was vac line wet. i am just tring to rule that out . my vac line is dry. is there some other way to check.

nolife · May 3rd, 2007, 01:10 PM

Well I doubt that an FPR leaking through the vacuum line is a common problem but it apparently does happen

I did not find it until I had fuel dripping out of the bottom of the throttle body where the plate linkage comes through. While looking for the source of this fuel that was where it should not be, I pulled the vacuum hose for the FPR and started the car and fuel came out of it. I also had a failed FPR that was pushing about 80PSI at idle that caused hunting as well. I would say these things are far down the list of things that would cause hunting.

clint c · May 3rd, 2007, 01:31 PM

i have a spare fpr i know is good, i will try swaping them out. i also need to get a fpr gage

BrianNV · May 3rd, 2007, 03:48 PM

http://www.latemodelrestoration.com/...0%201&comp=LRS

here is one for sale on 50Resto

April 29th, 2007, 09:36 PM	#1
clint c Newbie Join Date: Apr 2007 Posts: 23 iTrader: 0 reviews	hunting idle hello, new to site. ive got a 90 gt with 5 speed. i just rrebult the motor with b cam, 1.7 rr, lightly port e7s, long tube flowtechs and off road h pipe. the problem im having is with idle. its hunting up and down and then dies. runs fine when im on the throttle, and pulls strong. any help would be greatly appreciated

May 2nd, 2007, 09:27 AM	#9
nolife MM Fanatic 91GT, 88GT, 02GT Join Date: Dec 2006 Posts: 3,057 Blog Entries: 3 iTrader: 0 reviews	I had a hunting problem in the past and it was caused by fuel leaking past the FPR through the vacuum line directly into the upper intake. Frustrating because I went through the entire list of common problems like the 10 pin connectors, the IAB, EGR, TPS, water temp sensor, MAF, vacuum leak, and others. Looking back, I guess this was a little more then just hunting at idle, it was hunting at anything below 1500 even with some throttle applied while driving. Oh well. Good luck! __________________

May 3rd, 2007, 01:10 PM	#11
nolife MM Fanatic 91GT, 88GT, 02GT Join Date: Dec 2006 Posts: 3,057 Blog Entries: 3 iTrader: 0 reviews	Well I doubt that an FPR leaking through the vacuum line is a common problem but it apparently does happen I did not find it until I had fuel dripping out of the bottom of the throttle body where the plate linkage comes through. While looking for the source of this fuel that was where it should not be, I pulled the vacuum hose for the FPR and started the car and fuel came out of it. I also had a failed FPR that was pushing about 80PSI at idle that caused hunting as well. I would say these things are far down the list of things that would cause hunting. __________________

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April 29th, 2007, 09:57 PM	#3
clint c Newbie Join Date: Apr 2007 Posts: 23 iTrader: 0 reviews	new plugs, around 600 mile. been in since i replaced motor. just pulled them and they have a red tint .

April 30th, 2007, 07:54 AM	#5
clint c Newbie Join Date: Apr 2007 Posts: 23 iTrader: 0 reviews	i changed iac with ford unit, did not change anything. last night i was looking around the web and found a mass air adjuster by ist products. they say with the b cam and long tubes ive got the air fuel ratio out of range and the computer is running from one end to the other of the tables trying to correct the problem . they say with their unit u can adjust mass air meter. has anyone ever use this or have any opinions on it. check it out at mass-air.com

May 1st, 2007, 08:37 PM	#6
Red Hot 92 Newbie Join Date: Apr 2007 Posts: 6 iTrader: 0 reviews	I was dealing with this, and just resolved it on Saturday with my 347. It is basically due to air starvation, the IAC can't compensate enough, the engine rpm fluctuates, as does the ouput (voltage) of the alternator. The idle hunts, and unless you throttle it some to preovide more air is can stall. Mine was intermittent but I think it had to do with how I would slow down or let the engine idle down. First you may want to try to increase the idle speed, maybe try 900 rmp or so. Reset thr TPS also to .98-.99 volts. If that dosent help you can try drilling a hole in the throttle blade, start with a 1/8". I did not want to do that. I used an idle air bypass plate that was used in a Ford TSB entitled engine hard cold starts, hesitation, stalls on startup. (TSB 91-25-7). The kit listed is Ford part #f2pz-9f939-a I went to the dealer they didn't have one and it was $50.00. I went to pick-n-pull seared all the fords and found 2 of them on older Tarus's. I installed it. It basically has 2 need an seet style orfices that are the air bleeds. I opened them both about 3 turns (adjusts with 2.5mm allen) and it works great! Note the larger u shaped operning of the bypass plate faced the connector end of the IAC. If the parts department is nice they will print the TSB for you. I will try and attach a picture.

May 1st, 2007, 09:59 PM	#7
fogged306 MM Fanatic 89 GT Join Date: Apr 2007 Location: NY Posts: 4,875 iTrader: 2 reviews	Check out this page too. someone posted this a few weeks back and I saved it because I had the same problem with my car before I took it apart.http://www.fordmuscle.com/archives/2...in/index.shtml

May 2nd, 2007, 08:42 AM	#8
clint c Newbie Join Date: Apr 2007 Posts: 23 iTrader: 0 reviews	thanks for the info guys, fogged 306 that was some good info i didnt even think of. i tried that but still no luck. red hot 92 i will stop by the local dealer for the plate. until then i will just idle it up with tb screw. thanks again for the help guys.

May 3rd, 2007, 12:06 PM	#10
clint c Newbie Join Date: Apr 2007 Posts: 23 iTrader: 0 reviews	nolife hw did you find fpr leakin was vac line wet. i am just tring to rule that out . my vac line is dry. is there some other way to check.

May 3rd, 2007, 01:31 PM	#12
clint c Newbie Join Date: Apr 2007 Posts: 23 iTrader: 0 reviews	i have a spare fpr i know is good, i will try swaping them out. i also need to get a fpr gage

May 3rd, 2007, 03:48 PM	#13
BrianNV Newbie Join Date: Apr 2007 Posts: 22 iTrader: 0 reviews	http://www.latemodelrestoration.com/...0%201&comp=LRS here is one for sale on 50Resto

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