Surging idle makes the car die after new engine combo

dashapht · 07-23-2001, 12:24 AM

I put new heads, cam, and intake on my car. MAF has a 24# tube in it for my 24# injectors, base idle is set to around 650 so it'll idle around 750 when the car is normal. TPS voltage is set to .987 Is this TPS setting too high? I know it's supposed to be between like .9 and 1v, but is this too close to 1v to work? The car will sometimes start fine and idle ok, but other times will surge like hell and die. It's worse with the a/c on. Also, when driving and i step on the clutch like to coast, it'll drop down sharply and die. Other times when I do that, it'll step down and idle normally. Again, usually worse when the a/c is on. I know there is a part from Ford that is supposed to go between the IAB and the TB to take care of this. Does anyone know the part number and/or what it's called? I followed the procedure in the corral.net tech section to set idle and still no dice. I'm going to try cleaning my IAB unit tomorrow and see how things go. Thanks for any help you offer.

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93 Coupe, long tubes, pro chamber, flowmasters, 3.73, auburn, alum driveshft, subframes, tri-ax, pulley, 73mm MAF, cold air, TFS TW heads, stage 1 cam, track heat intake, 1.6 roller rockers, 24 lb injectors, mac 70mm throttle body, edelbrock water pump, be cool radiator. best ET of 8.73 @ 79.2 in 1/8th before heads, cam, intake, rr's, and tb.

elmir50 · 07-23-2001, 03:26 AM

Have you checked your vacuum? Look for any vacuum leaks. I don't really think it is a vacuum leak because you mentioned the car only dies intermitantly, but give it a try anyways. Anyways check the ECU for any possible codes. Check the fuel pressure, drive around with a fuel pressure gauge and see what happens. Are you sure you have the proper sampling tube for the meter? All I can really do is give you suggestions on what to try. Good luck.

go4it · 07-23-2001, 09:01 AM

Try setting your idle speed up a little, 650 seems a little low.

------------------
93GT, S-trim (2.95 pulley), SFMU, Stage 2 TFS TW heads, Stage 2 Cobra intake, AFM powerpipe, PRO-M 75mm massair, 75mm throttle body, 42lb.inj. 1 5/8 headers, 2 1/2 h-pipe and exhaust, 2 chamber Flowmasters, 3.55 gears, Ultradyne cam, Elder.timing gears, Black Magic fan, FMS aluminum radiator, MSD6al/BTM, MSD coil, MSD shift light, subframe connectors, A-pillar gauges, Pro-5.0 shifter.

jimberg · 07-23-2001, 09:51 AM

Your car should idle at 650 rpm or what it says on your emissions sticker. If that 750 is from the tach, it's a good bet that it's correct. What you need to do is reset the computer and let your computer relearn to idle.

Here are the instructions: Resetting EEC-IV

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351W 89 Mustang GT Convertible

[This message has been edited by jimberg (edited 07-23-2001).]

2FastLX · 07-23-2001, 09:56 AM

I cleaned my IAB and have read since that cleaning the IAB isn't a good idea. The guy said that the IAB will never be the same through cleaning and the only real fix was to buy a new one.

Idle speed isn't going to make any difference on a surging problem (but 650 is kinda low). My car did this for a couple days after the new combo. How long have you had the car running since hooking the battery back up? Your computer will take a couple days to get used to the new combo. Don't touch the IAB just yet.

Go take the car for a long drive and try to keep a constant RPM for at least 10 minutes. And give it a couple days before changing anything.

------------------
Gunning for 12's!

Buy your parts here
ICQ# 42269241

07-23-2001, 12:24 AM	#1
dashapht Registered Member Join Date: Jan 2001 Location: nashville, tn Posts: 72	Surging idle makes the car die after new engine combo I put new heads, cam, and intake on my car. MAF has a 24# tube in it for my 24# injectors, base idle is set to around 650 so it'll idle around 750 when the car is normal. TPS voltage is set to .987 Is this TPS setting too high? I know it's supposed to be between like .9 and 1v, but is this too close to 1v to work? The car will sometimes start fine and idle ok, but other times will surge like hell and die. It's worse with the a/c on. Also, when driving and i step on the clutch like to coast, it'll drop down sharply and die. Other times when I do that, it'll step down and idle normally. Again, usually worse when the a/c is on. I know there is a part from Ford that is supposed to go between the IAB and the TB to take care of this. Does anyone know the part number and/or what it's called? I followed the procedure in the corral.net tech section to set idle and still no dice. I'm going to try cleaning my IAB unit tomorrow and see how things go. Thanks for any help you offer. ------------------ 93 Coupe, long tubes, pro chamber, flowmasters, 3.73, auburn, alum driveshft, subframes, tri-ax, pulley, 73mm MAF, cold air, TFS TW heads, stage 1 cam, track heat intake, 1.6 roller rockers, 24 lb injectors, mac 70mm throttle body, edelbrock water pump, be cool radiator. best ET of 8.73 @ 79.2 in 1/8th before heads, cam, intake, rr's, and tb.

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07-23-2001, 03:26 AM	#2
elmir50 Registered Member Join Date: Mar 1999 Location: Tsawwassen BC Canada Posts: 413	Have you checked your vacuum? Look for any vacuum leaks. I don't really think it is a vacuum leak because you mentioned the car only dies intermitantly, but give it a try anyways. Anyways check the ECU for any possible codes. Check the fuel pressure, drive around with a fuel pressure gauge and see what happens. Are you sure you have the proper sampling tube for the meter? All I can really do is give you suggestions on what to try. Good luck.

07-23-2001, 09:01 AM	#3
go4it Registered Member Join Date: Sep 1998 Location: Wise,Va. Posts: 248	Try setting your idle speed up a little, 650 seems a little low. ------------------ 93GT, S-trim (2.95 pulley), SFMU, Stage 2 TFS TW heads, Stage 2 Cobra intake, AFM powerpipe, PRO-M 75mm massair, 75mm throttle body, 42lb.inj. 1 5/8 headers, 2 1/2 h-pipe and exhaust, 2 chamber Flowmasters, 3.55 gears, Ultradyne cam, Elder.timing gears, Black Magic fan, FMS aluminum radiator, MSD6al/BTM, MSD coil, MSD shift light, subframe connectors, A-pillar gauges, Pro-5.0 shifter.

07-23-2001, 09:51 AM	#4
jimberg Registered Member Join Date: Oct 1998 Location: Rogers, MN Posts: 2,089	Your car should idle at 650 rpm or what it says on your emissions sticker. If that 750 is from the tach, it's a good bet that it's correct. What you need to do is reset the computer and let your computer relearn to idle. Here are the instructions: Resetting EEC-IV ------------------ 351W 89 Mustang GT Convertible [This message has been edited by jimberg (edited 07-23-2001).]

07-23-2001, 09:56 AM	#5
2FastLX The Photoshop Guru Join Date: Feb 2001 Location: Mecca, Indiana Posts: 1,419	I cleaned my IAB and have read since that cleaning the IAB isn't a good idea. The guy said that the IAB will never be the same through cleaning and the only real fix was to buy a new one. Idle speed isn't going to make any difference on a surging problem (but 650 is kinda low). My car did this for a couple days after the new combo. How long have you had the car running since hooking the battery back up? Your computer will take a couple days to get used to the new combo. Don't touch the IAB just yet. Go take the car for a long drive and try to keep a constant RPM for at least 10 minutes. And give it a couple days before changing anything. ------------------ Gunning for 12's! Buy your parts here ICQ# 42269241