'03 GT Cold Hesitation

StangLou · Sep 17, 2003

Yeah man I plan to, just the gear install, chip, and custom program set me back a bit . Im hoping I can get up to the dyno in a couple of weeks and do a little tune session after my funds get a little better. I let my gas run down to like 1/4 of a tank then filled it up with premium after the chip install, but its still spark knocking a touch at really high rpm, so I think I need to lower my timing just a bit. Im going to burn this tank out then fill it up all the way with premium, and if that dont help then I will definately be going to get a full tune/dyno just to have some before and after #'s.

About your problem, Im with these guys above now, the only other thing that comes to mind would be the tps. I dont really think a throttle body would help a stock stang overcome this, it might even make it worse. This sounds dumb, but Im not sure what the heads on 99+'s are. Are they aluminum or did you just put some aftermarket heads on yours? Did it start this problem after you switched heads? If so then the new heads might be a bit starved for air with the stock intake and throttle body assembly. Most aftermarket throttle bodies use the stock tps though, so you still might have to get a new one of those. I think the ford motorsport 70mm tb comes with a new tps Im not sure

Thats all I can come up with for now lol, gotta get ready for work

03stang · Sep 17, 2003

[QUOTE='03Vert]I vote for the TPS adjustment, too -- and a trip to the dealer to have them sort it out. My '03 GT only has 1250 miles on it (only a month old ), but it's never even hinted at bogging, stone cold or otherwise, so yours isn't "normal."

BTW, I completely understand the desire to have throughly diagnosed the problem before you take it in (I'm *exactly* the same way) -- but you need to at least get a "baseline" diagnosis from the dealer to confirm that everything is/is not in spec, before the speculation as to possible causes drives ya batty. Just my $0.02.[/QUOTE]

I'm kind of curious to see if anyone has experienced this after removing the stock exhaust. I put my new exhaust system on at 1,500 miles. A few guys seem to have this problem, and they don't list any mods. Also, mine did not do this when it was new, but I'm not ready to blame the problem on the exhaust. Could be the assembly line T.P.S. is a piece of crap...

trinity_gt · Sep 17, 2003

I've written about this before here. I think it's "normal" only in that they all do it but it's not right. There's no way any 2000+ fuel injected OBD-II car should have a flat spot like these cars do when they're cold. I usually give mine 10 second of idling while the garage door closes and I fiddle with CDs before heading out and it's still doing it a minute later. The fact is, with this level of technology it just shouldn't happen.

Why does it do it? IMVHO it's definitely a calibration issue. Ford may have either opted intentionally to run the car lean when cold to prevent loading up the cats with unburnt HCs as an emission reduction technique and just went too far (or noticed the problem and said "Meh, people can live with that...it's not too bad.") or they simply screwed up the cold-air and cold-coolant corrections in the fuel trim, something I seriously doubt.

I think the reason therefore that Ford cannot "fix" it is because it's an engineered-in "feature". There's no fix because they intended it to be this way.

I can live with it: it just helps remind me not to get into the throttle too heavily when the engine is cold lest I batter the also oddly-designed loose-fitting pistons that slap themselves silly when cold...

03stang · Sep 17, 2003

StangLou said:
Yeah man I plan to, just the gear install, chip, and custom program set me back a bit . Im hoping I can get up to the dyno in a couple of weeks and do a little tune session after my funds get a little better. I let my gas run down to like 1/4 of a tank then filled it up with premium after the chip install, but its still spark knocking a touch at really high rpm, so I think I need to lower my timing just a bit. Im going to burn this tank out then fill it up all the way with premium, and if that dont help then I will definately be going to get a full tune/dyno just to have some before and after #'s.

About your problem, Im with these guys above now, the only other thing that comes to mind would be the tps. I dont really think a throttle body would help a stock stang overcome this, it might even make it worse. This sounds dumb, but Im not sure what the heads on 99+'s are. Are they aluminum or did you just put some aftermarket heads on yours? Did it start this problem after you switched heads? If so then the new heads might be a bit starved for air with the stock intake and throttle body assembly. Most aftermarket throttle bodies use the stock tps though, so you still might have to get a new one of those. I think the ford motorsport 70mm tb comes with a new tps Im not sure

Thats all I can come up with for now lol, gotta get ready for work

Cool Stang Lou. I hope you keep us posted when you get to doing the dyno run. I'm still tormented by trying to figure out if I want a blower or turbo. For now, I'll go w/ the pullies and 3.55 gears. I hemmed and hawed about that decision too. 3.73's or 3.55's? Well, I have the 3.55's and just have to put them in too. Man, the more I think of it, my to do list is growing...Problem is, living here near Canada, I'll have to put my Pony into the stable in little over a month. Last year it started to snow on like Nov. 2.

My car has the stock PI heads, which have been used from '99 on. I agree that as far as a new T.B. goes, it seems that the 70 mm unit won't help until you start force feeding the Pony.

From what I've found the FoMoCo 70 mm is the only one the includes a new T.P.S. If I don't come up with anything else, my might go that route, thanks to our Canuck Mustang friend. :canflag:

StangLou · Sep 17, 2003

Might be worth a shot to try the FMS throttle body. I like what Trinity is saying, but I dont like it at the same time. Its really frustrating that Ford would have put some many quirks into a high performance car and assume that people would understand and learn to live with it.

Not to highjack the thread, but Trinity, did you ever get your starting/hesitation problem worked out?

03stang · Sep 17, 2003

trinity_gt said:
I've written about this before here. I think it's "normal" only in that they all do it but it's not right. There's no way any 2000+ fuel injected OBD-II car should have a flat spot like these cars do when they're cold. I usually give mine 10 second of idling while the garage door closes and I fiddle with CDs before heading out and it's still doing it a minute later. The fact is, with this level of technology it just shouldn't happen.

Why does it do it? IMVHO it's definitely a calibration issue. Ford may have either opted intentionally to run the car lean when cold to prevent loading up the cats with unburnt HCs as an emission reduction technique and just went too far (or noticed the problem and said "Meh, people can live with that...it's not too bad.") or they simply screwed up the cold-air and cold-coolant corrections in the fuel trim, something I seriously doubt.

I think the reason therefore that Ford cannot "fix" it is because it's an engineered-in "feature". There's no fix because they intended it to be this way.

I can live with it: it just helps remind me not to get into the throttle too heavily when the engine is cold lest I batter the also oddly-designed loose-fitting pistons that slap themselves silly when cold...

Man, I'm getting some great feedback. I completely agree with your assertion that this should not be an issue with this level of technology. That's exactly why it's been driving me batty. Plus, the analytical/engineering mind that I have won't rest until I resolve this matter ...Thank you! :canflag:

03stang · Sep 17, 2003

SliverStang said:
When I first fire mine off it is kinda sluggish. If I rev it up a little it will kinda spit and spuder a little but its done that since day one. I figure it just like to heat up a little before you tear the back tires off. I had a 65 Mustang that did that, it would die if u didn't let it warm up so im used to it i guess.

I love that Gm QC logo. I'm passing along a copy of it to some of my friends who are working on the GM fuel cell project...

Winston · Sep 17, 2003

Cold enrichment

You guys may want to change the cold_enrichment_decay tables. I do not know if it works as I have not tried it altho I do have a little bit of cold off line stumble.

03stang · Sep 17, 2003

Winston said:
You guys may want to change the cold_enrichment_decay tables. I do not know if it works as I have not tried it altho I do have a little bit of cold off line stumble.

Do you know how this is done? Can it be done in the "backyard"?

Winston · Sep 17, 2003

A reflash or a chip is required. i will try it out with a reflash since the weather s getting cooler.

94BossGT · Aug 20, 2004

My new '03 Mach 1 did the same thing, with or without the new single catted H-Pipe and Magnaflow exhaust. I put up with like all of you until I found there is a newer computer program available from Ford.

I had the computer Re-Flashed from the dealer, seems to help some...There is a Technical Service Message on it.

Before, when starting, I noticed if I Just throttled up, push the throttle a bit when starting, it seems to clear up faster...

03redfiregt · Aug 20, 2004

ITs nto something they should be doing thats for sure , though i have'nt noticed it. But i take it easy with thecar most of the time especially when its cold. thats the worst thing you can do to a cold motor is lean on it. BUt to each his own. But regardless it should nto have that issue.

GTsleeper · Aug 20, 2004

You also have to take in a fact that its a V8 takes time to warm up, also the majority of mustangs do this. My brothers 85 does the same thing cold and his is carbourated, plus a freind of mine has an 02 Z28 and he has to wait a few minutes after starting to get on it. And having a new exhaust you will have back pressure, first cold start and you have to give her a little while to spit out the build up pressure. At least thats what I believe, could be wrong though.

Matt's03GT · Sep 7, 2004

Have the same problem on my 03 GT...only mods are x-pipe, KN, and shifter.

I fixed the problem by doing the following.

1.Get in Car
2.Stomp the pedal a few times (WITH THE CAR OFF!)
3.Start the car...no problems...

Don't ask me how or why this fixed it, but it did...

03stang · Sep 7, 2004

Cool. I'll give it a try tomorrow morning. Thanks for the tip. I'll let you know how I make out.

mrpositraction · Sep 7, 2004

I know many have said and backed it up, but my 01 GT does the same thing, a slight hesitation while accelerating right after start up.

As for stomping the gas, I know with the older computers in cars, pushing the gas without the ignition on was a way to reset it. I am alway scared of pushing the gas in fear of flooding. I know it shouldn't do anything with key off, buy I am scared.

GinoGT · Sep 7, 2004

Okay, I'm not going to bother reading this whole thread but from what I've scanned, this is what I see being the problem.

The car doesn't feel like hauling ass RIGHT when you start it up. You want to beat on a totally cold engine.

Now, let me pose this question: Why in the name of all things holy would you want to do something so absolutely retarded? Let the damn thing warm up for Pete's sake.

Marks5.0! · Sep 7, 2004

my old 00gt used to be like that if i didnt let it warm up before driving.

CManT1914 · Sep 7, 2004

I know mine's not exactly a new 4.6, but it does it too. When I start it up, if I try to instantly go somewhere, it jerks around when I'm driving. I just have to let it warm up for a minute, problem solved.

Matt's03GT · Sep 10, 2004

GinoGT said:
Okay, I'm not going to bother reading this whole thread but from what I've scanned, this is what I see being the problem.

The car doesn't feel like hauling ass RIGHT when you start it up. You want to beat on a totally cold engine.

Now, let me pose this question: Why in the name of all things holy would you want to do something so absolutely retarded? Let the damn thing warm up for Pete's sake.

Its not that at all...I let it run for a bit in the garage, back out with no problems - and then try to drive (nicely, not peeling out or anything) forward and it just bucks and stutters until you just slam on the gas to get it to go... I think it is a sticking TB -- but not sure...Hitting the gas before starting the car works for me...

'03 GT Cold Hesitation

StangLou

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trinity_gt

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