Engine Help With Never Ending Hessitation/bad Idle Problem I Cant Figure Out...

5point0stang88

Active Member
Sep 9, 2011
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Im onto something, I seemed to have fixed my horrendous surging idle by hooking up a working vacuum line from the ac tree to the egr. Idle works much greater now, no stalling or rpm dips.
Also noticed I need to back off the timing since the change.
 
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5point0stang88

Active Member
Sep 9, 2011
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Not to hijack but my idle is perfect now. Just always vacuum in egr. And yes computer showed egr opening not detected
 

tonydalrymple

Active Member
Nov 27, 2004
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Allot of good advise here..... Have you checked for vacuum leaks? Spraying engine starting fluid around the intake & listening for an rpm increase might lead you to something you might have missed IMHO.....

P.S. Link to pictures please..... I absolutely love the McLaren Mustangs!
 

jrichker

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Allot of good advise here..... Have you checked for vacuum leaks? Spraying engine starting fluid around the intake & listening for an rpm increase might lead you to something you might have missed IMHO.....
Use a squirt can of motor oil to squirt around the mating surfaces of the manifold & TB. The oil will be sucked into the leaking area and the engine will change speed. Avoid using flammable substitutes for the oil such as starting fluid, propane or throttle body cleaner. Fire is an excellent hair removal agent, and no eyebrows is not cool...
 

more4u2c

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May 2, 2014
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Keep in mind this idle/hesitation issue has been an issue since i bought the car before I did any of these repairs upgrades. the car was completely stock owned by an old lady.

here is what Ive done so far:

New Parts:
All intake sensors
All coolant sensors
Gt40 intake (explorer)
Gt40 fuel injectors (explorer)
Bbk H-pipe
Fuel pump
Fuel filter
Fuel pressure regulator
Coil (accel), cap&rotor, wires, plugs (accel)
Distributor (I did not buy this or install it. It was already on the car when I bought it, but it is brand new. not sure what brand and the car did sit for over 7 years)
3G Alt
All vacuum lines
O2 sensors
TPS

New to the list:
70mm MAF from 95 mustang
The vacuum line solenoid thingys mounted on the pass side shock tower
the vacuum valve thingys on the smog pump line.



Cleaned Parts:
EGR
ICV
TB

Checked for vacuum leaks via propane test = passed

no fault in computer cyl bal test pass

I have also changed out the IAC with another known working IAC and still not fixing the problem.

the only two things I haven't touched is the MAP/BAP sensor and the ignition control module. But I was told that the ICM doesn't go out slowly it's more of a just quits working type of thing so could it be the map/bap sensor would that cause idle and hessistation issues? Can I clean this sensor or is it a replace only type of thing? I'm also thinking maybe I have a vaccum leak in the havc system cuz that's the only place I can't test for a leak with the propane method so is there a way to bypass the entire havc vaccum system. To rule that at?
 

more4u2c

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May 2, 2014
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Have you read my posts? I've stated many times that I've checked the for codes there are none and have done the surging idle check list as well over and over again still not fixing the issue. It's not a surging idle it's a dipping idle it goes from 700 rpm down to 500 rpm and the hessitation is like a feeling that the car is starving for fuel or that the firing order is off but only happens after the car is in closed loop when in open loop the car runs fine! So it's gotta be some sort to sensor that makes the car flip out but doesn't flip out enough to throw codes. During the damn tests the car idles dips and hessistates but still won't throw a code so I'm totally confused to what's the problem.
 

jrichker

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Have you read my posts? I've stated many times that I've checked the for codes there are none and have done the surging idle check list as well over and over again still not fixing the issue. It's not a surging idle it's a dipping idle it goes from 700 rpm down to 500 rpm and the hessitation is like a feeling that the car is starving for fuel or that the firing order is off but only happens after the car is in closed loop when in open loop the car runs fine! So it's gotta be some sort to sensor that makes the car flip out but doesn't flip out enough to throw codes. During the damn tests the car idles dips and hessistates but still won't throw a code so I'm totally confused to what's the problem.
Looks like you are on your own from this point forward.
Let us know what you find...
 
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more4u2c

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May 2, 2014
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Clean the fuel injectors, replace the spark plugs.
As stated in my previous postings I have new sparkplugs and new fuel injectors.
Do people just read the posting headline then jump into the convo without reading the actual post around here or something?
 

Bullitt347

man bewbs please...
Mar 23, 2007
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Well, in my defense I don't consider Accel as a supplier of ignition parts. They do sell stuff that looks like ignition parts as such, but they are not really. As far as the fuel injectors, all I saw was GT-40 and skipped ahead. If you had said 24 lb/hr injectors I would have seen that.
Otherwise the real reason for your trouble is this quote "completely stock owned by an old lady."
 

more4u2c

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So a wealthy old lady who had it serviced religiously by ford and kept all repair work records since she bought it brand new off the lot who had a complete new motor and transmission put in back in 2003 and only has 24k on the new motor as of right now and because of the old lady was an old lady she didn't race the car just drove it around Sunday driver this is a limited production ASCMclaren we are talking about so it was taken care of a lot better than a run of the mill mustang. So I'm having a very hard time tryn to figure out how u think my problem with hessitation and idle has to be because it was owned by such a person? Please elaborate on why an old lady owner would cause the car to have these problems and how do I tell the car it's no longer owned by a old lady and to stop acting like it is?

Second like I've said before in my post this issue has been with me since day one when the car had crapy platinum autolites in it so I did change out the plugs and my local part store only had accel header plugs for my car that weren't platinum plugs cuz in my experience platinum plugs are good for longevity but suck for performance. I take it you don't care for the accel brand and that's cool you have the right to your own opinion but I'm looking for real constructive answers to my issue not a fan boy of a certain brand of sparkplug trolling on my post that the sparkplugs I have some how are creating the issue I had before the plugs were even installed especially since you have already figured out my issue and that was according to you because the car was owned by a old lady whom maintained the car better than anyone ive ever seen cuz that's using logic right?
 

more4u2c

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May 2, 2014
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Plus the stock gt40 injectors on the explorer is a 19# injector same as the stock mustang injectors just these have 4 holes vs the stock mustang has just one. This post is obviously over your skill level bro I appreciate you tryn to help but it's better to only comment on posts you know what your talking about
 

jsw81

5 Year Member
Mar 19, 2007
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Plus the stock gt40 injectors on the explorer is a 19# injector same as the stock mustang injectors just these have 4 holes vs the stock mustang has just one. This post is obviously over your skill level bro I appreciate you tryn to help but it's better to only comment on posts you know what your talking about
1314011768_talking_fried_egg_zps0d7d1a55.gif
 
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jrichker

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You must be a really great guy. In 1 month and 14 posts, you have managed to cut yourself off from all serious help.

jsw81 has a pretty serious ride with 91 Mustang GT: turbo 331, AFR 185, TKO 600, 468rwhp/520rwtq, so he deserves some polite attention.

Before you tell me to go away and don't post anymore to your thread, I will ask you a question:
What happens when you disconnect the IAC? Does the engine keep on spittering and sputtering or does it smooth out and settle down? You may have to press on the accelerator to keep it running, but what happens?