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post #1 of 25 (permalink) Old 06-05-2019, 11:43 AM Thread Starter
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rough idle in gear

hey guys so I sold my 95 tbird to buy a 97 tbird with 4.6 motor. car drives great and looks pretty good. only thing is when im stopped in gear with my foot on the brake the motor idles rough. In park i dont have this problem.
Also when im driving along and my rpms are in the 2 grand area and I come to a stop sign this occurs: I let my foot off the gas to begin braking but its almost like the car wants to keep going. The rpms dont drop as the should.
Yesterday I changed my plugs and wires with new motorcrafts. she is a little more peppy but those same 2 issues didnt go away.
I did some searching and only thing I came up with is maybe a bad IAC valve? my car isnt throwing a code either.
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post #2 of 25 (permalink) Old 06-05-2019, 12:29 PM
No, Mr. Lemmywinks, No!!!

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Both of those things could be a bad vacuum hose somewhere.

Check all the hoses, especially the hard to get to EGR ones.

Also, gently pull the spark plug boots, and see if there's fluid in the wells.

Vacuum leak+coolant is probably a bad intake manifold gasket.

I've had all these problems.

In my experience, a bad IAC won't idle at all, but you can keep it running with your foot on the gas.

Red '96 Cougar XR-7 240k mi. '02 4R70W, PST DS : '03 PI engine, 04 maf, 24lb injectors, 2.5" exhaust, '02 4r70w + Jmod, DirtyD0g TC + cooler + 3/8" lines, 255 walbro fp. Alpine system.
Black '96 Cougar XR-7 (Lazarus) 210k mi PI Intake, '02 4R70W, Jmod, PST DS, GrogTune, Konis, Mark LCA+Poly, racecougar Custom Engine Chain, and JL and racecougar Bracing.
Black '97 Tbird Limited Edition, '02 4R70W, 255 walbro, PST DS, PBR Brakes&SS lines, Toicko Blues & Springs, GrogTune.


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post #3 of 25 (permalink) Old 06-05-2019, 01:17 PM
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Sounds like your power brake booster. I had a neighbor that had that had a massive leak on his Bronco II brake booster, it would start up run for a couple seconds then die. He ended up selling it to a guy I worked with and the buyer figured the problem. It's just one of those things that get over looked.

Read ya later, Nick
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post #4 of 25 (permalink) Old 06-05-2019, 05:05 PM
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x3 sounds like a leak to me as well

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post #5 of 25 (permalink) Old 06-06-2019, 12:19 AM
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was having some rough idle almost stalling at times from cold start to hot did not matter.

was ready to replace the idle control valve.

turned out to be a bad Air temp sensor.. no check engine codes at all.

I Unplugged it and engine ran nicely.

replaced and running good again.
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post #6 of 25 (permalink) Old 06-06-2019, 11:46 AM Thread Starter
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ill check out these cpl areas this weekend and see what i get. Ill keep you guys updated thanks for the help
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post #7 of 25 (permalink) Old 09-23-2019, 07:56 AM Thread Starter
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So Ive changed out the IAC valve, cleaned my MAF, changed out all the bad vac lines. She still has a the occasional vibration when stopped in gear. Definitely noticeable performance difference with changing bad vac lines. She sounds beautiful when Im on the gas or in park. I tell ya this vibration thing is aggravating the hell out of me. I never did check the brake booster so ill probably do that next. If anyone has any helpful advice I appreciate it.
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post #8 of 25 (permalink) Old 09-23-2019, 08:29 AM
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In the meantime, just put the car in neutral while stopped.

Do you realize you were just passed by a NASCAR? I didn't think so.
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post #9 of 25 (permalink) Old 09-23-2019, 10:37 AM
No, Mr. Lemmywinks, No!!!

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If it's the original IAC, you might try a new one.

I'd grab one cheap from a JY; and if it changes the problem, it's worth buying a new motorcraft one.

Don't buy a cheap one, you'll be disappointed.

Red '96 Cougar XR-7 240k mi. '02 4R70W, PST DS : '03 PI engine, 04 maf, 24lb injectors, 2.5" exhaust, '02 4r70w + Jmod, DirtyD0g TC + cooler + 3/8" lines, 255 walbro fp. Alpine system.
Black '96 Cougar XR-7 (Lazarus) 210k mi PI Intake, '02 4R70W, Jmod, PST DS, GrogTune, Konis, Mark LCA+Poly, racecougar Custom Engine Chain, and JL and racecougar Bracing.
Black '97 Tbird Limited Edition, '02 4R70W, 255 walbro, PST DS, PBR Brakes&SS lines, Toicko Blues & Springs, GrogTune.


"War Is Peace. Freedom Is Slavery. Ignorance Is Strength." - George Orwell.
Truth Isn't Truth. - Rudy Giuliani, 2018 Award winner, “Most Outrageous Diversion” by MSNBC for this quote
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post #10 of 25 (permalink) Old 09-23-2019, 12:32 PM Thread Starter
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ya I already made that move but exactly. I just went to advanced auto and bought a BWD brand IAC valve. I didnt notice any change in performance untill I changed those hidden vac lines going to the canister behing pass headlight
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post #11 of 25 (permalink) Old 09-23-2019, 01:33 PM
No, Mr. Lemmywinks, No!!!

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There are 8 pieces of hose in that line; did you get them all?



There's a thread here somewhere; but TB, frame rail, evap cannister is 3 pieces, under pass fenderwell plastic, next to fuel filter, near gas tank.

Red '96 Cougar XR-7 240k mi. '02 4R70W, PST DS : '03 PI engine, 04 maf, 24lb injectors, 2.5" exhaust, '02 4r70w + Jmod, DirtyD0g TC + cooler + 3/8" lines, 255 walbro fp. Alpine system.
Black '96 Cougar XR-7 (Lazarus) 210k mi PI Intake, '02 4R70W, Jmod, PST DS, GrogTune, Konis, Mark LCA+Poly, racecougar Custom Engine Chain, and JL and racecougar Bracing.
Black '97 Tbird Limited Edition, '02 4R70W, 255 walbro, PST DS, PBR Brakes&SS lines, Toicko Blues & Springs, GrogTune.


"War Is Peace. Freedom Is Slavery. Ignorance Is Strength." - George Orwell.
Truth Isn't Truth. - Rudy Giuliani, 2018 Award winner, “Most Outrageous Diversion” by MSNBC for this quote
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post #12 of 25 (permalink) Old 09-23-2019, 01:37 PM
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You never said what the idle RPM is, but assuming it's low? Cleaning the throttle body will bring up a low idle a pinch. When it gets dirty it's restricted so there isn't as much air going around the throttle blade.

Al

97 T-Bird LX 4.6 - 80k miles
94 Supra TT Auto - street/strip car
04 CVPI- Brenda's car - 76k miles
Previous Fords:
95 T-Bird LX 4.6 - fully optioned, owned 15 years, 220k miles
96 Cougar XR-7 4.6- Brenda's car, owned 11 years, 187k miles
88 T-Bird 3.8 - first T-Bird, owned 5 years, 206k miles
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post #13 of 25 (permalink) Old 09-23-2019, 01:51 PM Thread Starter
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hmm maybe thats the rest of my issue. I didnt change any vac lines near gas tank or near fuel filter but did change the rest. As for idle RPMs, shell normally idle around 800 after warm up but when its idling sloppy more like 550-600ish
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post #14 of 25 (permalink) Old 09-23-2019, 02:00 PM
No, Mr. Lemmywinks, No!!!

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If you pull the inlet tube off, hold the throttle blade open and look at it.

If it's black, it needs to have the blade and throat area cleaned.

Spray it with carb cleaner, then use a rag to remove all the black crap in the throat area, and get the backside of the blade; Especially the edges.

Be careful not to bend it, lol.

The black crap where it closes will cause off idle problems, in that transition region; I guess if it's bad enough, it could make it not idle.

Don't indiscriminately spray a bunch of carb cleaner down in there; you'll wash the black crap in the intake into the cylinders as a glob, and that's not good.

This being a 97, you could do a PI intake swap, and thoroughly clean the throttle body; eventually the EGR passages muck up.

It's a lot of hassle to clean out the intake/TB, so having a reason to unbolt it makes it easier.
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Red '96 Cougar XR-7 240k mi. '02 4R70W, PST DS : '03 PI engine, 04 maf, 24lb injectors, 2.5" exhaust, '02 4r70w + Jmod, DirtyD0g TC + cooler + 3/8" lines, 255 walbro fp. Alpine system.
Black '96 Cougar XR-7 (Lazarus) 210k mi PI Intake, '02 4R70W, Jmod, PST DS, GrogTune, Konis, Mark LCA+Poly, racecougar Custom Engine Chain, and JL and racecougar Bracing.
Black '97 Tbird Limited Edition, '02 4R70W, 255 walbro, PST DS, PBR Brakes&SS lines, Toicko Blues & Springs, GrogTune.


"War Is Peace. Freedom Is Slavery. Ignorance Is Strength." - George Orwell.
Truth Isn't Truth. - Rudy Giuliani, 2018 Award winner, “Most Outrageous Diversion” by MSNBC for this quote
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post #15 of 25 (permalink) Old 09-23-2019, 02:56 PM Thread Starter
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The previous owner did update the intake to the aluminum crossover style. Im not sure if its a pi though. I can't see into the valley enough to tell whether its pi or not. there must be another way to determine this and I just don't know of. somebody else mentioned to me the TB elbow can build up junk that will cause this idle issue.
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post #16 of 25 (permalink) Old 09-23-2019, 04:11 PM
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There's a way to tell if the intake is a PI; the runner in front is opposite sides, IIRC.

The thing you don't want is a Dorman intake, lol.

Cleaning the TB blade up will probably help a bunch; I do that every few oil changes, so I think of it as maintenance.


This is a PI intake:


The stock one is different looking in front, iirc.

You also need a different coolant tube, and other parts; and you will want to order the second temperature sender drilled and tapped, unless you have a set of NPT taps.



The Butt dyno loves this mod, and it doesn't really require a tune.

Red '96 Cougar XR-7 240k mi. '02 4R70W, PST DS : '03 PI engine, 04 maf, 24lb injectors, 2.5" exhaust, '02 4r70w + Jmod, DirtyD0g TC + cooler + 3/8" lines, 255 walbro fp. Alpine system.
Black '96 Cougar XR-7 (Lazarus) 210k mi PI Intake, '02 4R70W, Jmod, PST DS, GrogTune, Konis, Mark LCA+Poly, racecougar Custom Engine Chain, and JL and racecougar Bracing.
Black '97 Tbird Limited Edition, '02 4R70W, 255 walbro, PST DS, PBR Brakes&SS lines, Toicko Blues & Springs, GrogTune.


"War Is Peace. Freedom Is Slavery. Ignorance Is Strength." - George Orwell.
Truth Isn't Truth. - Rudy Giuliani, 2018 Award winner, “Most Outrageous Diversion” by MSNBC for this quote
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post #17 of 25 (permalink) Old 09-24-2019, 06:31 AM Thread Starter
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Thanks for that information bud. Im gonna pop the hood and look at my intake so i can determine what I have.I got the rest of the vacuum lines I missed except the one near gas tank. I got a pick under it and gave a tug but didnt budge. I didnt want to break the hard plastic line that runs up side of gas tank. Also correct me if Im wrong but thats just a ventilation line and doesnt actually vacuum pulling threw it. The vac line appeared to be in decent shape also so i left it alone.
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post #18 of 25 (permalink) Old 09-24-2019, 09:18 AM
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I left the one near the tank alone also, too hard to get to. There is a vacuum pulling on all of those lines, to varying degrees based on the operation of the solenoids.

Al

97 T-Bird LX 4.6 - 80k miles
94 Supra TT Auto - street/strip car
04 CVPI- Brenda's car - 76k miles
Previous Fords:
95 T-Bird LX 4.6 - fully optioned, owned 15 years, 220k miles
96 Cougar XR-7 4.6- Brenda's car, owned 11 years, 187k miles
88 T-Bird 3.8 - first T-Bird, owned 5 years, 206k miles
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post #19 of 25 (permalink) Old 09-25-2019, 10:22 PM Thread Starter
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Unfortunately I do have the non PI intake. At least its been updated with aluminum crossover. After driving car a few days after changing all vac lines but that one near gas tank I noticed shes a little smoother on the acceleration. Vibration at an idle is still there but not as bad.
Im wondering if maybe the vapor canister or vapor purge solenoid are bad. Vibration goes right away once you give her gas so must be a vac leak somewhere. Does anyone know if theres a way to test those 2 components?
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post #20 of 25 (permalink) Old 09-26-2019, 05:24 AM
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Quote:
Originally Posted by jtavares0701 View Post
Does anyone know if there's a way to test those 2 components?
Check Engine light?

Joe

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post #21 of 25 (permalink) Old 09-26-2019, 06:02 AM Thread Starter
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No check engine light. It came on once a cpl months ago for a p0402 egr excessive flow on recirculated exhaust gases. I installed a new EVR and cleared the code and it didnt come back on. Other then that no check engine light.
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post #22 of 25 (permalink) Old 09-26-2019, 09:13 AM
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If there is anything remotely wrong with the EVAP solenoids, the CEL will illuminate, so no need to test them.

FYI, an EGR stuck open is a common cause of a rough idle. They are not supposed to be open at idle. Maybe the EGR controller or solenoid was bad all along, CEL be damned. The EGR doesn't just open on its own, so don't see how an EGR could cause excessive flow on its own.

The way to check an EGR is to apply a vacuum to It at idle. If the idle gets rough, then it's fine. In your case, if no change, then it was already open. You can actually hear the EGR diaphragm open and close when you apply a vacuum to it.

Al

97 T-Bird LX 4.6 - 80k miles
94 Supra TT Auto - street/strip car
04 CVPI- Brenda's car - 76k miles
Previous Fords:
95 T-Bird LX 4.6 - fully optioned, owned 15 years, 220k miles
96 Cougar XR-7 4.6- Brenda's car, owned 11 years, 187k miles
88 T-Bird 3.8 - first T-Bird, owned 5 years, 206k miles
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post #23 of 25 (permalink) Old 09-26-2019, 07:11 PM
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Quote:
Originally Posted by Grog6 View Post
If you pull the inlet tube off, hold the throttle blade open and look at it.

If it's black, it needs to have the blade and throat area cleaned.

Spray it with carb cleaner, then use a rag to remove all the black crap in the throat area, and get the backside of the blade; Especially the edges.

Be careful not to bend it, lol.

The black crap where it closes will cause off idle problems, in that transition region; I guess if it's bad enough, it could make it not idle.

Don't indiscriminately spray a bunch of carb cleaner down in there; you'll wash the black crap in the intake into the cylinders as a glob, and that's not good.

This being a 97, you could do a PI intake swap, and thoroughly clean the throttle body; eventually the EGR passages muck up.

It's a lot of hassle to clean out the intake/TB, so having a reason to unbolt it makes it easier.
I had an erratic idle situation, but it went away after I cleaned the TB. Thanks for the reminder.

Do you realize you were just passed by a NASCAR? I didn't think so.
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post #24 of 25 (permalink) Old 10-06-2019, 07:55 PM Thread Starter
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finally got time to play around some and cleaned the TB out as much as I could without unbolting anything. def noticed she idled a solid 50% better and had better acceleration.

soon when I can get the time I'm going to take the TB and elbow off and clean thoroughly. I also ordered a new egr valve because i found an original motorcraft egr with right PN and the vacuum line spout up top is offset instead of centered.
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post #25 of 25 (permalink) Old 10-06-2019, 09:19 PM
No, Mr. Lemmywinks, No!!!

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Any time you clean something and it works better, reset the computer and let it relearn everything; otherwise it take a while to go back to normal.

Pulling fuse 15 under the hood and trying to start it clears the computer in a second.

Before you do plugs next time, do a seafoam treatment; search, there are directions.

It will make your plugs dirty if it's never been done, or at least it did to mine.

Red '96 Cougar XR-7 240k mi. '02 4R70W, PST DS : '03 PI engine, 04 maf, 24lb injectors, 2.5" exhaust, '02 4r70w + Jmod, DirtyD0g TC + cooler + 3/8" lines, 255 walbro fp. Alpine system.
Black '96 Cougar XR-7 (Lazarus) 210k mi PI Intake, '02 4R70W, Jmod, PST DS, GrogTune, Konis, Mark LCA+Poly, racecougar Custom Engine Chain, and JL and racecougar Bracing.
Black '97 Tbird Limited Edition, '02 4R70W, 255 walbro, PST DS, PBR Brakes&SS lines, Toicko Blues & Springs, GrogTune.


"War Is Peace. Freedom Is Slavery. Ignorance Is Strength." - George Orwell.
Truth Isn't Truth. - Rudy Giuliani, 2018 Award winner, “Most Outrageous Diversion” by MSNBC for this quote
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