Hesitation Issues

[MadStang]

Hey guys, figure I might as well post up a thread with my Roush's issue. It's become really frustrating and I want to get this resolved asap.

I have a very good idea of what is causing the issue just wanted to see your guys' opinion on the matter.

What I'm experiencing is a slightly delayed startup, the car hiccups every once in awhile, no matter the engine temps, and the idle just all around is rough.

Between 2k and 1k on decel, the car begins to buck... On full throttle acceleration, after I shift and get back on the throttle it hesitates BIG time. Any time I go from no throttle to light throttle while the car is moving it has a small surge. when the clutch is in the rpms hang no matter what I do. And after the car has been run hard, say I'm go from one stop light at full throttle going through the gears and come to a stop at a red light, the car just dies. Lastly when the car has less than 1/4 of a tank of gas it runs even worse...

I do have an off-road h-pipe but I've had all of the above symptoms since before installing it. Only code I'm throwing is because of no cats and I don't have MIL's or a tune.

I run 91 octane in the car if that makes a difference. And I've already had 1 injector fail... I went to the junkyard as a quick fix to get it back up and running. From what I understand the injectors are not balanced since they're from different vehicles (same injector of course). So I'm rebuilding the 7 injectors I took out of the jy + the 1 bad one from the roush to hopefully resolve that issue.

Next thing is the fuel filter was changed by the previous owner when the car had 52,200 mi. the car is now at 67,300 mi.

Plugs are brand new. the COP's are stock.

I'm starting off by changing the fuel filter and getting the injectors squared away. then get a tune for 91 and no cats. then I'm going to throwing in a sump fuel tank with twin 310lph fuel pumps (going boosted), then upgrading the fuel rails as well to handle a lot of boost. I'm just really hoping this cures the problem. I don't have a gauge to check fuel pressure, but if the injectors, filter, and tune don't solve the problem, i will invest and check where I'm at on the rails as well as at the tank...

Any thoughts or opinions would be great, I just want my baby to run perfect again. thanks guys!

 

[AaRoN]

When did you last check the DTC's?

Definitely sounds like it may be a fuel pressure and/or volume issue.

 

[MadStang]

When did you last check the DTC's?

Definitely sounds like it may be a fuel pressure and/or volume issue.

Checked it two weeks ago. the only time I ever threw a code was when the injector stopped working on cylinder 5. I had a cylinder 5 misfire code, but nothing since.

yeah I'm hoping it's not a major issue and I can resolve it with filter and injectors. the car sat in storage unit for awhile before I bought it so I just hope it didn't gum up the entire fuel system.

 

[AaRoN]

Also, check for old, dry-rotted vacuum lines. Make sure everything is connected. If I were you (just as a double-check), I'd run the codes again. You never know. Sometimes the PCM won't illuminate the MIL until a component or system has failed more than a couple times.

 

[MadStang]

there were a couple of lines that looked like they were chewed on by a rodent but nothing that punctured it (plastic fittings). I'll go back through everything and make sure. Thanks!

 

[vermilion]

i emailed you about those injectors i have. im putting money on a vac leak as your issue. sounds like what i was experiencing. i replaced half of my hoses and been problemless thus far. this was about 2 weeks ago.

 

[MadStang]

i emailed you about those injectors i have. im putting money on a vac leak as your issue. sounds like what i was experiencing. i replaced half of my hoses and been problemless thus far. this was about 2 weeks ago.

Got it but I'm kind of weary about going to 21# injectors without a tune for it. I dunno if the PCM can adjust itself. besides that I don't know the condition of the injectors (nothing against you) and that $60 I would use for the 21#'ers I could just rebuild my 19's.

if someone can tell me that the PCM can adjust for the difference in 19 to 21 I'll do it...

if it's a vacuum leak that'd be great. That reminds me, when the A/C is on, it brings out the hesitation issues a LOT more.

also, could it be an exhaust leak? when the car is warm I hear a slight tick from the passenger side...

 

[mygreengt]

.... at least u have an idea of what your problem is

 

[MadStang]

.... at least u have an idea of what your problem is

lmao I'm doing what I can, coming up from the simplistic 3.8 pushrod motor to the complex modular is difficult. I can tear down and rebuild a pushrod motor no problem, these modulars are 100% foreign to me lol.

 

[Lee12609]

first suggestion is check for a leak between the MAF and throttle body, sounds like metered air leaking. if you find nothing in that area move to the manifold/plenum and look for leaks. the most common leak is going from the center of the plenum (back side towards firewall) going to the evap solenoid, or from the solenoid to the inner fender, but most of the time a small vacuum leak from a hose wont cause any noticeable problem. the decel bucking really makes it seem like metered air leaking, not like unmetered air entering. think of a turbo car that recirculates from the bypass valve (bov), when the ricerboys run an open blow off they have the same problem because the MAF reads that incomming air, then its released instead of injested with the fuel.

exhaust leak wont cause any of the above issues.

i thought in another thread you said one of your injectors failed due to being at like 98% duty cycle? i have 2 sets of #19 injectors you can have for shipping, both worked flawlessly, although i doubt it will fix your problem (one set off my friends boosted 95 cobra upgraded to #30s, other set off my boosted gt upgraded to #42)...

start by checking ANY connection from the MAF to throttle body, that includes the breather hose to the valve cover.

 

[MadStang]

Lee, you are a wealth of knowledge thank you. Gonna make it slightly easier to resolve the matter.

Little update here.

Changed the fuel filter, car started right away but still had that miss at idle. So I decided to just stand in front of the engine bay and just listen. What did I hear? A whistling noise. Found where it was coming from. It was an extra vacuum line on the plenum (plenum came from an Automatic Cougar). I plugged it up with a plastic plug and RTV. well there was gaps in the seal. Took it off put a rubber cap on it. The car ran quite a bit smoother but still, have a miss and hanging idle.

Also decided to change the oil and run some seafoam through it. Smoked like crazy for a bit, put some sea foam in the tank, hopefully that helps clean the injectors for the time being.

The car overall, didn't change much as far as the things I did. I did the cheaper things first also they needed to be done anyway. I didn't drive it very far so I can't give accurate description of the differences at this time but I will tomorrow since I have a couple long drives.

I'll see if I can find anymore vacuum leaks or anything. I'm going to get a tune for no cats ASAP so I can rule that out for anything.

Keep throwing suggestions at me guys, Lee, I'll take those injectors. And yes my injectors are at 95% duty cycle... my zip is 92026. Tell me what the shipping will be. Thanks man!

 

[Lee12609]

Why are your injectors at 95% duty cycle? People run #19 with 300whp and don't Max them.

I'm guessing around $10 to ship injectors, I just shipped a MAF to California for $8.

any way you can make a video of the idle? How long since you've done a tune up, what's done to the car, and how long has it done this?

 

[MadStang]

Why are your injectors at 95% duty cycle? People run #19 with 300whp and don't Max them.

I'm guessing around $10 to ship injectors, I just shipped a MAF to California for $8.

any way you can make a video of the idle? How long since you've done a tune up, what's done to the car, and how long has it done this?

My guess is that they are clogged. The car sat for an extended period of time before I bought it...

Send me your paypal.

I really wish I could make a video of what I'm experiencing. I'll try to explain what I'm experiencing. The car will idle just fine, it sits between about 750-900rpms. Every couple of seconds or so you can hear it either go lean or rich as it makes a small hiccup which is where the rougher idle is coming from. it's not wanting to die just idling, just comparatively to other 2v's I've been in, it idles a bit more rough.

It's been about 3 months since I did plugs. Oil & filter, and fuel filter were done yesterday along with seafoam. I'll have to check when the previous owner had the radiator maintained. Now that I think about it I've overlooked the air filter. it's a drop in k&n god only knows how long since that thing was cleaned...

It was doing it since I bought it but it was on slight at first and has progressively gotten worse.

 

[Lee12609]

I'll pm my paypal when I get off.

I would pick up some CRC brand MAF cleaner, hose it off real good, that filter has likely been over oiled in its life. This may take care of all your issues other than the deceleration stall, I'd personally build a iac restrictor plate to fix the hangine idle, clean the maf and go from there.

Do you have any means of watching live data, specifically maf counts/voltage, o2 switching and fuel trims?

 

[MadStang]

I'll pm my paypal when I get off.

I would pick up some CRC brand MAF cleaner, hose it off real good, that filter has likely been over oiled in its life. This may take care of all your issues other than the deceleration stall, I'd personally build a iac restrictor plate to fix the hangine idle, clean the maf and go from there.

Do you have any means of watching live data, specifically maf counts/voltage, o2 switching and fuel trims?

Okay I gotta little update. Drove long distance today, the car feels much stronger than before. there's a little bit of bucking between 2-1k Rpms on decel, the deceleration stall is gone. Idle hang is there and exponentially worse with A/C on. Would having no cats cause that? Other than that I resolved most of my issues. I think the long drive helped because I poured seafoam into the fuel tank, so it definitely cleaned out the injectors, I'm still getting horrible mileage though and at times i can smell a raw fuel smell...

Lee, I've cleaned the MAF previously, because I thought that was the issue. I haven't touched anything with the filter itself though, so I'll get to it tomorrow since I've got nothing else to do lol.

I bought a tuner on Friday and it should be here Tuesday/Wednesday. so I can catalog with that and my laptop.

 

[Lee12609]

what tuner did you get?

 

[MadStang]

SCT X-Cal 2

 

[vermilion]

have you cleaned your IAC valve? i noticed you said you had a hanging idle. on my own vehicle, i had no cats myself(sometimes raw smell and running rich). i swapped pipes for emissions testing and noticed my o2 sensors were baked. i cleaned them up and several emissions hosing and relieved some idle like poo issues. i also purchased an xcal 3 and had a local tuner can tune my car. that in itself helped. on the back of the hvac panel there are some vacuum lines that get aged quick. have a look at those. i had a jam nut loose.

 

[MadStang]

have you cleaned your IAC valve? i noticed you said you had a hanging idle. on my own vehicle, i had no cats myself(sometimes raw smell and running rich). i swapped pipes for emissions testing and noticed my o2 sensors were baked. i cleaned them up and several emissions hosing and relieved some idle like poo issues. i also purchased an xcal 3 and had a local tuner can tune my car. that in itself helped. on the back of the hvac panel there are some vacuum lines that get aged quick. have a look at those. i had a jam nut loose.

The IAC is newish along with the plenum. Hm, well I'll check the o2 sensors when I swap the catted h back in. I gotta pass smog next month so we'll see if that could be an issue. The vacuum lines are good. I inspected them all and I'm currently cleaning the air filter.

Lee, you were right about the air filter. chunks of shit, and just pure black dirt came out when I cleaned it. Got the K&N cleaner and oil kit and now am just waiting on the oil to set to reinstall.

I also ran the car hard this morning before cleaning the filter, came to a stop and it died... The idle is all over the place, it's really annoying.

 

[Lee12609]

madstang reset your base idle, dont search as i just did for the procedure because there is alot of misinformation regarding this procedure.

all you do is get the car to full temperature, turn off ALL electrical loads (lights, a/c, etc), disconnect the IACV connector, set idle to 700-800rpm by adjusting throttle stop stud on throttle body, turn car off, reconnect IACV, disconnect negative battery terminal and turn headlight knob on/off, reconnect battery, let idle for 10 minutes, go for a drive, normal driving for first 5 minutes, then go about your business as usual. this will ensure that the IACV isnt keeping the car idling, only assisting in the idle process.

the reason the car stalls when coming to a stop is because the throttle stop screw has likely worn enough to allow the throttle to close more than it should, so the IACV picks up all the idle duties. while cruising the IACV shuts, let off the throttle and the blade shuts, no air entering the engine, and the IACV cannot react quick enough. once your reset the throttle stop screw on the throttle body air continues to be drawn into the engine even when no throttle input. the IACV is designed to aid in idle speed when needed, not as the sole source of air.