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This car is seriously BUCKING on me!

QUIKQUEST

By QUIKQUEST,
in Advanced Virtual Mechanic

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QUIKQUEST Newbie

QUIKQUEST

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Hey Guys,

I know you can get me through this one, after helping me with my other troubleshooting issues. I have a 19C, MSD ign, 2.5 DP, Manual Boost controller.

My problem is when i drive the car and stay out of boost mode she runs fantastic, the minute i hammer down on it, it bucks and shutters on me briefly then takes off. The weird thing is that if i play with the throttle about 60% from wide open through the boost..it drives hard!!

Otherwise it shutters and bucks on me. I checked my vac advance and thats working properly. My vac lines for the most part are correct. One thing though when i bypass my boost cotroller and run stock , it drives fine???????????????????????????????????????????????? :hangman:

 

Thanks for your help and HAPPY THANKSGIVING TO YOU ALL!!

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QUIKQUEST Newbie

QUIKQUEST

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I have an aftermarket summit fuel regulator and its reading 32 psi at idle. I just routed the vac lines so that i omit the boost controller and it actually does the same thing but very faintly. It seems like when its at a higher boost it does the same thing but magnified.

It could very well be the plugs, because the car does run a little rich under hard acceleration. Doesnt hurt to check , but it feels like something else...

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JustPaus_88TSi Newbie

JustPaus_88TSi

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Also, if you performed the "suck test" on the vacuum advance, do it again with a "mity-vac". Human lungs aren't powerful enough to provide a real test on the unit, unless the unit is very bad.

 

Which would make sense with what you said about it running fine with stock-ish boost levels.

 

 

The variance of problems(rips, tears) with the VA's internal diaphram is pretty large. It could be a pin hole sized issue that only becomes present at higher loads, or it could be a one inch tear that will be noticable with any boost pressure.

 

 

Also, bump up the baseline fuel pressure as was mentioned. :)

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QUIKQUEST Newbie

QUIKQUEST

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I did just do the "suck test" and it clicked. Didnt think about the hole variences in the diaphram. I dont have a vac tester/gauge on hand. For the cost of the tester it wouldnt hurt to replace the VA unit and eliminate that as a source for the problem,

 

Going outside shortly to plug up the line to VA and see if the problem persists and will get back to report the findings.

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Technology Newbie

Technology

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Yeah, I've ridden in a few quests with bad secondaries, does the same thing.

if you are in 3rd gear at 1000rpm and just stomp it does it buck really bad? What rpm does the bucking start? around 3000 rpm?

 

You can try a secondary from another conquest, if you know someone nearby that will let you try theirs, that's the only real way to find out if that's the problem, but pretty much every starquest I have ever worked on or played with has had injector problems. It should be the first mod anyone does their car.

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JustPaus_88TSi Newbie

JustPaus_88TSi

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I did just do the "suck test" and it clicked. Didnt think about the hole variences in the diaphram. I dont have a vac tester/gauge on hand. For the cost of the tester it wouldnt hurt to replace the VA unit and eliminate that as a source for the problem,

 

Going outside shortly to plug up the line to VA and see if the problem persists and will get back to report the findings.

 

 

Very true about the mity-vac cost. I picked one up when I flushed my brake fluid.

 

The "suck test" isn't for trying to hear the VA click. Once you apply suction to the vac hose/vac advance, plug the hose with your tongue and see if the suction stays. If it does stay, then the VA is likely good. If you lose suction, the internal diaphram is bad(hole, tear etc).

 

 

Clogged fuel filters(mostly the "conical" one) can exhibit the same issues, but instead of "bucking" once and then continuing to pull hard isn't one of them. If the fuel isn't "there", then it simply isn't there which means that it won't continue to pull strongly at all. You'll have to let off the throttle to stop the "studdering".

 

It's a good idea to check the filters though, as it doesn't take long at all if you use the access panel in the hatch. The conical filter is in the fuel supply hose that goes to the pump, the filter is right where the hose meets the pump. The other filter is in the tank, on the end of the pickup tube.

 

http://starquest.i-x.net/viewtopic.php?t=1031 (fuel tank, pump, filters etc..)

 

There's lots of pictures on that site, in this forum specifically:

http://starquest.i-x.net/viewforum.php?f=12

 

You will have to join the forum to see that section though, but it's free just like SQC.

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JustPaus_88TSi Newbie

JustPaus_88TSi

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Also, to spot a bad injector..

 

http://starquest.i-x.net/viewtopic.php?t=902

 

 

One way an injector goes bad is by getting clogged with deposits to where it doesn't flow what it should. The other way is when it starts leaking, which causes an overly rich condition, fouled plugs, contaminated oil, spun bearings etc..

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QUIKQUEST Newbie

QUIKQUEST

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Yeah, I've ridden in a few quests with bad secondaries, does the same thing.

if you are in 3rd gear at 1000rpm and just stomp it does it buck really bad? What rpm does the bucking start? around 3000 rpm?

 

You can try a secondary from another conquest, if you know someone nearby that will let you try theirs, that's the only real way to find out if that's the problem, but pretty much every starquest I have ever worked on or played with has had injector problems. It should be the first mod anyone does their car.

 

Yeah dude it starts the bucking right around 3000 rpm, also exhibits the same symptom like you described when in third gear. So just replace the prim+secondaries together. Thats probably the best thing to do and arent they sold in pairs anyway? Dont have any starquest buddies nearby besides "Fanta" A.K.A. Justin. But i haven talked to him in awhile. I see that you have links to Fuel injectors, is that a good resource to get them. Have you bought any from them and have you had any issues?? Thanks Man

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QUIKQUEST Newbie

QUIKQUEST

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Also, to spot a bad injector..

 

http://starquest.i-x.net/viewtopic.php?t=902

 

 

One way an injector goes bad is by getting clogged with deposits to where it doesn't flow what it should. The other way is when it starts leaking, which causes an overly rich condition, fouled plugs, contaminated oil, spun bearings etc..

 

Thanks for the links JP :thumbsup: I will check the filters tomorrow afternoon if it isnt raining out and start there and eliminate that issue. Then move to check to see if I have injector leakage.

From what Technology said it sounds really close to what is going on right now with the car. Wouldnt doubt it that its a combination of the two...fuel filters and injectors. I dont know if the previous owner replaced either of them. At least if i do that i will have some piece of mind and know whats in the car for sure

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QUIKQUEST Newbie

QUIKQUEST

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Please tell me you got an aftermarket boost gauge installed before you hooked up the manual boost controller man....

 

Wish i could tell you that i did but....

LOL!!! :lol: The urges got to me dude!! lost my old phone and some important numbers including yours. Needless to say the boost controller is not hooked up. How have you been? I'll pm you man and get you up on the latest :party0049:

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QUIKQUEST Newbie

QUIKQUEST

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I adjusted the fuel pressure to around 38 psi at idle. Now I tried to drive the car today and it was very cold this morning. I let the car warm up , but not that long. I tried to take off and the car fell on its face around 3000 RPM. I put my foot to the floor at this point and NOTHING!!

I could only get it back to my house barley tapping the gas pedal. It stumbles ever so slightly at idle, while it was idling i tried to move or play with some of the injector connectors to hear any audible changes in idle and there was none.

By this time the car was up to full temp and it then drove all the way thru the RPM range at any throttle with the brief bucking around 3000 or just before boost. What Gives man?????

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Shelby Newbie

Shelby

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what gives it a poor connection to the injs,, the engine runs on ONE inj at a time,, now what do you think happens if you unlug one inj clip ,you can ratioilize it all you want,, the injs must have good solid clean connections no if's and's or but about it

 

low end rpm it uses the pri inj,, 2500 and under load it uses the sec inj,, only when under full throddle and under boost does both injs come back on

at idle any time you hit the gas quickly the pri inj stops working and the sec kicks in,, no connection and the engine will stop runing and drop back to idle

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