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Part throttle cut out under boost


BlueCuda
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My car that I only have 20 miles on since I got it running is running well for the most part.  If I am pulling a hill where it is making boost but I am not applying the throttle hard it cuts in and out a little bit.  It runs great under heavy throttle or cruise but part throttle under boost it could be better.  

I do know the vacuum advance is in good shape, the original car I purchased happened to have two distributors in the trunk and one of them appeared to be brand new and I have checked the diaphragm on it and it works.  My only drives have been with the timing set at 5*, I have since set it to the correct 10* but I haven't driven it yet.  The 5* was the lucky stab that I forgot to double check.  

EGR, I plugged the passage in the intake when I had the intake off. I tapped a freeze plug into it on the engine side.  However the actual EGR valve is still there and has no vacuum or anything hooked up to it.  I do plan on making a block off plate for it I just haven't yet.  I am thinking this may be my problem?  

It has all new plugs, wires, cap, rotor, and fuel filter.  I found a receipt showing the injectors were flowed in 2019, they were flowed pretty close to the time of death of the original engine best I can tell.  

Anyways, thoughts?  

 

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You can always tap the EGR port to use a threaded plug for it. But it may be better to do that on the head itself so you aren't allowing hot exhaust gasses into the intake manifold (keeps it cooler) 

As for the part throttle concern what did you gap your spark plugs to? Should be around .26-.28

Mechanical or hydraulic lifter setup in your engine? Done a TPS reset?

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I don't recall what I gapped them at, it was whatever was printed on the underhood sticker.  

I have not done a TPS reset, a little scared to mess with it because it starts and idles perfect haha, I will add that to my list of things to try.

On the EGR I blocked it off right at the head but on the intake side.  I happened to have a freeze plug that press fit perfectly in there.  I'm going to make a block off plate this weekend and remove the old valve.  

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Turbo Cary mentioning the TPS made me think of something. The TPS might have bad spots in it--they wear out over time. If you have an analog multimeter, you can sweep test the TPS and see any bad spots. If you search here for "sweep test" you'll find the procedure. I think it's in the FSM too but it's been a while since I've looked.

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For the record it doesn't need to be an analog meter; a digital one will work fine. Just make sure the voltage across the TPS increases and decreases smoothly as you slowly open and close the throttle plate

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In the end your going to have to have a way to monitor your fuel pressure and air flow. I suggested in a prior post about how to  achieve it. If you don"t have a way to see how much fuel pressure and airflow (via a Wideband and a FPG) your producing at idle, midrange and on boost ,your just spinning your wheels and it will be difficult for anyone to be able to help you with any kind of  a viable or accurate answer.

Bill

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I have been doing this with an open stock downpipe with a stub of pipe off of it.  The car came with a 3" system that looks real nice but didn't fit worth a damn.  That is getting taken care of this weekend and I will have a wideband going soon, this weekend if the AEM one that came with the car works.  If not I am going to upgrade the wideband setup on my other car and move the LC2 over to the conquest.  

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If I were you I would put the Maf Translator and 3"Maf back on the car. This set up is the quickest and least expensive way to achieve control over your fuel/air  along with a Fuel pressure gauge, adjustable RRBCFPR and  a Wideband AFR  to have control over your engine and what it is doing as far as air and fuel . Been at it since 2002 and this is the best advice I can give you to keep a car as close to stock as possible and still have some control over how it runs. I have been the modified stock air can and the 1st gen mas route. Unless you decide to go MPI or a engine transplant (LS1 or the like) I feel the MAF Translator is a good way to go.

 

P.S. Don't let the 6.5 thousand posts fool you!! I had over 14,000 prior to the website crashing.

 

Bill

Edited by Caliber308
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Bill, I sold the Maf T haha a little late now.  If I can't get a handle on things I will megasquirt it.  I have an MS3X on my other car so I know the platform well and I like it.  I really just want this one to be right stock at the moment and its getting there.  

I got a ton done on the car yesterday, fixed the alternator, and got the exhaust system adjusted to fit right and mounted securely.  Its a nice mandrel bent 3" system with a Dynomax muffler.  Super quite in the car but is pretty loud on the outside.  I don't know what brand or if it was custom made but it sure didn't fit very good, we had to cut the turbo flange %95 off and twist it and reweld so it would all fit. Then put a 3" V band underneath, welded the slip joint up, and added some hangers to catch some stock mounting points.  So far no rattles.   I am not sure how the previous owner even got it hooked up?  The floor is beat up where it was hitting at one point.  

 

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Glad you got your exhaust in. Back in the mid 2000s myself and my buddy who owns a muffler shop in Montana built from scratch a 2 1/2" downpipe back exhaust.Then a couple of years later I installed D-2 coilovers adjusted all the way down. Always on the look out for speed bumps, deep dips and never park on dry grass.  😉

Bill

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