Pulsing throttle issue - turbo mopar content

I've been resurrecting an '87 Shelby Charger and have run into a situation I'm not sure how to attack. The PO has hacked/deleted elements of the vacuum and wiring harness which makes diagnosis, um "interesting." I have a wiring diagram arriving Sat so hopefully that will help with wire identification but there is a throttle issue where I am confused. BTW, this is my first drive down "turbo" lane so I have no clue how things should be plumbed, etc.

First off, the details: 1987 Shelby Charger GLHS clone 2.5 block with 2.2 GLHS head, intake, turbo, etc. AC compressor removed Stock intercooler, aftermarket BOV POS looking grainger valve Computer looks to be modified but not sure what was done No current extra gauging (that works). EGT sensor and gauge but needs to be reconnected. New gas tank, new Walbro 255 fuel pump and new fuel filter installed

The issue: The car starts and runs and idles fine. The problem is when I press on the throttle the rpm's will come up and then with no backing off the throttle the rpms will drop for a few seconds and then jump back up for a second, drop, jump up, drop, repeat. All of this without taking my foot off the gas. I don't have it floored, just depressed to bring the rpm's up.

My thoughts: Vacuum leak Wastegate not actuating properly Fuel pressure issue

I have a boost gauge and a AFM gauge I plan to add. I would like to add a fuel pressure gauge but am unsure at what pressure this system runs. I'm guessing is it over the 15 psi of the fuel gauge I have laying around the shop.

The questions: Any immediate thoughts as to what this might be?

If not, what to attack first? I've pulled the vacuum lines off the car in prep of pulling the fuel pressure regulator. Can this be done without removing the intake/fuel rail?

Should I add a fuel pressure gauge or will the AFM gauge be a better "read"?

Can I confirm that the wastegate is actuating properly?

The manual will help immensely with the wiring portion but I'm concerned that it won't help diagnose the other issue.

Thanks for any help..

EFI? Should be around 35-45psi.

I too would suspect an unwanted rush of air into the engine to cause the hunt in RPM's. Got a vacuum gauge? Have you checked your hose couplings? If they are OK, I would back probe the TPS signal at the sensor and ECU. See if you have a fluctuating signal. If that were to check out, I would look at an IAC that is gummed up or just not working.

Wastegate can be checked for free movement and then apply some pressure to it to test the diaphragm.

Hey... We might be related... I have a entire shop full of Turbo Mopar stuff (wana buy a GLHS) and a whole backyard full of Hobie stuff... Winds are howling today.. Need to get out of work early for sure... 20mph gusting to 30mph.. and the 18 hasn't been on the water in some time... Ya gona make nationals... I am going to try.. but I have a seasonal business.. that well.. keeps bread on the table and that would be a rough week to miss...

oh.. yeah.. The Charger.. have you driven the car? Or does it just do that sitting and makes you afraid to drive it? It is possible you are hitting a launch control if someone has popped their own tune in there... Which is VERY possible given the 2.5 engine.. in fact it needs either a custom tune and or larger injectors or both... For years I would run 2.5 engines on 'stock' GLHS calibrations with the +20 injectors..

So drive the car... and see if it still does it... You may be just hitting a feature someone programmed in for drag racing.. When the speed distance sensor reads above a couple mph... the engine should rev normally...

Have you check the Codes? I assume you don't have a steady Check engine light... It may be blinking 'normally' if someone has programmed a launch control...

http://minimopar.knizefamily.net/fault/index.html

And your Fuel pressure running at idle should be 55psi with the regulator unplugged... Drops to upper 40's lower 50's under vacuum typically...

Oh.. and as far as hacking Vacuum systems... You need boost control.. A line to the MAP sensor, Fuel Pressure reg, your boost guage, BOV.. That is really about it...

The plastic lines that mopar had under the hood were going to be so brittle at this point due to underhoood heat.. Don't sweat 'custom' vac stuff to much... and unless you live in a emissions state.. The factory diagrams are more complicated than the car needs to run properly.

And set up properly.. Grianger Valves work awesome... Although.. If you already have a custom tune... It makes more sense to fine tune boost using computer control

http://www.gusmahon.org/index_main.htm

http://www.thedodgegarage.com/

ronholm wrote: Hey... We might be related... I have a entire shop full of Turbo Mopar stuff (wana buy a GLHS) and a whole backyard full of Hobie stuff... Winds are howling today.. Need to get out of work early for sure... 20mph gusting to 30mph.. and the 18 hasn't been on the water in some time... Ya gona make nationals... I am going to try.. but I have a seasonal business.. that well.. keeps bread on the table and that would be a rough week to miss... oh.. yeah.. The Charger.. have you driven the car? Or does it just do that sitting and makes you afraid to drive it? It is possible you are hitting a launch control if someone has popped their own tune in there... Which is VERY possible given the 2.5 engine.. in fact it needs either a custom tune and or larger injectors or both... For years I would run 2.5 engines on 'stock' GLHS calibrations with the +20 injectors.. So drive the car... and see if it still does it... You may be just hitting a feature someone programmed in for drag racing.. When the speed distance sensor reads above a couple mph... the engine should rev normally... Have you check the Codes? I assume you don't have a steady Check engine light... It may be blinking 'normally' if someone has programmed a launch control... http://minimopar.knizefamily.net/fault/index.html And your Fuel pressure running at idle should be 55psi with the regulator unplugged... Drops to upper 40's lower 50's under vacuum typically...

Good to find another cat/car nut. 20 to 30 sounds a little too steep for me. I tend to like under 20 if possible. I used to race an 18 Magnum. Now I've got an H16, a N5.5, a N18sq and a H3.5. Never been to nationals but used to race the FL circuit fairly heavy. Now I'm just happy when I can get the boat out.

This is my first foray into the turbo mopar realm so I'm trying to come up to speed quickly (one week<). I have not driven the car. It is on jack stands waiting for the new tires to get mounted (today, hopefully). When it is on the ground I'll try and drive it to see if there is a launch type setup. I do not have a code reader so no luck there.

Concerning vacuum, where is the MAP sensor located so I can track it down? Also, do I need ANY vacuum connections to the bank of 4 vacuum solenoids on the passenger inner fender well?

No need for a code reader... Something like an OTC 4000e or whatever is very handy...

but just follow the instructions on the mini mopar site... just flip the ignition on and off a couple times then leave it on.. It will blink the code numbers... and detailed code descriptions are all on that site... you should get a 12 and a 55... Which 12 is battery disconnected in last 100 starts... and 55 is end of codes...

If the car is running GLHS electronics (86 style even on 87 GLHS) the MAP sensor is on the Logic module under passenger side kick panel.. If it is running 87 electronics the MAP sensor will be under hood wherever they mounted it... LM is still in same place...

Out of those four solenoids.

Here.. The one labeled in the picture "map" is actually the barometer solenoid.. technically you don't 'need' it.. But it if driving up/down hills where barometric pressure is changing and will keep MAP sensor tables in Check...

Boost control you don't need if you are using mechanical control for the wastegate... Like your Grainger Vavle..

Others... no need for them at all unless required in emissions state.

http://www.omnilith.net/teamomni/repair.htm

The Idle speed stepper motor sounds like it is going crazy.

The Knize minimopar site has instructions on how to reset the AIS motor.

Most people put larger throttle bodies on and that throws off the idle calibrations.

Since you have a BOV, make sure it is plumbed properly and that it is sealing properly. Maybe try to remove it and plug it off to see if it works better/different.

Vacuum harness should be setup like an GLH-S and I believe that is available online.

Good luck! Sounds like it will be a lot of fun once you get it running properly :)

Sounds like you might have the vacuum lines to your baro solenoid hooked up wrong.

As for vacuum lines, start with the bare minimum and work your way up as needed.. Dont try to recreate the factory setup.

So start with vacuum to MAP, FPR, brake booster, and wastegate. The baro solenoid is basically in line with the map sensor line.

Well..

What did ya find out?

In reply to ronholm:

Hard to tell. We were so pressed for time last Wed night that when we got it on the ground and running I wasn't paying much attention but the car was running well and tacking up ok. So, whatever we did at some point fixed the throttle pulsing issue. Of course, then we had to deal with the shift linkage totally failing, a massive power steering leak and then the car not wanting to stay running after starting. About 11:30 we called it and I haven't looked at the car since. I ended up taking my '67 Volvo 122S to the Challenge.

It will be a few weeks until I can dig back into the Shelby and begin to sort things out. As soon as I have some more info I will post. Thanks agai for all the suggestions.