BAD EGR?

[BRONCADONK]

ok guys bare with me. i have a 79 bronco 400m auto. the motor is all stock. i live in california so i need to get this thing smogged. i have spent countless hours sourcing all the smog equipment from my local junk yards. when i bought it the previouse owner had stripped it of anything smog related. the problem is it has never ran the way it should, it does run better just not smog worthy. now that i have everything i need to smog it i can't get it to idle. it has a rebuilt motorcraft 2150 from holly, rebuilt smog pump, new air check valve, new coolant temp switches, i've replaced the intake gasket four times( i suspected a vac leak), i even had the intake inspected and resurfaced along with the egr adapter. it also has all new ignition parts, plugs, wires, distributor, cap, rotor, coil, and ignition module. this past weekend i installed a carb off my jeep cj7 that i know works, so that ruled out the carb. the fuel pump is new, along with the fuel lines and filter. i have tried to tune it with all the smog, vac lines capped to rule out any faulty delay valves or leaks. i've sprayed carb cleaner looking for vac leaks and have found none. my compression is 150 on all eight cyl. i'm runnin out of ideas so my questions are, can a faulty egr cause a rough idle? even if it is disconected? what about a leaky brake booster? (it makes a woosh noise when i press the brake pedal.) vac modulator? i realy love this bronco, and i don't want to give up. please help me. oh and if anyone out there needs smog info i know way more than i ever wanted.

 

[Broncobill78]

Yes to both questions. A bad EGR will giv you a rough idle, but no it shouldn't if/when the EGR is blocked off. If it's still running poorly with a block-off plate in place then you have other problems. A bad brake booster can be the source of a fairly large vacuum leak (or it can just cause a small one, it all depends) and that will ***** up your idle.

 

[BRONCADONK]

thanks bill. i purchased an egr today, i will install later today. i never blocked the egr i just unpluged the vac line. i've got

my fingers crossed. i'll isolate the brake booster and see what hapens.

 

[BRONCADONK]

i installed the new egr, ran a little better. but not good enough. it still stalls out when i come to a stop. i sprayed carb cleaner all aroud searching for a vac leak. the carb base gaskets might be leaking. the idle jumps when i spray aroud the base of the carb. i installed the air cleaner to try and limit the spray being sucked into the carb and got the same results. tomarrow i'll replace the gaskets and install a seal for the air cleaner. maybe i'll get lucky.

 

[Broncobill78]

Sounds like this is one of those combination problems, no one issue is causing it. It looks like you've made progress w/the new EGR and a possible leak at the carb. Hopefully a set of new gaskets will get you where you need to be (be sure to get both carb gaskets the one from the manifold to the EGR spacer & the one between the EGR spacer and the carb)

 

[BRONCADONK]

ok i installed the new carb gaskets. ran a little better. still feels like a vac leak, so i checked the vac modulator. noticed a large trasmission fluid leak. when i unpluged the vac line tranny fluid squirted out. i'm no expert but i'm pretty sure transmission fluid should not be in the modulator. the motor idles decent at 1000 rpm, as soon as i shift into reverse or drive it runs like crap. do you think my engine has been sucking trany fluid, and wouldn't that be a large vac leak?

 

[Yardape]

Thats definately bad. I stripped a truck because of that, thought the engine was hooped. Never checked the modulator til I yanked the motor. Now its happening to everyone and their dog. replace that, you will notice a world of difference. Your rubber vaccum lines might need replacing now. Tranny fluid loves to make rubber soft and squishy.

 

[Broncobill78]

Yes, that's part of the problem as well. Fluid in the vacuum line or modulator means the diaphragm is torn. Replace the modulator, be sure that you get one with the same color stripe around it (usually either purple or black as I recall). You frequently get gray smoke from the exhaust when you're burning tranny fluid but even without it you've got a problem there. It's not going to be a huge leak (that vacuum line will only support so much of a leak) but it will contribute to the problem and collectively all these leaks are probably the root of your driveability issues

 

[BRONCADONK]

well i installed the vac modulator. got better results, just not quite good enough. i know there is still a leak. i think it's small. my vac guage only reads about 13. i also noticed my egr is slow to close, ad sometimes stays open. i've double checked the vac routing and everything looks correct. the egr is the main reason for the stalling when i come to a stop. i bought the bronco from a guy off craigslist, the description said it had a performance cam. when i picked it up he then said he had a cam for it in his garage. i just assumed that was the cam he was talking about. i know i should have asked him to clarify, but is thier any way to know if my engine has a cam in it. that would explain the low vac readings, and the rough idle? the motor does look to have been rebuilt recently.

 

[BRONCADONK]

ok i disconnected the egr vac line and was able to tune the motor. it's still not perfect. i'm getting 18 - 20 on the vac guage. my timing is set at 4 deg btc, and the idle mixture was actualy responsive. it idles decent at 1000 rpm in park, and drops to 6-650 in drive. still a bit to high, but any lower and it will stall when stopping. i don't know what to do about the egr. it just closes way to slow. takes about 3-4 seconds, and by that time the egine just stalls if i dont feather the throttle. i hooked the vac guage to the vac line for the egr and watched as i opened the throttle and closed it. it seemed to respond ok. the emissions decal shows a dual delay valve, i'm going to try a regular delay valve and see what hapens. i think i'm going to just drop it at a repair shop and tell them to just fix it! anyone know of a good shop in sacramento california? most places i've called "dont work on anything that old". is there any real mechanics left, or are they all just parts changers?

 

[BRONCADONK]

the dual dv was the problem. i replaced it with a vrdv, and now it closes faster. maybe the dual dv was bad? don't know why ford put one there ayways. i don't know why they would want to delay the egr from closing. anyways this week i'll istall a fuel mixture guage that way i'll be able to tune the carb for smog. may still have to take it in. thank you guys for all you'r help.

 

[BRONCADONK]

well it still runs like crap! but the egr is now working properly. i know it's a vac leak or bad carb. i pulled the intake again today and it looks like # 4, and maybe # 3 were leaking? also i noticed #4 and # 8 intake runners looked diferent from the rest. the walls inside the first set of runners were moist, but #4, and #8 had a chalky residue. the same as the exhaust ports next to them. is that normal? do you think maybe the intake is cracked internaly? or is it the heat from the exhaust keeping them dry? anyways i'm tired of lifting that heavy pos out, so i bought an edelbrock #3771 and will install it this tuesday when the gaskets come in. has anyone installed this intake before? if so do i need a valley pan? i'm not sure if the edelbrock gaskets come with it. i have a stock gasket just in case, but edelbrock "highly recomends" their gaskets "for a perfect fit".

 

[BRONCADONK]

just so you guys know, the edelbrock intake gaskets they list is for a 351 clevland not a 351, 400m. wasted 15 bucks on that lesson. you could modify the gasket, but i'm not takig any chances. anyone ever use mr. gasket intake gaskets? they look similar to the edelbrock, just without the silicon rings. oh and they are for the 400m. i don't want to use the stock gasket. this will be my fourth time and i don't have much faith in the metal gasket, or myself.i thought i had it this last time, but the stock manifold is so freakin heavy i think i keep damaging the metal gasket?

 

[Johnny Reb]

You might also want to chek the CHECK VALVE at the brake booster. I have had seen and had them go bad and cause havic. They used to cost about $4 bucks-hard tellin now.Good luck

 

[BRONCADONK]

thanks Johnny i thought you guys forgot about me. i did supect the check valve, and still do. before i pulled the manifold off i disconnected everything but the vac. advance. capped all the vac sources, and fired her up. like Broncobill said it's a whole combination of problems contributing to my headache. i'm just eliminating them one by one. i will replace the check valve, along with the vac booster once this beast is running. thanks again, i realy apreciate all you guys taking the time to help me. i would be lost without this forum!

 

[BRONCADONK]

ok, i just got it all back togather. i runs pretty good without any adjustments. i dropped the idle to 800 rpm in park, shifted it into drive and no stall. still runs strong. can't test drive it yet. the rebuilt carb i just installed sticks, but only when it's running. anyone have that problem? oh well, i'm just waiting for it to cool off so i can put my old carb back on. if it works i'll just return the new one.

 

[Johnny Reb]

ok, i just got it all back togather. i runs pretty good without any adjustments. i dropped the idle to 800 rpm in park, shifted it into drive and no stall. still runs strong. can't test drive it yet. the rebuilt carb i just installed sticks, but only when it's running. anyone have that problem? oh well, i'm just waiting for it to cool off so i can put my old carb back on. if it works i'll just return the new one.

The sticking-could be a spring binding or you could have a bad rod on your carb that goes through the side.Even new ones(carbs), can have them. Why don,t you take the throttle spring off and see if it binds. If it doe not-the carb should be ruled out and put the blame on the location of the spring.Also it could be the strengyh of the spring. They do come in different strengths.Good luck

 

[Johnny Reb]

The sticking-could be a spring binding or you could have a bad rod on your carb that goes through the side.Even new ones(carbs), can have them. Why don,t you take the throttle spring off and see if it binds. If it doe not-the carb should be ruled out and put the blame on the location of the spring.Also it could be the strengyh of the spring. They do come in different strengths.Good luck

So,the carb only sticks when running.------does it have a vaccum on it and something else--what carb do you have?

 

[BRONCADONK]

it's a rebuilt motorcraft 2150. it was rebuilt by tomco. not a bad job, they even re bushed it. i can't figure out why the throttle sticks when it's running. so i took it off. i wanted another rebuilt carb from holly, but the parts guy couldn't figure out what carb i needed. i'm going to install my old carb tomarrow. if it works i'll just return the tomco carb. if not i'll just go to another kragens, or ask for a different counter guy. hopefuly i can try to smog it next week.