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Post by bobchees3 on Nov 3, 2014 2:11:05 GMT -5
Did a Weber carb swap on my '88 a few weeks ago. Since then my mpg has plummeted to mid teens. Even with the sh!tachi I broke into the mid 30's.. I've gone through the mixture and fast idle tuning a few times and haven't seen much improvement. Idles rough below 1000 rpms and when I apply the brakes idle decreases even more causing it to die sometimes.
Basically driveability hasn't improved that much and mpg has gotten worse.
I'm going to double check for vacuum leaks, and I ran a dry compression test this weekend... results were bad. From left to right: 100, 140, 82.
I'm looking for instructions on a valve lash adjustment and but I need some guidance working on these two things (mpg and compression).
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Post by sp0ngebob on Nov 3, 2014 13:25:39 GMT -5
compression numbers can be lash related, but those are some wild swings.
do a dry and wet compression test to see if theres a difference. if the wet compression test yields much higher numbers, its likely rings thats the issue. if no change, it could be a bad head gasket of valves. but youd know its not rings.
after a carb swap i almost guarantee you have a vac leak if you are having problems like you describe. do you know how many CFM the new carb is rated at? also was it a new off the shelf carb or a used unit?
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Post by bobchees3 on Nov 4, 2014 0:38:31 GMT -5
compression numbers can be lash related, but those are some wild swings. do a dry and wet compression test to see if theres a difference. if the wet compression test yields much higher numbers, its likely rings thats the issue. if no change, it could be a bad head gasket of valves. but youd know its not rings. after a carb swap i almost guarantee you have a vac leak if you are having problems like you describe. do you know how many CFM the new carb is rated at? also was it a new off the shelf carb or a used unit? I'd get on that compression test and see if I notice any change. As for the carb it was a new Weber 32/36 DGEV (Redline Kit # K 731). I don't know how many CFM the carb is rated for though. As for a vacuum leak: first am I missing any attachments for the carb? Maybe some clarification on these images would help: I tried to number/label them the best I can. imgur.com/a/L27Ff#0If everything looks ok I'll remove the blue tape and start trimming hoses so I can get the engine bay looking better.
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Post by bobchees3 on Nov 7, 2014 20:47:06 GMT -5
Still really need help here.
Ran another compression test: From left to right - (dry/wet) 95/105 140/x 80/85
I tried to find a vac leak and couldn't. used carb cleaner one time and soapy water another. When I brake, rpms decrease and symptoms haven't changed.. Frustrating.
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Post by Mato393 on Nov 8, 2014 14:43:56 GMT -5
Try to check Valve clearance it should be: Intake: 0,15mm Exhaust: 0,25mm If you have 1,2l engine
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Post by bobchees3 on Nov 9, 2014 18:28:06 GMT -5
Adjusted the clearance to those specs this morning, we'll see how it runs this week.
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Post by Mato393 on Nov 10, 2014 9:32:58 GMT -5
Adjusted the clearance to those specs this morning, we'll see how it runs this week. Was there big diference of valve clearance?
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Post by sp0ngebob on Nov 10, 2014 12:04:51 GMT -5
you have 140 in one hole and under 90 in the others. those numbers are WAY too far a part to be valve lash.
Either you did the compression test wrong or your motor is done. you either have a bad head, head gasket or otherwise. its not the rings. if you had 90 in a hole dry then 145 in that same hole wet, youd have indication of rings.
if you want to keep testing, do a leak down test in a quiet area. set a piston at TDC, and pump 90-140psi in the hole. If it leaks out the throttlebody/carb then its a valve issue. if it leaks out the oil cap its rings or a head gasket. and if it comes out the radiator cap, thats definitely a head gasket
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Post by sp0ngebob on Nov 10, 2014 12:07:44 GMT -5
also your vacuum cap job is all kinds of farcleed up.
you cap vacuum at the metal ports not the end of a 5ft line. thats 5 extra feet of possible leaks. ditch those "vacuum adapters" you have on the ends of those lines and plug them AT BOTH ENDS of where the vac line should go.
do that first and then go for a test drive. tell us the results.
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Post by Deleted on Nov 10, 2014 14:32:12 GMT -5
I tried to find a vac leak and couldn't. used carb cleaner one time and soapy water another. When I brake, rpms decrease and symptoms haven't changed.. Frustrating. Rpms dipping down when you brake is usually from either a faulty brake booster or faulty vapor canister purge valve.
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Post by bobchees3 on Nov 10, 2014 16:17:30 GMT -5
Adjusted the clearance to those specs this morning, we'll see how it runs this week. Was there big diference of valve clearance? There was a huge difference, all of the valve lashes were too tight. and spo0ngebob, I'll fix all the vacuum hoses too. I just didn't want to remove any lines I was might have had to keep. Like the vapor canister hoses that may or may not be effecting the low rpms?
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Post by Mato393 on Nov 10, 2014 16:33:03 GMT -5
There was a huge difference, all of the valve lashes were too tight. So I think (maybe I am wrong, that is what mechanic says me when adjusting valve clearance on my car) intake valves need to be removed and washed because there could be coal coat on surface where it should not be and it can cause pressure leak again... So You gonna need to remove cilinder head and replace head gasket too...
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Post by sp0ngebob on Nov 10, 2014 17:38:32 GMT -5
mato is referring to gunk on the valve seats causing the valves to not actually touch the bowles properly. Ive never actually seen that on a carbed motor. mostly because of how the gasoline washes over the valves on a carbed motor. however if that were true, pouring some cleaner that will bust up carbon deposits into the intake manifold runner would work, provided that hole was at TDC.
when doing a compression test did you have the gas pedal floored?
did you run the motor with the fuel pump pulled so you "bleed" the float bowl of all the fuel you can?
Did you then crank the motor a bunch to try and get every last drop of fuel out?
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Post by bobchees3 on Nov 10, 2014 17:56:04 GMT -5
mato is referring to gunk on the valve seats causing the valves to not actually touch the bowles properly. Ive never actually seen that on a carbed motor. mostly because of how the gasoline washes over the valves on a carbed motor. however if that were true, pouring some cleaner that will bust up carbon deposits into the intake manifold runner would work, provided that hole was at TDC. when doing a compression test did you have the gas pedal floored? did you run the motor with the fuel pump pulled so you "bleed" the float bowl of all the fuel you can? Did you then crank the motor a bunch to try and get every last drop of fuel out? Maybe I did the compression test incorrectly. I really hope so. I disconnected ignition coil, and opened the choke and throttle all the way. I had all the sparkplugs removed with the compression gauge screwed in fingertight. I didn't remove the fuel pump though, and I think it's under the driver's seat on the '88 if I remember correctly. Should I just disconnect the electrical component?
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Post by sp0ngebob on Nov 11, 2014 0:51:05 GMT -5
ok slow down.
the compression tester needs to be in there more than finger tight. i always kind of wrench on the hose as much as i can by hand to get the best "seat" i can.
when you do a compression test if fuel is getting sent into the carbureator and that fuel is going down into a cylinder the results are completely void. that fuel acts like a wet test and really honks up the numbers. hers a step by step compression test walk through. do all of this then report back the numbers both wet and dry. k?
1. drive the car for 15 minutes at speed. not idling for 15 minutes. 2. Loosen all the plugs and then re-seat them. Start the car and drive for 5 minutes (just around the block is good enough). this will make sure that any carbon deposits on the plug that break off are spat out of the cylinder. 3. look at the fuse panel inside the car. the fuse marked "FUEL"...pull that fuse. 4. start the car and revv the engine to 2000rpm. 5. the car SHOULD die of fuel starvation. 6. FLOOR the gas pedal. Crank the engine for 15 seconds. wait 1 minute, repeat. 7. unscrew 1 spark plug and insert the compression testing gauge. make sure there is no nresidual pressure in the gauge. 8. FLOOR the gas pedal again. Crank the engine for 10 seconds with the gas pedal floored. Go read the gauge. record the number. 9. remove the compression tester. reinstall the spark plug in that hole. 10. remove another spark plug and reinsert the compression tester. repeat steps 8-10 until complete.
WET TEST: prior to doing step 8, take a cursory measured amount of oil and pour it into the cylinder. a small spoon full is enough. now perform the EXACT same compression test using steps 8-10.
11. reinstall fuel fuse. 12. Start car to ensure everything runs fine. crank time will be long unless you let the pump prime. it will be audible like someone patting their hands quickly on a desk.
post the numbers by the holes when complete.
btw, me writing that all out doesnt mean i think youre an idiot. it means that i think you may have honked up the compression test so i thought id write it all out.
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Post by sp0ngebob on Nov 11, 2014 0:53:21 GMT -5
no idea why the hell thats so big font wise.
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Post by bobchees3 on Nov 11, 2014 2:11:50 GMT -5
no idea why the hell thats so big font wise. Yeah, no need to shout it at me! But thanks for the directions, I was previously going off a very generalized guide.. Will report back soon.
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