idle weirdness and gas mileage sucks
10-31-2007, 11:26 AM
#1
Burning Brakes
Thread Starter
idle weirdness and gas mileage sucks
I blew a radiator hose a few weeks ago and tracked the pressure problem down to a malfunctioning radiator cap. The burst hose soaked the engine, hood, windshield, etc., with coolant.
The car sat for a few days until I got a new hose and put it on and when I started the car for the first time I heard a pop (like a heavy gauge balloon exploding). I immediately stopped the engine, looked around and didn't see anything odd, then started it again.
The car ran normally for a few minutes and then the idle dropped to the point that it would stall if I didn't keep half my foot on the gas while breaking on the drive home.
I replaced the radiator cap and adjusted the air/fuel mix to get the car to idle consistently when warm at about 1000 RPM. It doesn't seem to be running rich, but I do get a slight puff of black smoke out the tailpipe at red-line revs. When I start the car cold, it goes up to 2000 RPM, then settles back down to 1k. Most of the time, the car says pretty steady at 1k when warm, but intermittently revs slightly on its own.
I drove it to work one day and it sucked fuel --I used almost half a tank of gas to get back and forth to work --22 miles total (w/ traffic).
Any ideas where I should start troubleshooting?
The car sat for a few days until I got a new hose and put it on and when I started the car for the first time I heard a pop (like a heavy gauge balloon exploding). I immediately stopped the engine, looked around and didn't see anything odd, then started it again.
The car ran normally for a few minutes and then the idle dropped to the point that it would stall if I didn't keep half my foot on the gas while breaking on the drive home.
I replaced the radiator cap and adjusted the air/fuel mix to get the car to idle consistently when warm at about 1000 RPM. It doesn't seem to be running rich, but I do get a slight puff of black smoke out the tailpipe at red-line revs. When I start the car cold, it goes up to 2000 RPM, then settles back down to 1k. Most of the time, the car says pretty steady at 1k when warm, but intermittently revs slightly on its own.
I drove it to work one day and it sucked fuel --I used almost half a tank of gas to get back and forth to work --22 miles total (w/ traffic).
Any ideas where I should start troubleshooting?
10-31-2007, 11:33 AM
#2
Drifting
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on mine (81 euro S; 82 model) , I adjust the mixture at 700 rpm. Odd revving does sound like a mixture problem.
Sorry no idea why you use so much gas. In my limited experience of my own car vacuum leaks do not cause high gas use. I assume the motor starts OK?
I assume you checked for gas leaks, normally the smell is enough?
Marton
Sorry no idea why you use so much gas. In my limited experience of my own car vacuum leaks do not cause high gas use. I assume the motor starts OK?
I assume you checked for gas leaks, normally the smell is enough?
Marton
10-31-2007, 11:58 AM
#3
Rennlist Member
What I found on my '81 was the vacume advance/retard was disconnected inside the distributor. Not paying attention I never wondered or explored why the adjustment for distributor was turned all the way counterclockwise. While it did run o.k., it did have a strange idle that would drop intermitently and mileage was about 10mpg. Last may it would not pass smog (it did 2 previouse times) and tech showed while vacume would hold on accell and decell the advance and retard was not working. Loosened the 2 screws holding vac advance on and unit fell out.
Pulled distributor and retimed to correct spec after hooking up advance corrrectly. Car gained 9mpg and passed flawlessly.
With your problem I would check vacume lines. A pop as you describe could be a backfire and possibly blew one or moe off somewhere.
Pulled distributor and retimed to correct spec after hooking up advance corrrectly. Car gained 9mpg and passed flawlessly.
With your problem I would check vacume lines. A pop as you describe could be a backfire and possibly blew one or moe off somewhere.
10-31-2007, 12:40 PM
#4
Chronic Tool Dropper
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I'll hazard a guess that you popped a connector off the intake somplace that's causing a pretty good air leak. The car starts from cold OK with the cold-start enrichment valve open, but goes lean again when that closes. That leaness is the cause of the hunting idle, etc. Find and fix the vacuum/intake leak and you'll be on your way again.
CIS is a fickle system, in that you can't have air leaks. Too many time, there will be a small leak that you can adjust around so it's sort of OK. Then another leak and another adjustment, until there are enough leaks to get a good intake pop on start-up. Plenty of air thanks to the leak, and fuel through that cold-start valve. Add a small spark and suddenly there's a bigger air leak.
I'll hazard a guess that you popped a connector off the intake somplace that's causing a pretty good air leak. The car starts from cold OK with the cold-start enrichment valve open, but goes lean again when that closes. That leaness is the cause of the hunting idle, etc. Find and fix the vacuum/intake leak and you'll be on your way again.
CIS is a fickle system, in that you can't have air leaks. Too many time, there will be a small leak that you can adjust around so it's sort of OK. Then another leak and another adjustment, until there are enough leaks to get a good intake pop on start-up. Plenty of air thanks to the leak, and fuel through that cold-start valve. Add a small spark and suddenly there's a bigger air leak.
11-04-2007, 04:17 PM
#6
Burning Brakes
Thread Starter
I started the car yesterday morning and moved it to where I could work on it. It started fine, but later in the day it wouldn't start. I removed the battery, cecked it to find it low and charged it overnight.
This morning, I put the battery back in, started it and the same thing happened that happened after I replaced the radiator hose --it popped, again sounding like a small explosion in the engine compartment. This time I think the pop pushed the big vac hose that goes to the plenum out of it's connector --the little plug it seats into.
I let it set, started it again and it started fine --revving at 2k at first and then dropping down to 1k after 3-4 minutes.
I used a small dowel with a piece of paper on the end to try to find a vac leak, but no luck. I'm not even sure where to start on this.
I have a new set of silicone hose that's supposed to fit my whole system --I'm hoping that if I replace all the vac lines in the engine compartment that I'll find the leak --wish me luck.
This morning, I put the battery back in, started it and the same thing happened that happened after I replaced the radiator hose --it popped, again sounding like a small explosion in the engine compartment. This time I think the pop pushed the big vac hose that goes to the plenum out of it's connector --the little plug it seats into.
I let it set, started it again and it started fine --revving at 2k at first and then dropping down to 1k after 3-4 minutes.
I used a small dowel with a piece of paper on the end to try to find a vac leak, but no luck. I'm not even sure where to start on this.
I have a new set of silicone hose that's supposed to fit my whole system --I'm hoping that if I replace all the vac lines in the engine compartment that I'll find the leak --wish me luck.
