Troubles today

[Gfrank]

No sure what to even start with on this one. Drove my car to work a few days this week (45min drive each way. Pretty much 80kmph the hole time). Enroute home this evening about 3/4 the way home doing about 90kmph and headed down a light hill the car started pulsing, then it would stop, give it some more gas and it's fine for a bit then back to pulising on and off. Come to a stop light, now idling lower then normal (550 give or take) and is a bit rough. Pull away from the light, bit of pulsing, fine for a moment, then at one point during normal acceleration from the light it's almost as if I had nitrous. Next light my idles high 1500. Gentle on it the rest of the way to my subdivision, once on my street she seems normal again. Haven't gone out again, but it's idling just fine in the drive way now WTF? Any pointers?
81, 5 speed

Cheers

[Jonathan]

The low idle, dying part sounded like a starving fuel pump at first. The kind where either the pick-up hose is plugged or pinched.

After you mentioned it spiking high to 1,500 RPM, it makes me think it's a problem with the idle speed control system.

Check the electrical connections for that system. Clean, wiggle, connect/reconnect the two connectors on the back of the ECU behind the driver's seat. Do the same with the bulkhead connections. Same for the ones on the individual components in the engine bay, ISM (idle speed motor), solenoid, idle microswitch, etc. Confirm the vacuum hoses are fine and not loose or cut/cracked on the ISM and vacuum advance solenoid.

Could be the ISM is sticking. You can remove and clean it as well as testing the connections on it for a particular resistance across the terminals. You can watch it rotate while installed too if you tilt it back with the CSV hose off of the ISM and look in through that opening.

The 1,500 RPM part might tell you the thermistor connection is bad. That might not explain the low RPM though.

Did you get the idle linkage stuff adjusted we chatted about a while ago? The idle microswitch engagement screws and the linkage adjustment underneath the throttle spool if it has too much/too little slack? Did you find a throttle spool spring yet? I think you mentioned that was missing on either your car or Sam's?

[Gfrank]

Had pondered the fuel pump myself. Boots new, pick up filers new, fuel filters newer

All the problems from before to my knowledge had been sorted, I snagged the throttle spool spring off Sam's car so that all should be good, cars been running great the last few weeks. Aside from still runs a bit rough for the first 25-30sec in the morning when the cars sat 2 days or so

[David T]

Had pondered the fuel pump myself. Boots new, pick up filers new, fuel filters newer

All the problems from before to my knowledge had been sorted, I snagged the throttle spool spring off Sam's car so that all should be good, cars been running great the last few weeks

How low are you on fuel? Sounds like a problem in the gas tank. See if it is any better with more fuel.

[Gfrank]

Going off my fuel gauge I got a good 3/4 tank, now not that we can always trust the gauge but I can say forsure I put 25$ in it yesterday

[David T]

Going off my fuel gauge I got a good 3/4 tank, now not that we can always trust the gauge but I can say forsure I put 25$ in it yesterday

Did you fill it before or after the problem? Are you still having the problem with the 3/4 tank?

[Gfrank]

Had put in gas the day prior. Nothing had changed on the car during the day yesterday, drove it to work, ( about 45min and I do about 80kmph all the way aside from the odd stop light) then left work at 5 and made it abit more then 3/4 the way home before it started pulsing. If it makes a diffrance it started as I was headed down a light hill, so I was off the gas a bit. I first though it may have been an odd bumpy pavement, but it continued into the fresh pavement about 1/2 mile down the road

[David T]

Had put in gas the day prior. Nothing had changed on the car during the day yesterday, drove it to work, ( about 45min and I do about 80kmph all the way aside from the odd stop light) then left work at 5 and made it abit more then 3/4 the way home before it started pulsing. If it makes a diffrance it started as I was headed down a light hill, so I was off the gas a bit. I first though it may have been an odd bumpy pavement, but it continued into the fresh pavement about 1/2 mile down the road


I would start in the gas tank. Pump out as much fuel as you can and pull the fuel pump. Check all of the parts inside. Inspect carefully the pick-up hose. If it is soft and swollen it can collapse under vacuum or kink easily. I like to put a spring inside it. If there is a lot of dirt it can cover the filter on the end of the hose. Make sure the tank is clean. One fill-up of bad gas can mess up everything.

[Gfrank]

Thanks Dave , I was afraid you were going to say that, I just put that bastard together a few weeks back (new pump boot and pick up filter. Was kicking myself after tho for not doing a full clean of the tank.
I do recall my pick up hose being rather soft. Perhaps I may have to steal the hose off the girl friends car, I take it, it can not be replaced with just regular fuel hose as it need to take shape? . Love the spring idea, anything particular u grab the spring from?
Had also been suggested I replace the stock fuel pump connector

[David T]

Thanks Dave , I was afraid you were going to say that, I just put that bastard together a few weeks back (new pump boot and pick up filter. Was kicking myself after tho for not doing a full clean of the tank.
I do recall my pick up hose being rather soft. Perhaps I may have to steal the hose off the girl friends car, I take it, it can not be replaced with just regular fuel hose as it need to take shape? . Love the spring idea, anything particular u grab the spring from?
Had also been suggested I replace the stock fuel pump connector

I go to Lowes and they sell a long skinny spring for screen doors. The hose is a formed part so you shouldn't use any short hose. The tank MUST be clean.

[Gfrank]

30872
30873
30874

Well, can't say it's my problem forsure, but indeed needs attention, new filter = filthy, not sure I'll be able to clean it, really didn't like this style from the beginning, what came out of the car had a hard shell.
my pressure line from the pump to the hard line on the car, would appear perhaps a bend in the line cracked the inner liner and allowed a tumor or two if you will between it and the outer rubber
Tank if completely dry, plan to clean it out tomorrow, believe acetone was recommended

[David T]

30872
30873
30874

Well, can't say it's my problem forsure, but indeed needs attention, new filter = filthy, not sure I'll be able to clean it, really didn't like this style from the beginning, what came out of the car had a hard shell.
my pressure line from the pump to the hard line on the car, would appear perhaps a bend in the line cracked the inner liner and allowed a tumor or two if you will between it and the outer rubber
Tank if completely dry, plan to clean it out tomorrow, believe acetone was recommended

The filter isn't all that dirty but it does have some dirt on it. It is cleanable. As for the tank, yes, Acetone is what to use to melt any residue. Use plenty of ventilation and wipe it as clean as you can with plenty of paper towels.

[Gfrank]

Spring worked stunning! Thanks, all clean, back together. Took it for a quick rip, only about 10-15min, seems to run great, almost peppier. How ever once or twice at a stop my idle was again a bit high 1400ish, but then other times just perfect?

[David T]

Spring worked stunning! Thanks, all clean, back together. Took it for a quick rip, only about 10-15min, seems to run great, almost peppier. How ever once or twice at a stop my idle was again a bit high 1400ish, but then other times just perfect?

If the spring fix worked you had a pick-up hose that was either collapsing or kinked starving the fuel pump and hte motor for fuel. The high idle is a different problem. See if you have a lot of play in the ends of the quadrant link. It goes between the throttle spool and throttle arm. Make sure when the throttle arm is at idle it sets the idle micro.

[Gfrank]

In Theroy yes, but both problems showed up at the same moment, micro switch is clicking on, linkage is fine and tight Sticking idle motor perhaps? Completely random, one stop its fine next its up

[Gfrank]

Just wanted to finish the thread up for people searching in the future, went through all my throttle linkages again, and that's when I noticed the plug for my mixture screw had fallen out and went god knows where. Put a make shift one in for the time being as a order a new one. Took her a few miles to become
Happy again, but knock on wood all is great!.... For this week lol