Occasional hard start, stall at lights, now stumbling?
10-19-2015, 02:02 PM
#1
Burning Brakes
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Occasional hard start, stall at lights, now stumbling?
Hey guys- I've spent a pile of time searching around for info on this, and just can't get a clear picture from the mix of threads I've seen so far, so I figured I'd just ask.
I've got an 84 NA that had periodic issues with not cranking at all when I bought it a few months ago. I replaced the ignition switch, so now it cranks every time. But occasionally it'll decide to be difficult to start - it'll crank for a while, and the tach bounces as expected. Every time it's done this, trying a second or third time will get it to start just fine, and once it's started, it was running just fine.
The hard starts have gotten more frequent over the past month, and in the past week, it's occasionally started, but immediately died. Giving it gas immediately does seem to get it to stay running just fine at that point, but putting the pedal in while starting doesn't prevent the hard start- it only helps after it catches.
Maybe half a dozen times over the past week, it's died when clutching in coming up to a light, but always restarts just fine, and without the extended crank. This morning, after it died coming up to a stoplight, it started stumbling as well, esp in low rev range.
I recently replaced the throttle response cam, which I know isn't going to be a cause of any problems. When I did the replacement, I adjusted the limit screw so that the idle switch does actually 'click' closed the way it's supposed to. It was previously set to not actually close 100% of the way.
Is it possible that this is an issue with the aux air valve being clogged or otherwise not working correctly, and that the throttle being set to not close completely was someone's half-assed workaround? I've seen it mentioned in a lot of threads talking about rough idling and the like, but what confused me is the stumbling. That's new, and wasn't happening in the first 8 miles of driving before the stall at the light.
Any guidance would be much appreciated- I'm guessing I have two different issues coming into play here, but maybe I'll be lucky and it'll be a straightforward fix... I've just seen so many of these threads where there's a list of 8-10 replaced parts totaling $1k+, and if it's possible to avoid that, it'd be awesome.
I've got an 84 NA that had periodic issues with not cranking at all when I bought it a few months ago. I replaced the ignition switch, so now it cranks every time. But occasionally it'll decide to be difficult to start - it'll crank for a while, and the tach bounces as expected. Every time it's done this, trying a second or third time will get it to start just fine, and once it's started, it was running just fine.
The hard starts have gotten more frequent over the past month, and in the past week, it's occasionally started, but immediately died. Giving it gas immediately does seem to get it to stay running just fine at that point, but putting the pedal in while starting doesn't prevent the hard start- it only helps after it catches.
Maybe half a dozen times over the past week, it's died when clutching in coming up to a light, but always restarts just fine, and without the extended crank. This morning, after it died coming up to a stoplight, it started stumbling as well, esp in low rev range.
I recently replaced the throttle response cam, which I know isn't going to be a cause of any problems. When I did the replacement, I adjusted the limit screw so that the idle switch does actually 'click' closed the way it's supposed to. It was previously set to not actually close 100% of the way.
Is it possible that this is an issue with the aux air valve being clogged or otherwise not working correctly, and that the throttle being set to not close completely was someone's half-assed workaround? I've seen it mentioned in a lot of threads talking about rough idling and the like, but what confused me is the stumbling. That's new, and wasn't happening in the first 8 miles of driving before the stall at the light.
Any guidance would be much appreciated- I'm guessing I have two different issues coming into play here, but maybe I'll be lucky and it'll be a straightforward fix... I've just seen so many of these threads where there's a list of 8-10 replaced parts totaling $1k+, and if it's possible to avoid that, it'd be awesome.
10-19-2015, 02:14 PM
#2
Rainman
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Aux air valve only works on cold starts.
After a little while (minutes?) the aux air valve shuts itself off.
When the car is warm the AAV is closed.
Check something - you adjusted the throttle stop screw, but the TPS was not adjusted at all.
It is possible that you adjusted the stop screw to where the TPS would click, but in doing so opened the throttle plate too far (or closed it too far) to get a good idle.
In recent months I've had a low-idle issue that messing with the bypass screw didn't affect at all..I would have to give a little gas to start up and idle at 1000rpm or so.
Turns out, when I swapped throttle bodies, I hadn't put the throttle stop screw in far enough (to just crack the blade)...now car starts and idles no problem.
After a little while (minutes?) the aux air valve shuts itself off.
When the car is warm the AAV is closed.
Check something - you adjusted the throttle stop screw, but the TPS was not adjusted at all.
It is possible that you adjusted the stop screw to where the TPS would click, but in doing so opened the throttle plate too far (or closed it too far) to get a good idle.
In recent months I've had a low-idle issue that messing with the bypass screw didn't affect at all..I would have to give a little gas to start up and idle at 1000rpm or so.
Turns out, when I swapped throttle bodies, I hadn't put the throttle stop screw in far enough (to just crack the blade)...now car starts and idles no problem.
10-19-2015, 02:19 PM
#3
Burning Brakes
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Sounds like a great place to start- turns out looking at the TPS diagnosis/adjustment page on Clarks Garage gives the following potential symptoms, which certainly overlap mine pretty well:
Poor idle - particularly a high idle condition
Engine cuts out to an idle condition during acceleration
Poor power at various RPMs (various throttle positions)
Surging idle
Misfire
Stumble during acceleration
Intermittent boost problems (turbocharged cars)
I'll do some checking on the TPS and see what that gets me- thanks!
Poor idle - particularly a high idle condition
Engine cuts out to an idle condition during acceleration
Poor power at various RPMs (various throttle positions)
Surging idle
Misfire
Stumble during acceleration
Intermittent boost problems (turbocharged cars)
I'll do some checking on the TPS and see what that gets me- thanks!