GW sometimes stalls as stoplights....

[jeepthing]

Been having this problem, thought it was gone before when I put in the newly rebuilt carb. I notice this more on hot days (hot being 80 degrees), but sometimes when I've been driving for a while, and this is in stop and go traffic. When I get to a stoplight, and sit there for at least 30 seconds, I feel the ever present "bump..bump..bump" of my rough idling GW, and then instant silence! The engine stops running. Have to put it back into park, restart (it always starts right away) then put in drive and I'm good.

Now, I've done the TFI conversion, so new coil, plugs, wires, dist cap, etc. Also new pro rebuilt carb. Any ideas about this one guys? It makes it so that I sometimes time the lights so I won't have to sit anywhere for too long.

It never shuts down at other times...only when I'm sitting, and also when it's hot out (not sure if hot is related). Also, I'm not running hot at least by my temperature gauge.

It used to sit right at the tip of the blue, but now that it's hotter out, it goes a little beyond ( maybe 2 mm)

[JeepFreak]

Did you adjust your carb for best lean idle? Sounds to me like vacuum leak or mis-adjusted idle mixture.

[jeepthing]

I adjusted the idle speed, then adjusted the idle mixture screws with each one going lean until the engine started to get rough, then backed off 1/2 to 3/4 turn. Did the same for the other side, and made sure they were set the same.

Is that what I do? Also, why does it appear to be related to how hot it is outside. In fact I haven't noticed it hear when we were having our rain, etc when it was down to 50 degrees. Only now is it showing itself as it gets hotter.

[89grand]

Maybe you've got the dreaded Duracrap module random failure action going on.

Replace the Duracrap with a MSD6A.

[89er]

I have the same issue - but only when the A/C is on - which is almost always here in Houston. Man I was sure hoping that adjusting the idle, etc would solve it - have yet to do it though. Mine's bone stock.

[jeepthing]

Well it guess it could be the spark module, but how would you test that? Could it be that since my engine is running rough anyways, and since our drive rpm has to be so low (500 rpm) that if I miss or something, it isn't able to keep the engine turning and hence we stop?

I'm going to just drive it home, and leave it there parked and running and see if it happens again. If not, I'll put it in drive and check then.

Now if it's heat related, what about this vapor lock thing I hear...could it be that? I don't know anythign about it, but I've seen that term mentioned here before.

[89grand]

You can only test the duracrap for problems by replacing it with a known good one, you really can't troubleshoot the thing. As far as vapor lock, it's like "Bigfoot", everybody has heard of it but how real is it. Alot of problems are blamed on the mysterious "vapor lock" but I have never experienced it on any car in my entire life and I live in one of the hottest places on earth. I'm not saying it doesn't exist but I'm skeptical.

[jeepthing]

Then how would you know if you have a known good one to replace it with smile.gif

[jeepthing]

I was just searching around and found this about a 1990 GW. Sounds like my problem. I'll have to check out that module. Does anyone know what they cost new? Or is it a junkyard trip.

http://www.carsurvey.org/review_12192.html
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The Ford Duraspark ignition works well, provided that the ignition control module doesn't go bad. The distributor is a solid design, but the module is the weak link. The stock unit went 115k, but aftermarket replacements I've found only last about 5-7k tops. Their failure is marked by sporadic stalling, and usually occurs at higher engine temperatures. Keeping a spare ziptied to the mounted one is good insurance against being stranded. Should one fail, you just switch two connectors, and you're on the road again.
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[89grand]

Well they're not cheap(about $90) but it's either get a new one, find someone with a running Grand and borrow it or better yet just get the MSD.

[jeepthing]

Is that msd6a a direct replacement? Probably just have to change the pigtails on the connectors right?

[Zacko]

500 rpm seems a bit slow for idle in drive. That is a possible problem especially for a tired engine. You may also need to replace or adjust the throttle dashpot (that vacuum motor on the throttle lever) I had a GMC that had the same problem and adjusting the idle up a little and setting the dashpot right fixed it.
The dashpot just keeps the throttle from slamming shut.
If the thing starts right back up I don't think it is the module. If it started a half hour later I would suspect that. Especially since it chugs a little first, and the module wouldn't be so specific as when you go to idle. When I've seen modules crap out it can be at any RPM.

[89grand]

The MSD6A is not a direct replacement but it's pretty easy to do, it only took me about an hour total to do, and the Grand actually runs a little better too now. You will need to purchase the MSD harness to the Ford distributor seperately (about $16) which plugs into the distributor and the MSD unit but everything else is just hooking up your power wires to the MSD and one of the coil wires to it.

[jeepthing]

Well I guess I could try to raise the RPM. If that really is the root of my problems then I should be able to make it worse if I go even lower (not sure if it will go lower though) due to the anti stall solenoid??

I'll bump up the rpm tonight and see if it helps out anything.
I'll just have to drop it down again when I go in for my smog check.

[Matthew W. Woodruff]

I had to adjust my throttle solenoid to bring the curb idle up to 600 rpm; before that, I was shifting into neutral at stoplights to keep it running.

I also had to replace the "coil clip" on my stock ignition (which holds the wires in place on the coil); one of the connectors was broken and the wire was loose -- which contributed to a very rough idle.

I would check those things before getting into the spark box.

[JeepFreak]

I always run my idle at around 650-700 depending on what sort of cam I am running but 650 seems to work on the stock rigs. Should drop to about 600 in drive. 500 seems a bit low.