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94 6.5TD Low idle

A

Acesneights1

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That 94 K1500 I have, I sold it today and notice it idles a little low IMO. It's idling at about 592 RPM. How do you adjust the idle or is there a problem ? Truck seems to run fine otherwise. Had a slight random fuel knock. I bumped the timing a touch and sounds better but seems like it idles too low. IIRC my Tahoe idled a little low too compared to my 2000. Any ideas ? Not sure what sets base idle on these. The only issue I could see with the truck is the pickup tube may be rotted of or the Fuel guage is way off cause ti was out of fuel when I got it. I made him aware he will have to drop the tank..
 
Not really, just sold the 94 tonight. Traded it for a Polaris 500 Predator. Thing is wicked fast. Better up my life insurance....:devil:
Is that better...:D
 
If memory serves, the GMTDScan Tech has a screen where it lets you adjust what it calls "rpm control". Don't know if this is some type of + or - offset, or something more sophisticated?

I'm just starting to try learn a bit about the 94/95 OBDI PCM coding/logic. Would expect there's somebody on the forum w/ a far better understanding of this than I.

I'd still be curious if anything sensor-wise has changed, to allow idle to change that much. The PCM can "see" where the engine is in it's rotation with a lot of precision (for injection timing) & I'd think the cylinder balance functions would require seeing rpm with good resolution as well. My point being - if everything's working well, shouldn't it be able to hold it pretty darn close to what it wants?

Far as I know, the target warm idle rpm is 650.
 
SmithvilleD said:
Far as I know, the target warm idle rpm is 650.
Click to expand...

on my auto enginuity it called for 597, of course it also bumps up when i put it in gear to around 650.

seems happy at 600 ish alternator stays chargin the steering and brakes are easy and it has a nice pur.

I have noticed however, that the fuel rate drops a tiny bit when the idle is bumped to around 900.
 
Don't know if there was any change in the idle spec for the later, '96+ OBDII trucks?

Would expect the primary rpm control mechanism is fueling changes? Don't know if it's playing with timing at all for idle control once everything's up to temp?
 
Computer adjusts idle rpm, and main factor what it uses is ECT.
There are lot of different calibrations from gm, but most lowest idle is 562 RPM when coolont is in right temp. It idles more if colder or hotter.
And amount of fuel is way how it adjusts idle. it adjust timing on all rpm's too but that is based to rpm and injected fuel.
 
Yeah I have the RPM control on GMTDScan but it only holds it there while you are in that screen. Doesn't change settings. I could buy into the 96+ trucks though being different since I'm comparing it to my 2000. One thing I did notice was the trucks dash temp didn't seem to match the ect that gmtdscan was seeing. GMTDScan was seeing about 156 deg and the dash gauge was at the bottom. However when I drove it around and got the truck up to 190 the dash gauge came up but not to where I would consider 190 deg but all the 6.5s I have owned until this truck had the 95+ dash/gauges so I may be used to looking at them. Just wondering if temps are playing a factor. The truck has 187K on it and most likely has original injectors so I'm sure they are sloppy. IP looks like it could have been replaced somewhere along the line although I didn't get a chance to check the IP # vs the Prom. I don't think the truck would run at all or very poorly if someone stuffed a 5521 in a 94 that had a 5068 prom.
 
I've been following his CUCV threads is all.... I'm with you Bison, I'm too poor now to pay anything else but attention to sigs.... I gotta find the wife a job already, enough's enough.

Mine also idles a touch under 600 kenny. I wouldn't worry about what the idle settings are unless its idling rough, or obviously too fast.

Ooh, google chrome spell checks for me now. Apparently it doesn't recognize the word google though.... :)
 
Acesneights1 said:
Yeah I have the RPM control on GMTDScan but it only holds it there while you are in that screen. Doesn't change settings. I could buy into the 96+ trucks though being different since I'm comparing it to my 2000. One thing I did notice was the trucks dash temp didn't seem to match the ect that gmtdscan was seeing. GMTDScan was seeing about 156 deg and the dash gauge was at the bottom. However when I drove it around and got the truck up to 190 the dash gauge came up but not to where I would consider 190 deg but all the 6.5s I have owned until this truck had the 95+ dash/gauges so I may be used to looking at them. Just wondering if temps are playing a factor. The truck has 187K on it and most likely has original injectors so I'm sure they are sloppy. IP looks like it could have been replaced somewhere along the line although I didn't get a chance to check the IP # vs the Prom. I don't think the truck would run at all or very poorly if someone stuffed a 5521 in a 94 that had a 5068 prom.
Click to expand...

The PCM/GMTDScan Tech see the coolant temp senser in the thermostat crossover. The dash temp gauge reads the temp senser in the driver's side cyl head.

Don't have the specs handy, but you could check each sensor's resistance at operating temps to see if it's where it should be.
 
Truck is gone now. was just trying to fix whatever I could for the guy before delivery. Probably end up in the hospital real soon with that quad. Damn that thing is fast. I gave him the link to the site so maybe we'll see him.
 
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