Im ready to push my new truck off a really high cliff...

[RED-85-Z51]

Ive been trying to diagnose a high idle problem on my 3500, I started off by checking for leaky TBI gaskets, they were great. Checked TPS voltage, it was dead on. I checked Coolant sensor..it was fine. Checked IAC..spotless, and working.


At that point, I replaced the IAC valve...no change. It runs great, but the idle settles into about 1000 rpms, and it should be around 750.

So...I jumped the A and B terminals on the ALDL...and keyed on for 10 seconds..unplugged th IAC...and cranked it. It fired up, and idled at 625....smooth. I plugged in the IAC...and it started to step back up...750..850..950...1000...and stays there.

shit...

So..I put in a junkyard ECM of the exact same part number today..fired right up...idled at like 700, sweet. Unfotunately, nothing else was right..it was trying to open the EGR valve, wouldnt rev up...seems like the MEM/CAL is for a 350 truck, so I swapped in my 454 stock chip, and it revved correctly again...but again..idled at 1000.

So...at this point, im thinking, I have a faulty PROM or (mem/cal) chip...

Damn it all to hell....

[CP]

Take it back to the transmission guy - he'll fix it.

[RED-85-Z51]

Take it back to the transmission guy - he'll fix it.

Its going back to him as soon as I get the idle right..I want no excuses from him as to why its shifting so hard on the 1-2.

[Turk]

Did it idle at 1k before you had the trans done?

[RED-85-Z51]

yes.

Id assumed it was a symptom of the trans not owrking right, however it obivously, now, is unrelated.

[63C2splitter]

How far to the nearest high cliff?

[RED-85-Z51]

PRobably...Tennessee...

[Knooger]

PRobably...Tennessee...

With the high idle you could put it in gear, aim it at a sweet jump and watch the destruction without needing to put a brick on the gas pedal. Hope this helps.

[Kerrmudgeon]

Ive been trying to diagnose a high idle problem on my 3500, I started off by checking for leaky TBI gaskets, they were great. Checked TPS voltage, it was dead on. I checked Coolant sensor..it was fine. Checked IAC..spotless, and working.


At that point, I replaced the IAC valve...no change. It runs great, but the idle settles into about 1000 rpms, and it should be around 750.

So...I jumped the A and B terminals on the ALDL...and keyed on for 10 seconds..unplugged th IAC...and cranked it. It fired up, and idled at 625....smooth. I plugged in the IAC...and it started to step back up...750..850..950...1000...and stays there.

shit...

So..I put in a junkyard ECM of the exact same part number today..fired right up...idled at like 700, sweet. Unfotunately, nothing else was right..it was trying to open the EGR valve, wouldnt rev up...seems like the MEM/CAL is for a 350 truck, so I swapped in my 454 stock chip, and it revved correctly again...but again..idled at 1000.

So...at this point, im thinking, I have a faulty PROM or (mem/cal) chip...

Damn it all to hell....

I would try another ECM from a diesel if you can find one. Same number or not, the one you tried may be defective as well, or the diesel one is programmed a little different after installation. :confused5:

[jaxgator]

Im ready to push my new truck off a really high cliff...

And this surprises you how? :D

[Cybercowboy]

Sell it on craigslist. :D

I'm sure he could by a new prom on craiglist. Just place an ad in the "men seeking men" section.

Wanted: Huge prom. Contact Papa Bear at 857-5309.

[vetteman9368]

There is more to the IAC than just working/not. Try another one.

[onedef92]

Supervettes, LLC'll hook you right the feck up! :seasix:

[6spdC6]

Red here is a wild guess do to the fact I had trany trouble and a very high idle combination of problems years back with a 454 pickup, check the throttle position sensor. That made my 1-2 shift totally crazy

That sensor goes wacky you can get many rather interesting problems.

[mrvette]

Red here is a wild guess do to the fact I had trany trouble and a very high idle combination of problems years back with a 454 pickup, check the throttle position sensor. That made my 1-2 shift totally crazy

That sensor goes wacky you can get many rather interesting problems.

I dunno about your TPS, but the early injection systems on like a TPI car will have 5 volts and ground, the idle is .56 volts, and it must swing smoothly when throttle opened, I put a scope on it, or at least the DVM, and watch carefully as throttle is opened.......:seasix:

You sure of the throttle adjustment?? set screw on closing, adjust it to allow more blade closing, also to spray carb/brake cleaner on a rag and clean the passages on the throttle body, they get carboned up for some reason, black grease looking crap so to wipe the barrels and blades clean also the IAC motor, take it off, spray down, remove all goop from passages and motor tip, blast out with air if necessary.....then give it a try.....

[1911fool]

I have a couple PROMs for a '90 454SS. One stock and one "upgraded" from TBIchips.com.
I can send you either to try for diagnosis, but I would like to get it back.....let me know if you're interested.

Did you go thru the IAC reset procedure?
It kinda sounds like a bad CTS. How did you check it? I have changed a CTS before and the brand new one was bad also.
By any chance did you try squeezing the EGR valve by hand with it running and get any change in idling?

[xXBUDXx]

Red here is a wild guess do to the fact I had trany trouble and a very high idle combination of problems years back with a 454 pickup, check the throttle position sensor. That made my 1-2 shift totally crazy

That sensor goes wacky you can get many rather interesting problems.

:iagree: same issue with a 4.3 S-10.

Pics of the cliff?

[RED-85-Z51]

I tested the TPS, I had .56v at idle, and 4.45 at WOT, right where it should be....I had hoped that was it ,but of course..no

A 90 model SS had some different stuff, the trans was the TH400, also the computers, as I recall, were different, as everything says 92-95 as one group, and 90-91 as another.

[1911fool]

yes the '90s had the TH400, in 91 they went to the 4L80E and 4.10 gears.

[6spdC6]

yes the '90s had the TH400, in 91 they went to the 4L80E and 4.10 gears.

I had a 91 SS that I bought new in the end of 1990, (made it into a show truck) and it had a lot of differences between it and the 90s.

I sold it to my son about 6 years ago and he had it for a few years and sold it for $16,000 last year. That truck was super clean and low mileage with bolt on mods that could easily be returned to a 100% stock if wanted. All stock parts including wheels and tires, hood went with the truck.

[island14]

Supervettes, LLC'll hook you right the feck up! :seasix:

They sure have a good reputation around here.. :lol:

[island14]

Red I have manuals for the TBI, and also one for the electronics side of the TBI if you need them..

Just Pm if you do and I will send you the download links.

:cert:

[1911fool]

Red, you can also get an EBL ecm for about $450. and it allows you to do your own tuning. however you will have to piggy back the original PCM to control the tranny. I have one on my son's SS. it works very well. I took that truck from 10mpg to 14.8 on the highway.

[RED-85-Z51]

I just really want it to work as the factory intended. im A-okay with a stock operating system, they are pretty reliable.

Apparently the guy at TBIchips.com doesnt want to sell me a chip, he keeps finding reasons why the chip isnt a problem, however, ive tested or replaced most everything else.

I knows its in the programming.

I guess its possible that the chip is for a 5 speed truck..those would idle higher...but it wouldnt shift the trans, I dont think..would it?

[vetteman9368]

I just really want it to work as the factory intended. im A-okay with a stock operating system, they are pretty reliable.

Apparently the guy at TBIchips.com doesnt want to sell me a chip, he keeps finding reasons why the chip isnt a problem, however, ive tested or replaced most everything else.

I knows its in the programming.

I guess its possible that the chip is for a 5 speed truck..those would idle higher...but it wouldnt shift the trans, I dont think..would it?

It's possible. I'd look at the wiring. It's possible that a section of wiring might be burned, crimped, etc. that could be affecting the feedback to the ecu

[1911fool]

I dont think a 5 spd chip would do anything for the tranny. It is probably similar to my TH400 chip.

[RED-85-Z51]

It's possible. I'd look at the wiring. It's possible that a section of wiring might be burned, crimped, etc. that could be affecting the feedback to the ecu

All the wiring I can get to, on top, underneath, and from the ECU..is all still in pristine shape, even still in the factory looms, still taped up.

You know anyone in pcola that sells Chips and stuff? I was thinking XXX or USA PErformance on 29?

[vetteman9368]

All the wiring I can get to, on top, underneath, and from the ECU..is all still in pristine shape, even still in the factory looms, still taped up.

You know anyone in pcola that sells Chips and stuff? I was thinking XXX or USA PErformance on 29?

Speed Unlimited on new Warrington, ask for timmy

[RED-85-Z51]

Speed Unlimited on new Warrington, ask for timmy

on the phone now

[vetteman9368]

Also, have you checked all if the chassis/engine grounds?

[RED-85-Z51]

He says he's never heard of a bad MEM/CAL causing a high idle unless it was programmed to do so..he is going to call me back with a quote on what chips that will work, cost..

[RED-85-Z51]

Also, have you checked all if the chassis/engine grounds?

Oh yeah, all the grounds I could find, but especially the block to frame ground.

[vetteman9368]

Oh yeah, all the grounds I could find, but especially the block to frame ground.

Double check the small harness leading to the IAC. Trace it back and there is probably a small ground hooked to the head or intake.

[Bill]

Supervettes, LLC'll hook you right the feck up! :seasix:

:rofl::rofl: :tapwaterspew: :rofl::rofl:

[RED-85-Z51]

One of the dudes up at that shop called Jet performance with my PROm broadcast numbers and JET CHIPs said that if its idling at 1000 and blowing out 2nd gear every time, it needs a new PROM..

He said an aftermarket chip would only make it worse, if the factory chip has gone tits up.

So...on the hunt now for a new PROM...

[UniqueDoug]

Whats ur bottom dollar on this, Nada retail has it at $2250, and can u text me pics of the dash?

[FasterTraffic]

There has to be an above-ground pool nearby that you can jump.

[Jeff '79]

What is a PROM?
Did you find one?
How much does one cost? :waiting:

[1911fool]

Why would an aftermarket chip make it worse if the stock chip is bad? One replaces the other.

[benny42]

Why would an aftermarket chip make it worse if the stock chip is bad? One replaces the other.

Most aftermarket chips piggy back on the stock prom for the transmission control.

[Steve Austin]

What is a PROM?
Did you find one?
How much does one cost? :waiting:

PROM, programmable read only memory. The chip. Red seems to need the MEMCAL. The assembly that holds the chip.

[1911fool]

Most aftermarket chips piggy back on the stock prom for the transmission control.

Oh ok, that makes sense. The only one I've replaced is in the 90 with the TH400.

[vetteman9368]

PROM, programmable read only memory. The chip. Red seems to need the MEMCAL. The assembly that holds the chip.

Correct

[RED-85-Z51]

Why would an aftermarket chip make it worse if the stock chip is bad? One replaces the other.

The guy at JET, said that on this setup, their chip goes in WITH the stock chip and alters its factory BIN files...if the files are corrupted, the jet Chip will still factor in changes, but it could only make things worse....he also said that their chips do not alter idle rpms.

Guy would have loved to sell me a 136 dollar chip..but like he said, he didnt think it would fix my problem, he told me to find a stock "BMHM" spec prom and put it in..and it would fix my problems.

If it works...this company has my business.

New chip ordered...bummer is it takes 2 weeks to get...75 bucks.

[tshirts and jeans]

hey red.....i got my mower back finally.....mows like a champ.......:hurray:

thanks for all your help.....

[RED-85-Z51]

Glad you got it back, wish they hadnt dragged their butts doing it. Also, would have been nice if they had done the correct belt inspections with the service, would have benefited everyone.

[tshirts and jeans]

now to get my push one going......but i swear i am goin to get it figured out myself if it kills me.......i am smart....i can read a manual....i can do this.....lol
:seasix: :confused5: :crazy: probably gonna need lots of tequila, too

[RED-85-Z51]

Alcohol is bad for mowers...and mower operators/mechanics...

[onedef92]

hey red.....i got my mower back finally.....mows like a champ.......:hurray:

thanks for all your help.....

Did you swap the chip out in it, too? :D

[tshirts and jeans]

Did you swap the chip out in it, too? :D

no .....he just kept me from setting my mower on fire.....and basically telling me what was wrong so that when i called the repair shop i would not sound like an idiot......he thinks they were taking advantage of me and weren't doing their job ...... HE WAS CORRECT...... so now i am thinking about taking some mechanics classes..... heck i have already taken everything else so why not...:confused5:

[onedef92]

no .....he just kept me from setting my mower on fire.....and basically telling me what was wrong so that when i called the repair shop i would not sound like an idiot......he thinks they were taking advantage of me and weren't doing their job ...... HE WAS CORRECT...... so now i am thinking about taking some mechanics classes..... heck i have already taken everything else so why not...:confused5:

Good deal. A female neighbor recently bought a new lawn mower and forgot to add the bottle of four-cyle oil to the crankcase, even though it was included in the shipping box. :kick:

The engine ran about 30 seconds, then siezed due to lack of lubrication. She told us she paid the lawmower shop $75 to unseize her new engine, but there was no additional damage. That's one expensive can of penetrating oil, if you know what I mean. :)

[mrvette]

Wife 3.0 has the processing power to ask questions about CARs 10.0 and so I esplain it like Dezi Arnez would.....

same for stepson 1.0 and SIL 1.0, not that they light any candles.....


Wife 3.0 is considerably the brighter candle in the shed......


:rofl::dance::seasix:

[RED-85-Z51]

Good deal. A female neighbor recently bought a new lawn mower and forgot to add the bottle of four-cyle oil to the crankcase, even though it was included in the shipping box. :kick:

The engine ran about 30 seconds, then siezed due to lack of lubrication. She told us she paid the lawmower shop $75 to unseize her new engine, but there was no additional damage. That's one expensive can of penetrating oil, if you know what I mean. :)

I doubt any shop would "breaker bar" a stuck engine and call it good. Id bet they pulled it, and removed the sump, and inspected the rod for metal transfer, and put it back together. Its rarely ever a top end seize, the rod andcrank lock up first.

[mike100]

Sounds like maybe the throttle body has a vacuum leak (or maybe somewhere else sneaky). The earlier computers only can compensate so much. If you can get it hooked up to a tech1 scanner or equivalent (like the snap-on type), I would like to know if the IAC count is zero. If so, the iac is max closed and you have bypass air from a leak.

[RED-85-Z51]

IAC is physically opening by command from the computer. I can manually force the IAC to close by jumpering the terminals....and it idles great, as soon as I let the IAC back into the loop, it opens back up.

[1911fool]

There is a procedure for resetting the IAC, I used it when I replaced mine.......I think it came with the IAC.

[RED-85-Z51]

There is a procedure for resetting the IAC, I used it when I replaced mine.......I think it came with the IAC.

jump Terminals a and b on the ALDL.

Key on for 10 seconds.

unplug IAC

Crank engine with jumper removed...confirm idle is within spec...

Engine off, plug in IAC...crank...idle should be slightly higher than base settings, meaning a captured computer controlled idle.

[1911fool]

I do believe that was the jest of it......I don't remember lunch today, instructions I used once a year ago is damn near impossible.

[RED-85-Z51]

Clearly the solution here is a real computer. Megasquirt that bitch!

Aww HELL no...

If anything, id go to the 4v Holly setup..

http://www.summitracing.com/parts/hly-550-830/overview/make/chevrolet/year/1995/model/k3500

[C5Nate]

Aww HELL no...

If anything, id go to the 4v Holly setup..



$2,743.90 :eek:

[RED-85-Z51]

$2,743.90 :eek:

If you wanna play...:lol:

[RED-85-Z51]

keep in mind, thats essentially the same setup used by NASCAR now...

[mrvette]

keep in mind, thats essentially the same setup used by NASCAR now...

Who the EFF gives a damn......2700 bux?? YGTBFSM......

stick with the stock shit, dope it out....


:issues::seasix: