installed 40hp chip, now it misses

[hayhauler69]

Hi,
I just installed a 40HP chip in my 1995 Gmc K2500 6.5TD and now when I push throttle more than half way it misses. I don't normally give it that much throttle but am wondering what could cause this. Turbo boost sensor?
It just cut's out and misses like a 'bad spark plug' would on a gas engine.
Any ideas?
Tell the truth I never did press on throttle more than half way with stock chip.
I should probably try that and see what it does. Not much of hot rodder I am.
Buzz

[DmaxMaverick]

If you can't duplicate it stock, contact the vendor of the chip. If you do, start the diagnosis process for that issue, and leave out the new chip until you solve it. Any codes?

[hayhauler69]

Yeah,
Did that. Sent the chip back for a reburn.
I don't think it's the chip. Had Walt put the chip in a newly (rebuilt) ECM.
I didn't see the ECM light flash on. Only drove down the road and back. I can only play so long at work:rolleyes:
So when I get home I'll put the old chip in and drive harder than l normally do.
I'll also check for codes.
Thanks for reply.
Buzz

[hayhauler69]

OK here's an update,
The hesitation or lag comes on only at 3/4 to 2/3 throttle, no matter the RPM or speed.
I get no code and no throttle light. I thought maybe throttle sensor. Can it be bad and still not send a code?
I put old chip in and the truck ran fine. Not as much power, but fine.
I think the new chip is bringing 'something' out in some sensor or module that would not show up otherwise.
Any ideas?
Buzz

[gmctd]

Post the DS4-xxx-xxxx number on your IP - some '95's had the dreaded 5068 IP which takes a special eprom, specific to that IP, only

BJAX on the oem chip is a good indicator - there are several more, depending on option

[hayhauler69]

Hi GMCTD,
The EPROM is a BPAK (my original).
I looked for the model number on the injection pump but only found a green metal tag with no markings. I assume tag is where ID would be?
Thanks for the reply,
Buzz

[DmaxMaverick]

Post the DS4-xxx-xxxx number on your IP - some '95's had the dreaded 5068 IP which takes a special eprom, specific to that IP, only

BJAX on the oem chip is a good indicator - there are several more, depending on option

That was the 1994's. 1995's didn't see it.

[hayhauler69]

Figured out where the ID plate is.
now if I just had that incredible shrinking machine.:)
What they put there for.
Buzz

[hayhauler69]

DMAX
Thought that the 94's had the 5068.
Walt at SSD never asked me for the pump ID.
Just the Vin F or S which mine is S.
Now I'm not so sure the chip is good. Had it "redone" because the same thing happened when I first got it. I'm not sure what's done when it's 'reburned'.
Have plenty of power.
I'll probably go and get it diagnosed at the local dealer this week.
I'll post what I find if anything.
Have left a couple of messages for Walt. He may have a good idea.
Buzz

[hayhauler69]

So most likely the pump is weak.
Only 100000 miles on the truck though.
Sending chip back to be checked again and perhaps de-tuned a little.:(
Buzz

[DmaxMaverick]

Try a different tune alltogether. Ask around, you may find someone to provide a loner, for diagnostic purposes.

[gmctd]

Green tag indicates the ceramic rollers, revised ESO, revised OS, and some other upgrades - use a small mirror and a flashlite to see the model number tag, on the back of the IP facing the intake manifold.

[hayhauler69]

Done that for many years being an aircraft mechanic.
Believe me, I thought about that first thing.
I'm sending the EPROM back to Walt at SSD. He's going to send it to another
vendor to check it out. I may have him de-tune it a bit.
Is there a way to check pressures at the pump? I'm skeptical about the pump putting out low pressure. With the OEM chip, I can floor it and no problem. You'd think there'd be some sort of lag or hesitation.
Thanks for the interest and replies.
This forum is great and an excellent learing center.
I really appreciate the knowledge all of you are willing to share.
Buzz

[gmctd]

A special "tune" is available for the 5068 - supposed to give ~100mm3 fuel - causes wierd problems with the 5288-5521 IP's.

[hayhauler69]

So looked real hard and my pump is a 5288.
Sent stuff back to get checked.
I'll post what happens.
Thanks, Buzz

[ECMProgrammer]

Walt should have asked for your original 4 letter code from your original PROM. Did you give him that ?

Lyndon
www.ecmprogrammer.com
Westers Garage
1-888-WESTER-1

[Kennedy]

The 2 main keys are pump model number, and transmission type. Without these, you have to rely on the 4 letter code which works, BUT not if someone upgraded the pump w/o changing the chip...

[hayhauler69]

Thanks for all the interest,
So the pump being a 5288 is from a 97 model?
The chip "I beleive" is stock, but the computer was replaced because it has a 'reman' sticker on it.
Walt did ask if was an auto, which it is and the OEM chip ID and if the Vin had the 'S' in it (I gave whole VIN#) Pump ID wasn't asked for.
I'm perhaps thinking, because pump wasn't the original stock pump that there lies the problem.
Walt is sending the chip to another vendor and hopefully all will work out.
When I did have the 40HP chip installed, wow! what a difference! I'm just hoping my fuel mileage won't drop to much. I know the 80HP chip, mileage would drop, but hoping the 40HP it won't because you don't have to get into the throttle all that much (if you can resist the temptation).
The turbo sure comes on quick, it's a completely different motor. And shift points are quick and crisp. All that outl of a little blue box, amazing.
Buzz

[Robyn]

The magic is incredible.

With all the different sensors feeding the computer these things have driveability that is wonderful when they are working properly.

And to thing we used to depend on a vacuum modulator on the tranny and the road speed governor to control the shifts.

The mechanical controls can be more reliable under nasty conditions but the electronics are sweet when they are all up and running right.

Everyone here at TDP knows my feelings about all the magic boxes so I wont go there.

Still own rigs with the electronics and enjoy the smooth operation.

I have been following your issues on this thread.

How long ago since the injectors were either tested or replaced??

If they have over 100,000 miles get them out and freshened up.

I would also be seriously thinking about getting the IP tested and possibly gone through.

To really get what you hope for out of a chip and other mods the fuel delivery system needs to be in tip top shape.

When I rebuilt my 94 the only reason it came down was a blown head gasket.

The compression was excellent on all holes (Except the one with the bad gasket) and it ran well.

The difference after the rebuild which included a fresh set of squirts and having the IP tested. (It was fine) was night and day.

The engine runs with a much more crisp cackle to it and the power is sooooooooooo much better and it is in stock trim.

Good luck with your quest.

Robyn

[hayhauler69]

I just got the truck earlier this year (a few months ago) So I don't know when anything was done.
I'm wondering if the engine is original. The truck had front end damage and was totaled before I got it. It was all repaired and 'running' before I got it for about a year.
I put a fresh trannsmission in it, did some upgrades, new batteries, thanks to you Robyn and battery cables.
I'm calling the local Chevy dealer up here in Washington and hoping to schedule a diagnostic test and ask about the IP pump check up.
The rig really runs good. I drive conservatively but not like Grandpa (old enough to be one though, but that's another story:rolleyes: )
When I put the pedal to the metal, there's minimal smoke and plenty of get up and go.
I suppose when I get the chip back and it still does it, I'll wait and do work a little at a time. I've put a lot of money into truck as it is. Paid 4000 for it with only 100100 miles. Think it had a rough past life, so I treat it real nice. It's a looker, very clean lines and straight and the interior is fantastic.
I've got the Bilstien shocks for it. Bull dog gauge package for pillar, new rotors and calipers for it to install, all in boxes in the garage. Just don't have time. There's that four letter word 'work' that seems to get in the way, but without that, well...........
Thanks for your interest Robyn.
I'll keep posting what I find.
Buzz
Waiting for summer to start had enough rain.

[Robyn]

Sounds good

The only way to be sure of the injector and pump condition is to take them off and trot them off to a pump shop and have them tested.
The IP is run on a machine that will test all its fuctions.
The injector nozzles are pop tested and the spray pattern observed.

A scan of the engine as running will tell some but not the whole story.

A pump has to be prety sick before a tech 1 scan will show you much.
I had a 94 Burb with totally sour injectors and a scan would show the little fellow as being fine.
The beast would cough up enough blue smoke on a startup to kill every mosquito in the country, but yet run fine after a few minutes of warm up.


Good luck and keep us posted

Robyn

[hayhauler69]

Robyn,
found your website, interesting.
Now you've got me wondering. That's a pretty neat rig.
Buzz

[JohnC]

I read the initial post and immediately said to my self "fuel filter's plugged or the lift pump isn't pumping..."

Guess I'm a simpleton...

[hayhauler69]

John,
You'd been right on, except..........we'll you know.
I'm hoping the reburn will work now that Walt knows the pumps a 5288.
I don't have a clue why that would matter. I'm the simpleton here, more ways then one.;)
It'll take a couple weeks to get the chip back.
Getting ready to put my gauge pack in (pillar mount). Got a red truck with the gray interior. Wondering what color I should paint the gauge mount. Make it blend and paint it gray or go wild with the red. I'll probably go for the gray. I'm not a wild and crazy guy:)
Buzz