Weird 1998 K1500

[matuva]

Something weird happened to a 1998 K1500.

The ECM was shot. As we had no 1998 ECM as spare (test with the ECM from another 1998, but could not left it on the truck) we tried a 1996 one... and she fired and runs fine & strong.

Security light stays ON, and we don't have glow cycle indication. Other then that, the truck run fine and strong.

It did run several weeks like that. Then, we changed injectors, BOSCH India. We added a Turbo Master.

Now the truck still start & run fine, but she can go beyond 87-90 MPH. Stays stuck at this limit, same as if there is a top speed limiter engaged :???: :???:


I don't think new injectors and Turbo master can do that? We adjusted the spring loose (2.5") as recommended for stock ECM, then tight (2") like if it is for an upgraded ECM, no change...

Any opinion?

 

[NVW]

If it runs strong up to that point, I would guess the ecm has a mph limit.

 

[matuva]

Yup, I think of it too, but what is weird is that it did run several weeks able to go beyond this speed limit. I don't understand why not now...

 

[NVW]

Is it possible the security system could cause this?

 

[matuva]

Could be Leo, but I think the security is for antitheft only if I'm correct

 

[matuva]

We put back the stock vacuum controler, and now she goes well beyond 90 MPH :WTF:

 

[Paveltolz]

What boost levels are you seeing and is it possible the ECM is 'protecting' the motor from too much?

 

[matuva]

That's probably what happens Paul, even though we adjust the spring almost loose to narrow stock boost, but as it is not the "right" ECM, it is probably fooled somewhere...

 

[bison]

ECM is reading high boost and goes in protect engine mode.
I had a similar situation with my 98 the other day.Mine has a KOJO tow tune but i think the there's still a max boost setting in it
I found i had a stuck waste gate(TM on it set to release at 15 PSI). The engine started cutting out( like it was short of fuel) when under load with 18 PSI of boost showing till i slowed down to under 15 psi boost, i could still get the speed up as long as i stayed under the 15 psi
After freeing the waste gate i had no more problems with speed limits with the go petal to the metal.

 

[matuva]

That 's a pretty similar situation Simon.

The guy is seriously thinking about an ATT and a Kojo tune custome tailored for his truck.

I think this should cure everything

 

[bison]

No telling till you try.
I can't see what is so great about that ATT.
I mean, the GM 8 produces easy 20 PSI boost in a hell of a hurry when you slam the go pedal

 

[matuva]

Yes sure Simon.

But from my own experience, I can say the couple ATT/Kojo works great, provide power and mileage at the same time.

The guy also wants an ATT because of that, and havin g a tuned ECM will give him the opportunity to order the right ECM with upgrades