One last shot... Breaking up!

[BoostedSUV]

Re: One last shot... Breaking up!

Wow, looks like you've covered just about everything... at this point I'd probably have to try swapping a few sensors (MAP and O2 being first). I haven't thought it through so don't know if a TPS could do it, or not.... if you sit with the truck off, key on, TPRT or DM running... can you slowly press throttle to 100% and check for linearity?

I did try testing the TPS with Datamaster running and ign on/truck off. The throttle percent slowly increased as well as the signal voltage. I even tried a spare TPS just to try it... I've had this exact problem in the past and I tried changing O2 sensor, MAP sensor, and ign module and I never did solve it. I've always had a "flat spot" at 2500 and It never really went away but it got really bad now! I'm thinking about sending my injectors to a local place to be cleaned and tested. I'm really out of ideas :tdown:

 

[Luke]

Re: One last shot... Breaking up!

Magnetic pickup coil.

thats a good thought, you have a spare dizzy sitting around?

 

[BoostedSUV]

Re: One last shot... Breaking up!

thats a good thought, you have a spare dizzy sitting around?

I actually just sold my spare.. I did have this issue a while back with the stock distributer as well, even after I changed the ign module. The MSD billet dist that's in there now is just over a year old so I would hate to think that's my issue. I guess I could pick up a reman dist from autozone and try it?

 

[SY2455]

Re: One last shot... Breaking up!

When you tried swapping O2 sensors did you use the factory part numbers? When I 1st got 2455 I was having a problem with the O2 and the problem only went away after ordering a stock O2 from GM. The only other thing that I was wondering about was the intake gaskets.

 

[BoostedSUV]

Re: One last shot... Breaking up!

I've replaced almost every sensor in the truck chasing this issue around.. I'm going to throw in a set of plugs tomorrow even tho I doubt that's what's doing it.

 

[BoostedSUV]

Re: One last shot... Breaking up!

When you tried swapping O2 sensors did you use the factory part numbers? When I 1st got 2455 I was having a problem with the O2 and the problem only went away after ordering a stock O2 from GM. The only other thing that I was wondering about was the intake gaskets.

I used what ever 02 that autozone had in stock that matched the description of the truck. I still have the box i will verify the part #. I'm doubting intake gaskets because I had this issue with stock heads a while back and now I'm having it with the vortec swap. It's not a recent swap but it existed prior to the swap and the intake gaskets were obviously all changed.

 

[BoostedSUV]

Re: One last shot... Breaking up!

I'm using a Bosch O2 Sensor # 13077 which it what the truck calls for... I could try a GM one which is $81!?!?

i can get a new pick up coil for the MSD dist for $23... worth a shot? Can anyone tell me what the exact problem people were having with the MSD distributors?

 

[BoostedSUV]

Re: One last shot... Breaking up!

I was out messing with the truck again tonight... I borrowed another 3 bar MAP sensor and tried changing that. Nothing.. that didn't solve my problem. However, when I was moving the map sensor around with the truck running I could hear the idle changing.. So I started checking all the connections at the MAP by gently tugging on the wire and the black wire broke off in my hand with hardly any force! The wire was broken off inside the insulation and with just a little tug the wire fell right off! I damn near crapped myself with joy thinking I finally tracked down the culprit. It all made sense, I ran the harness for the Elec FP gauge right near the MAP so it was possible I knocked the wire out of whack and that's why my problems started! Makes sense right? WRONG! I pulled apart the connector and repaired the broken off wire with a new pin and soldered the wire to it. I put everything back together and to my utter disappointment the problem was still there! :rant:

How the hell does a broken off wire inside the insulation to the map sensor right by where I was working on Elec FP gauge sender not be problem??? I swear I have no luck! I've been going through this truck with a fine tooth comb for hours almost every night for the last month!

Well I guess I solved a future problem that was going to exist at a later date... unbelievable!

 

[BoostedSUV]

Re: One last shot... Breaking up!

ok guys... one more wasted Saturday of working on the truck to no avail!

I changed spark plugs to NGK TR55's just to try things and that did nothing. All the plugs that came out looked perfect except for number 6. number 6 looked much richer than the rest. I checked the wire and the wire tested good .13 ohms.

I changed upper intake and TB gaskets, and I looked down intake ports and didn't see any sucked lower gaskets

I checked every wire from the ECU and verified they start and end where they should with a multimeter. Everything was good, no broken wires, everything was connected as they should be.

I replaced the connector and wires to the map sensor since I had one break off and that did nothing.

I ohm tested all the injectors across the terminals and got a .01 reading on all 6.

I vacuum tested each and every vac line and everything holds vacuum..


What's left guys?? Ign module? Coil pick up? Injector cleaning and flow testing? I need more ideas. I'm very close to pulling the motor and trans and selling everything off. This truck is worthless to me in this condition sitting in front of my Garage. I have other projects I put to the back of line for this thing and frankly I'm tired of the headaches. I'm open to more suggestions, if anyone local wants to stop by, or have me bring them the truck I will gladly pay you for your time.... Any more help??

 

[BoostedSUV]

Re: One last shot... Breaking up!

just ordered a set of Taylor wires -$36
Accel Ign Module - $41
MSD Coil Pick up -$20

I should have everything wednesday... hopefully something works!

 

[syty9933]

Re: One last shot... Breaking up!

just ordered a set of Taylor wires -$36
Accel Ign Module - $41
MSD Coil Pick up -$20

I should have everything wednesday... hopefully something works!

good luck man, ive always loved your trucks look and mods :tup:

 

[SY2455]

Re: One last shot... Breaking up!

Are you still running with a Cat in your exhaust system? The reason I ask, on a old truck that I had ,it would start breaking up around 2500rpm or 45 mph. Before those two reading the truck would run crazy fast and then it was like someone thru anchor out the back. What I found was the cat had broken up into 3 large pieces and some smaller ones. One of the larger pieces was acting like a trap door and would block off the outlet side of the cat. I found it by driving down the road at night and pulling to the side of the road when it acted up, I found the exhaust glowing red from the exhaust ports to the cat and normal after that. Once I replace the cat the engine would rev to 6000 rpm without missing a beat.

 

[BoostedSUV]

Re: One last shot... Breaking up!

That's a good thought but the cat is hollowed out. Had that issue a few years back already! :tup:

 

[Luke]

Re: One last shot... Breaking up!

I had bad luck with the Accel ign module. installed it and soon as 4-5 psi hit it backfired so loud the homies ran for cover. dunno if I just got a bad part or what but I put a stocker back in it.

 

[kentuc]

Re: One last shot... Breaking up!

Check the firing order one more time. Maybe two wires are crossed.

 

[BoostedSUV]

Re: One last shot... Breaking up!

I will give accel module a shot... If it corrects the issue I'm having then it at least puts me in the right direction. The MSD didtributor is only a year old so I don't see how it could be bad but anything is possible with these trucks!
I've verified firing order 12 times already so I'm sure that's not it...

 

[turboj91]

Re: One last shot... Breaking up!

Dave beat me to the basic idea. It was mentioned the problem is in closed loop only. If this is correct, think this way... Being incredibly specific, what is different between closed loop and open loop operations?

 

[BoostedSUV]

Re: One last shot... Breaking up!

I've stayed out of this thread for awhile now. But I see you haven't resolved the problem. here's what I would try next:

You say the problem only comes up in Closed Loop. Is this still the case? If so, disconnect the O2 sensor. This will force open-loop operation. Drive it, how does it run? If OK (other than a code 13) you are now able to consider that a lot of things are "not it". Spark, ignition, fuel delivery (pump and pressure) etc.

Try driving it with the O2 sensor disconnected, and report back.

Dave I tried running it with the O2 disconnected and I mentioned it in a previous post. That does not change anything and I dont even get a Check Engine light after letting the truck idle for 15 mins.. Shouldn't I get a CE code?

When I start the truck cold it's fine.. revs up and drives fine. As soon as it get up to operating temps I start having this issue. If I'm in boost it's fine from what I can tell.. I can't even drive the truck it surges that bad. I just slowly bring the RPM's up in park and it hits 1500, 1900, and 2500 and goes lean and breaks up... been chasing this for over a month.

 

[BoostedSUV]

Re: One last shot... Breaking up!

Dave beat me to the basic idea. It was mentioned the problem is in closed loop only. If this is correct, think this way... Being incredibly specific, what is different between closed loop and open loop operations?

obviously the difference between open and closed loop is that Closed loop uses the O2 sensor to control fueling and Open loop does not... However I'm not positive it's a Closed Loop related issue or if it's just coincidence and it starts once the truck warms up to operating temps. That happenes about the same time. Also when I'm into boost I'm passed 3000k RPMs and at that point the A/F and everything is fine. Truck runs perfect once it clears up passed 2500 which is the really troubled RPM... Wideband goes to 19+ and actually says LEAN..... The Warmer the engine temps, the worse the truck breaks up.. rather odd?

 

[BoostedSUV]

Re: One last shot... Breaking up!

well I took an unpaid day off from work today to give another stab at the truck. I changed Spark plug wires, Ignition module, and MSD magnetic pick-up. NOTHING! Truck is still doing it's thing... I tried taking it for a test drive and when I go WOT the truck pulls hard as hell and WB reads perfect! Under boost and hard acceleration this thing is a monster... I just can't drive it normal with out it going lean and breaking up.

One last thing.. injectors maybe? Anyone have a set I can borrow to try before I spend money to guess and replace them?