"Crawl, Crawl, Stagger, Stagger" Truck is limping

[Turbine Doc]

Some may or may not remember the origin of "Crawl..Crawl.... Stagger ....Stagger" this is how my 98 K1500 has been running since yesterday

It had been running fine locked in cruise control for about 100 miles @ 70-75 mph 2500-2600 rpm, then it started to stumble badly, like a load of crap fuel can do when trying to pass another vehicle, about 50 miles from home getting it progressively got worse, I got off interstate just coming out of Mobile AL on I-65 South, then I got onto US-90 West so I could limp it home to MS.

I was able to maintain to about 45-50mph, I had to put in neutral & rev engine to keep running at stop lights, finally got home pulled up my driveway with it missing/loping, I left it running so as to not clear any codes and see what might be going on.

My MT2500 scanner would not synch up with the truck so no engine data with that, I shifted to my (Amazon/China) TOPDON ArtiDiag900 it linked up ok, it was reading engine TDCO-1.15, time set & actual all over place but tracking together, cam reference and IP optic timing reference checked/tracked Sat.

I captured P1216 fuel solenoid response time too short, P1656 WG solenoid control circuit which is normal since my WG went with the GM8 turbo when I installed Mistu. TDO-7 22A in 2005 then ATT in 2009, P1643 WTS lamp control circuit, P0102 MAF sensor low frequency, (been disconnected for decades), P0251 IP Camshaft system, P0126 ECT insufficient, P0380 glow plug feedback circuit.

All codes cleared on but truck still running like crap, with the red illuminate MAF sensor constant High red numbers vs. black illuminated, but no code for that is stored ????

It also acted similar to a truck that had been limped from high IAT setting max fuel 55mm3 but it really struggle to keep the truck running, lift fuel pressure to IP holding 5-9 psi, gauged boost & EGT where they normally run, ECT good, just weird no power and struggling to run while idling.

I shut it down swapped FSDs, found one of my spares was no good, but truck started on 2nd spare I carry, truck started with it but no difference in operation,, codes cleared all good except MAP showing constant high+ 15psi illuminated in red,.

Today I ordered a new BOSCH MAP sensor Rock Auto had one for $27 hoping that fixes the issue, local part store had off name brand 12mos warranty also had to be ordered for next day $85, I opted to wait until Friday and get the Bosch with lifetime warranty.

In mean time I'll remove the/drain the Racor on frame rail, and stock on engine filters and check for water, replace with clean filters to confirm I don't have crap fuel.

Any other thoughts?

 

[MrMarty51]

My thoughts, thats a lot happening in such a small amount of space.
Thats all.

 

[Will L.]

Where is the fuel pressure gauge tapped at?
My push is always using a metal T fitting at the ip inlet like gm says. I’ve seen so many rubber hose failures just before the ip that a gauge tapped anywhere else is not trustable. Thats why the gm kit had the adapter there, but it was for a liquid line and the gauge would be suction cupped to the windshield.

 

[MrMarty51]

Where is the fuel pressure gauge tapped at?
My push is always using a metal T fitting at the ip inlet like gm says. I’ve seen so many rubber hose failures just before the ip that a gauge tapped anywhere else is not trustable. Thats why the gm kit had the adapter there, but it was for a liquid line and the gauge would be suction cupped to the windshield.

I had the sending unit screwed into the fitting right at the IP.
Before I knew about the snubbers I was replacing sending units right regular.
I’d have to lift the upper intake to get enough swing on the wrench so after I got the snubbers I did the remote hose system but used 5/16ths 30R9 hose and adapted to the 1/8th inch pipe out there.
And then even with the snubber in place another sending unit failed and Gloshift sent me a new one.
Now after driving to Rosebud this morning it appears that another of their SUs is going to crap.
So yeah, I’m mighty happy I did the remote mount.

 

[Will L.]

Yeah, unfortunately the glowshift rankings are high for people they last on and very low for people they fail on. They just seem home run or strike out.
I can’t remember how you ran your hose system from your LP. Do you have the return hose to constant circulation or dead heading into the ip?

 

[Turbine Doc]

Where is the fuel pressure gauge tapped at?
My push is always using a metal T fitting at the ip inlet like gm says. I’ve seen so many rubber hose failures just before the ip that a gauge tapped anywhere else is not trustable. Thats why the gm kit had the adapter there, but it was for a liquid line and the gauge would be suction cupped to the windshield.

My tee is at the outlet of the FFM before the IP my FFM is on the inner fender driver side on 2 pieces of 1/2"-13thread, clamped thru the fender with washers & double nuts, and "ears" on the FFM mount, both lift pumps running or single lift pumps make no change but I will verify rubber hose into lP not collapsing, hose run from FFM to IP is 2' or less. FFM on fender makes it easier to swap filters, and keeps the rubber hose out of the valley so I can see if any leaks easier.

 

[Turbine Doc]

Yeah, unfortunately the glowshift rankings are high for people they last on and very low for people they fail on. They just seem home run or strike out.
I can’t remember how you ran your hose system from your LP. Do you have the return hose to constant circulation or dead heading into the ip?

Returns are per GM back to the tank, most of the time I'm running single GM lift 32gph pump, I still have a mechanical gauge on the line, if I see due to heavy load I will swap over to the 45 gph Walbro FRB-5, or both if loaded and climbing a mountain

 

[ak diesel driver]

I'd be doing the CPS/OS test on your truck TD

 

[Turbine Doc]

I'd be doing the CPS/OS test on your truck TD

My 1st thought as well, oddly when observing data trend on scan tool, this Topdon lets me graph 6 parameters real time, while holding steady state rpm 1800-ish rpm in driveway, all parameters stable, desired and actual timing match, 3 psi boost on gauge, no active codes showing after clearing them, the only odd man out is the MAP sensor showing constant +15 psi., which I will swap when new one arrives, hoping that is the "smoking gun".

 

[Will L.]

Doing the unplug one or the other as our Alaskan friend is suggesting is far faster than trying to gather and interpret data, especially if it is any intermittent issue.
I think he is right, jump to that and maybe a go-pro or old phone recording the clear ip line for when it occurs just to verify it isn’t a momentary air intrusion or contamination.

 

[ak diesel driver]

I had a 94 that the scan tool didn't show any missed counts for the CPS. unplugging it showed it was bad

 

[Will L.]

I had a 94 that the scan tool didn't show any missed counts for the CPS. unplugging it showed it was bad

Not uncommon. My guess is because the scanner sees the cam sensor bleed into the signal in the ecm- cam sensor being in the ds4 of course. Not like GM did some tom foolery there…haha

 

[Turbine Doc]

I haven't played with CTS/Optic yet, the one thing that "taunts me" is the constant high boost level 15+ psi indicated in red on the scanner with truck running at idle or with engine off & key on, no other codes present. According to text in my DS4 training manual , and troubleshooting from both the 94 OBD-1 and my 98 OBD-2 manuals saying I should be having a high boost code being displayed now, but I don't; so I'm thinking when PCM was re-flashed the high boost codes have been moved out of the way to allow for higher than stock boost limits.

If you will recall tier-1 defense from factory is open WG to control high boost, tier-2 if you can't lower boost reduce fuel rate.

Boost sensing is supposed to be a 0-5V reference from PCM biased by boost sensor for normal 0-3.5V, with high boost being set at 3.9V for 2 sec, if I get time in next day or so I'll rig a 5V volt source across the MAP sensor and read output of sensor by itself, with engine shut down it should be reading 0, like the gauge. New MAP sensor is supposed to be here Friday, I'll probably do more diagnostics as well even for education if nothing else.

Another thing that caught my eye from the manuals is TTC lock up is also impacted by this defuel/limp and I noticed it taking a very long time to shift into OD, and cruise control was disabled as well.

One more thing I did find in my training manual for DS-4 IPs & control system high IAT is defined at least in OBD-1 as >than 202F for more than 2 sec, before prompting a defuel of max fuel 20mm3 reduction for max fuel fuel, which was acceptable for factory levels of boost, but not when running above 10psi hot day 100F, ECT 215, had this happen with my ATT years ago, I lost power/acceleration, and locked in at 55mm3 max fuel rate, deep cleaned the radiator & condenser fins and have never seen it since, possibly elevated trans. temp at play as well. I think GM looked at much more than what "tuners" do/did to keep the engine as safe as it can be from self destruction, boost and fuel rate tables are just a couple pieces of the pie.

 

[dbrannon79]

iirc the MAP and BARO sensors are the same only one reads manifold pressure the other reads atmospheric pressure. boost is calculated from the two. you can swap the two sensors and see if the bad signal reading follows on your scanner you should see both sensors data along with a calculated boost value. normally the baro should read around 14-15 PSI all the time.

 

[Turbine Doc]

iirc the MAP and BARO sensors are the same only one reads manifold pressure the other reads atmospheric pressure. boost is calculated from the two. you can swap the two sensors and see if the bad signal reading follows on your scanner you should see both sensors data along with a calculated boost value. normally the baro should read around 14-15 PSI all the time.

Not the same baro reads vacuum, MAP reads pressure, different part #s and indexed differently in connector socket. in F engine trucks the baro reading happens via MAP sensor at start PCM stores that value and then reads boost pressure after start.

In S trucks the baro is 2nd sensor mounted on firewall under wiper motor, looks exactly like a MAP but reads baro at start, but after start, it reads system vac changes real time to modulate ERG and EGR vent valves.

Which is why you can't just plug the EGR line in OBD-2 for sure though I think, the OBD-1's S ECM is a little less smart and you can plug it.