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  1. Markmartin01

    Stumble under load, out of ideas

    I've read conflicting opinions on the knock sensor. Some say without continuity the ECM defaults to a low timing default, some say the ECM only intervenes once knock is detected. I don't know enough about these early ECM tables to know which is actually correct.
  2. Markmartin01

    Stumble under load, out of ideas

    Partially solved. The stumble once warm was the temp sensor. It would ohm fine until it got nearly to operating temp, then it went to 4M ohms. Still has a warm idle hunt, so that's the next part. That also never occurred until recently, seems to coincide with the temp sensor failure.
  3. Markmartin01

    Stumble under load, out of ideas

    I did run it down the road with a gauge on it and it stayed steady at 12 PSI. HOWEVER....this morning I notice a no start and no fuel spray on startup. So it's entirely possible the FP had micro drops that the pressure gauge wasn't sensitive enough to reflect. Need to do some electrical...
  4. Markmartin01

    Stumble under load, out of ideas

    @Schurkey Fuel pressure gauge I tried on my '14 yukon as a control and it was accurate. Knock sensor is currently unhooked because it loves to come unplugged (not a good positive click) but has never caused an issue before....could it suddenly show different behavior out of the blue? Put a...
  5. Markmartin01

    Stumble under load, out of ideas

    91 RCSB Z71, stock under the hood other than a small Elgin RV cam. Has always ran fine, started it the other day and it has an occasional rough idle and what sounds like a lean condition under low RPM load, haven't tried WOT as that just sounds like a bad idea. Cap, rotor, wires are clean and...
  6. Markmartin01

    Gets hot after adding shroud?

    So I have a 91, 350, pretty run of the mill truck. Converted to 16" electric fan a couple of years ago after the water pump mount sheared and about threw the mechanical fan through my face. Cooled fine at speed without a shroud, wants to get hot after driving on the freeway and pulling off...
  7. Markmartin01

    To LS or not to LS, that is the question

    I have considered this myself. I think the question for me comes down to power curve and intended use of the truck. TBI was a torque focused motor that makes good power under 4k. LS engines have outstanding heads that flow great and make killer HP but generally at a higher rpm. So are you towing...
  8. Markmartin01

    Factory color that no one will admit to!!

    GM used multiple color variants of the same paint code and the only way to mix it correct is visual comparison and tinting. Nissan was the worst though, they had 11 variants of the same champagne color on sentras in the late 90's. I mixed a ton of PPG back in the day and it's a nightmare.
  9. Markmartin01

    Side molding

    Year 3 for mine and they've held fine. Make sure the paint is clean and temp is up. If it's a little cool you'll struggle getting the foam tape to stick. Hotter the better.
  10. Markmartin01

    Side molding

    I used the precut kit from LMC. You can get a roll and cut your own but the edges will be raw rubber and not finished edges.
  11. Markmartin01

    I want to replace the Moonie gauges in my 88

    Both valid points, thanks for the input. Just wanted to make OP aware of the issue before hand so he doesn't have to trial and error through it like I did.
  12. Markmartin01

    I want to replace the Moonie gauges in my 88

    If you huck the original cluster keep in mind you will have to find a way to excite the alternator regulator as the charge light in the original cluster completes that circuit.
  13. Markmartin01

    Pass on the intellitronix digital cluster!

    I did see the note @someotherguy , but that's a note about LS use. There are also no turn signals as it states, doesn't specify anything on speedo issues, doesn't mention that the alternator regulator is excited by the "charge" bulb in the original cluster, and so on. There is also apparently...
  14. Markmartin01

    Cold Air Intake on TBI 350.

    There is an episode of Enginemasters on Motortrend where they play with various air filters and configurations on a dyno. Granted, they were only testing single filter top mounted options on a carb, but the best possible config for HP on the dyno was an air filter that was breathing through the...
  15. Markmartin01

    Pass on the intellitronix digital cluster!

    for 88-91, originally the VSS was converted by the cluster itself so without the speedo plugged into the circuit, it's completely useless open circuit. Maybe if I did some PCB stipping and some solder work and enough trial and error I "might" have been able to make it work. In the end, I just...
  16. Markmartin01

    Pass on the intellitronix digital cluster!

    Sell it. My oldest bought it nearly a year ago and it just sit on the shelf until we got to it this weekend. It's for sale locally now with VSS buffer that I recalibrated for 3.73 and 33's. The thing is so far from compatible other than it fit in the original 88-91 cluster housing nicely.
  17. Markmartin01

    Pass on the intellitronix digital cluster!

    So over 4 days of wiring and work I have surmised that the intellitronix digital cluster for 88-91 as packaged does not work for 88-91. The speed wire requires a speed buffer box that didn't start until 92, the truck will not charge a battery as the original cluster charge light bulb is part of...
  18. Markmartin01

    Rear main seal

    You also need to dab the corners of that main seal block where it meets the pan. 100% chance of an oil leak if you don't.
  19. Markmartin01

    Halogen Or LED Headlights

    Word of caution on aftermarket LED headlights from someone who has owned several...most SUCK in the rain. The LED light just disappears in rain so expect sub par headlights in the rain. My HIDs were somewhat like that but not as bad.
  20. Markmartin01

    Nbs rear end swap questions

    I did a 99 disc brake rear in a 91. Have to cut and move perches and shock tabs but it's pretty easy. 99 rear is a half inch wider so negligible. But new perches and shock tabs bc they aren't worth trying to salvage. The ujoint was even the same between 91 Z71 and 99 Z71 so it was an easy swap...
  21. Markmartin01

    Power steering stop leak?

    Put a cap of brake fluid in it. It'll swell the seals a bit and buy some time. Did that in a Toyota Avalon years ago and it still didn't leak when we sold it.
  22. Markmartin01

    TBI can question

    I've read that site before, good info. I was hoping someone had tried the thumper style and could provide personal feedback.
  23. Markmartin01

    TBI can question

    So I know you can't do a radical cam in a TBI as it confuses the rudimentary ECU. However, the comp cam thumpers are a different story...less aggressive lobe with a short LSA so it makes noise but doesn't drop vacuum as bad so the ECU doesn't get as confused. My question is...have you done this...
  24. Markmartin01

    Truck gets hot randomly

    You know, it has blown the cap a time in the past but I'm not totally trusting the factory gauge. It showed to be above 260 once but wasn't bubbling so I'm not trusting the gauge. May put a mechanical gauge on it for shits and giggles.
  25. Markmartin01

    Truck gets hot randomly

    So I have a 91 RCSB Z71 that likes to get hot but completely random when it does. Sometimes at idle, sometimes at 55, air on or air off, no certain situation seems to trigger it. New radiator, water pump, with or without thermostat, electric fan with shroud. Engine was rebuilt a couple thousand...

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