Another Gremlin... Time to move on?

[pmndlt]

Hey All, Quick preamble: 1988 GMC C3500 5.7L TH400, previously had stalling issues while driving; with your help narrowed down to ICM. Replaced - all good... Sort of.

1) Very low oil pressure when in D and stopped (100kpa/14PSI and less - today 0 and still running check gauges on).
2) Occasional immediate stall when into D or R and little tough to start.
3) Under constant throttle surges in between 40KMH/20-30mph. Thought trans so new filter and Dexron III. Nope
4) Occasional smoke on start - suspect seals.

New: TPS, Plugs, Wires, Cap, Rotor, TS sensor, Coolant flush, Trans Flush and Oil Flush. Running 10W30. 89,000 kms.

I'm leaning towards the IAC and have purchased one.

If it is are there PROPER reset/relearn steps I should follow? Seems there are lots of opinions. What does factory recommend, and should I screw with base idle - already did a bit...?

Is this bigger than the IAC though? Am I looking at bearing wear? Thinking I may need to move on from this one as its beyond me now.

Appreciate any help on this. With how scarce trucks are these days I'm afraid to sell it lol.

 

[454cid]

The truck only has 89,000 kms??? That's only 55K miles!

 

[DonYukon]

mmm I have a simialer problems with my 1992 and for me the IAC did not fix it. I did not replace the ICM for the stall problem. but as far as the Oil pressure is concerned my gauge is reading within +/- 2 PSI within 30 PSI (minding the Bench test gauge is accurate). However I did have a small bit of luck putting a thicker weight oil in it. but to your point the oil passage tolerances will increase overtime. Ive checked my oil pick=up tube as others have pointed out to me. at this point it will blow up when it blows up the truck is 30 years old with over 200k. had a lot of idle time as a ranger service truck.

 

[DonYukon]

The truck only has 89,000 kms??? That's only 55K miles!

However as he pointed out regardless of the year unless yours had a lot of idle engine hours like mine 55k is NOTHING for a 350

 

[pmndlt]

Thanks @DonYukon and @454cid for the replies. Dont believe it idled much but who knows I guess. It was used by a farmer for hauling. I always forget the conversion is better going km to miles lol. I wanted a 4X4 but as a trailer hauler a RCSRW 1 Ton with that many KMs I couldnt pass up.

 

[Schurkey]

1988 GMC C3500 5.7L TH400

1) Very low oil pressure when in D and stopped (100kpa/14PSI and less - today 0 and still running check gauges on).
2) Occasional immediate stall when into D or R and little tough to start.
3) Under constant throttle surges in between 40KMH/20-30mph. Thought trans so new filter and Dexron III. Nope
4) Occasional smoke on start - suspect seals.

New: TPS, Plugs, Wires, Cap, Rotor, TS sensor, Coolant flush, Trans Flush and Oil Flush. Running 10W30. 89,000 kms.

I'm leaning towards the IAC and have purchased one.

1. Remove oil filter, cut it apart. Is the media crushed 'n' plugged? If it is, replace with a fresh filter and see what happens. Is the oil contaminated? Change oil along with the new filter. Still low pressure? Pretty-much going to have to open the engine and investigate. If you're lucky, the oil pump relief valve is stuck partially-open.

2 & 3. Connect a scan tool and a fuel pressure gauge. Stop buying parts, start diagnosing.

4. Replace seals. See what happens.

 

[pmndlt]

Thanks for the info @Schurkey. The oil filter was clean when I tore it apart, at this point I'm not going to tear down this engine, I'm not sure its worth it for me - it's taken a bit just to get the truck this far. The IAC was cheap and was continually suggested by some friends who have more skills than me.

But I have looked into a scan tool - do you have any recommendations? Far as the valve seals go, it was additional information I know I will have to get going on. I'm struggling to see how/if the oil pressure and stalling is all related or if they're separate issues that's why I mentioned it.

 

[Schurkey]

IF (big IF) the fuel pump relay isn't working right, the fuel pump is being run by the oil pressure switch.

Extreme low oil pressure = no fuel pump = stalled engine with hard restart (long cranking time--gotta build oil pressure to turn on the fuel pump again.



When it was my money, back in...2004 or so...I bought a used, professonal-grade scan tool from eBay rather than a new, consumer-grade tool.

It's served me well since then, although the rechargeable battery is shot, and it takes a long time to boot.

I bought a Snap-On MTG2500, similar to the MT2500 which is cheaper and more-common. I have software cartridges and vehicle adapters to use with 1980 1/2--2006 domestic vehicles. I can connect to the engine computer, ABS, Air bags, instrument cluster (depending on the vehicle).

 

[454cid]

The OP has an 88... how useful will a fancy scan tool be?

 

[LC2NLS6]

I'd throw a vortec fuel pump at it at this point and make sure all grounds are good, including the one for the fuel pump circuit, heck might even be worthwhile to run a new hotwire and relay (triggered by the factory FP relay to the fuel pump in case the fuel circuit is corroded up). Everyone starts replacing sensors, well, sensors just say there is a problem, not the problem themselves. Engine needs fuel air spark and compression. Verify timing as well, have to pull the diagnostic wire, in 88, is that behind the dash?