Engine stalling

I have a 1990 9C1 5.7 in my Land Cruiser. It has the 1228746 ECU (came with the engine). I almost feel like starting over with a 7727 ECU just so I can better read and mod everything, but it hasn't been an issue until recently. Note: ever since new Tuner Pro shows error codes 24 (VSS) and 42 (EST), no check engine light and has run perfectly until recently. I don't see any way to clear and reset these codes.

A couple weeks ago about 2 hours into a wheeling trip the engine stalled at idle. It had never done this before. It happened once more that day. No check engine light.

The next day I hooked up my laptop and couldn't see anything odd. Since I had spares I swapped out the IAC and EST. Everything ran fine on short drives. Base timing was right on. Injector spray patterns looked normal.

Yesterday I went on another long trip. About 2 hours in (heat soak?) the stalling began again. No engine light. Restarting the engine takes lots of cranking and a bit of throttle. I noticed that the injectors were noisier than I remembered. The engine stalled about 40 times before I made it home.

My data logs from 2017 show idle RPM is between 600 and 650 (my expected normal). IAC steps around 50 at idle, TPS volts .62

I ran a data log yesterday in my driveway after I got home (hot from 10 hours of driving). Idle RPM was 550 to 625 stumbling down to 500 (where it stalls, stall saver not quick enough?), IAC 11 to 18 (very low compared to 3 years ago), TPS .62v.

The only changes I ever made to the tune was changing the stoich (14.4) for our local fuel and removed the TCC locking values because my TC has it's own controller. I had to be careful since the $61 mask is not well built out.

The bin does show "Idle - Target RPM (a/c off)" is 550
"IAC - Desired C/L Idle Speed"
675.00
675.00
675.00
650.00
625.00
625.00
650.00
700.00
725.00

Suggestions? Buy another IAC?

Quote:

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Originally Posted by srgould41

I have a 1990 9C1 5.7 in my Land Cruiser. It has the 1228746 ECU (came with the engine). I almost feel like starting over with a 7727 ECU just so I can better read and mod everything, but it hasn't been an issue until recently. Note: ever since new Tuner Pro shows error codes 24 (VSS) and 42 (EST), no check engine light and has run perfectly until recently. I don't see any way to clear and reset these codes.

A couple weeks ago about 2 hours into a wheeling trip the engine stalled at idle. It had never done this before. It happened once more that day. No check engine light.

The next day I hooked up my laptop and couldn't see anything odd. Since I had spares I swapped out the IAC and EST. Everything ran fine on short drives. Base timing was right on. Injector spray patterns looked normal.

Yesterday I went on another long trip. About 2 hours in (heat soak?) the stalling began again. No engine light. Restarting the engine takes lots of cranking and a bit of throttle. I noticed that the injectors were noisier than I remembered. The engine stalled about 40 times before I made it home.

My data logs from 2017 show idle RPM is between 600 and 650 (my expected normal). IAC steps around 50 at idle, TPS volts .62

I ran a data log yesterday in my driveway after I got home (hot from 10 hours of driving). Idle RPM was 550 to 625 stumbling down to 500 (where it stalls, stall saver not quick enough?), IAC 11 to 18 (very low compared to 3 years ago), TPS .62v.

The only changes I ever made to the tune was changing the stoich (14.4) for our local fuel and removed the TCC locking values because my TC has it's own controller. I had to be careful since the $61 mask is not well built out.

The bin does show "Idle - Target RPM (a/c off)" is 550
"IAC - Desired C/L Idle Speed"
675.00
675.00
675.00
650.00
625.00
625.00
650.00
700.00
725.00

Suggestions? Buy another IAC?

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Howdy

I am not qualified to advise on the tune really but from recent experience, disconnecting the battery will reset a hard code 42 when a scanner will not reset. If it comes back without Tuner Pro connected, you may have an ECM malfunction. IAC counts 11-18 on a thoroughly warmed-up engine is what most seem to set for idle. The lower the number of counts, the closer to fully closed it is. Higher counts would indicate the computer is trying to keep the RPM's up.

If the ECM is in limp home mode it will run very similar to what you describe.

I have no experience with the VSS. Someone else will need to chime in on that one.

Thanks for the reply.

Update: I spent some time looking very closely. I found some issues with the wires to the injectors and repaired them (one had a cut halfway through it). I also found a bare wire at the distributor, the sense return wire which explains the code 42. I replaced the plug and some wire. Since the fuel pressure had been lower then I liked to see I took off the fuel pod. I installed a replacement set of injectors and also took apart the FPR. I rebuilt the TBI (including the shaft bushings) about 3 years ago. What I found inside the regulator surprised me. The spring looked like it had been at the bottom of the ocean for a while. It was crusted over with rust. I bought a "14 psi" spring and put that in there. At the same time I installed an adjustable FPR that I had on my spare TBI. I decided not to tempt fate so adjusted it for 12 PSI. That's as low as it goes.

Took it out for a warm up drive and data logged. It ran normally. The logs looked like previous logs, not greatly richer as I feared. No code 42! Came home and ran through the IAC close procedure, unplugged it then ran the engine. Idle was not perfectly stable, but it was 500-ish. At one point it dropped to 350 and recovered on it's own. Plugged the IAC back in, reset the computer to clear codes and ran it at idle. Mostly smooth at 550 with about 5 IAC counts. Strange how all past data logging drives were 650 idle RPM with lots of IAC counts. I had always assumed that was normal for the engine. I might increase the commanded idle RPM to 575, but later and only if I think the stalling is still there. I might do an 8th turn on the idle screw too, but only if I up the idle in the chip. First I need to get out on a long trip to see if the stalling condition is gone. If it is solved I would not be able to point at any one thing as the root cause since I changed several things at the same time. Since the stalling issue only started after the engine had been running for a few hours I am leaning towards heat soak causing increasing resistance in the dizzy and/or injector wires. Low fuel pressure could have played a role in it too.

I plan to take it out on the 21st or 22nd. Maybe a snow run. Fingers crossed.

run it at 14 psi. if the original injectors were on the engine you are better off getting them reconditioned and flowed (for example: witchhunter). i had an '89 9C1 Caprice 13 years ago. someone had out 4.3L injectors in it. i put in a set of OEM good 5.7L injectors. it ran better. swapped in a TPI fuel pump. it ran even better. shortly before selling (5 years later) it i finally rigged up a fuel preasure gauge. 9 psi, in spec but lame. modified stock reg and was able to get 13.5 psi. Ran the best it ever had, better idle, more power, it even ran cleaner emissions.


BTW, stock 5.7L 9C1 injectors actually flow a few pounds more than the "standard" 5.7L injectors.

if anything you would want to goto a '7427, it is a TBI pcm with higher data log rate,e-trans, etc. I would personally go with EBL if you dont plan on running an e-trans.

I would check your pickup coil & module. also monitor fuel pressure while the stalling happens. a TPI or vortec pump is a bice upgrade even for a stock TBI system like yours. gm performance sells a whole EFI distributor for a decent price this is the route i have gone a few times before...

No worries on the injectors. I am running 65 lb/hr ones. Flow matched and serviced.

Quote:

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Originally Posted by tayto

run it at 14 psi. if the original injectors were on the engine you are better off getting them reconditioned and flowed (for example: witchhunter). i had an '89 9C1 Caprice 13 years ago. someone had out 4.3L injectors in it. i put in a set of OEM good 5.7L injectors. it ran better. swapped in a TPI fuel pump. it ran even better. shortly before selling (5 years later) it i finally rigged up a fuel preasure gauge. 9 psi, in spec but lame. modified stock reg and was able to get 13.5 psi. Ran the best it ever had, better idle, more power, it even ran cleaner emissions.


BTW, stock 5.7L 9C1 injectors actually flow a few pounds more than the "standard" 5.7L injectors.

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I do have a pressure gauge installed under the hood. I would love to have one in the dash, but no way I am running a pressurized fuel line into the cab. I was wondering if I could use an Autometer oil pressure sensor and gauge (electric). I have one I removed for a mechanical set. It would probably only be temporary. Autometer would not comment when I asked :).

AutoMeter has fuel pressure transducer. I ran a 100 psi one with EBL many years ago. i have it for sale if you're interested.

I saw their transducer and gauges. Quite over priced like all their other products. :)

I found a different brand gauge/transducer combo that is inexpensive. It's listed for fuel, oil, hydraulic, etc. I just wondered if AM's oil pressure one would work safely with other fluid types. I use their temp transducer with coolant and ATF without issue.

Quote:

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Originally Posted by tayto

AutoMeter has fuel pressure transducer. I ran a 100 psi one with EBL many years ago. i have it for sale if you're interested.

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would probably work but are the internals ethonol resistant is the question.