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Intermittent EST / Code 42 — 1989 K5 Blazer 5.7L TBI, 700R4
- Thread starter clutch2k3
- Start date
I always try to buy the best plug wires I can, not just the cheapo parts store units.
I've been zapped by HEI before, and its not fun.
I've been zapped by HEI before, and its not fun.
It had been a long stretch without a code 42
Got an EST SES today. Engine wasn't fully warmed up, coming to a stop light, pointed down hill, it stalled but started right back up. I needed to pulse the throttle to keep it running at the stoplight.
I pulled over, turned it off for a minute or 2 and it started back up with timing working fine. Then I drove it around town doing errands for 3 hours and it was fine.
:shoulder-shrug:
Got an EST SES today. Engine wasn't fully warmed up, coming to a stop light, pointed down hill, it stalled but started right back up. I needed to pulse the throttle to keep it running at the stoplight.
I pulled over, turned it off for a minute or 2 and it started back up with timing working fine. Then I drove it around town doing errands for 3 hours and it was fine.
:shoulder-shrug:
I have had 43 show up on mine (intermittently) as well. Whenever it occurred, the Blazer started running/driving like s***. I would basically pull over and stop and then fire it up later and it would be fine.
There is a small tube that looks like a piece of macaroni... it bolts to the transmission bell housing on the passenger side... if I recall correctly one of the EST circuit wires runs through it. My macaroni tube piece was missing and my wire had a pretty significant nick in it. I wrapped it in heat-shrink and reinstalled the tube to protect it better. I haven't had a code 43 show up since then (a year or two ago).
There is a small tube that looks like a piece of macaroni... it bolts to the transmission bell housing on the passenger side... if I recall correctly one of the EST circuit wires runs through it. My macaroni tube piece was missing and my wire had a pretty significant nick in it. I wrapped it in heat-shrink and reinstalled the tube to protect it better. I haven't had a code 43 show up since then (a year or two ago).
I think code 43 is for ESC, the knock sensor, and the ESC sensor wire goes through the macaroni tube.
2 years ago my k5 was throwing code 43s until I replaced the ESC sensor, it's 1 wire connector, the ESC module and it's connector.
I'm not sure if an ESC issue (code 43) can cause an EST issue (code 42).
2 years ago my k5 was throwing code 43s until I replaced the ESC sensor, it's 1 wire connector, the ESC module and it's connector.
I'm not sure if an ESC issue (code 43) can cause an EST issue (code 42).
Iirc the code 42 is going to set everytime the engine stalls, no matter the reason. If by chance the egr was stuck open and stalled while coming to idle, code 42 will set.
Agh, my bad! I got the two circuits confused a bit there.
Back on the 7th, timing was lost, SES turned on, ran poorly for about 2 seconds and then stalled. I believe the timing issue caused the stall, not the other way around.
Yesterday we drove it for 15 minutes, parked it for an hour and then when leaving and getting back on the main road, it backfired! No SES.
Backfiring is caused by bad timing or lean fuel, right? Anything else that could cause a backfire?
Yesterday we drove it for 15 minutes, parked it for an hour and then when leaving and getting back on the main road, it backfired! No SES.
Backfiring is caused by bad timing or lean fuel, right? Anything else that could cause a backfire?
spark leak across spark plug wires, carbon traces/crack in cap. Yes a rapid lean condition could cause a back fire.
Hey @Wes Harden @dyeager535 @Fastereddie — what's y'alls opinion on replacing an 89 TBI setup with Megasquirt 2?
I've been chasing this intermittent code 42 for over a year now and I'm done troubleshooting it.
It shows up between every 10-20 startups. Feels like ~55% of the time it kicks off within a mile of startup, ~40% of the time while it's at operating temp sitting at a stoplight, and the other ~5% who knows. Sometimes it leads to it stalling on me.
So I've decided this 37 year old ECM has done all it's gonna do for me. The stall is the real dealbreaker — I don't feel right loading the family up for a road trip knowing I could randomly lose power steering and brakes. We want to tow a small camper with this thing too, so "probably fine" isn't good enough anymore.
So I've narrowed it down to two options:
**Carb swap** - non-computer HEI, regulator, manual TCC toggle. Cheap, zero electronics, fixable on the side of the road with hand tools. Downside is it tosses everything I've already got — TBI unit, injectors, IAC, all the sensors and pigtails I've sunk money into.
**Megasquirt 2 ** - keeps all that existing hardware, plus I get an actual adjustable idle target (the stock ECM is hard coded around 525 RPM and fights me every time I need ~650 RPM for the AC compressor and alternator), TCC lockup, and data logging. Runs TunerStudio, so I'd be doing my own tuning.
I'm leaning hard toward the MegaSquirt. Curious if anybody here has run one on a TBI 5.7, or if y'all think I'm nuts and should just throw a carb at it and be done.
I've been chasing this intermittent code 42 for over a year now and I'm done troubleshooting it.
It shows up between every 10-20 startups. Feels like ~55% of the time it kicks off within a mile of startup, ~40% of the time while it's at operating temp sitting at a stoplight, and the other ~5% who knows. Sometimes it leads to it stalling on me.
So I've decided this 37 year old ECM has done all it's gonna do for me. The stall is the real dealbreaker — I don't feel right loading the family up for a road trip knowing I could randomly lose power steering and brakes. We want to tow a small camper with this thing too, so "probably fine" isn't good enough anymore.
So I've narrowed it down to two options:
**Carb swap** - non-computer HEI, regulator, manual TCC toggle. Cheap, zero electronics, fixable on the side of the road with hand tools. Downside is it tosses everything I've already got — TBI unit, injectors, IAC, all the sensors and pigtails I've sunk money into.
**Megasquirt 2 ** - keeps all that existing hardware, plus I get an actual adjustable idle target (the stock ECM is hard coded around 525 RPM and fights me every time I need ~650 RPM for the AC compressor and alternator), TCC lockup, and data logging. Runs TunerStudio, so I'd be doing my own tuning.
I'm leaning hard toward the MegaSquirt. Curious if anybody here has run one on a TBI 5.7, or if y'all think I'm nuts and should just throw a carb at it and be done.
I have no info on the mega squirt, you just gave more info than I had.
Qjet is a great option, biased opinion, running one or 2 myself
Qjet is a great option, biased opinion, running one or 2 myself
Fitting a MS2 in place of a TBI ECU is really not that hard of a conversion, assuming you are comfortable doing the wiring. You could either mod your existing harness to now terminate to the MS2 connector or start over. There's always the chance some bad connection in the original harness is part of the problem. Support for HEI ignition, GM injectors and sensors is built-in, so you can keep all of your gauges with no changes. IIRC, there is more than one location for a CLT, so you could dedicate one to the MS ECU. You'll also want to add an IAT sensor, which should be easy to do somewhere in the intake tract. Otherwise, everything you need is already there. I recommend finding stock TBI spark and fuel tables at minimum, but even better would be a running tune file from a similar setup. That can save you a lot of effort dialing in the transient response.
Keep in mind that there are many dozens of settings to tell the MS what kind configuration you have, before it will even start and idle.
https://diyautotune.com/blogs/installation-guides/megasquirt-your-sbc-v8
Keep in mind that there are many dozens of settings to tell the MS what kind configuration you have, before it will even start and idle.
https://diyautotune.com/blogs/installation-guides/megasquirt-your-sbc-v8
@Blue85 is very well versed on this subject.
I have built and installed a half dozen MS’s on stuff over the last decade or two. In my opinion, you need to be very commited to learning and understanding the MS. You should be well versed in wiring and electronics. It is very diy. BUT, I love it.
Thanks a lot! I figured I'd need to tap an IAT. I'm going to read all the info at that link and reach out to DIYAutoTune.
I do a lot of wiring myself and I dabble in electronics. I've built 3 iterations of a flashing TCC override switch so far. I started with an analog astable multivibrator oscillator which did really well with all the noise from the alternator, then tried some 555 timer chips which failed miserably and finally went back to the analog flashers and added a fan override to help the AC at idle. The blue LED turns on when the ECM demands TCC lockup.
In case you're wondering, it started throwing code 42 before I added the override switch and it still throws it without the override switch. It was the very first thing I checked.
I do a lot of wiring myself and I dabble in electronics. I've built 3 iterations of a flashing TCC override switch so far. I started with an analog astable multivibrator oscillator which did really well with all the noise from the alternator, then tried some 555 timer chips which failed miserably and finally went back to the analog flashers and added a fan override to help the AC at idle. The blue LED turns on when the ECM demands TCC lockup.
In case you're wondering, it started throwing code 42 before I added the override switch and it still throws it without the override switch. It was the very first thing I checked.
Yeah, if you play with that kind of stuff make a squirt should be no problem for you and like blue said you can order them prebuilt already but if you enjoy that type of thing, it is fun to build them
