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Hmmm TBI code 42 UPDATE: no code and...

ccarley

ccarley

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I've done some searching, but just looking for some confirmation.

While driving to work today, my "Service Engine Soon" light came on (I thought they were a "Check Engine" light, but whichever). Checking the codes, the computer spat out 42.

Most of what I've seen while searching are issues with rough idle, popping and or snapping, backfiring, due to loose connections in the dizzy. I'm not experiencing any of these issues; my only problem was a lower idle when the light came on, and somewhat lack of power since.

I'm leaning more towards an issue with the module in the dizzy, as opposed to a loose connection. Anyone else have this same experience with a bad dizzy module?

I'm picking one up tomorrow anyway, just in case. Cheap insurance at like $40 or $50.

Thanks,
Clay
 
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Check engine light has been off, and still running OK. This afternoon I replaced the module in the dizzy just for good measure; the old one was crusty looking anyway. Fired it up, and it ran like the computer needed to adjust a little for the new module? After a few moments, it ran as smooth as ever.

Will take it out for a drive this evening to see how it does. I still have the old module just in case...

Clay
 
Well, that lasted about a day! Good thing I saved the old (original) module. It's back in... re installed in the pouring rain last night. When else would it die?

I drove it to work, and drove it home, and felt it was running great! We hopped in to get some food for dinner, and it would not fire. Oh well... might need another solution.

Clay
 
Yeah, well, it died again while on the way to work today. Got another module (this one made in Taiwan, not Hong Kong like the last one) and cleaned up the surfaces, used the included goo.

Now it running rough & sputtering. Maybe the other ignition box is bad too, the one under the air filter. It does make noise on & off while it's running... sounds like sparking from that box.

Clay
 
Code 42 is the EST system, and there is a lot of tests you can do to determine what they are. Do you have the shop manual? It will tell you exactly how to do that.

When does it die, while you are driving? Or at an idle? Or ... what are the exact symptoms?

BTW, if the tan wire with the black stripe (EST wire) is not connected to the distributor, or is shorted/grounded out, that can cause the truck to not start. Check that carefully for damage.
 
Jessie James said:
Code 42 is the EST system, and there is a lot of tests you can do to determine what they are. Do you have the shop manual? It will tell you exactly how to do that.

When does it die, while you are driving? Or at an idle? Or ... what are the exact symptoms?

BTW, if the tan wire with the black stripe (EST wire) is not connected to the distributor, or is shorted/grounded out, that can cause the truck to not start. Check that carefully for damage.
Click to expand...


I'll do some checking on it tomorrow; I left it at my office.

Exact symptoms: at first, the idle was low, and the check engine light was on. Later that day it ran fine, no check engine light, but code 42 was returned while checking.

I replaced the module in the dizzy, and it was running better! Just fine! Had more mid-range power. I parked it at home, and then we hopped in to go to dinner, but it didn't start at all. I put the original module back in, and it fired up just fine (although I think it took an extra crank or two to fire).

Today I was driving it to work, with the original module. It started sputtering & not running well under load. Cruising was fine. Then, close to work (20 minutes later), it died. I picked up a new dizzy module, and it fired up but sputtered the rest of the way to my office.

The other thing I notice though is the other module, the one under the air filter, makes noise. It's made noise for quite some time though, so I thought nothing of it; it could even be the fuel injectors for all I know. But, it sounds like a buzzing/ arcing/ sparking from time to time.

I'll go through the manual tonight, and tomorrow I should have some time to check out the wiring too. My wife wants to take it to a shop, but I tell her "it's a Chevy 350, how bad can it be?" :)

Thanks for the advice!
Clay
 
I spent the last 1/2 hr or so reading my Chilton's and Hayne's manuals. The Hayne's has some good info on testing; I'll be sure to check everything over tomorrow with my multimeter. Also I see the EST connector *should* be near the brake booster(?) and it should be checked over too.

Well, I guess that's it 'till tomorrow :)

Thanks,
Clay
 
UPDATE:

I cleared the computer by disconnecting the battery. Fired it up, ran fine when cold! It ran just fine until it warmed up, then started running rough, finally coughed & died. Won't start again.

I'm guessing whatever is going on only happens when the computer sees that the engine is warmed up at this point. It ran nice & smooth when cold, no problem!

My head is back to the books.

Clay
 
OK, so I'm leaning towards the coil. Tomorrow, hopefully, I'll have time to get my multimeter out to check everything.

Clay
 
That sounds about right. I presume you have also thought about the IAC? If the IAC is clogged that might be an issue. It's easy to take if off and clean the inlet with some carb cleaner.
 
JesseJames: I sure have thought about my IAC... with the air filter open, it makes some sucking sounds from time to time. The HEI module last time though was clearly blown. The white thermal compound was brown in a circle on the bottom, near where the coil connector is.

I'm heading to the parts store now to replace one of the modules that I bought :) I'm also picking up a coil, and a pickup coil. I'm hoping the generic parts will work together OK, but definitley looking for an upgrade to some higher quality stuff in the future. Imagine if I were in the woods when this happened...

Clay
 
Since the problem happens when the temperature gets up, you might want to check the coolant temp sensor as well.
 
Good call on the coolant sensor. Would that cause the HEI module to pop though? Whatever is happening is definitely killing the module in the dizzy... I will look into it though for sure!

Clay
 
That was my next thought, and to point out that the TBI engines have two coolant sensors, so you have to check them both. One on the block and one near the intake (I admit I don't know where though! :) )

The ECM definitely uses the coolant temp to help adjust things, so that should be easy to check. Does your coolant gauge work? That tells you if one works at least!
 
Haha yup, as far as I can tell my gauge works just fine. Good to know there are two sensors though... I've got my meter out today, so I'll be checking everything I can while I'm under the hood.

Clay
 
Ok, I got a chance to check out the manual. It says to check in this order:

> For water in the gas
> Fuel pressure
> TPS sticking or binding
> The EGR stuck open
> Fuel pump relay
> in-tank fuel pump check valve. (To test, ignition off, disconnect fuel line at filter, remove gas cap, connect pressure test pump to the line and apply 15 PSI. If pressure holds for 60 seconds, it's okay.)
> Coil ground
> Water in distributor cap
> Remove EST (tan with black stripe wire to distributor) and start. if it runs, replace distributor pickup coil.
> Check EST for short to ground.

Other things to check:

> Disconnect both injectors, crank engine. If either one sprays, replace it or the seals.

> Connect test light to each injector harness. Does light blink when you turn the engine over? If not, find problem with wiring.

> With both injectors connected, crank engine, both should spray.

After that it gets into some complex charts ... I should scan the whole thing in somehow...
 
Thanks for the tips Jesse James!

There are no codes in the computer at this point though. I replaced the coil, checked the wiring with my meter, and replaced the HEI module again. Same thing:

Starts right up! Ran fine while it was cold, revved fine, idled fine, etc. Once it was warm (according to the gauge, t'stat popped open), however, it started running really rough, and died pretty quick. I didn't try to continue running it. It did start again, but I don't want to risk killing another HEI module.

Yeah, I used the grease that came with the module, in every case. Good connections all around too. We are taking it (towing) to a friends place right now, so they can look at it. I'll keep everyone posted though!

Thanks for the tips! I do really appreciate the help.
Clay
 
So will a bad pickup coil in the distributor blow an HEI module? And, will it run fine until it warms up even with a bad pickup coil?
 
If it runs until it gets warm then it is starting to sound like a bad coolant temp sensor. There are two of them, so check them both. One is on the intake galley and one is on the side of the head (as I recall).

The ECM monitors the temp of the engine using the coolant sensor. If the sensor is bad, it tells the ECM to keep sending more fuel (like the choke works on carb engines). Of course, once it warms up the engine won't run because it's too rich. Check that link I just posted or the one in my signature for the diagnostics, code 15 and it tells you how to test it.
 
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