Spider injection issues

[stutaeng]

Well, it's pretty obvious that the injectors intermittently failing is the root cause. It's a cause and effect. Don't try to fix the effect.

I know intermittent sticking open or closed injectors are really difficult to diagnose. I think they sometimes only act up after engine is warm. But the fact that you've changed them twice, you can get them to pulse via scanner and 1 through 4 all fail at the same time makes me want to look at wiring.

There's also the very slim possibility that the ECU is at fault here. Not sure how to diagnose that. I'm just a DIY guy and know basic stuff.

Good luck!

 

[GoToGuy]

If you have changed the spider to a known good unit and the same problem persist. Either you installation is screwy or it's not a spider problem by elimination process. Look up river where control comes from. I'd analyse all the data I could get from the pcm.

 

[1998_K1500_Sub]

Perhaps there are two ICs in the ECU that drive the 8 injectors, and one IC has gone bad and hence this problem.

You’ve got a 2000 model year 2500 L31, yes, so your ECU us same as my 1998 L31 I believe.

I gotta think about this…

 

[BLACK&chrome]

Perhaps there are two ICs in the ECU that drive the 8 injectors, and one IC has gone bad and hence this problem.

You’ve got a 2000 model year 2500 L31, yes, so your ECU us same as my 1998 L31 I believe.

I gotta think about this…

Yes 2000 5.7 L31 4L80E. I think its 99+ but not sure on the 3/4 tons.. I know like 98 burbs have a 5 plug .. mine has 4. My 99 only had 4.

 

[Schurkey]

You have four misfiring cylinders, two on each bank.

Therefore, wildly excessive O2 driving both upstream O2 sensors nuts with false lean indication.

No surprise that the computer is going deeply into rich-command, so the four cylinders that run are running rich.

Since it's possible but very unlikely that you've got two defective spiders, I'd be looking at the ECM and/or the wire harness between ECM and spider. This could include bent/deformed pins in the connectors that attach the harness to the spider, or the harness to the ECM, or that attach two sections of the harness together. It could also be plain ol' pinched wires, or semi-failed injector drivers in the computer. Or something else.

Good luck. This is weird, so perhaps difficult to track down. This is also going to be hard on the catalytic converter(s); you're feeding them a heap of unburned hydrocarbon, plus a heap of air. They're gonna get HOT. (If they don't get HOT, it's because they've already failed.)

 

[Steve A]

I don't know but it seems to me that the cylinders with wet plugs are the ones misfiring and all that raw fuel is being sensed by the pcm, causing it to pull fuel and driving the other cylinders lean.
The old black box pcm had two boards inside, GM issued a TSB and kit to fix a bad ground issue between the two circuit boards on early 1996 models. Supposedly that was corrected in late 1996 but I suspect that may not still be a good fix. The 1996 and 97 (I think) had the pcm with 5 plugs and the later black boxes had only 4. I believe the two different black box pcm are interchangeable provided all installed equipment is the same, i.e. engine, trans, etc. This may be a factor that drove some to do a 0411 pcm swap too.

 

[Schurkey]

I don't know but it seems to me that the cylinders with wet plugs are the ones misfiring and all that raw fuel is being sensed by the pcm, causing it to pull fuel and driving the other cylinders lean.

The engine does not have an exhaust fuel sensor. It has an O2 sensor. A misfire leads to lots of O2 and unburned hydrocarbon (fuel) in the exhaust stream--but the computer doesn't know about the hydrocarbon, just the O2..

 

[PedroC]

Alright folks I've got a problem noone can seem to track. Front side injectors work intermittently. Can fire all through scanner. Fuel pressure good, filter good, pump good, ecm fuses good. I hooked up 3 more grounds and tried 2 different spiders, new plugs, wires, distributor and all sensors are new still no difference. Anyone have any ideas what else it could be?

My advice for what it’s worth is to K.I.S.S the problem, move injectors see if the problem moves with the injectors you can rule out electrical problem, if it’s coils near place move coils. Hopefully it useful.

 

[BLACK&chrome]

My advice for what it’s worth is to K.I.S.S the problem, move injectors see if the problem moves with the injectors you can rule out electrical problem, if it’s coils near place move coils. Hopefully it useful.

Tried this with pretty much the whole harness. Can't seem to make anything happen. 02 sensors are also new. All 4 Voltage readings are within range at all times. Im going to see if I can find another computer at the local yard this week.

 

[BLACK&chrome]

Played around with scanner a bit more and all O2 sensor are in proper range at all times. I did notice fuel trims are out though. Bank 1 is within range long and short however bank 2 long term is out of range positive 14 ish on average which I believe is lean correct? The spider still proceeds to kick in and out from 4 to 8 with no rhyme or reason and still have yet to be able to cause it myself. I haven't gotten a chance to try a different computer yet either.