1989 K1500 5.7 350 TBI running rich and pinging after engine rebuild, LOSING MY MIND

[poolguybri]

1989 Chevy K1500 5.7 350 TBI. Had motor professionally rebuilt and have been chasing electrical gremlins ever since. Truck ran fine before rebuild, aside from at end of life due to age. Engine was rebuilt to factory specs but with factory-style roller cam instead of the original flat tappet cam. I am experiencing rough / surging idle, especially once coolant temp reaches approx 110 degrees. Idle surges between roughly 575 and 850 rpm and runs rich. When driven for any length of time I get a code 43. I can hear pinging at idle, seems to get worse as engine warms up. I have observed the engine bay in total darkness and can see blue flashes at all 8 of the spark plugs. I can't actually see sparks arcing, but can definitely see blue flashes once my eyes adjust to the darkness. I'm not sure if this is actual arcing or "corona effect"??

All grounds are good as far as I can tell, and multiple "extra" grounds have been added.
Distributor has been replaced. Cap, rotor, and ignition module inside distributor have all been replaced repeatedly.
Ignition coil has been replaced and tests within spec.
EGR valve has been replaced.
IACV has been replaced.
TPS has been replaced.
ESC module has been replaced.
O2 sensor has been replaced.
Fuel pump has been replaced.
Spark plugs and wires have been replaced repeatedly. Spark plugs are gapped correctly to 0.35, are installed with copper antiseize, and torqued to spec.
Plug wires are run so as not to touch each other or anything grounded like firewall.
Plugs are AC delco conventional.
Thoroughly checked for vacuum leaks.
Performed compression test, all cylinders are within 10% of each other.

I have WINALDL and will post datalog. Scanner shows low BLM (confirms running rich).

I am about to light this truck on fire and push it out into the street. Any ideas????????

 

[poolguybri]

Also, base timing set to 0 with timing wire unplugged.
Fuel pressure is 11 psi
Fuel filter was replaced.
Knock sensor was replaced.
Coolant temp sensor was replaced.

 

[Schurkey]

1989 Chevy K1500 5.7 350 TBI... ...Engine was rebuilt to factory specs but with factory-style roller cam instead of the original flat tappet cam.

Original block? Some of the 350 blocks in the early years of the GMT400 production didn't have provisions for the lifter dogbone spider, or for the cam thrust plate. All those parts were installed...right?

Was the cam degreed, or just shoved-in "dot-to-dot"? What is the cranking compression pressures of all eight?

I am experiencing rough / surging idle, especially once coolant temp reaches approx 110 degrees. Idle surges between roughly 575 and 850 rpm and runs rich. When driven for any length of time I get a code 43.

ESC fault. Follow service manual diagnosis procedure. Service manuals are available for free download via links in a "sticky" thread on this site.
www.gmt400.com/threads/88-98-service-manuals.43575/

88-98 Service Manuals

Over the years I have collected a bunch of GM service literature. Links to PDF Scans of service and STG manuals and a links to the Parts manuals. You'll need the FREE Adobe Acrobat reader to open these files. Get it directly from Adobe here {http://get.adobe.com/reader/} If you're not...

www.gmt400.com

I'd begin by assuring that the timing mark on the damper is aligned with "0" on the timing pointer, when #1 is at TDC.

I can hear pinging at idle, seems to get worse as engine warms up.

That's REALLY unusual. Pinging at idle would tend to indicate enormously-advanced ignition timing, although there's other potential causes. A "potential cause" is that you're hearing something other than "ping". Lifter tick, carbon knock, loose torque converter bolts, failed accessory belt tensioner, exhaust leak, etc.

I have observed the engine bay in total darkness and can see blue flashes at all 8 of the spark plugs. I can't actually see sparks arcing, but can definitely see blue flashes once my eyes adjust to the darkness. I'm not sure if this is actual arcing or "corona effect"?

Almost certainly corona, you'd likely hear the snapping of actual arcs otherwise. Maybe the arcing is the "pinging" you hear.

Time for new plug wires, and/or to assure that the plug porcelains are clean and non-conductive. Have you been using dielectric grease on the insides of the plug boots? They didn't spray-paint the spark plugs along with the rest of the engine...did they?

Distributor has been replaced. Cap, rotor, and ignition module inside distributor have all been replaced repeatedly.
Ignition coil has been replaced and tests within spec.
EGR valve has been replaced.
IACV has been replaced.
TPS has been replaced.
ESC module has been replaced.
O2 sensor has been replaced.
Fuel pump has been replaced.
Spark plugs and wires have been replaced repeatedly. Spark plugs are gapped correctly to 0.35, are installed with copper antiseize, and torqued to spec.
Plug wires are run so as not to touch each other or anything grounded like firewall.
Plugs are AC delco conventional.
Thoroughly checked for vacuum leaks.
Performed compression test, all cylinders are within 10% of each other.

I have WINALDL and will post datalog. Scanner shows low BLM (confirms running rich).

Replacing parts does not fix wiring harness faults. Connect a scan tool, verify EVERY sensor.

HOW are you testing the ignition coil? An ohmmeter can tell you if a coil is defective. It cannot tell you that the coil is "good". You'd need to verify spark output in addition to having reasonable results from the ohm-testing. A spark-tester calibrated for HEI ignitions is the simplest, cheapest way to verify coil output.

A recent thread on this forum displays EGR valve differences; some of the "correct" part number have no orifice at the vacuum nipple leading to excessive EGR application.
www.gmt400.com/threads/psa-1988-1995-stumble-after-egr-valve-replacement.61043/

PSA: 1988-1995 stumble after EGR valve replacement

Hoping this helps somebody else who's pulling their hair out (potentially after replacing the solenoid and vac lines). I only found one other GMT400 thread which addressed the issue (gmt400.com/threads/which-egr-valve.60874/post-1290515) and it didn't have pictures, so see attached. Code 32 on...

www.gmt400.com

Plug wire routing is more than just making sure they don't "touch". Especially critical is the routing of #5 and #7, if #7 cylinder gets induced voltage from #5 spark, #7 cylinder fires 90 degrees early and tries to turn the crankshaft backwards.

Cylinders are within 10%, but are they all "low" or "high" pressure? What are the pressure readings?

"Low "Block Learn"" does NOT indicate "rich". High O2 sensor voltage indicates "rich". Low Block Learn indicates "lean command" which is not the same thing as "rich".

Also, base timing set to 0 with timing wire unplugged.

Correct damper/timing pointer used on the "rebuilt" engine? There's AT LEAST two different timing mark alignments on SBC engine, one is 13 degrees different from the other. Then there's the possibility of having the inertia ring of the damper rotating on the hub due to faulty rubber between the two.

Fuel pressure is 11 psi
Fuel filter was replaced.

Does it maintain 11 psi under heavy load, or when the engine is running poorly?

Knock sensor was replaced.
Coolant temp sensor was replaced.

It doesn't matter if they were replaced. What matters is that they work properly and that the computer receives the correct signal, indicating that the wire harness connecting the computer to the sensor is intact. Connect a scan tool, verify ALL sensors.

Was the knock sensor torqued to spec? Failure to properly tighten the knock sensor affects it's sensitivity. In general, too tight makes it too sensitive, not tight enough makes it less sensitive.

 

[poolguybri]

Hi, thanks for taking the time to reply, I appreciate the advice and level of detail.

Original block? Some of the 350 blocks in the early years of the GMT400 production didn't have provisions for the lifter dogbone spider, or for the cam thrust plate. All those parts were installed...right?

Was the cam degreed, or just shoved-in "dot-to-dot"? What is the cranking compression pressures of all eight?

It is the original block, rebuilt by a local old-timer who has been rebuilding engines for 30+ years. I don't have an answer for you as to whether the cam was "degreed or just shoved in 'dot-to-dot'", I'm not even sure what that means tbh this is my first engine I've ever had rebuilt. I will ask engine builder when I speak with him later this afternoon, he said to call him back for the part # of the camshaft he put in. He said rebuilt engine is bone stock aside from factory-style roller cam and insists everything was put together perfectly. We didn't perform a compression test when we first got the engine back (rookie mistake :-/) but did recently, after approx 125 total miles of test-driving and maybe 6 hours (total guess) of idle time trying to troubleshoot these issues. The compression test was performed COLD due to the proximity of the exhaust manifolds to the spark plug holes and results were as follows:
cyl 1: 169 psi
cyl 2: 155 psi
cyl 3: 168 psi
cyl 4: 162 psi
cyl 5: 166 psi
cyl 6: 161 psi
cyl 7: 160 psi
cyl 8: 159 psi
From what I understand these numbers are low for a freshly rebuilt engine (possible damage from test drives and idling so far?) but not low enough to cause problems in terms of low compression. I retested cylinder #2 (lowest compression) with a little squirt of oil in it and the compression result did not change.

ESC fault. Follow service manual diagnosis procedure

Knock sensor is new and ohmed out to confirm within spec before install, and ground verified. I will follow the manual troubleshooting procedure though and update.

I'd begin by assuring that the timing mark on the damper is aligned with "0" on the timing pointer, when #1 is at TDC.

Will do this and update.

That's REALLY unusual. Pinging at idle would tend to indicate enormously-advanced ignition timing, although there's other potential causes. A "potential cause" is that you're hearing something other than "ping". Lifter tick, carbon knock, loose torque converter bolts, failed accessory belt tensioner, exhaust leak, etc.

Definitely possible, the blue flashes in the dark combined with code 43 made me think it was pinging that I was hearing. Should code 43 set at idle or only after certain driving parameters are met? It only triggers for us on test drives not just idling in garage.

Almost certainly corona, you'd likely hear the snapping of actual arcs otherwise. Maybe the arcing is the "pinging" you hear.

Time for new plug wires, and/or to assure that the plug porcelains are clean and non-conductive. Have you been using dielectric grease on the insides of the plug boots? They didn't spray-paint the spark plugs along with the rest of the engine...did they?

I don't think I'm hearing the snapping of arcs but I ordered a powerful magnifying glass to try to get a better look at the flashes at the spark plugs in the dark and will update. We have been through 4 sets of plugs and wires already trying to chase down. One set of NGK v-power spark plugs and 3 sets of delco. The first 2 wire sets were in the $40-$50 range, blue streak and delco, the second 2 sets were in the $130-$150 range, a better set of blue streaks and MSD, which is what's on the truck now. We have been using dielectric grease on the inside of the boots. The plug porcelains are cleaned and all have also been ribbed not smooth. They did not paint the spark plugs with the rest of the engine. Spark plug body where it goes into the block tests good for ground.

Replacing parts does not fix wiring harness faults. Connect a scan tool, verify EVERY sensor.

Will do this and update.

HOW are you testing the ignition coil? An ohmmeter can tell you if a coil is defective. It cannot tell you that the coil is "good". You'd need to verify spark output in addition to having reasonable results from the ohm-testing. A spark-tester calibrated for HEI ignitions is the simplest, cheapest way to verify coil output.

I had just been using an ohmmeter. I ordered an HEI ignition spark tester that arrives later today so will test and update.

A recent thread on this forum displays EGR valve differences; some of the "correct" part number have no orifice at the vacuum nipple leading to excessive EGR application.

will look into this and update, thanks.

Correct damper/timing pointer used on the "rebuilt" engine? There's AT LEAST two different timing mark alignments on SBC engine, one is 13 degrees different from the other. Then there's the possibility of having the inertia ring of the damper rotating on the hub due to faulty rubber between the two.

How would I verify any of this? I believe it is same damper/timing pointer from the original engine, it was painted with the engine, are those parts typically replaced during a rebuild?

Does it maintain 11 psi under heavy load, or when the engine is running poorly?

The gauge is under the hood so I can't see it while driving, seems constant in garage even when engine is revved. There is some "vibration" of the gauge needle, not sure if that is significant at all, going to try hooking up a different gauge to see if the "vibration" is still present.

Was the knock sensor torqued to spec? Failure to properly tighten the knock sensor affects it's sensitivity. In general, too tight makes it too sensitive, not tight enough makes it less sensitive.

The knock sensor was torqued to spec but will loosed and re-torque just to make sure. I also looked back at receipts and realize that the new sensor was by Napa Echlin. I posted my issues to Reddit r/AskMechanics and r/GMT400 as well and one or two people stated that only delco knock sensors work properly, so I have ordered a new delco sensor which arrives Monday.

I should also mention that the truck seems to drive well on test drives until the code is thrown, usually a few miles into the drive.

 

[Erik the Awful]

I don't think I'm hearing the snapping of arcs but I ordered a powerful magnifying glass to try to get a better look at the flashes at the spark plugs in the dark and will update. We have been through 4 sets of plugs and wires already trying to chase down. One set of NGK v-power spark plugs and 3 sets of delco. The first 2 wire sets were in the $40-$50 range, blue streak and delco, the second 2 sets were in the $130-$150 range, a better set of blue streaks and MSD, which is what's on the truck now. We have been using dielectric grease on the inside of the boots. The plug porcelains are cleaned and all have also been ribbed not smooth. They did not paint the spark plugs with the rest of the engine. Spark plug body where it goes into the block tests good for ground.

There shouldn't be arcs. How's your distributor cap? If you need to replace it, the United Motor Products version with brass contacts is the recommended piece.

More Information for UNITED MOTOR PRODUCTS DC840X

While the #2 cylinder is a little low on compression, those aren't bad numbers. I'd check that cylinder's rocker adjustment to see if it's a little tight.

 

[TreeGeared]

As usual Schurkey has hit most of the points. One thing we have not touched on is the cam. You stated that you replaced it. How different were the cam specs? Also going to a roller lifter changes how quickly the lifter reacts to changes in the cam profile. Your contact area is different between the two items. So even if the profile of the CAMs were the similar the rate that the valves open and close could be different. If no changes to the computer were made this may be part or all of your problem. These speed density computers do not respond well to major changes like this. Maybe you had the computer updated and I missed that?

A datalog would help. You are on the right path looking at the BLM. Also look at your 02 sensor fluctuation and if you have before data compare the fuel pulse width of the injectors.

 

[Schurkey]

I retested cylinder #2 (lowest compression) with a little squirt of oil in it and the compression result did not change.

Compression seems adequate to me.

I will follow the manual troubleshooting procedure though and update...

...Will do this and update.

OK.

the blue flashes in the dark

DO concern me. You've replaced plugs and wires multiple times. There should be no corona, and no arcing.

This is one of those times where I'd just love to connect an ignition oscilloscope and discover what the ignition secondary voltage is. My suspicion is that it's unusually high. But WHY is it high? Huge spark-plug gap? Huge rotor-to-cap gap? Something else?

Should code 43 set at idle or only after certain driving parameters are met? It only triggers for us on test drives not just idling in garage.

Again, follow the service manual procedure for diagnosing Code 43.

I ordered an HEI ignition spark tester that arrives later today so will test and update.

Good.

How would I verify any of this? I believe it is same damper/timing pointer from the original engine, it was painted with the engine, are those parts typically replaced during a rebuild?

Bring #1 (or #6, either one) to TDC. You can use an actual piston stop, but for this check a drinking straw down the spark-plug hole (long straw, not a Starbucks coffee stir-stick so it can't fall entirely into the cylinder) should be a good enough indicator that the piston is all the way "up" in the bore. Turn the crank with a long-handled ratchet until the straw stops coming up, and just starts to go "down". Reverse direction until you're satisfied the piston is as high as it goes.

Then check the damper timing mark against the timing indicator. When the piston is all the way "up" at TDC, the timing mark should align with "0".

The gauge is under the hood so I can't see it while driving, seems constant in garage even when engine is revved. There is some "vibration" of the gauge needle, not sure if that is significant at all, going to try hooking up a different gauge to see if the "vibration" is still present.

Maybe the vibration of the needle is the result of engine shake.

I'm more interested in fuel pressure under load, is there a way to check pressure while driving, especially when the engine is acting-up?

The knock sensor was torqued to spec but will loosed and re-torque just to make sure. I also looked back at receipts and realize that the new sensor was by Napa Echlin. I posted my issues to Reddit r/AskMechanics and r/GMT400 as well and one or two people stated that only delco knock sensors work properly, so I have ordered a new delco sensor which arrives Monday.

Ehhhh. I don't have a problem with quality aftermarket parts most of the time.

"I" would assure it's torqued properly. Then check function using a small hammer at idle, fully warmed-up. Tap the head or the intake manifold, make sure the engine RPM drops for a moment, then recovers.

Beyond that...service manual procedure for Code 43.

There shouldn't be arcs...
...While the #2 cylinder is a little low on compression, those aren't bad numbers. I'd check that cylinder's rocker adjustment to see if it's a little tight.

Worth checking, but those numbers don't scare me. I infer from the adequacy of the compression pressure that the cam is installed correctly, or close enough.

As usual Schurkey has hit most of the points.

[Elvis Voice]Thankyew, thankyew verra much.[/Elvis Voice]

 

[tayto]

- cam specs, preferably a part number for what was used please post

- have you got injectors professionally cleaned? is there play in the throttle shafts? i like to see 13 or 14 psi for fuel pressure, it makes a big difference. you can mod the stock regulator easily. i also like to use a vortec or TPI fuel pump even on stock stuff.

-does it start easily or is there lots of cranking and pedal manipulation to get it started?

 

[Sabinoerc]

First, would preface that those commenting above have much more experience than me and my scar tissue is only possibly relevant to one of your comments.

I am experiencing rough / surging idle, especially once coolant temp reaches approx 110 degrees. Idle surges between roughly 575 and 850 rpm and runs rich.

I had similar once on my 93 5.7 TBI and it seems many things can cause this but in my case, it was marginal fuel pressure. I measured 11 psi between filter and TBI and assumed that was good. I replaced and checked everything without joy and finally spent the time to get datalogging capability and noticed that surging was in sync with some “idle enrichment” flag. The idle would slowly get slower and slower until the idle enrichment save would kick in, dump fuel and idle would surge up and flag would disable, repeat.

I went back to fuel pressure and saw that it would dip slightly if I nailed throttle and in desperation replaced the pump with good name brand recommended at time in forum. Fuel pressure was then a solid 13 and no dip when nailing throttle. Problem went away. It appears the fuel pressure with my old tbi/injectors was not enough. So even though fuel pressure was low, engine was getting periodically flooded/running rich at times when being saved. My lesson was to be dang sure fuel pressure is more than good before chasing other things. Someone here has thread on replacing pump with later model for better supply. Good luck!