SOLVED! 1987 350 TBI Timing advance issues

troyfolley · Jul 20, 2023

I have a 87 Chevy R1500 w/ 350 TBI. Truck sat for about 7 yrs and am getting it road ready for my nephew. Installed stock rebuilt engine a few weeks ago. New MAP, EGR, O2, TPS, ESC, distributor and coil. Disconnected spark advance and started up. Got timing roughly set around 0. Plugged the advance wire back in and Engine was idling fine but would not increase RPMs without it spitting and stalling. We were stumped...Started was not working consistently so we got a new one and installed today. Now with no changes to any other components I am not getting any spark or fuel delivery. Could it be a ECM failure? HELP!!

Side note: while my nephew was removing the bad starter he did not disconnect the battery and arced the wrench across the frame momentarily. Could that have fried something else?

fast 99 · Jul 20, 2023

Never a good idea to ground power like that, kill the ECM or module? Possible but unlikely. You say fuel delivery does that mean no fuel pressure or no injector pulse? If no injector pulse with a test light ,key on, check for power on each injector. If power is available attach the ground lead to the other terminal. Cranking, test light should pulse.

Bextreme04 · Jul 20, 2023

Check your fusible links on the smaller wires on the starter. Check your fuses in the fuse block. Arcing stuff in an EFI car can do bad things to the ECM... hopefully its just a bad fusible link or blown fuse

troyfolley · Jul 20, 2023

We checked all the fuses. None were blown. I will try checking the injectors now. But why no spark? They both failed same time. I pulled a ECM out of an 86 with EFI but nothing changed. 86 was in pieces and has been a parts Truck for a while so ECM may not be good either.

fast 99 · Jul 20, 2023

There is a different diagnostic procedure with or wo pulse. My guess is a module or related but guessing isn't a good idea.

Have said this before here. Don't replace good working parts. I would use a 40-year-old working GM part before anything available today. Exception being a fuel pump. Most is offshore and of dubious quality.

GTX63 · Jul 20, 2023

fast 99 said:
There is a different diagnostic procedure with or wo pulse. My guess is a module or related but guessing isn't a good idea.

Have said this before here. Don't replace good working parts. I would use a 40-year-old working GM part before anything available today. Exception being a fuel pump. Most is offshore and of dubious quality.

I put an ignition module in a 74 c10 about 6 months ago. I bought it off ebay, so yes, it came over on a steamer from the far east. It lasted about 2 months. Ok, so an American made IM was about $70 locally. I figured, what the heck, I can get a whole distributor with a coil, cap and module for the same money. Back to Chinabay I went. The IM went out last Monday while I was driving down the road. So, 60 days on the first one, and 300 miles on the 2nd one. Just for relevance, when I was a teenager in the 80s, I could count on one finger the ignition modules that went bad on me.
All that said to say, just because it was just replaced doesn't mean it is any good. Double check everything.

fast 99 · Jul 21, 2023

GTX63 said:
I put an ignition module in a 74 c10 about 6 months ago. I bought it off ebay, so yes, it came over on a steamer from the far east. It lasted about 2 months. Ok, so an American made IM was about $70 locally. I figured, what the heck, I can get a whole distributor with a coil, cap and module for the same money. Back to Chinabay I went. The IM went out last Monday while I was driving down the road. So, 60 days on the first one, and 300 miles on the 2nd one. Just for relevance, when I was a teenager in the 80s, I could count on one finger the ignition modules that went bad on me.
All that said to say, just because it was just replaced doesn't mean it is any good. Double check everything.

Our shop had a Cadillac in for a starter a few years ago. One of those under the intake. We bought a new China starter, not reman. Worked less than 5 times. Never bought another new one.

gmbellew · Jul 21, 2023

I'd highly suspect the ignition control module under the distributor cap. and replace it with an AC Delco for the greatest chance at success with the new part.

troyfolley · Jul 21, 2023

Ok. Thanks fellas. The issue was bad connectors at the coil to dist. $35 each!
Engine surges at idle (2000rpm) a little but settles down after warm up. Still cannot rev engine without stalling/missing. Where do I start?

Bextreme04 · Jul 21, 2023

Check for vacuum leaks. Then check the timing. Then do an IAC reset.

gmbellew · Jul 21, 2023

Bextreme04 said:
Check for vacuum leaks. Then check the timing. Then do an IAC reset.

all good advice right there. you may also plug the vacuum lines for the EGR and see if that makes a difference. sometimes the wrong type of EGR gets installed mistakenly.

also check the fuel pressure.

troyfolley · Jul 22, 2023

Ok fellas. I appreciate all the advice. I combed through the vaccum lines and confident those are good. Reset the IAC by jumping 1-2 terminals on OBD 1 and turn key to on. Is that the correct way? I did plug off EGR and idle changed a little. Also took ICM to Autozone for them to test. I was able to get the engine to 2300 rpm without missing or backfire. I bench tested knock sensor. Good to go. I am curious if the ESC is working properly. Getting 12v from red wire (B) and 9v from black wire (C) and good ground continuity from blk/red (D). Blue wire (E) goes to knock sensor. . When I tap on the block next to the KS the voltage drop from 9v to 5v - 8v depending on how hard I hit. My question is is 9v correct for the black wire and should it be showing a decrease in voltage as a signal?

One last thing: Does anyone know what reading I should be getting from the wires at the ICM harness? I read somewhere tan/blk wire needs to have 5v from ECM. It is the same wire that is disconnected when setting timing. The wire has good continuity on both sides but no voltage while key on and no voltage while idling. I feel this is my problem. Nothing changes with timing when I reconnect or disconnect Thoughts?

gmbellew · Jul 22, 2023

if you disconnect the tan/black EST wire and nothing noticeable changes with the engine running, then that is an issue. does the check engine light work? do you have a code 42 stored?

I'd start reading up Section 6 of the drivability and emissions manual that covers the EST system.

troyfolley · Jul 22, 2023

Yes I have 42 and 43 code stored.

gmbellew · Jul 22, 2023

troyfolley said:
Yes I have 42 and 43 code stored.

SOLVED! 1987 350 TBI Timing advance issues

troyfolley

Junior Member

fast 99

Full Access Member

Bextreme04

Full Access Member

troyfolley

Junior Member

fast 99

Full Access Member

GTX63

Full Access Member

fast 99

Full Access Member

gmbellew

Full Access Member

troyfolley

Junior Member

Attachments

Bextreme04

Full Access Member

gmbellew

Full Access Member

troyfolley

Junior Member

Attachments

gmbellew

Full Access Member

troyfolley

Junior Member

gmbellew

Full Access Member

Attachments

Similar threads

Latest posts

Forum statistics