88 GMC 1500 no start

[Dieselsj]

Problem: stalls out at idle consistently. Worse when hot, I can barely keep it going in neutral at a stoplight with the two foot driving method. Lately it’s gotten progressively worse, it feels “electrical” like it comes on quick.

Work done so far:

New fuel pump, filter, rebuilt TBI with higher pressure spring (I did check fuel pressure at the TBI)
Two new injectors
New MAP sensor
New coil
New Idle air controller
New temp sender
New throttle position sensor
Good egr
No obvious vacuum leaks

120k original miles, passes Cal Smog easily but puffs a little oil smoke at start up

Based on the latest info, I have ordered a new GM ignition pickup coil and see if that helps.

First things first -

Have you set minimum idle speed mechanically on the TBI?
After that, did you adjust the TPS?
Did you set base timing with the firewall connector unplugged?

How much higher of a pressure spring did you use?

Also, new injectors don't mean squat. I chased an issue for a long time that turned out to be a bad "new" injector.

[Double Snowman GMC]

TBI throttle shaft felt good to me, no rebushing done
14 psi spring is in use
Delco CR43TS plugs look fresh & clean, .035 gap
Idle speed set properly, base timing set, new TPS adjusted
I still have all the replaced parts.
EGR was replaced a while back, looks clean & vacuum actuation is good

[sbnova]

I bet your entire problem is the pickup coil in the distributor. They commonly fail, and are frequently mis diagnosed as a bad fuel pump, bad injectors, or whatever. If the ecm doesnt see the engine cranking- youll get no fuel from the injectors. This pickup coil, can work, then stop, then work again. Its a cheap part and 99% of the time it is the problem. Buy yourself a whole new distributor if you cant find a pickup coil at your local parts store. I bought my truck (1988 c1500) "not running" with your same symptoms, swapped the pickup coil and had it running in 15 minutes. I bought a new ebay distributor after seeing how worn the stock distributor was, and its been going strong for about 15,000 miles in the last two years. I think the whole distributor was like $50

[dave w]

Pic of GM Ignition Module showing the signals starting at the Pickup Coil ending with the Distributor Reference Signal to the computer.

dave w

GM Module.jpg

[Double Snowman GMC]

Ya sbnova.....I’m thinking the pickup coil is the root cause
My replacement is coming in the mail
I tried downloading Tunerpro with a bypass of my antivirus, it still has bad dll files and won’t run
It’s a good thing this rig is non essential ��

[Double Snowman GMC]

Closing the loop here.....
I’m happy to report that my truck is successfully back on the road and idling well.
The pickup coil was apparently the root cause, I threw in a new ICM while I was in there.

Mucho Thanks for all the help found here!

Cheers,
Bob W

[trlrider]

Ya sbnova.....I’m thinking the pickup coil is the root cause
My replacement is coming in the mail
I tried downloading Tunerpro with a bypass of my antivirus, it still has bad dll files and won’t run
It’s a good thing this rig is non essential ��

I have TunerPro and Tuner Pro RT on 3 different computers of varying vintage. No such issues as you are describing.
What version of Windows are you running?

[PlayingWithTBI]

The pickup coil was apparently the root cause, I threw in a new ICM while I was in there.

Glad to see you got it!

[Double Snowman GMC]

I’m running Windows 7 on an lenova IBM Thinkpad.

PS. My Win ALDL only registers 5 rows of info, no “dashboard “ , so my computer set up seems a little suspect
Any suggestions for future diagnosis?