Mystery Cold Start Misfire

[niles]

to add to the misfire questions: my 87 misses whenever I cold start, like in the mornings. it will miss for about 30 seconds on one cylinder then miraculously start working perfectly after a few. I am thinking its either my coil or dizzy or igniter at the moment. I don't think its a bad wire somewhere because its too consistent. any ideas?

here is what I have replaced so far with no changes to the issue:
all injectors
resistor
cap n rotor
plugs (gap verified)
wires
timing verified
valves verified

[niles]

Nobody wants to take a stab at it? Anyone replace the igniter or coil that fixed a problem like this? What are the symptoms of a bad igniter?

[Dr_Snooz]

It's worth at least testing the igniter and coil. There's a test for both in the manuals. If they are out of tolerance, change them. Symptoms of a bad igniter can include rough running and a no-start condition. On our cars, the igniter usually signals its demise by causing the tach to hop around wildly while cranking the starter.

[Oldblueaccord]

Im thinking its too rich on start up. Fouling a plug out for a minute.

[niles]

my O2 sensor was replaced last summer but I have been wondering if it's too rich. I will do some tests this weekend. is the fuel pressure regulator a likely cause for too rich?

[niles]

Coil tests good. Now that the weather has dropped to around 20 to 30 degrees the problem vanished. I will troubleshoot more when the problem resurfaces.

[Oldblueaccord]

TW sensor.

https://www.3geez.com/forum/efi-tech/...tw-sensor.html

If you follow the helms book I think you can test it or just jump it out with a paper clip but I would do search on that.

[niles]

Thanks for the link Oldblueaccord, really good read and I will consider this as I troubleshoot my problem. I checked for codes this weekend and there were none, so whatever it is - isn't bad enough for the ECU to flag it. I wish it did because that would make things a lot easier

I am going to do the distributor rebuild this winter that's listed in the How-To section. I am suspecting that the seal/bearing might be going bad and some vibration or oil inside might be a part of the problem. And that will provide a good opportunity to replace the Ignitor since I already have a spare.

[niles]

Update: I had given up fixing this issue until I solved the problem unintentionally.

I was getting a really loud tick from my engine and I thought I had a bad valve or head. Turned out it was one of my NEW fuel injectors. I hope this helps future troubleshooting.

After dealing with the misfire and all kinds of idle problems because of the bad injector I will NEVER buy a mechanical product from GP Sorenson again. Buying used Bosch injectors from the JY gives you a better chance of getting a good injector than a new GP Sorenson out of the box.

The injectors we use are compatible with so many different models of cars I find that the quality GP Sorenson's injecors is inexcusable.

The rant from my valve noise thread: https://www.3geez.com/forum/3geez-acc...djustment.html

Off topic a little: I don't recommend GP Sorenson fuel injectors. Two were bad out of the box when I replaced all four of mine over a year ago. This is also why I am blaming an injector as a possible problem source of my current issue, and it may also be the reason I have a cold-start misfire. I will check their resistances tonight as well, but even if the coil of the injector is intact, there may be something mechanically wrong with the injector on cylinder 4. I hope the problem is the injector so I can go to Pick-N-Pull, get a set of OEM injectors and just throw that $200 I blew on GP Sorenson in the trash. I get why all new injectors have a 1-year warranty but then the OEM injectors last for 25 years! Rant over.

Edit: I recently had to replace my head gasket due to failure. So damp/fouled/rusty spark plugs due to leaking coolant into the cylinder could have also been the cause of the cold-start misfire: https://www.3geez.com/forum/3geez-acc...ml#post1154104

[Dr_Snooz]

Jeepers. I've never heard of injectors causing problems. Thanks for closing the loop for us.

[gp02a0083]

I was wondering if it was the injectors or the IACV. Now with your findings it does make more sense where the ticking sound came from. Really if you boil it down i've considered injectors more like a relay. I'm with you on the brand of the injectors, i've kept a collection of them for that reason, i've been skeptical about the quality of other brands. Good work hunting down the problem

[niles]

Injectors are basically a relay, or a solenoid controlled valve. And not all were created equal lol.

I replaced my IACV a year or two ago with a brand new one. In hindsight I think I tend to replace things more than I drill down to the actual issue. I replaced my IACV for idle control issues, but it was a two-part problem that also involved my idle adjustment valve o-ring being rock hard and leaky as hell. So I replaced an expensive part, but the solution may have been with a $0.25 part...

These cars have so many parts, when they malfunction they can cause ambiguous symptoms. So that's kindof annoying, but also makes solving the problem that much more rewarding.