Bryceman

iTrader: (1)

Well .. with my daily driver down, I have been driving my '89 Trans Am 305TPI as a daily driver. Recently I have noticed that upon start up the car will run great .. but once you have driven it a little bit, it will run choppy at idle (as a light) but fine with normal driving. However, normal commute is about 5-10 miles each way.

Today at lunchtime, I drove from my office out to Texas Parks and Wildlife (25 miles) and it ran fine. Left from their office to grab some food and it ran fine. After eating, I fired it up and it was really rough and decided to turn off. After that I could never get it to fire back up again -- just keeps cranking. Battery is nice and strong. The gas was low (1/4 tank) .. so we put 2 gallons back in it. No difference. The car has spark (pulled coil wire) and has gas (checked the bleeder valve on fuel rail).

Recent Maintenance: (~1k miles ago) new plugs, new wires, cleaned cap / rotor, new fuel filter.

Thoughts????

John 89 Formula

Bad ignition module or pick up coil. either will cause the injectors to not fire.

Bryceman

iTrader: (1)

Is there any way to test the module or pickup coil?

I am thinking that it might have had vapor lock .. so going back tonight it might just fire up .. just didnt like it when it was 'hot'. Its 95 degrees out...

John 89 Formula

For the pick up coil, take off the dist cap and disconnect the plug from the pick up off the module and probe the contacts with an ohm meter a good one will read between 800 and 1200 ohms give or take, anything outside that range it's probably on the way out.
The ignition module, your local autoparts store should be able to test it for you.

Bryceman

iTrader: (1)

control module tested successfully and the pickup coil was over 800ohms (about 880). Fuel pressure is over 40psi. not sure what to check next?

LS7Roc

How old is the pickup coil?

camaronewbie

I know alot of folks state to 'test the ICM' - but I was thinking, wouldn't a cool ICM test fine? They seem to go bad under heat, unless it's been running, yanked out quickly, and put on the tester immediately, it might test good when it's cool. I never had mine tested - when I started having issues similar to these, I just replaced it and the troubles went away. My car would run fine cold, and for about 20-30 minutes it would run fine, but after that, it would start running rough until it just died. 45 minutes later, it was good as new, until it got warmed up again. Replacing the ICM corrected the issue entirely.

Bryceman

iTrader: (1)

The pickup coil is probably 3-4 years old (20k miles or so).

The ICM was actually replaced and did not make a difference.

This weekend I had to pull the car out of the garage and it started ok. But when I went to put it back in, it wouldnt fire up any more. Just cranks away. Checked fuel pressure, spark, rotor, ICM, etc.. and all look good. Injector fueses are ok.
Car is not throwing any codes.

89-bird

Check your TPS and your injectors . Next time it will crank and not start hold the gas pedal to the floor and see if it starts if it does you may have a problem with your TPS or injectors so as I said before test both .

Bryceman

iTrader: (1)

Will test that tonight as well as with some starting fluid. Also, going to see if i can grab a noid light and check that the injectors are firing.

Bryceman

iTrader: (1)

Ok .. did some testing tonight .. car fires right up with starting fluid, but runs rough. If you turn it off and try again, it just cranks like before. Tested each bank with a noid light and see it flashing from one injector on each side -- do i need to test them all?

Did a resistance test on all of the injectors and most were between 15-17 Ohms .. except the rear two that were at 1.8 and 2.5.

So, I realize that those injectors are bad, but would that cause a no-start situation that I am in now? Ordering a $200 set of injectors to find out the problem is still there will be pretty annoying.

vetteoz

iTrader: (13)

Wouldn't be helping
I know if ECM sees a short on a injector it will shut down whole bank ;don't know how low a resistance the trigger is

John 89 Formula

try unplugging the 2 bad injectors to see how it runs

89-bird

If the bad injectors are in the rear on both sides it will not fire the whole bank of injectors . If you unplug the bad ones it will run just like it did on the starting fluid . If you can get two good injectors to replace the bad ones I would go that route as the other injectors are good . You replace the two bad ones for some good ones and get back with the results .

Bryceman

iTrader: (1)

Good point, but why would the noid light still show up correct when plugged into a different injector? I can give this a try tonight though ..

89-bird

The ECM is still fireing the injectors but with the bad injectors hooked up with the good the injectors can't fire because the bad ones kill the whole bank . In short you are still getting power to the injectors but with the bad ones hooked up you have an open circuit . I would bet that if you had two of the same noid lights hooked up inplace of the bad injectors it would run but run like poo .

Bryceman

iTrader: (1)

Well .. by unplugging the drivers rear plug (the lowest one) the car starts and runs (though a little rough). Unplugging a different one will not yeild the same result.

Ordered a set of Bosch III's from SouthBay .. should be here soon to replace

TG Goose

I recently had a no start, turned out it was my Remote Ign Coil. It was putting out energy to the cap, but would barely arc. Swapped it out, new one would arc almost an inch, car fired right up.

Bryceman

iTrader: (1)

The bosch iii's arrived yesterday .. going to start the replacement process tonight possibly. Found a great writeup on how to do the replacement:

https://www.thirdgen.org/injectorswap

Anything I should check / replace at the same time since I have everything off?