kmascotto

I’m in need of a little help:

My 89GT is having a hard time running after initial start up (engine at room temp). I’m at a loss for what’s causing the issue. I can keep the engine running by modulating the throttle for the first few minutes and when a little heat builds it functions perfectly. Restarting the engine when its warm, there is no issue at all.

Here is what I’ve done to date.

1. New temp 2 sensor which has been tested (2.65 ohms @ both prongs to ground, room temp)
2. Tested the continuity between Temp 2 and LH (pin13) and temp 2 and EZK (pin19) plugs (both good)
3. Resistances to ground at both LH (pin 13) and EZK (pin 19) was 2.3 ohms for both.
4. Replaced LH and EZK computers with no change
5. Replaced MAF with no change.
6. Replaced fuel regulator and both dampers
7. Fuel pressure gauge on rail show 55 psi

What am I missing?

Thanks for your suggestions

Kent

kmascotto

Mrmerlin

I would suggest you replace the fuel pump check valve,
then add some techron to the fuel ,
and do short runs .

NOTE if no joy then remove the injectors and have them cleaned
NOTE New aircleaner is upside down

FredR

Resistance values should be about 3k ohms pin to ground each channel at room temps.
Maybe a typo in your post?

kmascotto

Thanks Fred, my meter was set at 20k ohms. It’s just a decimal points issue

kmascotto

Thanks Merlin I’ll have a look at that check valve. I ran some injector cleaner.
I’ve noticed this evening when I took it for a run, it was running lean. I have a wide band O2 sensor and it was showing between 16 and 17.2 at idle. And not much better driving. So I’m going to pull the plugs and check their colour. I’ve had the injectors all professionally cleaned a few years ago…but maybe they are dirty again.

FredR

Sounds as though the NBO2 is out of whack

worf928

‘scope the crank speed/position sensor when cold and when warm.

kmascotto

Unfortunately I don’t have an oscilloscope.

kmascotto

It’s possible…it’s really not that old…about 10k kms on it.

worf928

Eyeball the CPS to LH-harness connector: if you see cracks in the plastic, replace the CPS. If you see deterioration of the sender side harness, replace the CPS. CPSs last about 10 to 15 years. Most 87+ should be on CPS number three at this point.

*most* of the time they are either “alive” or “dead.”

But, every once in a while they enter a “Schrödinger state” where they are somewhat dead when cold and somewhat alive when warm with results exactly as you describe.

kmascotto

thanks, I’ll give it a closer look. I believe it has about 5 or 6 years and about 15k kms on it as I replaced it too.

kmascotto

my A/F ratio is still lean. It’s at the 16.5 range at idle. But at 2K rpm is back at the 14.7 range. I’ve replaced the O2 sensor with no change at startup or at idle.


I’ve pulled the plugs. They are a little on the light side

kmascotto

5-8

FredR

Why are you using GTS multi prong plugs?