Hey everyone! First post here, but we've got a 40th anny that is giving us quite the issue. Now, we've done our research, and we still can't figure it out. Anyway... On occasions, we go out in the morning, and It'll start right up. Run smooth as silk for about 5 seconds, then it'll start to run rough, and eventually cutoff a few seconds later. You can keep it running by revving it up, but runs like crap, and very rich. If you try to restart it, it struggles, but does start. Symptoms are duplicated. Runs smooth 5 seconds, runs rough, cuts off. Odd thing is... You can let it sit for a few hours, go back outside, and start it up. It'll run smooth as silk, and never do it. While it doesn't apply every single time.. I can definitely say it applies more times than not. Side note: If the car does not exhibit the symptoms when you start it, It'll never do it. You can drive it around for an hour straight, let it idle, etc... As long as it doesn't do it in the beginning, it'll run perfect throughout that point. If you're curious about outside temp... 80's to 90's.

The PO did have the optispark changed out within the last year (and the H16 code was pulled). Concerning other codes... at the beginning, we only pulled a C12 and H16. Other codes were pulled, but those we from us, and are all H codes at this point. We have also replaced:

MAP sensor
Fuel pressure regulator
Charcoal canister
Purge valve
coolant temp sensor

Thought we had it with the FPR as we never get it to do it after a week. Fuel pressure would drop off quite largely (about 20 lbs in 30 minutes!)which is why we thought it was. FPR did need replacing regardless. Then it pulled it again. To say we are running out of ideas is an understatement. If any of yall can help us out, I'd be grateful.

 

12 is good 16 is opti clear and clean and check connections and check codes again. Report back. I would take the coil and ICM in to test if no codes come back and make sure thermal grease was and is used.

What is your fuel pressure and have you changed the fuel filter?

 

I'll be out later in the day and I'll check the codes then (car is at different location). I'll update when I do.

 

Wish I could be certain about the thermal grease. That I cannot be sure of. FP was around 40#, give or take a #. We haven't changed the fuel filter, and knowing how bad the vapor tube to the purge valve was (cracked and filled with charcoal), I'm bordering on "I doubt the PO changed it".

 

Sorry about the delay, but went by and got the info. Oddly enough... the C12 code has mysteriously disappeared. I'm guessing that ain't a good thing. Codes I pulled were:

Module 1:
H74

Module 4:
H16
H22
H26
H34

Car started fine, though I had been informed by my dad that the symptom has slightly changed. While it still does have the odd cutoff issue, It now takes about a minute of running to trigger it instead of the 5 seconds. This changed after we swapped out the charcoal canister, purge valve, and section of EVAP hose (was cracked). Line was also blown out, but nothing came out the end. Must have only been stuck in the one section of hose.

 

Start soaking the three bolts on your pulley I would do the wires at the same time as the opti.

 

You think the Opti may have failed again? I just checked the report and saw that it had been replaced on March 14th of this year. Mileage was 121,040. Current mileage is 121,1xx at this point. Pretty short time for and Opti failure.

Could the wires cause something like this though?

 

I would clear the codes and see what comes back. Is it still under warranty? Check and clean all connections. On the coil and icm too.

 

No clue. With the mileage and time being so close, it's a possibility. However, that is something we'll have to talk to the PO about. Getting a bit late at this point, but I will be able to mess with the car tomorrow. Clearing the codes though... well, the SES light isn't on, but is there a way to clear the stored H codes? I looked a few places online, but I do remember some having little to no luck clearing the old codes. Even when removing the negative post of the battery for 30+ minutes. Don't have any OBD I diagnostic tools though. All I had been doing is using a wire to jumper the connections. Here's when I pulled the codes. Video wouldn't focus worth a crap.

 

So you do not know if it was ever cleared of codes. I would take the icm and coil in and have them tested at a few differant places. Do not start with the paperclip in!!!!!!!!!

 

That I have not done, ha ha. I thought something bad would happen, so I only turned it to the on position. You are correct though. All we were told is that he had the optispark replaced, and we were able to confirm that on the report. Concerning the codes, the H16 code was there from the first time we checked it. All other codes occurred afterwards, but only after we started swapping in new parts. With each new code, they all pertained to what we had just replaced. The only one that was new to me was the initial H74 code. Today was the first time I had seen the code, and the first time I had not seen the C12 code.

 

74 is traction control 12 is a good all clear code. Have checked the fuel pressure yet? Might be a simple fuel filter. Did you pull the power to reset the puter? It might not clear the codes but needs to be done after some part swapping and should be pulled whe doing anything electrical.

 

To my knowledge... We may have at one point. Definitely can do it tomorrow just to be certain. A lot has gone on my end in life (truck is still in the shop after being totaled, and I've got a bulging disc from the wreck at the age of 24, yikes!), but we did check the fuel pressure. It holds pressure more firmly at this point where before the swap, pressure would slowly, but noticeably drop after turning the key off. Would go to about 38-40# with the key on, but then would drop to about 30 within 10 minutes. After the swap, it goes to about 40#, and holds pressure longer. It does drop a bit, but nowhere near as bad as it used to. One curious thing is... the pressure doesn't fluctuate or jump when quickly revved. It pretty much stays at a constant 39-40# while running.

 

Mine will key on right to 42 and hold all nite just dropping a bit but mine is all original. Not concerned about holding pressure that was for the epa. Pull the vacumm line off while running it should jump up. But if it was mine I would change the fuel filter and get a friend to blow through it.

Did this ever run right before you started tossing parts at it. Some times you can make it harder by doing this.

 

For a while, yes. For about 2-3 weeks (maybe longer) when it was doing it more is when we decided to throw parts at it. First was the MAP sensor, then fuel pressure regulator, I forgot about this one, but the TPS sensor, then the charcoal canister and purge valve (both installed same day), then finally the coolant temp sensor today.

I had forgot about the TPS. Interesting thing though. Messing with/unplugging the TPS had instant results. Car would run like it should with the TPS sensor unplugged, and would duplicate the results while messing with it. Blocking off the tube to the purge valve also had instant results. In the end though, the issue always came back. A rough running car that would cutoff.