PontiacBonnevilleClub.com

Guys/gals,
Supposed to get do a baseline dyno run today. Not happening.

Got a service engine light code P0128. Car misses underpower. Can the ECT Sensor cause a miss? That is the only code it threw.


Don

It would be a help to also post the description of the code.
P0128- Coolant Temp Below Thermostat Regulating Temp.

The most common cause for that code is the thermostat. Ir it is stuck open, partially open, or opens too early, that code will be set. First, check to make sure that your coolant is at the proper level. If it is, then the quickest, and easiest thing to do is replace the thermostat, along with the rubber seal. If that was the problem, the light will go off after the 3rd cycle of normal operation, or you can have it cleared then see if it comes back. Other than the SES light shining in your face, most notice no difference in performance when that code is set.

A bad ECT can cause various problems, but would likely be more than just a misfire under load.

Changed the ECT. Car is running a little better but still misfiring under load. SES light flashes underload during the misfire condition. Going to take it back and have the code cleared and see what happens next. Running NGK TR55ix plugs, bosch wires. The PCM is not throwing any other codes.

Don

The SES light flashing indicates a potential catalyst damaging condition. It may, or may not set code P0300 - random multiple misfires. It's something that should be addressed soon so that your cat is not damaged.

Has the LIM gasket been done, yet? Any pooling of what appears to be oil, or coolant near the bolts of the lower intake? Any loss of coolant? Also, check for any vacuum leaks.

It did set the P0300 code. The car runs fine if I ease it up to about 4lbs of boost, then it falls flat on its nose and the SES light flashes. Could it be a fuel filter? I don't think it is in the ignition system and I cleaned the MAF.

I have never (in 6 years here) seen a fuel filter cause a misfire.

Pull your front three plugs and shoot a good close-up picture and post it here. We need to see how they're burning. Check your coolant level, report that back, and after running a few minutes, pull your dipstick and inspect inside the front valve cover with the oil filler cap and adapter removed. Describe the condition of the oil. What's your oil pressure when the car is warmed up?

Less than 5% of misfire problems are fuel-related. 95% of them are ignition-related only, or something CAUSING an ignition failure.

willwren wrote:I have never (in 6 years here) seen a fuel filter cause a misfire.

Pull your front three plugs and shoot a good close-up picture and post it here. We need to see how they're burning. Check your coolant level, report that back, and after running a few minutes, pull your dipstick and inspect inside the front valve cover with the oil filler cap and adapter removed. Describe the condition of the oil. What's your oil pressure when the car is warmed up?

Less than 5% of misfire problems are fuel-related. 95% of them are ignition-related only, or something CAUSING an ignition failure.

Ok will do all that. Thanks for the input, I was getting ready to go buy the filter. Have the posts up in an hour or so. Thanks

Don

Almost sounds like a coil, although, wouldn't it be doing it all the time if it was the coil? I'd check the coils, and while you are at it, make sure you didn't get a bad plug wire. Bosch isn't the greatest product for these cars.

Here is the complete story with all the facts so I can get this resolved:

Bought the car 12/26. 88K 1 owner. Car had a half a tank of 87 octane in it, topped it off with 92. Car ran great, full boost no probs 12/28 changed oil; syntec and mobil 1 filter. Changed plugs and wires. Bosch wires and bosch platinum plus plugs (didn't know I shouldn't use the plugs). Jan 1, drove the tank almost all the way empty, added lucas fuel system cleaner and filled up with 92. 3.7 gallons into the tank, the missing started and I got an SES light. Talked to a buddy that runs a gtp 3.1 pulley, nice car. He said plugs suck and he had a set of used tr55ix, that were good when he took them out, they weren't cold enough for him, no sure how many miles on them but he said less than 1000. Changed the plugs this morning, no help. Scanned it got the p0128 (ECT) code. Changed that, p0128 went away, car runs better. Cleaned the MAF today as well. Missfires underload now, p0300. SES light flashes at me under load, the boost is 9.5. I can ease the car up to speed as long as I stay under about 4lbs seems to run fine.

willwren, not sure that pulling the plugs for pictures will help as they were used when I got them

There it is what do you think.


btw Dan is coming over tonight with HP tuners so that we can see exactly what is going on.

Let's see the OLD plugs.

Check all the other stuff I mentioned above first. A coolant leak from the LIM gaskets is fairly common, and can cause this.
A bad plug wire (and yes, Bosch sucks in our cars) can too. And you may only feel it under load.

Your new plugs may still tell a story even with a few short miles on them. I gaurantee one or two of them will look different already, which can help you home in on the problem cylinder(s).

Willwren,

Shooting the bosch plugs right now, have them up in about 10 minutes. Thanks again guys

Don

Here are the bosch plugs. They were only in the car for about 100 miles.


Don




Front



Rear

I see bone white plugs. Even after 100 miles there should be some tan on them, if you're running right. Almost looks like a lean condition to me. Have you changed fuel filter yet?

Haven't changed the filter. Thought I would wait till Dan gets here later today with HP Tuners to see exactly what is going on before I spend any more $$$ on guesses.

Don

Changing the filter would be good practice if you don't know how old it is, but don't expect it to solve this issue.

You have one of the following problems with the car:

1. Bad coil
2. Bad plug wire(s)
3. Coolant leak from the LIM gaskets


HP Tuners won't tell you a whole lot if your misfires aren't isolated to one or two cylinders. You need basic troubleshooting of an ignition miss first, a scantool less so.

It ran fine for 3 days after I changed the plugs wires and plugs. Does that help narrow down the problem at all?


Don

Ok, all coil packs read .8 (.5-.7) on the primary and 9.12 -9.14 (5k-11k) on the seconday. Car is still throwing the P0300 (random missfire), HP tuners doesn't report a missfire on any cylinder, but shows the P0300. In park, you can rev the car to the rev limiter. It revs easily with no miss. I can ease it up to highway speeds, but if I try to push in into any boost more than about 2lbs, it misses and the SES light flashes at me. It has new plug wires and ngk tr55ixs in it. Needing some help here, not sure what else to do.


Don

Have you checked the oil, and coolant levels as asked above? How about for vacuum leaks?

oil and coolant are fine, no mixing. I would love to have a vacuum line diagram. Don't now where to find one.

Don

These may help.
Vacuum Routing


Evap Routing.


The vacuum routing shows 2 MAP sensors, but your car will only have one. Common problem areas are the hoses to the multi-port connection on top of the supercharger, and the T under the supercharger.