FastandBlue

So....suspected my misfire was caused from dirty/bad injectors. It all makes sense. Here is my timeline:

1. Replaced plugs and wires...nothing happened.

2. Fiddled with injector clips and injectors...made it better, but still shook slightly from intermittent misfire, but initially stumbled under light load. This was probably due to the gunk in the injectors initially being knocked loose. Stumbling got better but intermittent misfire continued.

3. Replaced fuel filter...nothing happened. Discovered at this time my fuel pressure was 5-7psi below what it should be.

4. Added SeaFoam 10 miles ago while filling up from empty at a rate of 1.1 ounces/gallon (entire bottle). Misfire gets worse and now car is stumbling randomly at different times, presumably from the gunk the SeaFoam is knocking loose from everywhere.


So, I think all this indicates that the injectors are still to blame, because whenever I try to mess with the fuel system, it gets worse, presumably because of the gunk I am knocking loose into the injectors.

What should I do next? Take a look at the fuel rail? Buy new injectors? Clean the current injectors? Run through an entire tank of the SeaFoam treated gas and see what happens? Get a new fuel pump? C4 the car? Drive it off a cliff? Haha....

my1994z28

Try running the seafoam through the brake booster hose..start the car,disconnect the booster hose,insert the hose into the can of seafoam.Be prepared for alot of stinky smoke.You can also buy some throttle body cleaner and clean the tb,also they sell cleaner for the MAF,try that as well.

Injuneer

Are you still running low fuel pressure?

FastandBlue

I am. But would that cause an intermittent?

dodge69874

I ran Seafoam on my Crown Vic, right when it hit the 75k mile mark. I put it in, ran it for a few hours pour out smoke and crap, went home and replaced the plugs and oil and it was better than ever.

I'm too scared of trying it on the T/A due to the high mileage (116k, I've heard Seafoam might damage some seals and give you problems in a higher mileage car) and because people on here have had crappy experiences with it, which leads me to believe Seafoam+LT!=Headache.

dodge69874

And yeah, I ran 1/3 in the gas tank, 1/3 in the oil, and 1/3 in the brake booster. Feeding it in slowly and then pour it in at the end so it would stall out. Then I waiting like 15 minutes and started it up to watch all the smoke pour out. I had to go to a more rural part of town, because around here that would have attracted alot of attention.

bw_hunter

The product is very much like GM top cylinder treatment. I know it's mentioned on the label that you can add it to the oil but I wouldn't as frequent changes using good oil and filters will keep the engine just fine.

I have added it to the intake, through a vacuum line and it does, certainly, loosen up whatever deposits are there and smoke up the joint. I didn't have tro replace the plugs but I did the O2 sensors....lol

To the OP. You must fix the pressure problem first before diagnosing other fuel system symptoms. You might get faulty diagnostic results if you don't.....

Injuneer

You're injectors are flowing 8 to 10% less fuel than they are supposed to, if your fuel pressure is 5 to 7psi below where it is supposed to be (43.5psi, without the vacuum compensation). I don't recall if you actually tested the fuel pressure under load, because low pressure at idle could turn into even lower pressure under heavy load. The PCM is trying to adjust the A/F based on the O2 sensor feedback, and it can add up to 25% extra fuel, so it might be running OK, or it might be running lean under heavy load. Depends how far "off" the long term fuel correction are without the fuel pressure being too low.

At some point, you have to address the poor fuel pressure. Why not do that now, and eliminate it as the possible cause or a contributor. You won't be wasting money by replacing the pump, because if it can't maintain the required fuel pressure, it needs to be replaced. You also need to rule out the fuel pressure regulator as the cause of low fuel pressure.

If you have a lot of loose material in the fuel system, the injectors aren't going to get cleaned up with Seafoam. The loose particles will be sitting on top of the little screens in the injectors, or plugging the tiny holes that the fuel flows through when the injector opens. If you know you have dirty injectors, they have to be cleaned.

FastandBlue

Alright, any good suggestions for a fuel pump? I don't want cheap, but I don't want to spend tons of money. I also want to upgrade my engine a few HP eventually. I'm thinking to 450 hp or so until I possibly turbo.

F550maranello2

if you want to replace it just cut a hole above it in the trunk you dont need to drop the tank at all.. we just got dont doing my friends z28 like that.. i only took like 3 hours total (beer was involved)

FastandBlue

Lol, yes. As per previous posts, I will not be dropping the tank. Trap door method is so much easier! Still need to know what kind of fuel pump to get (see my previous post).

RamAir95TA

Go with the Racetronix pump and harness kit. A bit pricey but WELL worth it.

FastandBlue

Like this one?

http://www.racetronix.biz/customkiti...c=RFPK-003&eq=

my1994z28

Correct that is the one

slopokrodrigez

I got a hundred reasons your problems are not even related to a fuel pump issue.

Here's a good example. Suppose the "gunk" you refered to in the fuel rails got in the FPR holding it open and releasing some of the pressure back into the return line?????

I seriously doubt your pressure problem is from the pump.