TMaxxTim

So my car has been stumbling whenever I give it completely full throttle, or sometimes startup idle.

Either time I'll either just let off full throttle or give it a tad of gas at idle and the car is fine.

I had some Bosch plugs in so I thought that might be it, I put in 6 new NGK Platinum Iridium (The $8 ones at NAPA because it costs just as much to get them from rockauto too). I broke a spark plug wire in the process so I ended up getting a new set of wires while I was at it too.

Cap & rotor were replaced when I got the car at 142K 1 year ago, I now have 155k on it.

I still have the exact same problem, nothing has changed.

After searching I see that people may experience the same thing with one of these three possible things with the first being what I think may be the problem.

1) TPS, however I have no CEL. I guess it could still go bad but I thought it would throw a code. Any other way to check if the TPS has gone bad.

2) FPR - Fuel Pressure Regulator, sounds like this could be the lack of fuel at the absolute top end, creating this problem, although the engine performs exactly like it does when its on 5cylinders (I've had water in the rear plug hole before, so I know what it feels like).

3) ECU - Something's wrong with the ECU, I've read this but I think its probably unlikely.

Hopefully somebody has some insight. I'll try to do a little more research later tonight and go into my repair manual and see if it says anything about how to test the TPS and FPR to see if they need replacement.

codetoad

iTrader: (2)

Check your plugs again, and make sure you have no oil leaking in the plug holes/around the wires. One of them may have fouled since you installed them. It happened to me before on my no.6 cylinder. Keep it simple - you changed the plugs and wires its probably related to them - make sure your plug gap is correct. I had the same problem and I bought all new bosch plats and I still fouled one immediately after starting the car the first time. (actually, the electrode was completely missing when I pulled it out). Sounds like the same prob to me, so you should definitely pull them again.

Psionic

How new is your air filter? I would try that first.

codetoad

iTrader: (2)

Check your plugs and make sure you didn't accidently run a wire to the wrong cylinder from the distributor (not saying you did, but its worth a check) You said you know what it feels like when its running on 5 cylinders - well I know exactly what your talking about. Mine did exactly as you described to a tee and it was my #6 cylinders spark plug. If im wrong about this ill pay pal you a dollar for your trouble Gap em properly

TMaxxTim

I switched to the NGK because my car was doing this with the Bosch plugs, and now it still does it with the NGK. I'll re-check the plugs but I'm looking for other things because its doing the same things with both new plugs and old and new wires and old, so it must be something else.

My car drives normally and has all the power it usually has just until you would hit that full throttle, then it would bog down to 5cyl, like something was not getting spark, or the spark was arcing somewhere else.

I reset my ECU and it seems to be better, but not completely. It doesn't stumble at full throttle as much (it did once or twice but not badly). It still kind of does it at idle, but not as bad.

So I'm going to try to reset the ECU one more time and run it hard so it relearns that way and see what it does from there.

NoLongerA13bFan

iTrader: (2)

Did you ever figure this out?
Mine is having a very similar problem but I have traced it to number the number 5 cylinder not doing something.
My car is running on 5 cylinders. If you unhook the number 5 plug wire at the distributor it does not change the way the car runs. Put it back on the distributor and the car picks back up and runs fine for a while. It is getting spark because it wil shock you whne you unhook it if you are not careful. Why will it start getting No. 5 to do someting only after unhooking the plug wire and reinstalling it? I have replaced the plugs, wires, rotor, and cap with not change in the situation.

bmatsu

You can clean the 3 vac lines that lead in the throttle body. Use throttle body cleaner and spray it down the metal tubes that lead into the TB.

One time I cleaned the TB and I pluged up one of the holes, and the car acted as you described. With that many miles it is possible one of the holes that lead into the TB is pluged.

Good Luck, let us know how things turn out.

TMaxxTim

I ended up switching to the NGK top of the line plugs and reset the ECU twice and I've never had it happen since...so I guess it was just a combination of crappy plugs and the engine trying to compensate.

NoLongerA13bFan

iTrader: (2)

Mine is bizarre because it is running on 5 cylinders, which is known because if you unhook the no. 5 plug wire from the distributor it doesn't effect the idle, but when it is plugged back in the idle clears up and it runs perfect fro a while at least.

I swapped out the plugs to the factory NGK units and it did not seem to change it. I will try to reset the ECU again and see if it helps any.