ftransam1

I've tryed everything and am thinking the problem might be the opti. I scan the car all the time and nothing comes up. I just replaced the O2's, took off the cat, and changed the fuel pump and still can't figure it out. At around 3000 rpm the car seems to die and not want to rev anymore and the exhaust changes and kinda rumbles. Also the car vibrates a lot. But after a few seconds it stops and runs fine. Also when I start the car it takes forever to turn over. It happened all of the sudden the other day and any help would be appreciated. Thanks

Ryan

JDBlaze85

monitor the fuel pressure while the stumbling occurs. or change the coil.

ftransam1

Coil is new, so is the module. Don't have anything to monitor the fuel pressure.

Huntr1117

My car does the same thing, but it's between 1500 rpms and 2000 rpms. Once I pass 2000 rpms it runs fine. It also only does it in overdrive.

Zeueses 97 RamAir

Well Ryan lets see if i can get the silver star, my only guess is plugs fouled out and it leaned the plugs out... try that then check your fuel at 3000 rpms.... or might be your opti...remember your headers were glowing so your plugs are fouled out they shoud be donut white when you pull one...

slopokrodrigez

First of all, knowing what year the car is and some of the other particulars could help. Some vehicles like OBDII's can be troubleshot differently than say OBDI's. For example, by shutting down or even forcing open individual injectors via scanner. Also, based on the last persons post, it seems as though you may have left out some helpful information.

Be that as it may, usually hard starting is due to a fuel problem. In addition to that, I have seen air pockets in the fuel system that cause momentary stumbling when the air pocket arrives at the fuel rail. JDBlaze mentioned to monitor the fuel pressure. Good advise. Get a gage that has a hose on it and tape it to the windshield. Watch the pressure when the problem occurs at 3 grand and after the engine is shut down.

Chances are you will see the pressure fluctuate momentarily at 3K (if the problem occurs) and after the engine is shut down, you will see it drop off real fast.

Also, knowing what conditions must occur for the problem to show up would be helpful. For example, does the problem only occur after the car is hot and sits for say 1 to 3 hours or is it only from a cold start? I had an 84 TA with a vapor locking problem that was never correctly diagnosed until 2 years after I got rid of the POS. Turns out it did ALMOST the same thing yours did but only after it sat hot for 2 hours. Get the point?

Guest47904

Yours sounds like a typical EGR valve problem. Try removing and cleaning it and while your there, suck on the vac hose to it and see if it moves in and out freely. Don't forget to replace the gasket with a new one.

Huntr1117

I just replaced the EGR about a year ago. When that was bad the car stumbled when accelarating from a dead stop. Could this problem really be EGR again?

Hawk

I'd just block it off.

ftransam1

Mine doesn't stumble from a dead stop but I did have a coolant hose bust all over the opti a few days ago too.

JDBlaze85

ha, I've seen too many optis get moisture trapped inside of them, then they run like CRAP. But eventually the moisture comes out and its all good. My 94 T/A got coolant from the water pump hole seeping down into the opti and the car was barely drivable. I changed the water pump, drove the car around for a day until the opti fixed again. But if its only happening at 3,000RPM........I would still check the fuel psi first.

ftransam1

Well I'll try to get a hold of a fuel pressure guage tomorrow. Is there anyway I can check the injectors and fuel pressure regulator? Like I said I know the pump is good (new) and the filter I just changed.

Guest47904

Never assume that because something is new, it's perfect. When it comes to checking the injectors, there are 2 things to look at. One is supply, which the pressure gage will check. The other is if they are getting the pulse to open up. That can be checked with a noid light. Like this one.
http://www.lislecorp.com/tool_detail.cfm?detail=379

However, your problem is at 3k and the noid light will not help you at that RPM. Nor is it likely the pulses are dropping out momentarily at that RPM either.

The pressure regulator will also be checked with the pressure gage. check it with and without the vacuum line connected at idle. It should increase when the vac line is disconnected.

You still haven't told us what conditions are required to reproduce the problem. Does the problem only show up once and goes away during that period of driving? Will it happen sitting in the driveway or does the car have to be driven? Is it only on hot restart or after sitting for a long time? If it's on hot restart, will it only do it if it is driven right away, but if it sits and idles for say 20 minutes and is then driven, it will not show the problem? What's the deal?

ftransam1

It only shows up when I'm driving. I have to accelerate to make it happen. But, if I drive slowly it doesn't happen. It can idle all day long in the driveway and not have a problem.

jeenyus

ok i have a similar problem but mine stumbles at high rpms. i just changed the plugs a got new wires. the fuel filter is new.

what could this be is it the opti? it does it sometimes. but when it does it, it is at like 5000 rpm to 6000 rpm then it will stop when the car shifts to the next gear