Normal Fuel Pressure

[Dandy97]

Would fuel pressures of 42psi at idle and 52psi at idle with the vacuum line to the pressure regulator removed be in the normal range or a tad low?

[Aurora40]

The FSM lists the acceptable ranges, I think that sounds in the ballpark without looking at it?

[Dandy97]

FSM listed 48-55 psi but I realized after looking again last night that is for key on, car not running. At idle the FSM says 43 psi, so I guess I'm golden. I guess my problem lies elsewhere.

[bradslt5]

what is your problem?

[Dandy97]

what is your problem?

A long time ago I think I was in a few fights that started with that question.

I have been fighting (pun intended) with a very bad stumble when the car is cold for awhile. It idles fine but if I try to drive it before it goes closed loop it's like it's running on 3 cylinders up until about 2500 rpm's then it kicks in. If I start the car and let it idle for about 15 minutes and get up to operating temperature, it runs fine. It doesn't throw any codes when it runs bad.

I have run through the diagnostic charts in the FSM that relate to this problem and have not found anything wrong.

Two weekends ago I replaced all of the primary fuel injectors because I had three bad ones, one measured 9 ohms at the coil and the other two measured about 6.5 ohms. Needless to say they were not working very well. I also replaced the coils as long as I had the plenum off again. Also in the last 1000 miles the following has been replaced for one reason or another:
secondary fuel injectors
secondary vacuum pump
plugs (about 250 miles on them)
plug wires
pcv's and top & bottom hoses
iac
map sensor
fuel filter
replaced an unknown custom prom with a marc h. prom

None of replacements effected this primary problem, they all fixed other problems of course. The stumble problem when cold has been uneffected and has gotten continually worse over the last year.

I have pretty much run out of ideas. Whatever it is, I think it must be an electrical device because it starts working better when reaching operating temperature. One thing I have thought about is the ecm, maybe the fuel injector drivers are shot from driving bad fuel injectors. I am probably going to try swapping out the ecm this weekend and see what that does. So we shall see. I really want to get this solved as I originally purchased the car to be my daily driver in the summer.

[bradslt5]

man thats go to drive you nuts. the only thing i can think of other than the ecm would be a vaccume leak or i wonder if the fuel tank recirculation could cause this. one easy way to ck for vaccume leaks is to attach a 2-3ft hose to the end of a propane torch and just turn it on a little if you get an area that has a leak the motor speed will increase. on last thought you might ck around the plenum gaskets and throttle body. they might have a leak cold and it seals once things expand. dont know if this helps just thought to throw out some ideas . good luck hope you figure it out soon

[Dandy97]

man thats go to drive you nuts. the only thing i can think of other than the ecm would be a vaccume leak or i wonder if the fuel tank recirculation could cause this. one easy way to ck for vaccume leaks is to attach a 2-3ft hose to the end of a propane torch and just turn it on a little if you get an area that has a leak the motor speed will increase. on last thought you might ck around the plenum gaskets and throttle body. they might have a leak cold and it seals once things expand. dont know if this helps just thought to throw out some ideas . good luck hope you figure it out soon

I have a vacuum leak detector, there are no leaks that I can find. Also, if it was a vacuum leak why would it go away once the engine was up to operating temperature? Anyway, if I get time this weekend I am going to try swapping out the ECM.

[WB9MCW]

GOOD LUCK THIS WEEKEND WITH THE TESTS

[tccrab]

I'll bet dollars to donuts that it's your ECM.
I had the *EXACT* same problem.

Read about it here:
http://www.zr1netregistry.com/forum/showthread.php?t=2206

Good luck!

[Dandy97]

Well I swapped out the ECM after my son's football game and we fired it up and went for a ride. It ran perfect from the moment I started it up. I'm pretty happy I finally got to the bottom of it. Makes me wonder what in the ECM was failing, I'm thinking the injector drivers.

Tomorrow I think I'll hook up the Tech 1, go for a drive and see how everything looks. I'm also going to send in the old ECM for a rebuild, that way I'll have a back-up.

Now that I got it running good I can put in my Fidanza aluminum flywheel!

[gbrtng]

Well I swapped out the ECM after my son's football game and we fired it up and went for a ride. It ran perfect from the moment I started it up. I'm pretty happy I finally got to the bottom of it. Makes me wonder what in the ECM was failing, I'm thinking the injector drivers.

Tomorrow I think I'll hook up the Tech 1, go for a drive and see how everything looks. I'm also going to send in the old ECM for a rebuild, that way I'll have a back-up.

Now that I got it running good I can put in my Fidanza aluminum flywheel!
I doubt that the three low resistance injectors caused the ECM problem because they weren't really THAT low. From my experience it takes almost a complete short to wipe out a driver. Good luck on finding a rebuilder who will give you a post mortem ...

[Dandy97]

I doubt that the three low resistance injectors caused the ECM problem because they weren't really THAT low. From my experience it takes almost a complete short to wipe out a driver. Good luck on finding a rebuilder who will give you a post mortem ...

I wasn't really expecting to find a rebuilder who would do anything except rebuild. I was only speculating as to the failure mode, as you are that it isn't the failure mode.

[Paul Workman]

man thats go to drive you nuts. the only thing i can think of other than the ecm would be a vaccume leak or i wonder if the fuel tank recirculation could cause this. one easy way to ck for vaccume leaks is to attach a 2-3ft hose to the end of a propane torch and just turn it on a little if you get an area that has a leak the motor speed will increase. on last thought you might ck around the plenum gaskets and throttle body. they might have a leak cold and it seals once things expand. dont know if this helps just thought to throw out some ideas . good luck hope you figure it out soon

I agree w/ you. The part about stumbling, and "coming on" with some load (read: extra fuel being added) are classic symptoms of a 'vacume leak' in the open loop mode.

However, running OK when it warms up could mean that expansion is closing up the (gasket?) leak. But, it may be due to the fact that when it warms up and switches to "closed loop", the O2s sense the lean condition and the computer compensates by riching up the mix. This may well result in an increased idle speed in "closed loop"...or not...depending on method of idle control and/or where the leak is.

Just a thought!

P.

[Dandy97]

The ECM turned out to be the problem. Car runs like new now. Too bad the weather turned or I would still be driving it every day.

I put in the Fidanza flywheel a couple weekends ago and that turned out to be a great mod. The extra fun factor is worth the small amount of extra gear noise in my book. I also found my small transmission fluid leak and fixed it. Just when I get everything running right, winter shows up. Only about 12 weeks to go...

[gbrtng]

The ECM turned out to be the problem. Car runs like new now. Too bad the weather turned or I would still be driving it every day.

Who rebuilt the ECM and how much $$$ ?

[WB9MCW]

Way to go there Dandy!!

Hey dere what part of WI are you in?

[Dandy97]

Who rebuilt the ECM and how much $$$ ?

I purchased one from Parts America when they still had them in stock for $119.00. I do want to have my old one rebuilt. I found a place in Jacksonville FL that will rebuild them for $219.00 including shipping. They also sell rebuilt ones outright for $499.95. It's Called ECU Direct and they claim they have a lifetime warranty on their rebuilds.

[Dandy97]

Way to go there Dandy!!

Hey dere what part of WI are you in?

I'm in Greenfield which is on the south west side of Milwaukee. I drive through McHenry every time I go down to St. Charles, I'll have to stop and say hi next time.

[WB9MCW]

I'm in Greenfield which is on the south west side of Milwaukee. I drive through McHenry every time I go down to St. Charles, I'll have to stop and say hi next time.


Sure no doubt on the way to BG each year right?

Just Pm me b4 you make all the plans and we will be glad to have you stop by for an eyeball:thumbsup: