Rough Idle and Stall on take off

[Tinman95]

All,

I have a 95 MTX 3.2

there is a rough idle after warm up and when I goose the throttle it will rumble like it is starved for air or fuel and will stall. If I gradually increase the throttle it will rev up just fine.

Once going it will go great and the secondry's open when they are supposed to.

I am getting codes 114, 157 and 542 for the key on engine off

116 for key on enginer running

I get 9 on the cyl balance test

I have replaced plugs and wires, cam position sensor, fuel filter

I have swapped a DIS and MAF and get the same thing. When i unplug the MAF there is no noticable difference

I took off the Idle air bypass valve and sprayed it with MAF cleaner and when I unplug the IAB the car stalls

I have tried spraying the vacume lines with carb cleaner and get nothing.

It was running fine before I put it away for the winter and this is new behavior as I am getting it out for the spring.


I have searched the forum and my candidates are:
1. The IAB is just bad and cleaning it was not enough and it needs to be replaced
2. Throttle position sensor
3. Coil?
4. Fuel Pump?

Any hlep would be appreciated.

 

[93rev2sev]

Coil is suspect after it's been sitting. Seems like I've had to replace a few that way...not on SHOs, but it's apparent that sitting is bad for coils in general.

 

[SHOracer14]

I think a fuel pressure test will show what sounds like a weak fuel pump. That 157 may show that the MAF is bad anyways but shouldn't cause the above concern. I'd check that fuel pressure before anything else.

 

[93rev2sev]

I would check fuel pressure, too. Its quick and free if you have a guage.

The car stalling when you unplug the IAB indicates the IAB is doing it's job, so don't bother too much with that.

If the MAF is dirty or failing, unplugging that will seem to help. HOWEVER, it may also make the car want to run rich...which may disguise the fuel issue.

Check fuel pressure with the key "on" and the engine off.
Then check it with the engine idleing.
Then watch the guage when you open the throttle and the engine revs up.

Report here with your findings.

Questions:
1. The original post indicates 3.2 MTX. Who did the swap?
2. Have you checked your crank pulley? It's extremely important to keep an eye on the crank bolt after work has been done to the engine. It's not in any sevice manual that I can remember, but I ALWAYS check the crank bolt after a hundred miles and again after a month and again every oil change. Crank cancer happens when the crank bolt works loose, usually because the person that worked on it last was unable to achieve the minimum 180 foot pounds of torque (or they didn't even check and just used an impact on it...typically a "reputable" shop).

 

[Tinman95]

I just don't get the math...

I see a bunch of posts and experience with the fuel pressure, and I just don't get how at WOT there is plenty of gas but at idle there is not enough? I just don't get that. But then again I have to call my Dad when I do a 3-way electrical switch.

I will run the test and let the results be known - Thanks

Answers to you questions:
1. My 3.2 was Kirked ( or was it really Chris'ed aka "Mr Who"?)
2. I have not checked the crank bolt. I would be shocked if the bolt was done anything but right. I am confident that I had a reputable shop.

 

[Tinman95]

Zippo nothing...nada

I have no fuel pressure

I hooked up the gague and turned on the key and go no reading. Thought i had it hooked up wrong so I released the fitting and there was some gas there so I tried again. Key on engine off - ZERO.

The pump cycles like it always has then goes off after about 3 seconds.

So I took off teh guage with key off and depressed the valve at the rail - I got a small hiss

I turn the key on engine off and depress the valve at the rail and get a small hiss and no gas

when running push the valve and get a slow flow

connect the gauge and start the car - zero pressure. let it run a little bit and it will build pressure. rev to about 2500 rpm and the pressure will build to about 30 psi and hold.

Turn the car off and presure drops to zero in 15 seconds


So Fuel pump right?

 

[93rev2sev]

Fuel SYSTEM, for sure.

Here's what I would fiddle with to make sure it was the pump...

eventhough you already replaced the filter, double check your installation and ensure the fuel lines are not blocked or kinked...

Disconnect the line at both ends; at the filter and the fuel line snap fitting at the rails. Make sure there is no blockage. You should be able to put a piece of heater hose on the fitting at the rail and pour gas through the line...it should come out unobstructed at the filter end.

Next, jumper the fuel pump, I think this bypasses the IRCM and has the possibility of ruling it out as the culprit. I could be wrong here, but it's a good way to empty the tank in preparation of fuel pump replacement.

The fact that "once it gets going, it runs great", makes me think it's not the pump. I'd probably swap in a known good IRCM before I dropped the tank.

Edit:
It would be good to know that the fuel pump is getting all the juice it needs, too. My review of your location (Vermont) reminds me that the power to the fuel pump goes through a harness that runs along the drivers seat, under the carpet. The harness is broken into 2 sections, forward and aft. The connector for the 2 sections on one of my 93s had seen moisture and corroded. It was nasty green and the wire was swollen close to the connector. the large black and pink wire fell off when I wiggled the connector. I fixed the connection and was very happy when I flipped the key and heard the pump prime.

Were you able to see the fuel guage when you first turned the key, while the pump was priming?

 

[Tinman95]

Thanks for you help so far

when the pump primed the pressure gauge did not move

 

[Tinman95]

So when I turn the key on and have the rail valve open the pump will turn on and it will prime and I will get gas out of the valve.

then the pump shuts off and that is the end of the gas, no pressure build up.

I don't think I have a blockage in any of the lines since I get gas through from the prime and I get ok acceleration.

So what causes the pump to turn off? I would have thought that there would be pressure and then it would stop.

Is it possible that I get the prime and that allows the car to start then the pump is not working and it is pulling gas using vacume?

 

[Tinman95]

just baffled now

So I take off the connecter to the ICRM and put it back on

I take the motion switch out of the trunk and jumper from the + side of the battery to the connecter and the fuel pump cranks, pressure builds up to almost 40 psi.

I start the car after removing the jumper and it runs and keeps the pressure at a litttle over 30 psi. Turn the car off and pressure goes to zero. Then I pump it back up using the trunk jumper and it goes to almost 40 psi and remove the jumper and it stays right there. And takes about 15 min to release pressure to about 20 psi.

now when I initailly start the car and pressure is at 0 the pump will give the prime and the car will start and at idle will increase and hold at about 30 psi.

At this point I have to believe that the fuel pump is ok since it will pump up to close to 40 psi when asked and will hold.

I still get the same symptom as I started with the rumble and stall from idle.

I will win it is only a matter of time.

I am now questioning the
1. Fuel pressure regulator
2. Throttle Position Sensor
3. IAB - back to that...

 

[Tinman95]

Still searching - changed parts - any advice?

So I have changed:
The coil, TPS, DIS, wires, plugs, CCRM - these made no difference.

No CEL
Tried the Idle reset procedure

I have the intake off and am changing the idle air valve.

Is there a good way to check the injectors?

Any new advice to get this resolved?

thanks

 

[elarm1]

I would check the DIS and tighten all intake couplings. I was having the same problem until I changed the DIS and tightened the couplings.

 

[Tinman95]

not crank cancer..

I just pulled the timing belt cover and it is clean, no red dust, no shavings nothing.

I am going to put it all back together with the new IAB and clean all connections I can find again and try it again tonight.

 

[Tinman95]

still the same problem uuuuggggg

So the new IAB did not solve it.

I put it all back together and made sure the connections were all good.

When I drive it i will get the CEL on for about 7 seconds then go off for about a minute then back on for 7 seconds and it will do that a bunch of times.

I pulled the codes and I get Key-on-engine-off code of 157 and with the motor on I get 111.

Any advice would be appreciated

 

[Tinman95]

Making Progress

I went to JiffyLube and asked them to do the fuel injector cleaning and the guy comes out and takes the vacume hose off the brake booster and puts a hose in it, hangs a bottle off the hood, starts the car and let's the drip start. So I'm thinking that there is another bottle that will connect into the fuel rail for the injectors. NOPE. So I'm asking how the juice gets to the injectors and "it just does". Well it can't. So the process finishes and did nothing for me.

So I got a replacement MAF and changed it and changed a number of things. It got rid of the codes - so now I have no codes and a 9 on the cylindar test.

So there was definately something with the MAF. Then I did the idle reset then took it out and drove it. Better.

I still have the stumble from the resting idle but it is much better, and I am still looking to solve that.

 

[Tinman95]

No more problems

I gave it away this weekend.

:wave: