I recently installed several performance parts on my '90 (headers, T-Body, EGR block off, 8.5 plug wires, plugs, AFPR, smog pump elim.) Before I started the project - I had a EGR code and the car was running a little rich...

When I pulled the car in the garage and started my project, the car was spitting raw fuel out the exhaust - I pulled the old plugs and 6 of the 8 plugs were fuel fouled (the car was running like crap!)

After everything was installed, i had a friend put it on his diagnostic machine and check everything - The timing was a little off and he set the AFPR to 45lbs and the TPS to .5v - the car ran good, but was still running a tad rich....

Now (with fresh plugs and wires) and only about 40 miles on the car since the parts and tune was done, the car will not pull it self.. when I throttle the car quickly it goes to about 2k rpm and the dies off - like the key was shut off... when i drive it around the block it runs like crap still and acts as if its only firing 3 or 4 cyl.

I have been told it was the fuel pump or fuel filter - how could this be if the car is running rich??

I don't want to keep changing parts until the problem goes away - does anyone have an idea of what could be going on?

I'm going to replace the cap and rotor today, but i really don't think this will fix my problem....

I also noticed a huge sucking sound from the breather - I never noticed the before - could I have a vacuum leak that would cause these problems?

Any help or advice would be great!!

 

Double check the little things.

• Pull the EST connector and double check the timing.
• Check the fuel filter.
• Make sure the IAC is set properly.
• Make sure, this will sound dumb, all of the plug wires are pushed on both ends and all connectors are plugged in.
• Recheck fuel pressure with the vacuum line disconnected.
• Also check it after the car has been turned off for a few minutes to look for a leaky injector.
• Check the O2 sensor.

The mods you have done, I also did to my 90 with exception of the EGR plate. I also had an EGR code. Mine was caused by a leaky EGR diaphragm. The EGR actually when functioning properly made the car run, get this, better. The AFPR shouldn't make a difference at part throttle or idle. It will make a difference at WOT. You can also tape the fuel pressure gauge to the windshield and test pressure under load.

Also it has been said you can't be too rich. I am not sure that applies to cars.

 

They did pull the EST connector when he set the timing, so I'm pretty sure this was done correctly

I'll pick up a fuel filter today with the Cap and Rotor

What is a IAC?

I did double check the plug wire ends - that was my first thought...

One thing I did notice when he was working on it - The fuel pressure did bleed down after a couple of min. - he said it was normal... Is this true or should it hold pressure? (It dropped about 5lbs within about 30 sec. of the car being shut off)

Thanks for the reply!!

 

The IAC, Idle Air Controller, is the 4 wire controlled, motor looking thing that threads into the right side of the TB. It is basically a computer controlled, callibrated vacuum leak. When adjusted properly, it is open just a little to keep idle speed where the computer says it should be. When adjusted improperly, it can cause a "sucking noise" from the port in the front of the TB.

Out of curiosity, which brand of TB did you install? I used a BBK on my 90 with very good results.

As far as the fuel pressure bleed off it is normal for it to fall off a little after you turn it off. I don't know the bleed off spec's though. I am sure there are some on the Forum that will.

 

I installed the 52mm BBK

I'll check the IAC and see what I can figure out...

Any more ideas?

 

The IAC is NOT the problem, here. The IAC controls the idle speed. And there is no way to adjust or set it. The pintle should be retracted for installation and for some cars there is a procedure to set it initially, but normal driving will "set" it, also. Once installed and operating, there are no IAC adjustments.That sounds like a leaky injector. It often causes hard starting because the injector has drained the fuel rail and flooded the affected cylinder(s). It could also make it run rich. The problem with exceeding 2000 rpms should checked while monitoring a fuel pressure gauge. You MAY have a fuel system that can't deliver enough fuel under high load, like with a weak pump, clogged filter or sock, coupled with leaky injectors, supplying TOO much fuel at low speeds.

The "huge sucking" sound at the breather sounds like a vacuum leak. Very likely between the intake manifold and the valley. If that is the case, the engine is running off of air that isn't passing through the MAF. The O2 sees lean and adds additional fuel to make up for the introduction of the unmonitored air intake.

Just a couple of "shots" to keep you busy. Don't just start replacing parts until they have tested bad. Good lick, and...

RACE ON!!!

 

Maybe I sould have said adjust the TB blades for a minimum of IAC counts. Would that have been more accurate? Sorry about the miswording.

 

I thought the throttle blades were adjusted to the "minimum air" specs. In any case I don't see the IAC or the throttle opening as playing any part in these problems.

RACE ON!!!

 

Take a can of spray carb cleaner and spray around the area where you hear the "SUCKING" sound. Hit the area around the intake where the tubes are bolted down, also hit the upper plenum connections as well. If the engine picks up RPMs in that area you know you have a vacuum leak. What happened to the fuel that was going into the two cylinders? What was the resolutions for that problem? It seems to me that if you had two cylinders wet with fuel that would indicate two leaking injectors. If your fuel pressure drops just 5 PSI that is pretty much normal. There is a check valve in the fuel pump and the pressure regulator that prevents back flow. But they are not totally bubble tight. A little drop in pressure is acceptable. It is the drastic drop that we look for that indicate further problems.

 

The one thing that bothers me the most is - The car sounds like it's only running on 3 cyl..... and there is no power at all.

On our racing karts, we use carb cleaner to check for intake leaks (spray arond the area we think is leaking and the idle rises) - will this work on the intake on the car?

I have never removed the runners or the lower intake, just the plenum for the EGR & AFPR - However, I don't think that this is the problem as it was evident before I took anything apart..

I'll check more when I get home...

This is really driving me crazy!!! we had bad weather while I was installing my parts and now the weather is great and I can't drive the car!!!

Thanks for the help!

BTW - what is the best way to check for leaking injector?

 

i was told to check for leaking injector, before you turn the car on press the gas pad for 30 sec then start the car , if it starts right up you have bad injectors

 

if all the plugs are fouled yiou may have a bad injector, take the connectors off each injector and ohm each inj out. This is a batch fire system and one shorted inj will cause your problem.
frank

 

What ohm load should the injectors be?

 

I'm headed home to work on my car.... Does anyone know what the Injectors should read? (ohm's)

Thanks

 

Check HERE. Mine says 1.4 ohms, but I'm quite sure that is incorrect for your year.

RACE ON!!!

 

Ok... this is where I am now..

I bought a new MAP sensor and it did nothing.. A fellow CF member loaned me his ECM, but it was for a 6 speed and wouldn't even start the car (not sure if it works either)

I then decided to pull the codes, I found code 13 "Open O2 sensor circuit" - I checked the sensor lead to see if it was broken and it wasn't.. Is there a way to test the O2 sensor?

I'm wondering if the computer is stuck in some sort of limp mode, it will not rev over 1k rpm - it dies out like it is getting flooded..

The O2 sensor is a single wire type and it was installed in the collector (top of collector for clearance) about a week ago when the headers were installed. The car ran great when I picked it up, but was running a little rich and it has just progressively became worse since then..

I don't know where to go from here other then replace the O2 sensor and if that doesn't fix it, the ECM??

What else would limit the RPM and cause the car to run rich?

 

don't worry too much about readings look for the one that is extremley different then the others, if I remember they read between 15-17K, again look for the one that is very different.

 

You sure you got good vacuum on the AFPR???

 

There is vacuum there, but it makes no differance when it is off (vacuum line)