Nick86

iTrader: (1)

Ok, my car has been off the road for weeks and I am SO frustrated with it right now. I've spent hours reading threads, the haynes manual and FSM, but I am simply stuck. Here's the history of the problem:

Car (86 GXL, no emissions) had been running poorly for a while. Sluggish and ultra rich. I got the timing light out and the car was way off TDC. I reset it all to factory spec and it did nothing... infact it made it worse. The car hesitated under load and backfired between shifts. So, this is what I did:

- Removed all 4 injectors and had them cleaned and tested.
- Cleaned and inspected the injector connectors.
- Timed the car while warm - set to factory spec.
- Replaced Fuel filter.
- Cleaned air filter.
- Replaced spark plugs.
- Tested MAF: in Spec.
- Tested CAS: in Spec.
- Tested Leading coil: in Spec.
- Tested Thermo Switch: in Spec.
- Regrounded the engine.
- Regrounded the pressure sensor.
- Plugged in the test light: The car throws NO CODES!

I thought it was the infamous 3800 rpm hesitation, as that's where the car started missing and bucking - so I did the regrounding. After regrounding the engine I thought I improved things, but really it hasn't done much at all. The current condition is this:

The car idles perfectly. At light throttle in first gear everything is normal. If I start to accelerate, the car bogs down low, then comes alive, then misses and bucks violently over 4K (3800 maybe?) and backfires when I let off the throttle.

I tested the TPS and was able to get 1 ohm at idle, but at WOT the reading was about 13 ohms. I replaced the TPS but still can't seem to get it to 5 ohm at WOT. The new one only gets about 3.8 ohm - I have a hard time believing that's the source of my problems, but could it be?

I've been looking for vac leaks with a tube to my ear and with a can of propane, but so far everything seems ok. I'm at a loss. Did I hook up the injectors wrong? The car idles perfectly so I doubt I hooked up the primaries backwards, and the secondaries are pretty much impossible to hook up backwards. Are all 4 injectors the same on an S4 NA?

Sorry for the long post but I am simply at my wit's end!

Thanks for the help,

Nick

Nick86

iTrader: (1)

Swapped in a new ECU (N326) and nothing changed. WHAT THE HELL IS GOING ON???!!!

KillaKitiie

Ok first of all get your TPS in spec..after thats done check your fuel pump to see whats its getting. Maybe you have enough pressure at idle but then not enough at load...Um is your EGR valve blocked off or is it just disconected? i say this becuase that alone will cause massive bucking and backfiring..

Nick86

iTrader: (1)

Thanks.

The EGR is blocked off, as is the ACV and there is no Air Pump either.
While I agree that the TPS is the first thing I need to address (again), could that alone be causing all this?

I had thought of the fuel pump and somewhat dismissed it, as the car was running rich. Then again, that may have been an unrelated problem. If the fuel pump was going screwy, would the ECU do anything to try and make up for it?

Thanks again!

KillaKitiie

Nope if your fuel pump is not pumping what it should or say it fails altogether the car will just die until it's replaced..Now on my 87 i had my EGR Valve and ACV blocked off too with all emissions gone and i had a rock solid idle and normal powerband..And yes a TPS out of adjustment will cause the car to go into a limp mode guttless,bucking frenzy..lol Ive been throught three TPS's in the 2 years with this car.

Nick86

iTrader: (1)

Ok, I put a fuel gage on the car in 2 places. First I put a "T" right after the fuel filter and started the car. I say just under 20 psi. I then went for a drive. At moderate throttle and WOT I saw 30psi.

Then I put the same gage right after the fuel pump and went for a drive - Same thing. 20psi idle and 30 at WOT.

I didn't put a jumper wire in the connector or fool with the AFM, just pulgged the gage in and went for a drive.

The FSM says Fuel Pump Pressure should be 64 - 85.3 psi. But it also says fuel line pressure should be 34-39 psi. Which one am I measuring with my test?

Also, I'm assuming that if the pump is bad, then my best bet is to just replace it with a stock replacement... right?

Thanks!

Nick86

iTrader: (1)

Ok, here's a visual representation of the test I did. In the pic, you can see that I have a "T" right after the fuel pump outlet hooked up to a gage. This pic was snapped with the a jump wire in the test connector, and the ignition set to "ON". As you can see, I got only 30psi. Should this be 34-39 or 64-85?



Now, my next test was to take the gage off the "T" and hook it up directly to the pump outlet. In other words the gas came out of the pump and the only tube it went into was the one attached to the gage. That measured 45 psi. Should that be at 64-85 psi? Is it safe to say that the pump is no good?

Thanks!

Nick86

iTrader: (1)

$260 on a new ******* fuel pump, and nothing changed.

Valkyrie

45 PSI is normal... plus those pumps almost never fail.

Valkyrie

BTW, fill up your tank to make sure that your gas hasn't gone bad (usually this takes a few months... but you should go ahead and eliminate all possible causes).


I know it's cliche, but you should also check for vacuum leaks. Check places you haven't checked... ie, use a light to look for cracks in the air intact duct. Or get a compressor and a pressure regulator, and a round piece of wood, with a pneumatic fitting in it to pressurize the intake and see if you can hear the leaks.

Also, hook the fuel pressure gauge up to the fuel line where the fuel is effected by the fuel pressure regulator (not sure which side that is)... what you should be checking is not what the pump is putting out so much as what the engine is actually getting (while running).

Nick86

iTrader: (1)

Thanks for the response!


The fuel is new, so I'm not too worried about that. 45 psi is normal? I understood that the regular line pressure was between 34-39 and the pump should be pushing 65+ when a gage is hooked up directly to the outlet like I had it. Hard to argue though, as the pump did sfa for me.

It's back to square 1 for me now. Like you said, check for vac leaks etc. I already spent a few hours in the engine bay with a piece of hose and a propane torch, but maybe I missed something.

I am just so frustrated with this thing now. I'm low on time money and patience. I spent less time getting the car running after the rebuild than I have on this problem!

Gotta just start back at the beginning. Thanks again....

scrip7

iTrader: (6)

When you checked your timing, did you ground the green check connector first?.....if not, you probably backed off your timing too far. Ground it and make sure you have your timing light on the correct plug wire and are looking at the right marks on the pulley.

scrip7

iTrader: (6)

You said your emissions were removed. Do you have the 5th and 6th ports wired or are they working? My s5 port valves weren't working until I found a cracked hose going to the actuators from the solenoid. Makes a noticeable difference when they open correctly.

Valkyrie

Backing the timing off too far would, imo, make it idle like crap, and you might get increased afterburning and reduced power, but it wouldn't cause hesitations (since the timing advances when you rev it)...

This sounds like the cars fuel supply is getting choked off. Either that or the secondary injectors aren't firing (although that's more related to the 3800 RPM hesitation...unless maybe you had one working and one not, causing uneven combustion).

When I tested the fuel pressure on my car where the inlet hose meets the metal hose, it read at 35-40 ish, and that shouldn't be any different than measuring it at the pump (unless 8-9 feet of hose makes THAT much of a difference...this is after the filter though...)... what's really important is that you're getting the proper pressure AFTER the pressure regulator, even when accelerating.

I would also suggest checking that

1. the auxiliary ports move when you try to turn them (if not, you'll be running uber rich at above 4000 or so, due the lack of air and no changes in port timing).

and

2. That the auxiliary ports are actually opening when you're driving... first check that you can actually blow them open with the vacuum hoses connected to them (it should only take a couple of PSI, which your lungs can generate...), and second.... well, as long as you've got exhaust backpressure to those hoses, they should be opening...


Also, make sure the fuel filter is pointing the right way, if you didn't when you installed it.

scrip7

iTrader: (6)

[QUOTE=Valkyrie;6981568]Backing the timing off too far would, imo, make it idle like crap, and you might get increased afterburning and reduced power, but it wouldn't cause hesitations (since the timing advances when you rev it)...


So you would say that reduced power and hesitation aren't related?.....Perhaps you should go to your car and back off your timing 5 or 6 degrees and see if you don't experience hesitation. I have worked on piston engined cars and trucks for a living for 31 years and rotaries for 21 years, and BOTH engine types will hesitate if the timing is too far retarded. And yes the spark is supposed to advance, but the total spark advance is lower if the base timing is lower. The control unit does not "compensate" for decreased base timing. The timing map is a fixed rate program written by the manufacturer.

HAILERS

Pull the vacuum line off the pressure sensor and plug it. Go for a ride and see if things have changed or not.

To prove the tps isn't the problem, go for another ride with the TPS disconnected and see if the problem changed.

Trail plugs hooked up right?

Nick86

iTrader: (1)

Check Connector? Which one? I followed the proceedure in the FSM and in the Haynes - no mention of grounding a check connector. Which one should I ground? As for the marks, when I rebuilt the engine I exagerated the marks on the pulley with a file and paint, so I'm confident they are right.



5th and 6th ports are functioning normally. I tested them by applying vacuum and also byloading up the rods with grease and going for a drive. Afterwards you can see marks in the grease where the rods were moving.



The pain is that the symptoms do also manifest themselves at lower RPS's too - like backfiring and bogging below 3800. And they also seem to becoming less and less predictable - which makes me think electrical issues, but who knows at this point!



The fuel pressure was at 30psi when I had a "T" in the fuel line. When the pump went straight to the gage I saw 45psi. When you saw 35-40 was the line "T'd" or was the pump going straight to the gage?



Trail plugs are correct - I even reversed the HT leads for ***** and giggles and it sure didn't help! lol

I unhooked the TPS and went for a drive too, and it did nothing different. I'll try the Pressure sensor now.



Thanks for all the input and suggestions guys! I appreciate the help!

Valkyrie

That would be T'ed at the inlet, after the new fuel filter (to be honest I was just testing it for the hell of it, nothing was wrong with it).

scrip7

iTrader: (6)

The timing check connector is a one-wire green connector located next to the driver's fender behind the front (leading) coil pack. When you ground this connector with a jumper wire, it puts the system in "timing mode" when the engine is running. This means that the control unit doesn't allow spark advance so that you can set "base timing". Usually, if the connector isn't grounded, there is a small amount of advance at idle, so if you checked it without grounding it, you would think the timing is off and you may have retarded it needlessly, which can give you reduced power/ hesitation. Warm up the engine, ground the connector and check it again. I bet you find it's retarded. With the timing light on the front trailing plug wire, you should see 5 degrees ATDC (yellow mark). All of this info is for an S5, I think the S4 is the same. Oh and this connector has more than one function. When grounded with the key on and engine off, it is used to flash trouble codes via the check engine light.

scrip7

iTrader: (6)

According to the FSM, REGULATED fuel pressure (gauge "teed" between pump and fuel rail) should be 34.1-39.8 psi. Full output pressure (direct gauge connection to pump) should read 64.0-85.3 psi. Again these are the specs for S5, i would think S4 would be the same, I don't have an S4 FSM handy. I have seen a few pressure regulators fail, most of them had ruptured diaphragms and when you removed the vacuum hose to it, gas would spew from the hose nipple.

EDIT: I just read post #8 where you said you had replaced the pump. I assume you replaced the sock filter on the bottom of the pump as well?

HAILERS

You jumper a series four green check connector.

You gnd a series five check connector.

All that backfiring and bogging sounds more like too much fuel to me...or the timing is way off. Just guessing.

TehMonkay

iTrader: (-1)

Did you test if you had a good 12 volts at the secondary injectors with the ignition on?

Did you disconnect the boost sensor vac line, plug it, and rev the engine above 4k to see if the secondary injectors have a good ground?

The grounds can also be bad in the harness where they all meet. Or the connectors can be bad too.

Shainiac

iTrader: (7)

Dont laugh at me for saying this or be offended for asking a stupid question, but are your plug wires on the right plugs? When I first got my car and changed the plugs, I swapped the trailing with leading and visa versa. Thing ran a lot like what ur describing. Uber rich, bucking and backfired. You seem to know your **** and plug wires seems like a given to know, but just thought Id mention it.

DemonicPupil

I had the exact same problem with my 86NA. Turned out that the AFM plug wasn't on all the way/bad connection. It had rattled loose and the car gave me crap for 2 miles before I got out and started fiddling with things.

Figured I'd throw in my experience with the same problem. I could be light pon the throttle and be ok, but I had to go up a hill and that made me get on the throttle and that's when I had trouble.

pfsantos

iTrader: (1)

This is more regarding your backfiring...

Since you got rid of your ACV (which has been blocked off), you also lost the AAV (anti-afterburn valve) in the ACV. This may explain the Backfiring. The AAV lets in a bit of fresh air when you close the throttle. Also, do you still have the dashpot at the back of the throttle body - and is it adjusted?

Also, did you cap the vacuum line to the EGR that you got rid of? Because that'll start sucking as soon as the EGR solenoid kicks in.

BTW, what is the story the spark plugs are telling when you take them off? Are you sure spark is getting to all the plugs? Have you also put a stethescope to the injectors to make sure all are clicking (follow FSM to activate the secondaries - I think a previous poster mentioned it). Is the solenoid resistor fine and sending 12V to all the injectors.

Good luck...all the other posts covered more than I can think of...and let us know how it goes...