A&Q about 350Z
Q:
Hello I have a 83 Alliance with only 22K miles on it but it has a problem.
It has a throttle body fuel injection setup and is running WAY to rich, so much that it wont run other than to idle it. Indications are thick black soot out the exhaust and the air filter gets soaked with fuel. ALso the engine backfires through the throttle body. Ive read the chilton book and performed the basic tests and it has not helped. Basically something is telling the injector to pump in too much fuel.
From the trouble shooting guide it suggested to change the Oxygen sensor on the exhaust which I did and no improvement. Getting the trouble code out of the ECU is a 3 which indicates a bad wide open throttle switch and or closed (idele) throttle switch which of course the book doesnt tell how to test either.
One thing I have observed, while its running for its brief time before stalling from flooding out there appears to be a leak at a gasket between the intake manifold and the throttle body lower base, can this cause this symptom?
So any suggestions are greatly appreciated. Its a car for my son and even though its 22 years old its like new if I could fix this problem.
A:
I don't know much about your car, but could it possibly be something with the fuel pressure regulator? I'm not sure how your's works, but if there's a vacuum hose on top of the FPR, check it. If it's cracked or leaking or something, it could think that it's at WOT and have fuel pressure dialed way up even though your not at WOT - thus dumping tons of fuel in at low RPMs.
A:
What are the backfiring symptoms? Constantly, accelerating, decelerating, idle only, cruise only...? Has other work been done recently? If there is a vacuum leak under the TBI, it needs to be repaired. Also, does it have a MAP sensor? If so, how much vacuum is at the sensor at idle?
A:
Hi thanks for the help, but what is a FRP? Its got an electric fuel pump located back by the tank. The injector has two wires going to it and its located at the mouth of the throttle body. Im thinking that it could be the WOT switch, ie thinking its in the ON position all the time, but only if when the WOT switch is activated then the injector is soposed to dump tons of fuel at it. Sound right? If thats the case I should be able to disconnect the cable to the WOT switch and test it?
A:
Reply to Benchtest - thanks for the ideas OK what I know. It backfires at idle just alittle, as I give it throttle the backfiring becomes pronounced and sever, lots of fuel flying out. Engine eventually stalls and needs to sit before starting again. Car has sat for 5-10 years. (little old ladys car, really) Yes it has a MAP sensor but dont have tools to test vacuum pressure. ANy simple test to try IE disconnect hose and start, disconnect and plug and try starting..... How can I test the MAP sensor? Thanks.
A:
how many injectors are on the throttle body, 1 or 2? the fuel pressure regulator is usually located on the return fuel line. The fuel pressure regularor is usually about two inches long and an inch around. As an increased load is put on the engine (throttle opened wider) the vacumm level in the intake manifold decreases. The fuel pressure regulator is relayed this information via the vacuum line running to it from a source on the intake manifold. This causes a diaphram in it to close, allowing less fuel to return to the fuel tank thus increasing the pressure to the injector(s).
If the vacuum line is missing or leaking, the regulator will think the car is at full throttle when it is not allowing the flooding condition you are experiencing to occur (like ridenour said). I would first check the vacuum line to the fuel pressure regulator making sure that all the connections are secure and there are no cracks or leaks. Since the car sat for a long time it is likely the hose may have rotted. If there are any problems with the line, you can easily purchase replacement hose from an autoparts store to replace the line. If the line checks out ok, get a vacuum gauge from an autoparts store (should cost about 20 bucks or so) and connect it to the intake manifold via the fuel pressure regulator vacuum hose. With the engine idling, the gauge should indicate around 15-20 InHg of vacuum. If the reading is normal, i would then replace the fuel pressure regulator and go from there. good luck!!
A:
I would suggest a different approach: First, do a compression test on all the cylinders (pull ALL of the plugs before you start). If all are good and even, check your ignition wires for the proper firing order. Next, check the timing. I suspect you'll find a problem with one of the three. The WOT switch is usually used to cut out a/c systems, not fuel control. Also, and I'm not trying to step on toes here, but TBI's are usually internally regulated for fuel pressure, so you probably won't find a regulator or vacuum line. Let us know what you find.
A:
I would clean the living fuck out of the throttle body, then inspect/replace whatever the trouble code says is wrong...
Just my suggestion, good luck with your problem!
A:
Thanks Guys, have to work today but will check these things when I get home tonight.
A:
OK I couldnt wait, I checked and first its a single injector. Also there doesnt appear to be a pressure regulator, the two fuel lines run down and out back to the tank, nothing inline on them. There is two small vacuum hoses that attach to the side of the throttle body, where they go I couldnt tell with a quick look.
As for compression and plug wiring. The car was running well. I did check the plug wiring order and thats correct. Ive also put new plugs, wires and distributor cap on already. I dont have a timing light but will work on borrowing one.
As for the vacuum issue, is it possible to FOOL the system and pull the hose or plug them to get the system to tell the regulator to slow the fuel supply down.
Also, the MAP sensor, how can I test that??
Thanks
A:
MAJOR DISCOVERY!!
Well Ive been going down the wrong road, appears to be multiple problems, the leaky throttle body gasket and this latest discovery. Talking to local friends they also suggested it was a mechanical problem but they thought it was a sticking valve. So off with the valve cover and I discovered one of the studs that holds the cam shaft?/rocker arms in place was not secure, totally loose.
I attempted to tighten it down and when I then screwed the nut on it popped out. Checking the threads I found metal strips, IE stripped in the head. So this appears to be the first major problem, valves must not be opening all the way or not at all in this one cylinder.
So how do I fix this? Does the head need to come off? Ive taken heads off before but fret on doing it, My first thought is to take the head off and bring to a machine shop but if it can be done on the car that would be great.
Thanks
~ Phil
A:
Im trying to answer my own questions but Id like some feedback. Found in the chilton book that you can drill the hole out and tap in a heli coil and thread the stud back in. Ive never done this and from reading it this is a one shot deal. Should I take it in to have it done? The hole does not go through to a opening (water jacket....) so I feel safe in trying. Do I need to go deeper to make it work?
I have to take the rocker arm shaft off to get at it with a drill, any gotcha to look out for?
Thanks
~ Phil
A:
Heli-coil is the fix. If you're confident, go for it. If not, tow it to someone. Follow the instructions to the letter. I wouldn't pull the head for that, but don't get shavings in the motor. Exhaust rocker? I hadn't thought of that possibility since it is very rare, but that's why I suggested the compression test...to see if the intake valve was closing or the head gasket blew between cylinders. Should fix most of your problems, but the TBI gasket is a must fix also. Don't sweat the MAP sensor unless it runs poorly after the rocker is fixed. Also, don't sweat the regulator. I may post a thread explaining regulators due to the confusion, but if not I'll post it here later. Rocker shaft: un-torque and re-torque evenly. Take your time. Did you hear any rattling when it ran from the rocker?
A:
Hi thanks, I think Ill give it a try or drag a friend over thats done it. and yes the engine sounded alittle noisy but it was new to me and just didnt know if that was how that engine sounded..
THanks again for the help.
~ Phil
A:
A plymouth reliance? AN OLD K CAR!? One with 22k miles!? The rarity!!!!! =)