Fuel Injection Problem

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.

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.

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?

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?

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.

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!!

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.

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!

Thanks Guys, have to work today but will check these things when I get home tonight.

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

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

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

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?

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 plymouth reliance? AN OLD K CAR!? One with 22k miles!? The rarity!!!!! =)

Actually an old Renault Alliance, another rarity....

Right up there with the Encore and Fuego.

Well the stud is back on the head, rocker arm assembly back on and ready to try, problem is I left something on and killed the battery, tomorrow morning hopefully will bring sucess!

Good luck!

Back again, OK I was able to fix the stripped stud, retorked the rocker assembly back down and appears all valves are moving. The engine runs, no backfiring now but has no power, Idles or runs wide open, moving the throttle slowing causes it to stall, sounds like its starving for air. The plugs get completely carbon fouled, which to me is indicating its running rich. Could this also indicate a timing issue? The engine has a chain for timing, no belt so Id think its just the ignition timing that would be off. Going to borrow a timing light this week.

Ive tried disconnecting various ignition devices one at a time and then all and the engine still runs the same. IE disconnected the throttle position indicator, MAP sensor, WOT switch and no difference.

I do not know how to trouble shoot this any futher, my understanding of throttle body fuel Inject is that when its cold, it only relies on the throttle position indicator, MAP sensor and maybe the engine speed to gauge how much to pulse the injector. How can a find out what part is broke or what is wrong??

Thanks guys.

~ PHil

I,m not a seasoned mechanic but was just dealing with my own fuel injector problem for the last couple of days. After searching several forums, I found that the crankshaft position sensor controls the timing for the firing of the injectors, via the Electronic Control Unit. The ECU shorts/grounds the 12 volt signal that is applied to the injectors which then causes them to fire. It was also mentioned that if you want to know if the injector is recieving the signal to fire, you can use a testlight (or a noid which is specificly designed for this). One guy said that he tried gounding the injector signal directly to the chassis ground. His result was that the injectors fired continuiosly causing the engine to run extremely rich. Don't Know if this is possibly something for you to check, but if your crankshaft position sensor, ECU, or Injector circuit (wiring being grounded somehow) are causing the injectors to dump more fuel than they should, the symptoms you have described may appear. Just thought I'd drop in my two sents.

Hi Pathfinder007 this car has a throttlebody injection, with only one injector so there isnt crankshaft position sensor. Thanks for trying to help though.
~ Phil

Mine is throttle body injected as well. The point is more this. The throttle body houses a fuel injector and is controlled by the ECU. The ECU needs a reference in order to know when to fire. Some vehicles use a cam shaft sensor and some call it something else. My crankshaft position sensor is located inside of the distributor. The injector should only fire once at the point when one of however many cylinders is pulling back for the intake stroke. For a four cylinder, the injector should fire four times. If the problem I stated previously is occuring. The injector could be on all the time. The noid or test light would tell you if the injector stays on all the time or if it pulses once for each cylinder.

Hmm OK, Ill have to read up to see how it sences when to fire, I have not read anything about the crankshaft sensor but will look into it. Thanks

OK well Ive read in the Chilton book and found nothing about a crank shaft position sensor. But also I cannot figure out from the book how it knows when to fire. To be honest I figured it was continuously firing and its timing didnt matter since its firing before the intake manifold. IE a carb is always supplying fuel, not pulsing to match each cylinder firing. Can anyone clairify this??

Thanks ~ Phil

l2sail, There are a couple TBI versions, but most can operate in synchronized or un-synchronized mode. Some will fire at a set time interval based on rpm and some will sync. to the ignition timing. It depends on engine variables and changes automatically. They trigger from the iginiton pick-up, thus have no need for a crank or cam sensor. You are correct that they behave like an electronic carb., not a port-fuel engine. Do you have a good vacuum signal to the MAP sensor? Also, is the TBI making a ticking sound when it's injecting, or just dumping fuel (this is what the noid light will tell you also)? And, does the ticking (if there) change when the throttle is opened and closed?

UPDATE!! Since I dont have a compression gauge or a timing light and havent had a chance to get them I tried testing what I can. On Wells Manufacturing Site it described how to test the MAP sensor and the TPI. Heres what I found:

MAP Sensor, had a hard time finding it, its located behind the firewall by the wiper mech area. The test basically consists of disconnecting from the 3 wire connector, jumpering the two outer wires and monitoring the voltage on the center pin to ground. With just the key on (engine not running I got 4.9 volts which it indicates as correct) I could not start the engine and thus couldnt check to see if its varying correctly.

TPI: This test was just measuring the resistance between pins 1 and 2 and between 2 and three with it unplugged from the harness. THen move the throttle through its range to WOT

Pins 1 to 2 at idle 2.79k
Pins 1 to 2 at WOT 5.65K
Smooth change in resistance, no drops through range.

Pins 2 to 3 at idle 3.82K
Pins 2 to 3 at WOT 3.82K
Same through the range.

THe test says both should vary smoothly. Im thinking this could be my problem.

I also tested the voltage change with the key on.

Pin one appears to be the sense lead, at idle it was 3.38 volts and at WOT was .21 volts. THis is opposite of what the test described should happen, says it should be near 0v at idle and increase going to WOT. The second pin had 4.37v always and the third pin was at .01v always.

So is the TPI the problem or is it different cause its a french car? Im french so I can make fun of it, but really any thoughts on this??

Thanks, Phil

PS Im going to also post this as a new thread so please ignore the other thread if you see it.

Reply to Benchtest - thanks for the help, I appreciate it. OK Dont know about good vacuum to the MAP, no vacuum guage, I will try just sucking on it to see if it leaks if thats valid. Whe the engine was running I do not recall hearing a ticking sound.

What is the Noid light? THis is a very basic test indication setup, there are two electrical connectors and I have test points for the following:

Tach
Ignition
ground
battery
fuel pump

trouble code
neutral switch
AC on
WOT switch
sensor ground
air temp sensor
egr solenoid
Canister purge sol
ISC moter forward
coolant temp sensor
Closed throttle switch
ISC moter reverse
Auto trans potentiometer.

The problem is the book doesnt describe how to test these items.....

Thanks Phil

No need to suck on the line. Just pull the vacuum hose off the MAP sensor and see if there is a good vacuum there when it is running. If not, trace the hose and find the problem. A noid light is a light that plugs-in in place of the injector. It flashes when the computer pulses the injector. Why couldn't you start the engine when you were testing the MAP?

Im not sure why it wont start now. Been frigging with it too much. I may have to pull the plugs and clean them again, they get excessivly carbon fouled. Ill try pulling the vacuum line tomorrow after getting it running,

As for the noid light, anything special about it? Certain voltage/current requirement? Can I make my own with a _______ bulb?

Thanks

~ Phil

Well I cleaned the plugs and it still will not even idle now, it will run on a few cylinders for 5 sec or so, not enough time to get over to the map sensor and check for vacuum. Im going backwards and I really havent done anything.

I double checked the TPI readings, they are just the opposite from what I read they should be. IE at idle I get almost 4v and at WOT its down to almost 0v. I tried for kicks holding just the TPI level so I got about .4v and then starting without applying any throttle and it still wont start.

Any suggestions?

A niod is just a 12 volt bulb with a connector on it so that it will easily plug into the connector that the injector plugs into. A 12v bulb or test light should do fine. I hear that you can find a noid at a local parts store for around $10.00, but even that much is alot for a one time test.

There are a couple options to keep it running. 1 - get help. Someone that can keep it alive while you test. 2 - it sounds like it is running very rich, so creating a vacuum leak at the TBI could keep it alive. This, however, makes checking the MAP more difficult. The leak would need to be away from the MAP source. 3 - if you have a vacuum pump, you could apply a vacuum to the MAP and see if it leans out. Once plugs are carbon fouled they may not fire even after cleaning.

Thanks, I got a syring today and will test map with that, also will test injector leads with the test lamp. Thanks for sticking with me. I am getting to the end of what I can do and Im considering taking it to a mechanic, Its probably something real simple but my digit head brain can recognize it.

~ Phil

OK another update, I did another test on the MAP sensor, jumpering the power leads and reading the voltage on the sense lead I applied vacuum to it with a syringe and the volts dropped from 4.99 to 3.3 something. Not a calibrated test but does prove it goes down with vacuum.

Testing the leads going to the injector showed a very immedate and constant flash, very fast and the off time was no greater than the on. Doing it with the throttle pressed half and then full did not appear any different.

Watching the flow of fuel from the injector I can SEE it while the engine is idling, even collecting and dripping off of the butterfly valve. Applying any throttle cause a large pattern right off, almost like its going to full throttle spray.

Another observation, remember in the beginning I stated seeing vapor/smoke rising from the gasket between the throttle body and intake manifold, I was wrong, watching it tonight its coming from the gasket between the intake manifold and the exhaust manifold, yes thats what I said. I dont understand why there would be one there and the book doesnt show or describe it. Can this be a leak thats causing the problem? Why would there be a connection there?

This same vapor/smoke/fog will rise out of the throttle body after several attempts to start it or after it eventually stalls.

I discovered I can restart the car by disconnecting the injector leads and cranking till it starts and stalls from starvation. I can then get it to run for a few minutes....

Any Ideas??

Did you ever check to see if your manual tells you how to read the error codes stored in the ECU. Many vehicles have a procedure which will allow you to veiw the errors via a series of flashes by some designated display. My pathfinder has a diagnosis switch on the side of the ECU and a red and green led which will flash the error codes. My Plymouth Acclaim requires me to turn the key switch on and off in a particular sequence and the flashes the codes via the engine warning light on the dash. My mothers Cadilac actully displayed the numbers on her temperature display for her environmental controls on the dash. If your vehicle has such a setup, it would be worth it to find out what it can tell you. My Acclaims trouble codes covered just about every emissions sensor under the hood. As for your leak between the intake gasket and exhaust gasket, I don't know of any engine where the exhaust is directly connected to the intake except for through the EGR valve. If your engine is a four cylinder and the intake is above the exhaust and you have a minor leak in your intake gasket, fuel can leak down onto the exhaust manifold and as it heats by the exhaust, the fuel will burn off and be seen as smoke. Just another concern to watch for is if you have lots of raw fuel going into the cylinders and not being burned, it can end up in your crankcase and mix with your oil and then attack your seals. keep an eye on your oil level an maybe make sure your oil hasn't gotten thinned out to bad. Killed my father inlaws newly rebuilt 351 engine. I know that problems like this can be tough and you have to decide how far you are willing to go in finding the problem yourself. For me, I enjoy the learning that comes with resolveing my own issue and I figure I've also saved quite alot of money.

Thanks for the idea, yes I have gotten the error code from the ECU, its was a three which by the book said it was a bad WOT switch (tested fine) or the closed idle switch which is part of the idle control solinoid and has too many wires to figure out which one is just the closed idle switch. The idle control solinoid appears to work so I didnt think that was it....

Using the electronics diagram in your manual should tell you exactly which two wires go to the idle cosed switch. If the ECU thinks the WOT swicth or idle closed switch are bad, it will not deliver fuel properly. It might be helpful if you list text on this thread for each error code that appears and maybe we (the readers who view your postings) can think of some things for you to check into. You need to eliminate the errors from the ECU by locating there cause. It also might be an idea to clear the errors from the ECU and see if they re-appear.

Hi PF007 I do not have a wiring diagram, it doesnt come with the CHiltons manual. I have gone through the process of getting the error codes out and its as I said in the prev msg, a three. There are only a possible six codes, thats what the book says anyhow. Unless anyone has grand Idea Im going to bring it in to the garage. My only real thought is maybe the bottom of the intake manifold is OPEN and relys on the connection to the exhaust manifold to provide the bottom side of it, IE thats why there is a gasket between the two. If thats the case it beyond what I want to tear appart.

~ Phil

I'm having no luck finding a picture showing your intake manifold. Haven't figured out that one yet. I hate to sound like a broken record, but is there good vacuum at the MAP sensor?

That I dont know, how do you test for vacuum? Car wont stay running long enough to do much. I do know that putting a syring on the hose going to the MAP I can cause it to output a lower voltage. And I also sucked on the hose going in the other direction toward the engine and there is no resistance, can suck all I want and not build up any vacuum but I figued this was normal and you would only get vacuum whith the engine running.

~ Phil

A vacuum gauge is the best method. You could apply a vacuum with the syringe and see if that reduces the injector spray. You can apply the vacuum before starting.

Hi just an update for everyone who attempted to help me. I should have started with the basics, the garage found two valves sticking open, and adjusted them. The car is running now but is still running rich, getting about 24mpg and is rated for 30+ but ill live with it.

THanks

~ Phil