EFI question

[kartracer55]

The car is a 1989 Pontiac Grand Am with a TBI/CFI setup, and it runs EXTREMELY rich and pretty rough too. Ive spent a few hours trouble shooting, and I still cant find anything (yeah yeah im a crappy mechanic) Ive checked the MAP sensor, it tested fine, but I shotgunned it anyway, no change, so I can rule that out. I also did some investigating for vacuum leaks with a can of carb cleaner, nothing there. Its got spark on all 4 cylinders (btw) and I did a leakdown & compression test, and its all in speck, no burned valves or anything like that.

I *think* the problem might be the injector itself, because Im looking in the bowl when it is "running", and it doesnt look like a fine mist, as it should, it seems to "rain" in a small area of the stream. Heres what gets me... despite this, it still runs rich and rough, not lean like its not getting enough fuel which I would have thought. Is it possible there is high fuel pressure AND a clogged injector? I dont have a way to check fuel pressure, its an odd size line and the guage Im using doesnt have any adapter for it(and theres no schrader valve). I wouldnt think this is the case, as it hasnt seen much fuel... less than 55k on the odometer. What do you guys think? Im getting ready to just get a new injector for it, but If I install it and find that its not the problem, I just wasted a good, what, 80$? Of course, I dont have the special Injector testing tool GM says I need to use either. I checked the resistence of the injector, and it is in Spec with what Alldata is telling me.

What do you guys think? I need some opinions!

Thanks Alot!

Jim

 

[Trooper04]

Check your O2 sensor, see if you have a clogged cat and check the grounds on your motor.

 

[kartracer55]

Check your O2 sensor, see if you have a clogged cat and check the grounds on your motor.

Well somebody did a "Tune up" on the car over the summer, including an O2 sensor, belts, etc but, I suppose I can pull it and check it out (kill two birds with one stone) as well as check for a possible clog.


I hate cars



Jim

 

[Brian]

A couple possible reasons for running rich:

The engine thinks it is running colder than it really is.
Test your temperature sensor/s.

In other vehicles I have seen leaks in the exhaust system before the O2 sensor cause rich running. Air gets sucked into the leak and the sensor sees the extra air causing more fuel to be injected.

Other than that I don't know much about GM toilet bowl injection, or how the fuel spray patten normally looks coming out of the injector.

 

[jarhed]

Check the fuel pressure regulator. If you have a vacuum hose going to it, pull it off and check to see if there is fuel in the hose - if so, you found the problem.
What engine do you have ?

 

[70BOWTIE]

http://www.gaownersclub.com/forum/index.php?s= Have you tried any injector cleaners like seafoam or ???Try this site it is a pretty good one

 

[kartracer55]

Alright, thanks for the replies. I pulled the O2 sensor today, and it looked pretty wet, but other than that not damaged. Started it without it in and it didnt make a difference.

Brian, I checked the coolant temp sensor, and it was in the specified range for the temp, Are there any others I am missign here?

Jarhed, Its a 2.5 straight 4. Your thinking the diaphragm inside might be ripped or torn? Could you go a bit more in depth in your thinking here? You might be on to something. I havent been able check fuel pressure (feed or return) because it has solid lines and compression fittings for the whole run inside the engine compartment until I get over towards the left wheel where it turns to a crimped rubber hose for about a foot. I COULD maybe splice this to hook up the guage (they give me a fitting to do this) but I really dont want to go cutting up lines

Thanks guys

Jim

 

[SuperKid]

Have you tried testing the injectors? If you don't have them, buy (or borrow if you can) a noid light set, and an injector pulse tester. OTC makes a quality noid light set as well as a quality injector pulse tester.

Noid Light Set

Injector Pulse Tester

Good luck.

 

[stimpy]

Jim , to test the O2 sensor it must be in place with the engine running and see if it makes a current level that fall s within the specified range ( let the car warm up first then test) pulling it out and looking at it is like trying to tell if a light bulb is burnt out over the internet , the sheilding covers the probe and it might look fine but the metals might be broken or burn't off inside, O2 sensors are lambda sensor it is basically a thermocouple when it gets warm it generates electricity ( very small amounts ) there are several gm sights on the net that list different specs on what it can be . most gm o2 sensors interchange but not all 1st thing you needto know is it a 2 wire or 3 wire type ? the 3 wire type has a light off heater inside it and if its dead it will screw things up, also if the o2 sensor has been spliced incorrectly the computer will read the signal wrong due to excessive resistance (remember very low electrical signal needs a very low resistance signal path )also check the harness for broken or corroded wires as I have run across cars where a so called mechanic used a peircing probe type tester and the hole caused the wire to corrode internally and set up high resistance values , the injector should have a wide smooth fan shape to it , it its off set or dribbles to one side it means it should be cleaned or replaced , the best way to clean them is to run the gm cleaning kit thru the system ( about 80 bucks so it might be chaeper to buy a new injector )and if you replace one replace all as the others will soon fail , look in your local yellow pages for a company that strictly deals with fuel injection ( some diesel shops will work on cars ) they can clean the old injectors or test them for a fee , ( the testing involves so pretty neat but expensive eqiupment that duplicates the running of the engine and varies the pulse width of the injectors signal to fire) theres a place here in chicago called midwest fuel injection that deals with cars and truck and are real good , to bad your in jersey. to check the line pressure you need an addapter that connects between the TBI housing and the fuel source ( connection should be on the back of the housing ) I doubt it is high pressure as these system are a low pressure type and the pumps are notorious for failing. sorry so long of a quick reply

tonight I will look in my books and see if I can find the values for the sensor it should be a 2 wire type

 

[BoostAddiction]

You said you saw the injector spray an uneven pattern that looked like rain instead of a conical spray.

If that is so, then that injector (and likely others) is clogged or worn. You can replace them or send them to RC Engineering or other injector service places to get them cleaned and certified. They can check for pattern as well as flow, both of which are suspect based on your explanation.

HTH,

-Will

 

[clarkandrew45]

Im doing my with a TBI/CFI setup, and it runs EXTREMELY rich and pretty rough too. Ive spent a few hours trouble shooting, and I still cant find anything (yeah yeah im a crappy mechanic) Ive checked the MAP sensor, it tested fine, but I shotgunned it anyway, no change, so I can rule that out. I also did some investigating for vacuum leaks with a can of carb cleaner, nothing there. Its got spark on all 4 cylinders (btw) and I did a leakdown & compression test, and its all in speck, no burned valves or anything like that.

I *think* the problem might be the injector itself, because Im looking in the bowl when it is "running", and it doesnt look like a fine mist, as it should, it seems to "rain" in a small area of the stream. Heres what gets me... despite this, it still runs rich and rough, not lean like its not getting enough fuel which I would have thought. Is it possible there is high fuel pressure AND a clogged injector? I dont have a way to check fuel pressure, its an odd size line and the guage Im using doesnt have any adapter for it(and theres no schrader valve). I wouldnt think this is the case, as it hasnt seen much fuel... less than 55k on the odometer. What do you guys think? Im getting ready to just get a new injector for it, but If I install it and find that its not the problem, I just wasted a good, what, 80$? Of course, I dont have the special Injector testing tool GM says I need to use either. I checked the resistence of the injector, and it is in Spec with what Alldata is telling me.

What do you guys think? I need some opinions!

Thanks Alot!

Jim

Jim. Apologize posting a response that is late in time. Just wanna share my experience with similar car model. Mine was a pontiac grand am 98. I had an overheat situation with complete power loss. After being towed and cooling down car will not start. What i did was that i had replaced the the head gasket and the checked the spark plug. I couldn't see any signs of watery substance there so i decided to go on the the compressor and Bang! There i see the crack. Just an update i replaced the gasket as well as the compressor and my car was running well.

 

[ddawg16]

Any chance you can get your hands on a OBDI scanner? Even though you checked the temp sending unit....you don't really know what the computer sees without a scanner.

To get an idea if it's temp related....if it starts up cold and runs ok....but then starts to run richer and richer as the engine warms up....I would lean towards a bad connection to the temp sensor.

Are you sure you don't have a vacuum leak?

Those systems are pretty robust and simple.

Your fuel ratio is based on the following.....

MAP Sensor - Measures the manifold vacuum. The lower the vacuum, the more you must be stomping on the throttle.

Throttle Pos Sensor (TPS) - Tells the computer how much your stomping on the throttle. Used in conjuntion with the MAP.

Temp Sensor - Tells the computer how much to vary the richness based on temp....

O2 Sensor - Helps the computer fine tune the fuel ratio....if this part is bad...it usually only has an effect once you get up to temp and into closed loop. Chances are, you are so rich you are not even getting into closed loop.

Both the MAP and TPS can be checked with a voltmeter while running. The TPS will have a linear voltage output from I think around 1v (closed throttle) to close to 4v at full throttle. The MAP will have full output with the ign on, but engine not running. Start it up and the voltage should drop real low. You should see the voltage change as you pop the throttle. A serious vacuum leak will cause the MAP to read lower than it should and cause you to run rich. Confirm your vacuum with a mechanical guage.

 

[bigdav160]

Those engines had a lot of problems with the TPS. It would get burned up by the heat from the EGR valve.

The coolant sensor and it's connector are always suspect on early GM's. Check it thoroughly.

edit: A vacuum leak on a TBI will make it idle fast, not necessarily run rich.

 

[35mastr]

Does it even reach operating temp in closed loop?

 

[formek]

I am concernd that the O2 was wet! was it fuel? condensation?

I tink everyone has posted a lot of good leads wich should all be looked in to but I am thinking fuel in the egsaust I would look at the coill pack I have seen one cyclender not get spark and mess up a lot.

The EGR is a big one also it sticks open so the O2 thinks if is lean so the conputer will make it full rich.

just my $.02

 

[ForceFed70]

To check for a leaky injector, run a jumper wire to the fuel pump and watch the injector. No fuel should come out of the injector while the pump is running as the ECU will not be seeing any spark/injection events.

TPS is also a likely problem. Check the TPS voltage as you move the throttle (key on, doesn't need to be running) it should increment smoothly and not "bounce around"

Fuel pressure is something I would check. TBI injectors are easily overwhelmed by too high of pressure as they run at about 1/2 the pressure of port injectors. TBI fuel pressure is typically 15-18PSI.

ODB1 scanner is a good idea for checking what the engine temp sensor is telling the computer.

If it's "very rich" I doubt that it's an O2 sensor problem, most ECU's will limit O2 sensor feedback to approx 10%. Meaning that a bad O2 sensor should only result in a mixture that is 10% too rich or lean.

 

[timewarp]

Since the original posts are 5 years old, I am assuming that he has already found the problem or sold the car!

 

[ddawg16]

Since the original posts are 5 years old, I am assuming that he has already found the problem or sold the car!

Are you sure you didn't use your "timewarp" super powers to fake us out?

Man....gotta check those dates more often....

 

[timewarp]

Are you sure you didn't use your "timewarp" super powers to fake us out?

I'll never tell!!!