88 F-150 4.9 EFI runs rich

Seeing as this in a EFI, I was curious if there is a way to adjust fuel/air mixture. The truck is hard to start, and when it is sitting at an idle, it smells like it is running very rich. So much to the point of almost burning your eyes

Reply to
David Coleman
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On Sun, 23 Dec 2007 23:41:18 -0600, David Coleman rearranged some electrons to say:

No, there isn't. But it almost certainly means something is broken. Is the check engine light on?

Reply to
david

I _think_ your truck is OBD I (on board diagnostics, level one), and you can buy a code reader for your truck for about $35. AutoZone will pull codes on an OBD II car or truck for free, but I don't know if they offer the same service to OBD I, I suspect they do not but you can ask.

I think your Check Engine light should be on, with the problem you are having. The Check light should come on every time you turn the ignition ON, and should go out again when the engine starts. This is a Self Check sequence that confirms the light works. When a problem crops up, the light should come on again. You need to confirm the light works, because if it does not work, then it should be on right now telling you there is trouble. If it does work, but is not on, then I'd still pull codes and reset the computer.

There are a couple of things that control the mixture, the Idle Air Control, the O2 Sensor, engine temperature, to name a few. Troubles with these things should throw a code and set the Check light on.

There is no mechanical adjustment -- idle screw to twist on, jets to play with, those sorts of things -- for your trouble.

Reply to
Jeff Strickland

Reply to
David Coleman

Ok. I did the code testing and here are the results:

1.) Code 32 - EGR pressure backfeed fault 2.) Code 42 - HEGO (H2)S) Voltage hight/System rich 3.) Code 52 - Power steering pressure switch open

So since it shows a fault with the EGR, is that what I need to replace? And what is with the power steering pressure switch? I've noticed no problems with the power steering.

Reply to
David Coleman

Some of the codes could be generated long ago, and I'd ignore the power steering for now. Reset the codes and test again to see what comes up -- you can pull codes later today, or in a week (or both) -- and see if the power steering fault comes back, then deal with it then.

I think the EGR is your fault today. The Code 42 is reporting conditions you already know about -- the engine is running rich -- but the Code 32 is reporting a condition that can cause the Code 42. Does that make sense?

The EGR itself can be okay, and your trouble is with the control circuit to it -- which is operated by heat or vacuum, I forget which. In any case, you should investigate the EGR control side, and if there is anything wrong there it should be reasonbly obvious. If you do not find anything, then you need to make a trip to the parts store.

Personally, I have never had an EGR problem, so I can't say with any conviction what the cause can be.

I assume that if you reset the codes, and took a ride to the parts store and pulled codes again, the Code 32 would be there again. Indeed, it could be there immediately upon starting the engine again. Sometimes it helps to know when the code comes up. I had a '95 Bronco and the Check light would come on in the middle of a trip, and eventually go off and not come back again for the remainder of that trip. It turned out I had problems with the O2 Sensor -- I don't recall the code. In any case, I could reset the codes, drive around, and the code would not repeat until the Check light came on again. Any stored code would remain, even if the Check light went out. The operation of the O2 is such that if it comes back into spec, the fault is turned off (the Check light goes out), then the light comes back on if the fault repeats.

I'm a bit perplexed that you have noticable gas fumes and no Check light. Since the main job of OBD I is to monitor emissions stuff, emitting massive quantities of gas should trigger a response.

PS Did you buy the code reader, or use it for free at Autozone?

Reply to
Jeff Strickland

In article , "David Coleman" wrote:

Code 32; Wrong code definition for code 32. Pressure sensors weren't used in 1988 on the 4.9 trucks. Your code 32 is a "pintle position sensor error." On top of the EGR valve is a position sensor, it is a basic potentiometer, the EGR closed sensor voltage should be under 1.0 volt, if carbon is holding the EGR pintle off of its seat, that

-could- set the code. You can backprobe the EGR signal wire with a DVOM and determine what the at rest sensor voltage is. Vacuum leaking past the EVR (EGR control solenoid) could also allow the EGR to open at idle and set the code. May be worthwhile to R&R the EGR and see if the pintle is seated as it should be. EGR position sensors are/were high failure items. (back in the 80s in the dealership, we jokingly referred to code

32s as "pass codes.")

Code 42; This can be caused by a number of things. An EGR valve stuck open will raise manifold pressure causing the engine to run rich based on an erroneous MAP sensor signal. Skewed MAP sensor. The MAP sensor reports the wrong altitude and/or wrong intake manifold pressure. Testing requires a meter capable of reading frequency, the frequency measurement is then compared to the altitude chart that Ford publishes. Air pump. When the engine is cold, the air pump flow is sent to the exhaust manifold or cylinder head upstream of the oxygen sensor, when the engine reaches operating temperature, air pump flow is directed downstream to the catalytic convertor or is bypassed to atmosphere. If the air pump fails to switch when it should, the O2 sensor sees a lean exhaust, the ECU then commands more fuel resulting in a rich condition. Pinching off the rubber tubing upstream of the O2 sensor will usually prove or disprove this failure. Leaking fuel pressure regulator. One side of the fuel pressure regulator diaphragm is exposed to manifold vacuum, if the diaphragm leaks or is ruptured or torn in any way, raw fuel is then sucked into the intake manifold resulting in an extremely rich condition. Shorted O2 sensor, if the 12 volt heater should become shorted internally to the O2 signal, the voltage signal to the ECU will be high which is an indication of rich fuel mixture, the ECU will lean out the fuel delivery and believe it or not, extremely lean and extremely rich smell pretty much the same to the human nose.

Code 52; P.S. switch only used on vehicles with automatic transmissions. Could be a false code if wrong ECU is used on manual transmission vehicle. Could also be false code if you performed a engine running self test and did not cycle the steering wheel when prompted. Could also be a bad P.S. switch but would normally be accompanied by a complaint of low idle speed or stalling when performing tight steering maneuvers at low engine speed.

Also; your check engine light is not set up to notify you when there is a problem or when codes are being stored. It is only wired to the STO circuit which means the only time it will come on is during bulb test and when a code reading device is connected, i.e., STI and STO connected in diagnostic mode.

Reply to
aarcuda69062

Reply to
David Coleman

I would not worry about the EGR or steering codes. Don't shoot the messenger on the EGO sensor either. It is telling you what you already know - it is rich. This means it must be working in the right direction. Known problems in that vintage include fuel pressure regulator failures. The nature of the failures results in a rich mixture especially at lower speeds. The hard starting is likely a result of a rich mixture and plug fouling. Pull the vacuum hose to the regulator. If there is fuel in the hose, it is a goner. If no fuel check the fuel pressure. I don't recall the correct pressure for the six but, I think it was in the mid 30's range at idle. Another problem that frequently crops up is the ECT sensor which will not set a code until it is completely dead. It can be checked for resistance with a meter to see if it is obviously out of range.

Good luck Lugnut

Reply to
lugnut

No. I think you need to replace the EGR. I think the EGR is vacuum controlled, and you may only have a cracked hose.

Reply to
Jeff Strickland

well on the 88 ford its the eec system not obd,

and code 32is the evp sensor on top of the egr valve (did you goose the throttle in koer test?) if not tha will set code 32

code 42 is its runnung rich

code 52 (did you turn steering wheel from stop to stop i koer test if not that will set it) with engine running dissconnect the red vac hose from the fuel press reg and if gas comes out(not good) if the egr was stuck open it would not idle very good then the isc would take over and raise the idle to about 2000 rpm then back down and sometimes stall(that can be taken off and ceaned out ) but do check the map senser they do al kinds of funny stuff when the go bad,,,jst find one from a friends car our truck in the 87 to 90 range and plug in and see if thats it ,,just dont start to through parts at it,,that costs money ,,hope this helps

Reply to
Jeff Guenther

if its throttle body, the injector may have an o-ring around it leaking, look for the drip .lucas

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Reply to
ds549

No I did not reve the engine...

Nope...didn't do that either...wasn't worried about the PS unit

I changed the MAP sensor about a year and a half ago, then again about 6 months later as it had failed. This time I bought a lifetime warrenty MAP.

The engine does "lug" at an idle. But not up to 2000 rpm. I think normal idle is like 800. It usually only varies by 200-300 rpm. Enough to be noticeable and enough to be a aggravation and embarrassment.

Granted this truck is almost 20 years old, but I just put a new engine in it about 2 years ago and other than this problem, it runs great. I live in S. Texas and would not be afraid to drive it to either coast and back without doing more than just a oil change before I left. So I would hate to get rid of it, or worse, just park it.

I appreciate all the help you guys are giving me. I am sure we will get this problem fixed. I am going to replace the EGR valve and hoses (to be safe) and see what that does

Reply to
David Coleman

David,

You can replace the EGR if you want. It is your money. But, consider this: If the EGR is closed at idle as it should be, it does no effect normal engine operation or fuel mix. The job of the EGR is to dilute the intake air charge with exhaust gases to reduce combustion temperatures and reduce NOX emissions. It has the effect of leaning the mixture. You are now too rich which probably means you have a different problem. Save your money and look for a problem that will cause a rich mixture instead. I would look for vacuum leaks before doing anything. A vacuum leak to the MAP sensor would be sure to cause a bad signal and rich mixture just like a bad MAP sensor. A bad FPR or a vacuum leak to it would be a sure cause. A bad ECT or ACT sensor would be a sure cause. Vacuum leaks can be elusive. You must be patient when looking for them. I suggest using something like carburetor cleaner when looking for vacuum leaks to spray on any suspect area. BTW, what you are looking for is not an intake manifold vacuum leak. Those cause high or bad idle accompained with lean readings. You are looking for a sensor related leak or a bad sensor.

If you want to test the EGR for effect, use a piece of vacuum hose to jumper vacuum to it from the extra port on the intake. Watch what happens when you apply vacuum. If the engine runs diferent, the EGR is working properly. The EVP sensor may not be working correctly but, that will not give you a rich mixture. IT usually results in a slight surge at light throttle in the mid range. Changing the EGR is getting the cart before the horse.

Reply to
lugnut

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